I know I'm going to get the "DAGS" for this question, but I just came from
there, and I didn't see this specific information. Lots of debate about how
much current the neutral wire carries, though :-)
With a 3-wire circuit, is it okay to wire both 120V and 240V outlets on that
same circuit? I know it's *possible* by using the two hots for 240 and
either hot and neutral for 120, but is it recommended? Maybe this is the
main reason for this type of circuit, so I didn't see reference to it on
Google. Much of the discussion I read was on balancing the load, which could
imply using the 3-wire circuit with all 120V outlets.
I've got a dust collector coming soon, and the extra 6-7 continuous amps is
going to result in some frequent breaker trips when I start a saw or planer.
Looked at my electrical service, and found there's an unused double-pole 30A
breaker, feeding an unused dryer outlet (house had a gas dryer when I moved
in). That should give me the 2 hots for a 3-wire circuit.
My thought on this type of circuit is to wire one outlet at 240V (re-wire DC
motor to 220V), and the rest wired at 120V. With that 30A breaker and 10 AWG
wire, should have no problem handling the loads from a DC and air cleaner
running, and startup surge from another tool.
An electrician would be a good idea, too. Hopefully I can find someone
willing to consult with me; I can do the wiring myself.
But I'm hoping to get some idea if this is the way I want to go so I can
cost materials. Won't get an electrician or the inspector on the phone
until next week.
TIA
In article <[email protected]>, [email protected] (Greg) wrote:
>If the breaker is double pole and the cable is 4 wire you can do it.
Actually, he wants 3-wire with ground (e.g. 10/3 WG). If he asks for 4-wire
cable at Home Depot, all he will get is blank looks. Or thermostat wire.
--
Regards,
Doug Miller (alphageek-at-milmac-dot-com)
Get a copy of my NEW AND IMPROVED TrollFilter for NewsProxy/Nfilter
by sending email to autoresponder at filterinfo-at-milmac-dot-com
You must use your REAL email address to get a response.
On Mon, 14 Apr 2014 17:43:21 -0500, Martin Eastburn
<[email protected]> wrote:
>Sorta...
Sorta (as long as we're being pedantic ;-)
>I have a degree in Physics and retired as an EE after 20+ years.
>Watts is the value in power if it were a resistive load.
Sorta, kinda, perhaps poorly worded. Power is measured in watts. W=VA
if the load is resistive.
>VA is the voltage times the current (and ignoring the phase angle
>between them) Which gives a completely different wattage for a reactive
>load like a motor.
Assuming there are no harmonics, which is a good approximation for an
induction motor but may not be a good assumption for other situations.
Electronic loads are often particularly bad. Fluorescent lighting is
another example where the power factor (W/VA) is often particularly
bad.
>ELI the ICE man.
>Voltage leads current (in time) in inductive (coil) circuits.
>Current (I) leads Voltage in a capacitive circuit -
> starting coil with cap. Cap larger than coil
>in reactive values. XL == ac resistance XC == ac resistance.
The important thing is that wiring and circuit elements (switches,
breakers, connections, generation) must be sized for volt-amperes,
where the power consumed (heat load, electric bill, etc.) is
quantified by watts. VA is always equal (only for purely resistive
loads) to or greater (all other cases) than watts. Reactive (either
inductive or capacitive) loads cause additional problems not
quantified by either.
Hello Keith,
I am just passing by and noticed your post , I am an electrician.
I do not know what level of experiance you have so let me start with
some warnings, if you know understand what you are doing ignore the
next few lines ;)
> (re-wire DC motor to 220V)
I am not sure what you mean here D.C. is NOT a.c.! Unless there is
some transformer-rectifier setup you didn't mention this just wont
work, AT ALL.You will end up in flames.Realize you are saying rewire a
?Voltage Direct Current motor to 220Voltage Alternating
Current...these are different beast.
> With that 30A breaker and 10 AWG
> wire, should have no problem handling the loads from a DC and air
cleaner
> running, and startup surge from another tool.
O.k. that is pretty reasonable there are many appliances that run on
220VAC and use one hot and a neutral to get 120VAC and use that for the
timer, controls, or whatever. Really there is no reason to have put in
a neutral wire in if you weren't needing to use it for that very
purpose, ok you can use it for a 3way or 4way circuit, but that only
holds for small wire...think about it.
If you don't already know the transformer outside your house sends 3
wires.
Grounding is done near your house.
This is what you get fromthe transformer: L1-N-L2
L1 and L2 are the ends of the winding and N is the center tap that they
ground. It is therefore in the middle between the two legs so between
L1-N there is 120VAC and between N-L2 there is 120V and between L1-L2
there is 220VAC DIFFERENCE cause it is really all about potential
difference between points ;) Also you might be fooled into thinking
Neutral is ground it is not . DO NOT use it as such it can be a lethal
mistake.
The only real problem that I see is this:
You have 30 amp double pole breaker.
You want to use 220 for *whatever*
You want to use 120 for *whatever else*
what if the 120v appliance or tool messes up and starts pulling a
higher load until it burns up ...
The breaker would stop it huh....Nope not always, not if it didn't
exceeded the 30 amp breakers capacity.
Which is why you should run a seperate line for your 120v loads and
your 220v loads that are not related.It is just a lot safer , also
ground everything especially on a motor load, it will help reduce
staitc and noise on the line as well. In this case I would run a new
line, but I am an electrician ;)
Oh and by the way always check your local electrical codes they are
always diffent and can sometimes surprise you!
Hth,
M.E.Farmer
Hello,
sorry that just isn't right I'm sure you meant ;
P=I*E
Or rearranged :
Watts = Amps*Voltage
Amps = Watts / Voltage
Voltage = Amps / Watts
etc..
But even that isn't fully all of the story if you are talking AC power
and Inductive loads.....
then you deal with Impedance and other fun things (power factor),
long story short ... it's complex.
Hth,
M.E.Farmer
Doug Miller wrote:
> In article <[email protected]>, "Chuck
Hoffman" <[email protected]> wrote:
> >Sorry...neglected to answer your original question. I believe the
NEC
> >frowns on connecting across one phase of a 230V circuit to get 115V.
That
> >WOULD double the current on the neutral and result in a potential
overload.
>
> Utter nonsense. It would do nothing of the sort.
>
> In a circuit wired as he described, with (for example) a 10A load at
240V and
> a 15A load at 120V, the current in the neutral conductor is 15A. (The
240V
> load places *no* current on the neutral.)
>
> Now add a 17A load at 120V on the opposite leg.
>
> One hot leg is drawing 10 + 15 = 25A. The other is drawing 10 + 17 =
27A. And
> the current in the neutral is 17 *minus* 15 = 2A.
Right on Doug,
Exactly thats the idea behind LOAD BALANCING! if the are equal there is
no current on the neutral. The whole idea of the neutral is a 0 volt
refrence <only>
We really try to achieve 0 volts potential across the neutral it is
technically a ground wire of sorts but is not the GROUND wire .
It isn't magic if you look at how they send it too you from the 'pole
pig' transformer they send L1 and Neutral (ever seen the ground wires
running down the light pole? That's were they ground the neutral at on
there side)
and then L2.
This is a simplification and is only meant to help illustrate the idea.
Please look into it if you want to verify any of this.
['pole pig' transformer step down]
the v's are windings and
the = is the seperator between the windings.
M1-vvvvvvvvvvvvvvvvvvv-M2 13.8kv or some other mains voltage
======================
L1-vvvvvv-N-vvvvvv-L2 240v split phase
| | |
|<---240v--------->|
| | |
L1<--120v-N--120v-->L2
Excuse my ascii.
The legs L1 and L2 are 180 degrees out of phase with each other that
means one should be at -120 and the other at +120 .
Notice that the Neutral is at the middle...that gives you a ZERO volt
refrence to ground. Why is it needed well we need a reference to ground
so we can use our appliances and not be subject varying voltage levels
from ground. A simple 240v circuit could actually be floating 1000v
above earth ground but between legs only have a potential of 240v but
since there is no ground reference it could be 1000v above earth ground
from just 1 leg, that would hurt a bit ;)
Once again it is all a bit complex.
One could study for years and still be confused.
And ponder this, what is electricity, is it the just the flow of
electrons ....
or is it more to it, like maybe the electrons are just buckets that
travel the circuit slowly tranfering 'photonic energy', hint they are
never consumed in the circuit yet we do get power from the circuit;)
M.E.Farmer
Chuck Hoffman wrote:
> This has become an obvious standoff and it will serve no purpose to
continue
> it.
Respectfully there is no standoff you are wrong.
there is only a single PHASE in household power supplies unless you
have a huge shop and have 3 phase power(rare). What you haven't noticed
was the fact that it is a SINGLE phase that is SPLIT by a transformer
with the center tapped to ground for reference. Not 2 phases , just a
split-phase.........DO NOT CONFUSE!
I don't really understand the difficulty if you have 40 years of
electronics you should have played with tranformers a little by now. Oh
wait a minute this isn't electronics........
Leave it to ELECTRICIANS. I also know electronics and love to build
things but when I started in the electrical field I discovered most of
electronics is diffrent than electrical even the symbols( capacitors
(electronics) look like open-contacts ( electrical) and it took many
years to sort it all out (oh yes I just knew that electronics would
help me....bahh).
Just to qualify myself I have wired many 3 phase transformers and
motors and know what the difference in a delta, wye or delta-wye
transformer, and can wire them correctly too.
M.E.Farmer
Family full of electricians even my mother.
Hello all,
First i want to say Merry Christmas all.
For the curious the point of three phase was to provide a better power
feed for motors.
the concept of the rotating magnetic field works better when instead of
a single coil; you have three . It gives you much more power available
at any one spot on the armature.
The three phases are 120 degrees out of phase with each other. A.C.
starts at 0volts and goes to +120v then return to 0v then goes to -120
then completing the cycle returns to 0v.
When you have 3 phases they(the power company) stagger them so the
first phase starts to rise then the second then the third and they
follow each other thru the cycle so they reach 120v slightly after each
other. Instead of only getting 120v 60 times a second we now get three
separate phases providing 120vac. So 3* 60 times a second = 180 times
a second we now get power, 3 phase motors run much smoother because of
this.
240v motors do run slightly more efficently than 120v motors but only
because of increased voltage, it has none of the advantages that the 3
phase motor does.
Three phase allows much more power to be used by a device by sending it
to the load at slightly different times so there is time to cool yet
always have potential between at least any two legs.
Power as used above means voltage not watts. This is a term
electricians abuse.
Also note that in actually three phase systems there are many
arrangements of voltages available. Depending on the system and the
need you could find 277v, 208v, 240v, 120v.. etc.....so ignore the
simplification above that they all go to +-120v.
M.E.Farmer
mefjr75 wrote:
<snip>
>The three phases are 120 degrees out of phase with each other. A.C.
>starts at 0volts and goes to +120v then return to 0v then goes to -120
>then completing the cycle returns to 0v.
<snip>
If you're talking about 120 volt RMS,and I think you are, the
voltage will peak at ~ +170 volts and -170 volts.
R,
Tom Q.
Remove bogusinfo to reply.
Roy Smith wrote:
> It is interesting that you mention that. It certainly is possible to
> build a 4-phase generator. I've never seen or heard of one, but it
> would be no big deal to build one. You would really have 4 windings,
> not four brushes, but that's a detail.
>
> Now, let's try an experiment. Label the 4 phases A, B, C, and D, in
> order. Assume the windings are star-connected, so there's a common
> neutral, which we'll label N. Let's further assume that the
leg-neutral
> voltage of each phase is 120 VAC.
>
> I'm going to give you two panels, each having three terminals on it.
> One both panels, the terminals are labeled X, Y, and N. One one
panel,
> X and Y are connected to phases A and C from our 4-phase generator,
and
> N is connected to the neutral. On the other, X and Y are connected
to
> L1 and L2 from a typical center-tapped 240V residential pole drop,
and N
> is connected to the center tap. On both panels, N is tied to earth
at
> the panel.
>
> Can you describe a measurement that you can make, which will tell you
> which panel is connected to the 4-phase generator and which is
connected
> to the pole drop? You can use voltmeters, ammeters, power meters,
phase
> meters, oscilloscopes, or any other tool or instrument you desire.
> Assume, however, that both are ideal voltage sources, i.e. you can't
> draw enough current from them to significantly load them down.
>
> My claim is that you can't tell the difference.
Ok this is a bit dirty but you didn't mention bonding the 4 phase
generator to ground anywhere but at the panel.
So I would take both panels and remove the ground wire from the ground
bus in the panel ( watch for all the heavy arcing! ) then i would take
my voltage meter and read voltages from any leg to the ground wire
coming from the ground. Since you did not bond your generator anywhere
but at the panel if you ever lose ground ( screw loosens ,cooper loss,
thermal stretching) at that panel voltage will float and be different
;)
M.E.Farmer
On Thursday, December 23, 2004 10:59:07 AM UTC-8, Keith Carlson wrote:
> I know I'm going to get the "DAGS" for this question, but I just came from
> there, and I didn't see this specific information. Lots of debate about how
> much current the neutral wire carries, though :-)
>
> With a 3-wire circuit, is it okay to wire both 120V and 240V outlets on that
> same circuit? I know it's *possible* by using the two hots for 240 and
> either hot and neutral for 120, but is it recommended? Maybe this is the
> main reason for this type of circuit, so I didn't see reference to it on
> Google. Much of the discussion I read was on balancing the load, which could
> imply using the 3-wire circuit with all 120V outlets.
>
> I've got a dust collector coming soon, and the extra 6-7 continuous amps is
> going to result in some frequent breaker trips when I start a saw or planer.
> Looked at my electrical service, and found there's an unused double-pole 30A
> breaker, feeding an unused dryer outlet (house had a gas dryer when I moved
> in). That should give me the 2 hots for a 3-wire circuit.
>
> My thought on this type of circuit is to wire one outlet at 240V (re-wire DC
> motor to 220V), and the rest wired at 120V. With that 30A breaker and 10 AWG
> wire, should have no problem handling the loads from a DC and air cleaner
> running, and startup surge from another tool.
>
> An electrician would be a good idea, too. Hopefully I can find someone
> willing to consult with me; I can do the wiring myself.
> But I'm hoping to get some idea if this is the way I want to go so I can
> cost materials. Won't get an electrician or the inspector on the phone
> until next week.
>
> TIA
Roy Smith wrote:
> I don't know much about the NEC, but I do understand polyphase
> circuits (4 years of EE in college). I don't think I've ever heard
> the term J-factor. What is it?
The "J" factor is the square root of -1. No, really.
it is mainly used for plotting how voltage/current leads/lags
current/voltage in inductive or capacitive circuits. I am no
electrical/electronic engineer, just a simple tech with enough knowledge
to know that everyone's argument is "a little" right.
The 2 110vAC "phases" that come into your home are 180deg "out of phase"
with respect to one another as a simple product of the physics of the
windings (secondary) of a transformer. You could, in fact, produce a
transformer where the 2 legs are in phase, but that would only go so far
until the "electrical lengths" of the 2 legs become different.
Two true phases of electricity deal with the physical location of the
wires as they come from the generator, and their phase relationship is
relative to their respective location. If you have a generator, and you
place 3 "brushes" equidistant around the amature, those 3 "phases" will
be 120deg "out of phase" with each of their neighbors. if you increase
the brushes to four, and place them equidistant, each will be 90deg out
of phase to its neighbor, and 180deg out of phase with its diametric
opposite cousin. Take any number, place it around the armature, divide
by 360, and you will get the phase relationship between any 2 legs. see
http://www.tpub.com/content/neets/14177/css/14177_67.html
take a look @ fig. "B". on the right side of the figure, you see the
three windings labelled "7". Those are 120deg out of phase with one
another.
Since, I believe, the original question was about wiring 110 and 220 on
the same circuit, and the dryer/oven timer wiring was mentioned,
remember that the 220 is stepped down to 110 usually as a
convenience(because the 110 is readily available, existing only to
become one of the additives for 220 when necessary to perform the
primary function of the device; i.e. the heating element), and is tapped
off of in parallel to run the power supply of the "convenience"
items(clock, timer, motor) at a much more friendly voltage-5 or 12vDC in
the case of the newer appliances.
The simple answer to the question is yes. 110 and 220 co-exist quite
nicely in a circuit. If you try to make up a home-brewed solution to
allow them to co-exist, it would be a good idea to get advice not from a
newsgroup, or the web itself. Consulting with a live electrician, an
electrical inspector, AND your homeowner's insurance carrier is a must!
Insurance will not cover incidents caused by wiring not done to code.
DAMHIKT!
Clint wrote:
>
> This type of setup is common on a stove, right? 240 for the stove heating
> elements, and 110 for the lights/clock?
>
Yes, and electrical dryers as well. At least NEC <used> to (I don't
have a very recent copy to check current, maybe someone else will) allow
the bare wire to be used as neutral in this specific instance (under
some other specific circumstances as well, basically being a single
dwelling). Actually, in a range, the burners typically only draw 110 as
well until they're turned to "hi"...
I think one of the problems in this thread is the confusion of using
"phase" to refer to both true phases as in 3-phase versus the 180-deg
phase difference between the two hot legs of a single-phase AC circuit.
I don't know when it became prevelant or popular (if it actually is or
whether it's still fairly isolated) to refer to the two hots as two
"phases" but I spent a significant amount of time trying to break my
hired hand of the misconception over the last year. He was trained as
an aircraft mechanic and was/is pretty darn good w/ hydraulics,
mechanics, most simple wiring, controls, etc., but apparently was taught
this as gospel regarding single phase AC power...
Todd Fatheree wrote:
...
> Well, I'm not an EE, but where I went to engineering school, sqrt(-1) = i.
> I also can't find a reference for it via Google. Do you have a reference
> for it? I'm not saying you're wrong, just that I've never heard of it, and
> I've been exposed to enough EE back in my school daze to know what reactance
> is and power factor and some of that cool polyphase stuff.
j for sqrt(-1) is quite common in EE, probably more so than i which is
more prevalent in mathematics or physics. One reason is that "i" is so
often used for current in EE.
As for reference, let's see...
Ok, here
T(jw) = G(jw)/(1 + G(jw)) --> ~1, |G(jw)| >> 1 Eq (8-60)
Closed-loop transfer function frequency response.
Feedback Control Systems, Phillips & Harbor, Prentice-Hall. ISBN
0-13-313917-4
Bruce wrote:
...
> Hey, I have that book!
> -Bruce (EE control systems engineer)
It's one of many I've picked up over the years -- not too bad although
I've not used it too much...I was NE at the time I was doing most
control stuff so most of my early exposure was to reactor controls...I
picked up the EE controls stuff much, much later... :)
Dave wrote:
>
> I have to confess that I never understood what the square root of -1
> was.
"i" or "j" depending on whose notation you want... :)
> ... The product of what times itself will equal -1?
"i" or "j" ... think of it simply as "by definition" that j*j = -1 and
anywhere you need it you make the substitution and carry on...leads to
the expansion of the "real" numbers to include the "complex" numbers of
the form "a +/- jb", for 2 + 3j. Rules for things like
addition/subtraction are add real and imaginary parts separatel,
multiplication is like algebraic...
(2+3j)*(1+2j) = 2*1 + (2*2j+3j*1) + 2j*3j
= 2 + 7j + 6j**2
= 2 + 7j + 6*(-1)
= 2-6 + 7j
= -4 + 7j
Clear as mud? :) Notice all that was done in last simplification was
to associate terms and substitute -1 for the j-squared term.
On Sat, 25 Dec 2004 07:34:46 -0700, Duane Bozarth wrote
(in article <[email protected]>):
> Todd Fatheree wrote:
> ...
>> Well, I'm not an EE, but where I went to engineering school, sqrt(-1) = i.
>> I also can't find a reference for it via Google. Do you have a reference
>> for it? I'm not saying you're wrong, just that I've never heard of it, and
>> I've been exposed to enough EE back in my school daze to know what reactance
>> is and power factor and some of that cool polyphase stuff.
>
> j for sqrt(-1) is quite common in EE, probably more so than i which is
> more prevalent in mathematics or physics. One reason is that "i" is so
> often used for current in EE.
>
> As for reference, let's see...
>
> Ok, here
>
> T(jw) = G(jw)/(1 + G(jw)) --> ~1, |G(jw)| >> 1 Eq (8-60)
>
> Closed-loop transfer function frequency response.
>
> Feedback Control Systems, Phillips & Harbor, Prentice-Hall. ISBN
> 0-13-313917-4
Hey, I have that book!
-Bruce (EE control systems engineer)
On Sat, 19 Apr 2014 12:16:04 -0700 (PDT), whit3rd <[email protected]>
wrote:
>On Thursday, December 23, 2004 10:59:07 AM UTC-8, Keith Carlson wrote:
>
>> With a 3-wire circuit, is it okay to wire both 120V and 240V outlets on that
>> same circuit? I know it's *possible* by using the two hots for 240 and
>> either hot and neutral for 120, but is it recommended?
>
>It used to be common, and my stove and clothesdryer both have 120V as
>well as 240V loads, and a three wire plug. This is now not recommended,
>and there's good reasons for a four-wire connection instead.
>In stoves, a convenience outlet is sometimes supplied, and this would
>have a separate fuse (or circuit breaker) so that the 30A fused stove
>doesn't cause a fire hazard on the 15A wiring plugged into that
>convenience outlet.
>
>The clean solution (ask an electrician to be safe) is to run a four-wire
>line from your main breaker to a subpanel; then put any combination
>of 240V and 120V breakers into the subpanel, and wire your sockets
>from that subpanel. There's lots of rules on subpanel size and
>wiring, but it's what an inspector would want to see.
I think most were asuming 3 wire+ground (nmd3) cable. I know I was.
The 3 terminal drier plug is history.
"toller" <[email protected]> wrote in message
news:[email protected]...
> It is not recommended. Anything confusing is dangerous, and this is
> confusing.
>
Saw quite a bit of this debate on various NGs. Some felt it's dangerous
because someone will screw up the neutrals at a later time, or a future
homeowner might replace the double pole breaker with two, and put them both
on the same leg of the service.
Others thought, anyone qualified to work on the wiring or panel should not
be confused by this type of circuit.
> However, if you lose the 30a breaker, it is possible. You cannot use a
> 30a breaker because the 120v circuit will not be rated for 30a. You must
> get a 20a breaker and use #12 for all of it. (I am assuming #12 is
> adequate, which might not be true if your run is too long and the current
> is too high; you have to check that first)
>
This might be my downfall. It's not going to be practical to use 30A outlets
so the whole circuit can be considered 30A rated.
> If 20a will cover the DC and whatever you want to also run on it, you can
> do it. Otherwise you can't.
>
It's looking more like that's what I'll do... back to the original plan and
see how it goes. My thinking, though, was that now on a 15A circuit, I'll
have the breaker trip sometimes on starting a machine. Table saw - about 10%
of the time. Miter saw - maybe 15% of the starts. Planer - probably 1/3 of
the starts trip the breaker.
So I was thinking 20A circuit. But now add the dust collector, drawing 6A
continuous (12 on startup). Now I've got about 14A "headroom" for other
motors to start.
> Overall it is a better idea to run two circuits. Did anyone mention that
> you will need 12/3 wire for the combination circuit but only 12/2 for the
> separate circuits? It is probably just as easy to run two 12/2 as one
> 12/3.
>
Yeah, I knew that. I'm running the wiring in EMT conduit though, so I don't
have to tear up finished walls. I thought I read somewhere that you can't
run more than one circuit in the same conduit run. If that's true, two
circuits means more cost.
I suppose another option is replace the 30A breaker with a 20A double-pole,
make it a 20A, 120/240V circuit. Could still use the 20A receptacles then.
Anyway, talked to my neighbor who referred me to another neighbor who's an
electrician. I may be able to get some inexpensive guidance from him.
> That was funny about not being able to change DC to AC.
>
In the U.S. I don't believe there is any such thing. Household supply
is obtained from a single phase of a three phase system. For all
intents and purposes, when the power grid appears in your
neighborhood, forget about two of those phases. You will never be
involved with them. Only single phase is getting into your house.
The single phase current is transformed from a fairly high voltage off
the feeders to 240V from the output of a center tapped transformer up
on the pole. With regard to that 240V, there is no neutral. The 240V
comes from the two secondaries of the transformer. And there is no +
or -. This is AC, not DC. It is 240V across the two poles.
Our well known 120V supply comes, as you know, from one hot leg and
the center tap of the transformer. Either hot leg will work.
Here is the most important thing: ALL of this; the 240V, and each 120V
is developed from the same single phase of the three phase system. It
is single phase power. There is no "two phase" power.
>...or "2 phase" 240v (two 120v hots 180 degrees out of phase). =20
There is no "two phase" power. The two legs or poles are 180=B0 out of
phase, as you say, because they come off the opposite legs of the
secondary of the transformer. They are NOT two phases of the three
phase system. It is single phase. All of the current in your house
comes from the same, SINGLE phase of the three phase system.
>However 3 phase electricity is very different. Or so I have heard.
Yes and no, but I will leave that discussion to those with experience
with it. I have none.
>I think that is why 240v is not called "2 phase"; it can be thought of as =
1
>phase,
It IS single phase. There's no "thinking" about it.
>but is completely different than 3 phase.
Sigh. Yes, you have stated a tautology.
- -
On Fri, 24 Dec 2004 17:14:26 GMT, "Chuck Hoffman"
<[email protected]> wrote:
>For the critics, I've been in electronics for 40-some years and have been a
>technical school instructor. And I worked for an electric utility. I do,
>in fact, know what I'm talking about.
I, also have been in electronics for more than 40 years. I have a
pretty good idea of what I'm talking about, too. I've known all sorts
of people over those years; some with the golden finger who didn't
even need schematics to fix complex equipment but who couldn't pour
piss out of a boot with the instructions on the heel.
I've known people that couldn't pass a Morse code exam if it was sent
one character every two minutes but who could teach brilliantly.
And now I know someone with more background and experience perhaps
than I have who can't explain a simple concept involving a single
phase, two pole, center-tapped electrical circuit without complicating
it beyond measure, and then when trying the simple answer gets it
completely WRONG.
>Now let's talk about your comments. First you say:
>
>"Phase angle, as a concept, is perfectly suited for all sorts of
>theoretical discussions...."
>
>It is far more than theory, I'm afraid. It's an important consideration
>when working with multi-phase circuits. Then you say:
Excuse me, but when you're discussing phase angles, AC circuits,
impedance, etc., THEORY is EXACTLY what you're talking about. Or, to
be even more precise, anything involving the movement of electrons is
electrical theory. Want me to prove my point? Let's discuss current
flow; electron or conventional current?
>"Opposite legs have opposite values (because they are 180° out of phase)"
>
>That seems diametrically opposed to your first disdainful comment. It is,
>however, precisely the point I was making.
But the issue at hadn is a special circumstance; it is the set of
properties that becomes simple, additive arithmetic when the phase
angle is 180°. It uniquely occurs in the center tapped, two pole
circuit that is residential house wiring. Discussion of other phase
angles overly complicates the simple additive (albeit with negative
numbers) process required to understand and calculate resultant
current in a two pole, shared neutral circuit.
>You also said:
>
>"I don't recall J-factor in the NEC.
>
>I've known people who could recite the NEC chapter and verse but had no clue
>about the physical properties of electricity or AC circuit analysis. Do you
>really understand alternating current and its physical properties ?
Yes, I'm afraid I do. But with all your experience and expertise,
explain this:
>> >That WOULD double the current on the neutral and result in a potential
>> >overload.
That was your response to a question about running a 120V load on one
half of a 240V circuit. I said then:
>> This is the part that Doug describes as utter nonsense. And he's
>> right. The ONLY current on the neutral would result from the
>> connection across one LEG of the 230V circuit (to get 115V). There is
>> NO current in the "neutral" of a 230V circuit because there is no
>> "neutral" in a 230V circuit.
And I stand by that question; how do you explain this?
You should have left well enough alone.
- -
LRod
Master Woodbutcher and seasoned termite
Shamelessly whoring my website since 1999
http://www.woodbutcher.net
"Keith Carlson" <[email protected]> wrote in message
news:%zEyd.245829$V41.11293@attbi_s52...
> I've got a dust collector coming soon, and the extra 6-7 continuous amps
> is
BTW, I read a lot trying to decide on a 1.5 - 2 HP dust collector. Finally
put whatever specs and prices etc. into a spreadsheet to compare them side
by side. (Ended up going with a Penn State unit).
If anyone else is shopping dust collector, and would find this info useful,
I'll be happy to email the sheet. (Hey, I'm a relative newbie, but I'm
trying to contribute *something*).
It's kinda interesting how they line up by price. The Harbor Freight unit is
way below anything in price, even adding on $67 for a felt bag upgrade.
There's a Grizzly and Jet at the high end. But most of them fall right into
a $330-350 range (including shipping and upgrade of bag if it comes with a
30 micron bag).
On Thu, 23 Dec 2004 23:18:38 GMT, "Chuck Hoffman"
<[email protected]> wrote:
>"Doug Miller" <[email protected]> wrote in message
>news:[email protected]....
>>
>> Utter nonsense.
>>
>No, it isn't. Look at my simplified description of the current in a
>two-phase circuit for a clue that I know what I'm talking about.
Right church, wrong pew.
All the stuff you wrote about phase angle and AC circuits, etc. seems
to be okay, however, you liberally sprinkled in terms that in the real
world of electrical wiring just aren't true. Let's take a look.
>There is no argument at all. In a two-wire 115V circuit, the current
>carried by the neutral is exactly the same as that carried by the hot wire.
True. You should have stopped there.
>In a three-wire 230V circuit, there is a property called phase angle
>or J-factor. This results in current flowing in both directions at the same time
I don't recall J-factor in the NEC. That could be me, though.
>(this is not exactly a true statement but a convenient way to consider
>current flow in a three-wire circuit).
And since it's not, you should have left it alone.
>As the current on one phase increases from zero to some positive
>value, the current in the other phase is decreasing from its positive
>value to zero.
Here's the crux of the problem. In electrical systems (the stuff the
power company provides) current is delivered in three phases. In the
average house, however (and that is what the discussion is about),
power is delivered from only one phase of the three phase system.
It is run through a center tap transformer which yields two "hot" legs
that are 180° out of phase and a common return leg. All three of these
wires, however, are delivered from a single phase.
There is no two phase power. It's either three phase or single phase.
No electrician calls either hot leg a "phase."
>The vector sum of the currents on the neutral is exactly the same as
>the total of both phases.
Yeah, you could say that...if you wanted to answer the question of
"what time is it?" by telling us how to build a clock.
>Because of the phase angle, however, that does not mean twice
>the current.
Phase angle, as a concept, is perfectly suited for all sorts of
theoretical discussions but is unnecessarily complex in single phase
wiring. The only "angle" to consider is the 180° that each leg of the
single phase power feed to house is out of to each other.
>It never exceeds the total current of each phase individually.
Correct (except for that "phase" thing), but you sure took the long
way around to get to it, and lost half the pack doing it.
>Confusing? Yes. One has to study alternating current and understand
>plane geometry and simple trigonometry to comprehend it.
Please. Opposite legs have opposite values (because they are 180° out
of phase) and the current is additive. It's simple arithmetic (albeit
incorporating negative numbers).
>Sorry...neglected to answer your original question. I believe the NEC
>frowns on connecting across one phase of a 230V circuit to get 115V.
Given that stoves and dryers sometimes do that very thing, I believe
you're wrong...unless you could cite the section in which they "frown"
upon it.
>That WOULD double the current on the neutral and result in a potential
>overload.
This is the part that Doug describes as utter nonsense. And he's
right. The ONLY current on the neutral would result from the
connection across one LEG of the 230V circuit (to get 115V). There is
NO current in the "neutral" of a 230V circuit because there is no
"neutral" in a 230V circuit.
- -
LRod
Master Woodbutcher and seasoned termite
Shamelessly whoring my website since 1999
http://www.woodbutcher.net
On Tue, 15 Apr 2014 23:01:32 -0500, Martin Eastburn
<[email protected]> wrote:
>You got it wrong. it is this : Power (measured in the watt) - Voltage
>(measured in the Volt) Times Current(measured in Amps) Times Cos(phase
>angle) (1 to 0 in value).
No, I certainly don't. That formula only for SINE WAVES (i.e. no
harmonics on either current or voltage waveforms). OTOH, PF=W/VA
*always* works.
>P = V*I*Cos(theta). When in DC Cos(0)=1. V is DC voltage in that case.
So? Again, sine waves are the trivial case. That formula doesn't
work for nonlinear situations. The DC case is more than trivial. PF
is meaningless.
>When in DC - it becomes : P = E*I where E is the DC voltage. I is the
>DC current and there isn't a phase angle or Theta is Zero and COS(0) = 1.
Trivial cases are irrelevant. Not sure why you insist on lecturing on
the trivial.
>A Watt is the unit of power. Not the plural form.
Plural is plural. Two times a watt is two watts. ...and if you really
want to get pedantic about the language, "watt" is not capitalized.
Proper names, when used as names of units are *not* capitalized.
Abbreviations for proper names are.
Correct Incorrect
W, V, A w, v, a
watt Watt
volt Volt
ampere Ampere
meter Meter
m M
>When V is used it is AC. When V is used I is AC.
Whatever that means.
>They are in R.M.S. scaling. Root of the Mean Square.
May be. That's the point, though. Your assumptions only work for
sine waves and the conversion between Peak, RMS, whatever, is trivial,
in that case. RMS is the voltage (or current) of a waveform that will
give the equivalent power of a DC value. It's one of many meaningful
numbers. The root of the mean square (for voltage or current) can be
calculated, as can the average of the voltage X current (power).
No periods in RMS.
>(A.C. volt meters and current transforms 'translate to these'.)
Again, "translate to" means "only valid for sine waves". If you
aren't dealing with sine waves, these "translations" are meaningless.
Worse, actually. They're wrong. A "true RMS" meter is always right
(within it's physical capabilities).
>Some times special voltages are used as design needs.
Was that supposed to mean something?
>Harmonics from inductive and capacitive circuits are very small
>compared to the main current / voltage waveform. They are ignored
>if anything normal.
Oh, good grief! Stop with the word salad, already. Harmonics from
inductors and capacitors are ZERO. They're linear devices. Switching
elements (semiconductors) are a whole different kettle, as is the real
world.
>One should always use the phase angle in the AC model. Meters do.
Wrong. Meters certainly do not. They integrate V, A, V*A, or measure
heat.
>So the task for the technician is just measure it using a quality meter.
No, one should always use reality. It may be impossible to measure
phase angle. It's always possible to measure V, I, and P. PF can then
be derived from that, if necessary.
>Even a reasonable multi-meter from Radio-Shack can measure Correctly
>(enough). I like three or four major makers and for the lab I use two.
If they're "true RMS" meters, they're integrating type. If they're
peak or average (rectified) meters, then they're calibrated assuming a
sine wave. If you have something else (harmonics) then they're wrong.
>V means AC voltage. E means DC voltage. I is the current that
>matches. Cosine(phase-angle) is Always used in AC.
Now you making stuff up. Wrong.
>One should design for several times that of V*A*Cos(0).
Whatever that means.
>Martin - Senior Scientist and former Technologist serving between and
>working for both Intel and the Schlumberger.
>I'm working on my computer I built in the late 50's and early 60's. It
>has just under a thousand gates. All hand wired.
Don't break your arm.
On Thursday, December 23, 2004 10:59:07 AM UTC-8, Keith Carlson wrote:
> With a 3-wire circuit, is it okay to wire both 120V and 240V outlets on that
> same circuit? I know it's *possible* by using the two hots for 240 and
> either hot and neutral for 120, but is it recommended?
It used to be common, and my stove and clothesdryer both have 120V as
well as 240V loads, and a three wire plug. This is now not recommended,
and there's good reasons for a four-wire connection instead.
In stoves, a convenience outlet is sometimes supplied, and this would
have a separate fuse (or circuit breaker) so that the 30A fused stove
doesn't cause a fire hazard on the 15A wiring plugged into that
convenience outlet.
The clean solution (ask an electrician to be safe) is to run a four-wire
line from your main breaker to a subpanel; then put any combination
of 240V and 120V breakers into the subpanel, and wire your sockets
from that subpanel. There's lots of rules on subpanel size and
wiring, but it's what an inspector would want to see.
On Thursday, December 23, 2004 10:59:07 AM UTC-8, Keith Carlson wrote:
> I know I'm going to get the "DAGS" for this question, but I just came from
> there, and I didn't see this specific information. Lots of debate about how
> much current the neutral wire carries, though :-)
>
> With a 3-wire circuit, is it okay to wire both 120V and 240V outlets on that
> same circuit? I know it's *possible* by using the two hots for 240 and
> either hot and neutral for 120, but is it recommended? Maybe this is the
> main reason for this type of circuit, so I didn't see reference to it on
> Google. Much of the discussion I read was on balancing the load, which could
> imply using the 3-wire circuit with all 120V outlets.
>
> I've got a dust collector coming soon, and the extra 6-7 continuous amps is
> going to result in some frequent breaker trips when I start a saw or planer.
> Looked at my electrical service, and found there's an unused double-pole 30A
> breaker, feeding an unused dryer outlet (house had a gas dryer when I moved
> in). That should give me the 2 hots for a 3-wire circuit.
>
> My thought on this type of circuit is to wire one outlet at 240V (re-wire DC
> motor to 220V), and the rest wired at 120V. With that 30A breaker and 10 AWG
> wire, should have no problem handling the loads from a DC and air cleaner
> running, and startup surge from another tool.
>
> An electrician would be a good idea, too. Hopefully I can find someone
> willing to consult with me; I can do the wiring myself.
> But I'm hoping to get some idea if this is the way I want to go so I can
> cost materials. Won't get an electrician or the inspector on the phone
> until next week.
>
> TIA
On 24 Dec 2004 12:41:29 -0500, [email protected] (Roy Smith) calmly
ranted:
>Chuck Hoffman <[email protected]> wrote:
>> "I don't recall J-factor in the NEC.
>
>I don't know much about the NEC, but I do understand polyphase
>circuits (4 years of EE in college). I don't think I've ever heard
>the term J-factor. What is it?
Rest breaks where union electricians would go toke up?
----------------------------------------------------------------------
* Scattered Showers My Ass! * Insightful Advertising Copy
* --Noah * http://www.diversify.com
----------------------------------------------------------------------
You got it wrong. it is this : Power (measured in the watt) - Voltage
(measured in the Volt) Times Current(measured in Amps) Times Cos(phase
angle) (1 to 0 in value).
P = V*I*Cos(theta). When in DC Cos(0)=1. V is DC voltage in that case.
When in DC - it becomes : P = E*I where E is the DC voltage. I is the
DC current and there isn't a phase angle or Theta is Zero and COS(0) = 1.
A Watt is the unit of power. Not the plural form.
When V is used it is AC. When V is used I is AC.
They are in R.M.S. scaling. Root of the Mean Square.
(A.C. volt meters and current transforms 'translate to these'.)
Some times special voltages are used as design needs.
Harmonics from inductive and capacitive circuits are very small
compared to the main current / voltage waveform. They are ignored
if anything normal.
One should always use the phase angle in the AC model. Meters do.
So the task for the technician is just measure it using a quality meter.
Even a reasonable multi-meter from Radio-Shack can measure Correctly
(enough). I like three or four major makers and for the lab I use two.
V means AC voltage. E means DC voltage. I is the current that
matches. Cosine(phase-angle) is Always used in AC.
One should design for several times that of V*A*Cos(0).
Martin - Senior Scientist and former Technologist serving between and
working for both Intel and the Schlumberger.
I'm working on my computer I built in the late 50's and early 60's. It
has just under a thousand gates. All hand wired.
On 4/14/2014 7:19 PM, [email protected] wrote:
> On Mon, 14 Apr 2014 17:43:21 -0500, Martin Eastburn
> <[email protected]> wrote:
>
>> Sorta...
>
> Sorta (as long as we're being pedantic ;-)
>
>> I have a degree in Physics and retired as an EE after 20+ years.
>
>> Watts is the value in power if it were a resistive load.
>
> Sorta, kinda, perhaps poorly worded. Power is measured in watts. W=VA
> if the load is resistive.
>
>> VA is the voltage times the current (and ignoring the phase angle
>> between them) Which gives a completely different wattage for a reactive
>> load like a motor.
>
> Assuming there are no harmonics, which is a good approximation for an
> induction motor but may not be a good assumption for other situations.
> Electronic loads are often particularly bad. Fluorescent lighting is
> another example where the power factor (W/VA) is often particularly
> bad.
>
>> ELI the ICE man.
>> Voltage leads current (in time) in inductive (coil) circuits.
>> Current (I) leads Voltage in a capacitive circuit -
>> starting coil with cap. Cap larger than coil
>> in reactive values. XL == ac resistance XC == ac resistance.
>
> The important thing is that wiring and circuit elements (switches,
> breakers, connections, generation) must be sized for volt-amperes,
> where the power consumed (heat load, electric bill, etc.) is
> quantified by watts. VA is always equal (only for purely resistive
> loads) to or greater (all other cases) than watts. Reactive (either
> inductive or capacitive) loads cause additional problems not
> quantified by either.
>
I have to confess that I never understood what the square root of -1
was. The product of what times itself will equal -1? I guess I have a brain
molded around neutonian physics, now a little too old to understand....
Dave
"Duane Bozarth" <[email protected]> wrote in message
news:[email protected]...
> Bruce wrote:
> ...
>> Hey, I have that book!
>> -Bruce (EE control systems engineer)
>
> It's one of many I've picked up over the years -- not too bad although
> I've not used it too much...I was NE at the time I was doing most
> control stuff so most of my early exposure was to reactor controls...I
> picked up the EE controls stuff much, much later... :)
In article <[email protected]>, "Chuck Hoffman" <[email protected]> wrote:
>This has become an obvious standoff and it will serve no purpose to continue
>it.
ROTFLMAO!! It's a "standoff" only because you won't [cant'?] answer the
question.
>
>"LRod" <[email protected]> wrote in message
>news:[email protected]...
>> On Fri, 24 Dec 2004 17:14:26 GMT, "Chuck Hoffman"
>> <[email protected]> wrote:
>>
>> >For the critics, I've been in electronics for 40-some years and have been
>a
>> >technical school instructor. And I worked for an electric utility. I
>do,
>> >in fact, know what I'm talking about.
>>
>> I, also have been in electronics for more than 40 years. I have a
>> pretty good idea of what I'm talking about, too. I've known all sorts
>> of people over those years; some with the golden finger who didn't
>> even need schematics to fix complex equipment but who couldn't pour
>> piss out of a boot with the instructions on the heel.
>>
>> I've known people that couldn't pass a Morse code exam if it was sent
>> one character every two minutes but who could teach brilliantly.
>>
>> And now I know someone with more background and experience perhaps
>> than I have who can't explain a simple concept involving a single
>> phase, two pole, center-tapped electrical circuit without complicating
>> it beyond measure, and then when trying the simple answer gets it
>> completely WRONG.
>>
>> >Now let's talk about your comments. First you say:
>> >
>> >"Phase angle, as a concept, is perfectly suited for all sorts of
>> >theoretical discussions...."
>> >
>> >It is far more than theory, I'm afraid. It's an important consideration
>> >when working with multi-phase circuits. Then you say:
>>
>> Excuse me, but when you're discussing phase angles, AC circuits,
>> impedance, etc., THEORY is EXACTLY what you're talking about. Or, to
>> be even more precise, anything involving the movement of electrons is
>> electrical theory. Want me to prove my point? Let's discuss current
>> flow; electron or conventional current?
>>
>> >"Opposite legs have opposite values (because they are 180° out of
>phase)"
>> >
>> >That seems diametrically opposed to your first disdainful comment. It
>is,
>> >however, precisely the point I was making.
>>
>> But the issue at hadn is a special circumstance; it is the set of
>> properties that becomes simple, additive arithmetic when the phase
>> angle is 180°. It uniquely occurs in the center tapped, two pole
>> circuit that is residential house wiring. Discussion of other phase
>> angles overly complicates the simple additive (albeit with negative
>> numbers) process required to understand and calculate resultant
>> current in a two pole, shared neutral circuit.
>>
>> >You also said:
>> >
>> >"I don't recall J-factor in the NEC.
>> >
>> >I've known people who could recite the NEC chapter and verse but had no
>clue
>> >about the physical properties of electricity or AC circuit analysis. Do
>you
>> >really understand alternating current and its physical properties ?
>>
>> Yes, I'm afraid I do. But with all your experience and expertise,
>> explain this:
>>
>> >> >That WOULD double the current on the neutral and result in a potential
>> >> >overload.
>>
>> That was your response to a question about running a 120V load on one
>> half of a 240V circuit. I said then:
>>
>> >> This is the part that Doug describes as utter nonsense. And he's
>> >> right. The ONLY current on the neutral would result from the
>> >> connection across one LEG of the 230V circuit (to get 115V). There is
>> >> NO current in the "neutral" of a 230V circuit because there is no
>> >> "neutral" in a 230V circuit.
>>
>> And I stand by that question; how do you explain this?
>>
>> You should have left well enough alone.
>>
>> - -
>> LRod
>>
>> Master Woodbutcher and seasoned termite
>>
>> Shamelessly whoring my website since 1999
>>
>> http://www.woodbutcher.net
>
>
--
Regards,
Doug Miller (alphageek-at-milmac-dot-com)
Get a copy of my NEW AND IMPROVED TrollFilter for NewsProxy/Nfilter
by sending email to autoresponder at filterinfo-at-milmac-dot-com
You must use your REAL email address to get a response.
In article <[email protected]>, "Chuck Hoffman" <[email protected]> wrote:
>Sorry...neglected to answer your original question. I believe the NEC
>frowns on connecting across one phase of a 230V circuit to get 115V. That
>WOULD double the current on the neutral and result in a potential overload.
Utter nonsense. It would do nothing of the sort.
In a circuit wired as he described, with (for example) a 10A load at 240V and
a 15A load at 120V, the current in the neutral conductor is 15A. (The 240V
load places *no* current on the neutral.)
Now add a 17A load at 120V on the opposite leg.
One hot leg is drawing 10 + 15 = 25A. The other is drawing 10 + 17 = 27A. And
the current in the neutral is 17 *minus* 15 = 2A.
--
Regards,
Doug Miller (alphageek-at-milmac-dot-com)
Get a copy of my NEW AND IMPROVED TrollFilter for NewsProxy/Nfilter
by sending email to autoresponder at filterinfo-at-milmac-dot-com
You must use your REAL email address to get a response.
The breakers you have may have a **very** short time current curve (you can
always get different breakers with longer curves) or the motor may pull
excessive startup currrent (tho this isn't my area of expertise). Once the
motor is up to speed, the current will stablize -- so you can judge by ear
how long the surge will last.
Matthew
>> The general idea is that larger overcurrents trip quickly, but that 2x or
>> 3x currents can run for a long time. This protects the wiring, which is
>> one of the reasons for circuit breakers; a "shorted curcuit" level of
>> overcurrent would damage wires quickly, but lower overcurrents would take
>> a long time to overheat the wiring.
>>
> Hmm. I do have trouble tripping the breaker on the current (present) 15A
> circuit. Could be that the breaker is old and trips easier? From what
> you're saying, starting up a TS or planer shouldn't draw a high current
> long enough to trip the breaker.
>
In article <[email protected]>, "Chuck Hoffman" <[email protected]> wrote:
>For the critics, I've been in electronics for 40-some years and have been a
>technical school instructor. And I worked for an electric utility. I do,
>in fact, know what I'm talking about.
Actually, you haven't the first clue what you're talking about. I hope that
your time in the tech school wasn't spent teaching how residential electrical
service works.
You wrote that adding a 120V load to a 240V three-wire ["Edison"] circuit
doubles the current in the neutral wire, and creates a dangerous overload.
It does nothing of the kind.
And I'd love to see your explanation of how it could.
>
>My late father-in-law was a union electrician and he didn't fully understand
>AC. He could follow the code, pull wires, bend conduit, install boxes,
>switches and outlets, etc., but he had no clue about the physical properties
>of electricity.
Apparently, neither do you.
--
Regards,
Doug Miller (alphageek-at-milmac-dot-com)
Get a copy of my NEW AND IMPROVED TrollFilter for NewsProxy/Nfilter
by sending email to autoresponder at filterinfo-at-milmac-dot-com
You must use your REAL email address to get a response.
This has become an obvious standoff and it will serve no purpose to continue
it.
"LRod" <[email protected]> wrote in message
news:[email protected]...
> On Fri, 24 Dec 2004 17:14:26 GMT, "Chuck Hoffman"
> <[email protected]> wrote:
>
> >For the critics, I've been in electronics for 40-some years and have been
a
> >technical school instructor. And I worked for an electric utility. I
do,
> >in fact, know what I'm talking about.
>
> I, also have been in electronics for more than 40 years. I have a
> pretty good idea of what I'm talking about, too. I've known all sorts
> of people over those years; some with the golden finger who didn't
> even need schematics to fix complex equipment but who couldn't pour
> piss out of a boot with the instructions on the heel.
>
> I've known people that couldn't pass a Morse code exam if it was sent
> one character every two minutes but who could teach brilliantly.
>
> And now I know someone with more background and experience perhaps
> than I have who can't explain a simple concept involving a single
> phase, two pole, center-tapped electrical circuit without complicating
> it beyond measure, and then when trying the simple answer gets it
> completely WRONG.
>
> >Now let's talk about your comments. First you say:
> >
> >"Phase angle, as a concept, is perfectly suited for all sorts of
> >theoretical discussions...."
> >
> >It is far more than theory, I'm afraid. It's an important consideration
> >when working with multi-phase circuits. Then you say:
>
> Excuse me, but when you're discussing phase angles, AC circuits,
> impedance, etc., THEORY is EXACTLY what you're talking about. Or, to
> be even more precise, anything involving the movement of electrons is
> electrical theory. Want me to prove my point? Let's discuss current
> flow; electron or conventional current?
>
> >"Opposite legs have opposite values (because they are 180° out of
phase)"
> >
> >That seems diametrically opposed to your first disdainful comment. It
is,
> >however, precisely the point I was making.
>
> But the issue at hadn is a special circumstance; it is the set of
> properties that becomes simple, additive arithmetic when the phase
> angle is 180°. It uniquely occurs in the center tapped, two pole
> circuit that is residential house wiring. Discussion of other phase
> angles overly complicates the simple additive (albeit with negative
> numbers) process required to understand and calculate resultant
> current in a two pole, shared neutral circuit.
>
> >You also said:
> >
> >"I don't recall J-factor in the NEC.
> >
> >I've known people who could recite the NEC chapter and verse but had no
clue
> >about the physical properties of electricity or AC circuit analysis. Do
you
> >really understand alternating current and its physical properties ?
>
> Yes, I'm afraid I do. But with all your experience and expertise,
> explain this:
>
> >> >That WOULD double the current on the neutral and result in a potential
> >> >overload.
>
> That was your response to a question about running a 120V load on one
> half of a 240V circuit. I said then:
>
> >> This is the part that Doug describes as utter nonsense. And he's
> >> right. The ONLY current on the neutral would result from the
> >> connection across one LEG of the 230V circuit (to get 115V). There is
> >> NO current in the "neutral" of a 230V circuit because there is no
> >> "neutral" in a 230V circuit.
>
> And I stand by that question; how do you explain this?
>
> You should have left well enough alone.
>
> - -
> LRod
>
> Master Woodbutcher and seasoned termite
>
> Shamelessly whoring my website since 1999
>
> http://www.woodbutcher.net
"David G. Sizemore" <[email protected]> wrote in message
news:[email protected]...
> Roy Smith wrote:
> > I don't know much about the NEC, but I do understand polyphase
> > circuits (4 years of EE in college). I don't think I've ever heard
> > the term J-factor. What is it?
>
> The "J" factor is the square root of -1. No, really.
> it is mainly used for plotting how voltage/current leads/lags
> current/voltage in inductive or capacitive circuits. I am no
> electrical/electronic engineer, just a simple tech with enough knowledge
> to know that everyone's argument is "a little" right.
Well, I'm not an EE, but where I went to engineering school, sqrt(-1) = i.
I also can't find a reference for it via Google. Do you have a reference
for it? I'm not saying you're wrong, just that I've never heard of it, and
I've been exposed to enough EE back in my school daze to know what reactance
is and power factor and some of that cool polyphase stuff.
todd
For the critics, I've been in electronics for 40-some years and have been a
technical school instructor. And I worked for an electric utility. I do,
in fact, know what I'm talking about.
My late father-in-law was a union electrician and he didn't fully understand
AC. He could follow the code, pull wires, bend conduit, install boxes,
switches and outlets, etc., but he had no clue about the physical properties
of electricity.
Now let's talk about your comments. First you say:
"Phase angle, as a concept, is perfectly suited for all sorts of
theoretical discussions...."
It is far more than theory, I'm afraid. It's an important consideration
when working with multi-phase circuits. Then you say:
"Opposite legs have opposite values (because they are 180° out of phase)"
That seems diametrically opposed to your first disdainful comment. It is,
however, precisely the point I was making.
You also said:
"I don't recall J-factor in the NEC.
I've known people who could recite the NEC chapter and verse but had no clue
about the physical properties of electricity or AC circuit analysis. Do you
really understand alternating current and its physical properties ? Or are
you like my father-in-law?
"LRod" <[email protected]> wrote in message
news:[email protected]...
> On Thu, 23 Dec 2004 23:18:38 GMT, "Chuck Hoffman"
> <[email protected]> wrote:
>
> >"Doug Miller" <[email protected]> wrote in message
> >news:[email protected]....
> >>
> >> Utter nonsense.
> >>
> >No, it isn't. Look at my simplified description of the current in a
> >two-phase circuit for a clue that I know what I'm talking about.
>
> Right church, wrong pew.
>
> All the stuff you wrote about phase angle and AC circuits, etc. seems
> to be okay, however, you liberally sprinkled in terms that in the real
> world of electrical wiring just aren't true. Let's take a look.
>
> >There is no argument at all. In a two-wire 115V circuit, the current
> >carried by the neutral is exactly the same as that carried by the hot
wire.
>
> True. You should have stopped there.
>
> >In a three-wire 230V circuit, there is a property called phase angle
> >or J-factor. This results in current flowing in both directions at the
same time
>
> I don't recall J-factor in the NEC. That could be me, though.
>
> >(this is not exactly a true statement but a convenient way to consider
> >current flow in a three-wire circuit).
>
> And since it's not, you should have left it alone.
>
> >As the current on one phase increases from zero to some positive
> >value, the current in the other phase is decreasing from its positive
> >value to zero.
>
> Here's the crux of the problem. In electrical systems (the stuff the
> power company provides) current is delivered in three phases. In the
> average house, however (and that is what the discussion is about),
> power is delivered from only one phase of the three phase system.
>
> It is run through a center tap transformer which yields two "hot" legs
> that are 180° out of phase and a common return leg. All three of these
> wires, however, are delivered from a single phase.
>
> There is no two phase power. It's either three phase or single phase.
> No electrician calls either hot leg a "phase."
>
> >The vector sum of the currents on the neutral is exactly the same as
> >the total of both phases.
>
> Yeah, you could say that...if you wanted to answer the question of
> "what time is it?" by telling us how to build a clock.
>
> >Because of the phase angle, however, that does not mean twice
> >the current.
>
> Phase angle, as a concept, is perfectly suited for all sorts of
> theoretical discussions but is unnecessarily complex in single phase
> wiring. The only "angle" to consider is the 180° that each leg of the
> single phase power feed to house is out of to each other.
>
> >It never exceeds the total current of each phase individually.
>
> Correct (except for that "phase" thing), but you sure took the long
> way around to get to it, and lost half the pack doing it.
>
> >Confusing? Yes. One has to study alternating current and understand
> >plane geometry and simple trigonometry to comprehend it.
>
> Please. Opposite legs have opposite values (because they are 180° out
> of phase) and the current is additive. It's simple arithmetic (albeit
> incorporating negative numbers).
>
> >Sorry...neglected to answer your original question. I believe the NEC
> >frowns on connecting across one phase of a 230V circuit to get 115V.
>
> Given that stoves and dryers sometimes do that very thing, I believe
> you're wrong...unless you could cite the section in which they "frown"
> upon it.
>
> >That WOULD double the current on the neutral and result in a potential
> >overload.
>
> This is the part that Doug describes as utter nonsense. And he's
> right. The ONLY current on the neutral would result from the
> connection across one LEG of the 230V circuit (to get 115V). There is
> NO current in the "neutral" of a 230V circuit because there is no
> "neutral" in a 230V circuit.
>
>
> - -
> LRod
>
> Master Woodbutcher and seasoned termite
>
> Shamelessly whoring my website since 1999
>
> http://www.woodbutcher.net
I think DC = Dust Collector...
Maybe AC = Air Cleaner?
Clint
<[email protected]> wrote in message
news:[email protected]...
> Hello Keith,
> I am just passing by and noticed your post , I am an electrician.
> I do not know what level of experiance you have so let me start with
> some warnings, if you know understand what you are doing ignore the
> next few lines ;)
> > (re-wire DC motor to 220V)
> I am not sure what you mean here D.C. is NOT a.c.! Unless there is
> some transformer-rectifier setup you didn't mention this just wont
> work, AT ALL.You will end up in flames.Realize you are saying rewire a
> ?Voltage Direct Current motor to 220Voltage Alternating
> Current...these are different beast.
>
>
> > With that 30A breaker and 10 AWG
> > wire, should have no problem handling the loads from a DC and air
> cleaner
> > running, and startup surge from another tool.
> O.k. that is pretty reasonable there are many appliances that run on
> 220VAC and use one hot and a neutral to get 120VAC and use that for the
> timer, controls, or whatever. Really there is no reason to have put in
> a neutral wire in if you weren't needing to use it for that very
> purpose, ok you can use it for a 3way or 4way circuit, but that only
> holds for small wire...think about it.
> If you don't already know the transformer outside your house sends 3
> wires.
> Grounding is done near your house.
> This is what you get fromthe transformer: L1-N-L2
> L1 and L2 are the ends of the winding and N is the center tap that they
> ground. It is therefore in the middle between the two legs so between
> L1-N there is 120VAC and between N-L2 there is 120V and between L1-L2
> there is 220VAC DIFFERENCE cause it is really all about potential
> difference between points ;) Also you might be fooled into thinking
> Neutral is ground it is not . DO NOT use it as such it can be a lethal
> mistake.
> The only real problem that I see is this:
> You have 30 amp double pole breaker.
> You want to use 220 for *whatever*
> You want to use 120 for *whatever else*
> what if the 120v appliance or tool messes up and starts pulling a
> higher load until it burns up ...
> The breaker would stop it huh....Nope not always, not if it didn't
> exceeded the 30 amp breakers capacity.
> Which is why you should run a seperate line for your 120v loads and
> your 220v loads that are not related.It is just a lot safer , also
> ground everything especially on a motor load, it will help reduce
> staitc and noise on the line as well. In this case I would run a new
> line, but I am an electrician ;)
> Oh and by the way always check your local electrical codes they are
> always diffent and can sometimes surprise you!
> Hth,
> M.E.Farmer
>
In article <[email protected]>, "Chuck Hoffman" <[email protected]> wrote:
>"Doug Miller" <[email protected]> wrote in message
>news:[email protected]....
>>
>> Utter nonsense.
>>
>No, it isn't. Look at my simplified description of the current in a
>two-phase circuit for a clue that I know what I'm talking about.
>
I read that. And you don't.
--
Regards,
Doug Miller (alphageek-at-milmac-dot-com)
Get a copy of my NEW AND IMPROVED TrollFilter for NewsProxy/Nfilter
by sending email to autoresponder at filterinfo-at-milmac-dot-com
You must use your REAL email address to get a response.
>I think one of the problems in this thread is the confusion of using
> "phase" to refer to both true phases as in 3-phase versus the 180-deg
> phase difference between the two hot legs of a single-phase AC circuit.
>
> I don't know when it became prevelant or popular (if it actually is or
> whether it's still fairly isolated) to refer to the two hots as two
> "phases"
As I understand it, everything is pretty much the same whether you have true
240v (one 240v hot and a 0v neutral) or "2 phase" 240v (two 120v hots 180
degrees out of phase). Everything will work identically. (With the
understanding you would need a 120v "neutral" in the first instance to get
120v to H-N)
However 3 phase electricity is very different. Or so I have heard.
I think that is why 240v is not called "2 phase"; it can be thought of as 1
phase, but is completely different than 3 phase.
"Matthew" <[email protected]> wrote in message
news:[email protected]...
>
> "Keith Carlson" <[email protected]> wrote in message
> news:%zEyd.245829$V41.11293@attbi_s52...
> Ground). The "3-wire" terminology was confusing. Hence 3-wire with
> ground is common, if a bit of a mouthful.
>
Yeah, this is what I was talking about: 2 hot wires, 1 neutral, 1 grounding
wire. In my HP Richter book, they called it a "3-wire" or "split-wire"
circuit. "3-wire" sounded less confusing to me. Don't know how common that
term is in sparky-land.
> Even if the startup surge would cause the current to exceed the breaker
> rating, the breaker probably would not open. Circuit breakers have what
> is called a time-current curve, which tells you how long a circuit breaker
> can carry excess current before it opens. Most breakers will carry 2x or
> 3x their rated current (ex: 30 or 45A on a 15A breaker) for ten seconds or
> so before they open; even short time delay models will do it for a second
> or so, which covers the startup surge. Google on "circuit breaker time
> current curve" to check it out for yourself.
>
> Once you go above this level, the breaker will trip very quickly. For
> example, when a hot wire shorts to the neutral or ground, a current of
> many time the rated current occurs (10x? 20x?), and the breaker trips
> within milliseconds.
>
> The general idea is that larger overcurrents trip quickly, but that 2x or
> 3x currents can run for a long time. This protects the wiring, which is
> one of the reasons for circuit breakers; a "shorted curcuit" level of
> overcurrent would damage wires quickly, but lower overcurrents would take
> a long time to overheat the wiring.
>
Hmm. I do have trouble tripping the breaker on the current (present) 15A
circuit. Could be that the breaker is old and trips easier? From what you're
saying, starting up a TS or planer shouldn't draw a high current long enough
to trip the breaker.
Sorta...
I have a degree in Physics and retired as an EE after 20+ years.
Watts is the value in power if it were a resistive load.
VA is the voltage times the current (and ignoring the phase angle
between them) Which gives a completely different wattage for a reactive
load like a motor.
ELI the ICE man.
Voltage leads current (in time) in inductive (coil) circuits.
Current (I) leads Voltage in a capacitive circuit -
starting coil with cap. Cap larger than coil
in reactive values. XL == ac resistance XC == ac resistance.
Martin
On 4/13/2014 10:53 PM, [email protected] wrote:
> On Thursday, December 23, 2004 10:59:07 AM UTC-8, Keith Carlson wrote:
>> I know I'm going to get the "DAGS" for this question, but I just came from
>> there, and I didn't see this specific information. Lots of debate about how
>> much current the neutral wire carries, though :-)
>>
>> With a 3-wire circuit, is it okay to wire both 120V and 240V outlets on that
>> same circuit? I know it's *possible* by using the two hots for 240 and
>> either hot and neutral for 120, but is it recommended? Maybe this is the
>> main reason for this type of circuit, so I didn't see reference to it on
>> Google. Much of the discussion I read was on balancing the load, which could
>> imply using the 3-wire circuit with all 120V outlets.
>>
>> I've got a dust collector coming soon, and the extra 6-7 continuous amps is
>> going to result in some frequent breaker trips when I start a saw or planer.
>> Looked at my electrical service, and found there's an unused double-pole 30A
>> breaker, feeding an unused dryer outlet (house had a gas dryer when I moved
>> in). That should give me the 2 hots for a 3-wire circuit.
>>
>> My thought on this type of circuit is to wire one outlet at 240V (re-wire DC
>> motor to 220V), and the rest wired at 120V. With that 30A breaker and 10 AWG
>> wire, should have no problem handling the loads from a DC and air cleaner
>> running, and startup surge from another tool.
>>
>> An electrician would be a good idea, too. Hopefully I can find someone
>> willing to consult with me; I can do the wiring myself.
>> But I'm hoping to get some idea if this is the way I want to go so I can
>> cost materials. Won't get an electrician or the inspector on the phone
>> until next week.
>>
>> TIA
>
> There is a common misconception about watts and volt-amperes. People misunderstands both
>
> the same. But there is a whole different way of calculating the both.
> W and VA are both units of measurement for power, but that's where the similarity ends.
>
> Watts do work or generate heat, while volt-amperes simply provide you with information you
>
> need to size wires, fuses, or circuit breakers. Watts add linearly, while volt-amperes doe
>
> not. And to measure W, you need a special wattmeter. You can calculate VA by using a
>
> standard multimeter to measure VRMS and IRMS and finding the product
> The idea for determining the Real power VS apparent power for ac is uncomplicated,
> We care less of apparent power, its the utilitys problem! it is true true,or CONSIDERED
>
> true for all practical purposes for circuits having motors,etc.
> Electronic products list ac line voltage,frequency, and Amp ratings.
>
> 100Watts = 100 VA
>
> 1 watt
> Watts (W) is calculated by multiplying Volts (V) times Amps (A), so 1W = 1VA
> true true,or CONSIDERED true for all practical purposes
> In reality A pf OF .9 WILL MAKE 1 AMP ABOUT .93 AMPS.
>
>
It is not recommended. Anything confusing is dangerous, and this is
confusing.
However, if you lose the 30a breaker, it is possible. You cannot use a 30a
breaker because the 120v circuit will not be rated for 30a. You must get a
20a breaker and use #12 for all of it. (I am assuming #12 is adequate,
which might not be true if your run is too long and the current is too high;
you have to check that first)
If 20a will cover the DC and whatever you want to also run on it, you can do
it. Otherwise you can't.
Overall it is a better idea to run two circuits. Did anyone mention that
you will need 12/3 wire for the combination circuit but only 12/2 for the
separate circuits? It is probably just as easy to run two 12/2 as one 12/3.
That was funny about not being able to change DC to AC.
On Fri, 24 Dec 2004 13:40:40 -0600, Duane Bozarth
<[email protected]> wrote:
>I think one of the problems in this thread is the confusion of using
>"phase" to refer to both true phases as in 3-phase versus the 180-deg
>phase difference between the two hot legs of a single-phase AC circuit.
>
>I don't know when it became prevelant or popular (if it actually is or
>whether it's still fairly isolated) to refer to the two hots as two
>"phases" but I spent a significant amount of time trying to break my
>hired hand of the misconception over the last year. He was trained as
>an aircraft mechanic and was/is pretty darn good w/ hydraulics,
>mechanics, most simple wiring, controls, etc., but apparently was taught
>this as gospel regarding single phase AC power...
Yes. It even confuses tech school teachers with 40+ years in
electronics who work for the power company...if you can believe that.
I think it's isolated. I remember years ago when I was "educated"
about it. All my prior knowledge of AC theory didn't count for squat
while my friend who educated me was pounding it into my head. Oddly,
one of the things he kept saying was, "the power company won't like
hearing you call it 'two phase.'"
- -
LRod
Master Woodbutcher and seasoned termite
Shamelessly whoring my website since 1999
http://www.woodbutcher.net
"Keith Carlson" <[email protected]> wrote in message
news:%zEyd.245829$V41.11293@attbi_s52...
>I know I'm going to get the "DAGS" for this question, but I just came from
>there, and I didn't see this specific information. Lots of debate about how
>much current the neutral wire carries, though :-)
>
Agreed, this is a confusing issue. But there are lot of people with
experience on the rec.
> With a 3-wire circuit, is it okay to wire both 120V and 240V outlets on
> that same circuit? I know it's *possible* by using the two hots for 240
> and either hot and neutral for 120, but is it recommended? Maybe this is
> the main reason for this type of circuit, so I didn't see reference to it
> on Google. Much of the discussion I read was on balancing the load, which
> could imply using the 3-wire circuit with all 120V outlets.
Yes, mixing 120V and 240V is possible, and many circuits are designed this
way. That is why (almost) all 240V installations have a neutral wire. If
you used only 240V loads, there would be no need for that neutral wire.
If you want to mix 240V and 120V on the same circuit, at least 4 wires will
be needed. Call them L1, L2, N, and G (for Line1, Line2, Neutral, and
Ground). The "3-wire" terminology was confusing. Hence 3-wire with ground
is common, if a bit of a mouthful.
My tablesaw and jointer have 3 prongs on their plugs (L1, L2, and G) -- no
neutral is needed, since only the 240V motor is used. My bandsaw has 3
prongs (L1, N, and G) If, however, I wanted to add a 120V light bulb at a
240V tool, 4 prongs would be needed (L1 L2 N & G). I would need to add the
neutral wire to carry the 120V current. That's a hassle, which is why most
people would just run a separate plug. :)
> I've got a dust collector coming soon, and the extra 6-7 continuous amps
> is going to result in some frequent breaker trips when I start a saw or
> planer. Looked at my electrical service, and found there's an unused
> double-pole 30A breaker, feeding an unused dryer outlet (house had a gas
> dryer when I moved in). That should give me the 2 hots for a 3-wire
> circuit.
> My thought on this type of circuit is to wire one outlet at 240V (re-wire
> DC motor to 220V), and the rest wired at 120V. With that 30A breaker and
> 10 AWG wire, should have no problem handling the loads from a DC and air
> cleaner running, and startup surge from another tool.
Even if the startup surge would cause the current to exceed the breaker
rating, the breaker probably would not open. Circuit breakers have what is
called a time-current curve, which tells you how long a circuit breaker can
carry excess current before it opens. Most breakers will carry 2x or 3x
their rated current (ex: 30 or 45A on a 15A breaker) for ten seconds or so
before they open; even short time delay models will do it for a second or
so, which covers the startup surge. Google on "circuit breaker time current
curve" to check it out for yourself.
Once you go above this level, the breaker will trip very quickly. For
example, when a hot wire shorts to the neutral or ground, a current of many
time the rated current occurs (10x? 20x?), and the breaker trips within
milliseconds.
The general idea is that larger overcurrents trip quickly, but that 2x or 3x
currents can run for a long time. This protects the wiring, which is one of
the reasons for circuit breakers; a "shorted curcuit" level of overcurrent
would damage wires quickly, but lower overcurrents would take a long time to
overheat the wiring.
> An electrician would be a good idea, too. Hopefully I can find someone
> willing to consult with me; I can do the wiring myself.
> But I'm hoping to get some idea if this is the way I want to go so I can
> cost materials. Won't get an electrician or the inspector on the phone
> until next week.
Calling qualified help is never a bad idea, but this sounds like a simple
project. And this group will be helpful.
Matthew
> TIA
>
Chuck Hoffman <[email protected]> wrote:
> "I don't recall J-factor in the NEC.
I don't know much about the NEC, but I do understand polyphase
circuits (4 years of EE in college). I don't think I've ever heard
the term J-factor. What is it?
remember that watts x volts =amps total your watts x if 240 take it times
240 if 120 take x 120 this will give you a idea if your over loaded your
breaker and yes a neutral dose carry some voltage if your circuit are
unbalanced the amps will go up on the neutral it's also the return of
current. some 240 stuff doesn't take a neutral
"Keith Carlson" <[email protected]> wrote in message
news:%zEyd.245829$V41.11293@attbi_s52...
>I know I'm going to get the "DAGS" for this question, but I just came from
>there, and I didn't see this specific information. Lots of debate about how
>much current the neutral wire carries, though :-)
>
> With a 3-wire circuit, is it okay to wire both 120V and 240V outlets on
> that same circuit? I know it's *possible* by using the two hots for 240
> and either hot and neutral for 120, but is it recommended? Maybe this is
> the main reason for this type of circuit, so I didn't see reference to it
> on Google. Much of the discussion I read was on balancing the load, which
> could imply using the 3-wire circuit with all 120V outlets.
>
> I've got a dust collector coming soon, and the extra 6-7 continuous amps
> is going to result in some frequent breaker trips when I start a saw or
> planer. Looked at my electrical service, and found there's an unused
> double-pole 30A breaker, feeding an unused dryer outlet (house had a gas
> dryer when I moved in). That should give me the 2 hots for a 3-wire
> circuit.
>
> My thought on this type of circuit is to wire one outlet at 240V (re-wire
> DC motor to 220V), and the rest wired at 120V. With that 30A breaker and
> 10 AWG wire, should have no problem handling the loads from a DC and air
> cleaner running, and startup surge from another tool.
>
> An electrician would be a good idea, too. Hopefully I can find someone
> willing to consult with me; I can do the wiring myself.
> But I'm hoping to get some idea if this is the way I want to go so I can
> cost materials. Won't get an electrician or the inspector on the phone
> until next week.
>
> TIA
>
On Thursday, December 23, 2004 10:59:07 AM UTC-8, Keith Carlson wrote:
> I know I'm going to get the "DAGS" for this question, but I just came from
> there, and I didn't see this specific information. Lots of debate about how
> much current the neutral wire carries, though :-)
>
> With a 3-wire circuit, is it okay to wire both 120V and 240V outlets on that
> same circuit? I know it's *possible* by using the two hots for 240 and
> either hot and neutral for 120, but is it recommended? Maybe this is the
> main reason for this type of circuit, so I didn't see reference to it on
> Google. Much of the discussion I read was on balancing the load, which could
> imply using the 3-wire circuit with all 120V outlets.
>
> I've got a dust collector coming soon, and the extra 6-7 continuous amps is
> going to result in some frequent breaker trips when I start a saw or planer.
> Looked at my electrical service, and found there's an unused double-pole 30A
> breaker, feeding an unused dryer outlet (house had a gas dryer when I moved
> in). That should give me the 2 hots for a 3-wire circuit.
>
> My thought on this type of circuit is to wire one outlet at 240V (re-wire DC
> motor to 220V), and the rest wired at 120V. With that 30A breaker and 10 AWG
> wire, should have no problem handling the loads from a DC and air cleaner
> running, and startup surge from another tool.
>
> An electrician would be a good idea, too. Hopefully I can find someone
> willing to consult with me; I can do the wiring myself.
> But I'm hoping to get some idea if this is the way I want to go so I can
> cost materials. Won't get an electrician or the inspector on the phone
> until next week.
>
> TIA
There is a common misconception about watts and volt-amperes. People misunderstands both
the same. But there is a whole different way of calculating the both.
W and VA are both units of measurement for power, but that's where the similarity ends.
Watts do work or generate heat, while volt-amperes simply provide you with information you
need to size wires, fuses, or circuit breakers. Watts add linearly, while volt-amperes doe
not. And to measure W, you need a special wattmeter. You can calculate VA by using a
standard multimeter to measure VRMS and IRMS and finding the product
The idea for determining the Real power VS apparent power for ac is uncomplicated,
We care less of apparent power, its the utilitys problem! it is true true,or CONSIDERED
true for all practical purposes for circuits having motors,etc.
Electronic products list ac line voltage,frequency, and Amp ratings.
100Watts = 100 VA
1 watt
Watts (W) is calculated by multiplying Volts (V) times Amps (A), so 1W = 1VA
true true,or CONSIDERED true for all practical purposes
In reality A pf OF .9 WILL MAKE 1 AMP ABOUT .93 AMPS.
In the U.S. I don't believe there is any such thing. Household supply
is obtained from a single phase of a three phase system. For all
intents and purposes, when the power grid appears in your
neighborhood, forget about two of those phases. You will never be
involved with them. Only single phase is getting into your house.
The single phase current is transformed from a fairly high voltage off
the feeders to 240V from the output of a center tapped transformer up
on the pole. With regard to that 240V, there is no neutral. The 240V
comes from the two secondaries of the transformer. And there is no +
or -. This is AC, not DC. It is 240V across the two poles.
Our well known 120V supply comes, as you know, from one hot leg and
the center tap of the transformer. Either hot leg will work.
Here is the most important thing: ALL of this; the 240V, and each 120V
is developed from the same single phase of the three phase system. It
is single phase power. There is no "two phase" power.
>...or "2 phase" 240v (two 120v hots 180 degrees out of phase). =20
There is no "two phase" power. The two legs or poles are 180=B0 out of
phase, as you say, because they come off the opposite legs of the
secondary of the transformer. They are NOT two phases of the three
phase system. It is single phase. All of the current in your house
comes from the same, SINGLE phase of the three phase system.
>However 3 phase electricity is very different. Or so I have heard.
Yes and no, but I will leave that discussion to those with experience
with it. I have none.
>I think that is why 240v is not called "2 phase"; it can be thought of as =
1
>phase,
It IS single phase. There's no "thinking" about it.
>but is completely different than 3 phase.
Sigh. Yes, you have stated a tautology.
- -
Sorry...neglected to answer your original question. I believe the NEC
frowns on connecting across one phase of a 230V circuit to get 115V. That
WOULD double the current on the neutral and result in a potential overload.
"Chuck Hoffman" <[email protected]> wrote in message
news:[email protected]...
> There is no argument at all. In a two-wire 115V circuit, the current
> carried by the neutral is exactly the same as that carried by the hot
wire.
> In a three-wire 230V circuit, there is a property called phase angle or
> J-factor. This results in current flowing in both directions at the same
> time (this is not exactly a true statement but a convenient way to
consider
> current flow in a three-wire circuit). As the current on one phase
> increases from zero to some positive value, the current in the other phase
> is decreasing from its positive value to zero. The vector sum of the
> currents on the neutral is exactly the same as the total of both phases.
> Because of the phase angle, however, that does not mean twice the current.
> It never exceeds the total current of each phase individually.
>
> Confusing? Yes. One has to study alternating current and understand
plane
> geometry and simple trigonometry to comprehend it.
>
> "Keith Carlson" <[email protected]> wrote in message
> news:%zEyd.245829$V41.11293@attbi_s52...
> > I know I'm going to get the "DAGS" for this question, but I just came
from
> > there, and I didn't see this specific information. Lots of debate about
> how
> > much current the neutral wire carries, though :-)
> >
> > With a 3-wire circuit, is it okay to wire both 120V and 240V outlets on
> that
> > same circuit? I know it's *possible* by using the two hots for 240 and
> > either hot and neutral for 120, but is it recommended? Maybe this is
the
> > main reason for this type of circuit, so I didn't see reference to it on
> > Google. Much of the discussion I read was on balancing the load, which
> could
> > imply using the 3-wire circuit with all 120V outlets.
> >
> > I've got a dust collector coming soon, and the extra 6-7 continuous amps
> is
> > going to result in some frequent breaker trips when I start a saw or
> planer.
> > Looked at my electrical service, and found there's an unused double-pole
> 30A
> > breaker, feeding an unused dryer outlet (house had a gas dryer when I
> moved
> > in). That should give me the 2 hots for a 3-wire circuit.
> >
> > My thought on this type of circuit is to wire one outlet at 240V
(re-wire
> DC
> > motor to 220V), and the rest wired at 120V. With that 30A breaker and 10
> AWG
> > wire, should have no problem handling the loads from a DC and air
cleaner
> > running, and startup surge from another tool.
> >
> > An electrician would be a good idea, too. Hopefully I can find someone
> > willing to consult with me; I can do the wiring myself.
> > But I'm hoping to get some idea if this is the way I want to go so I can
> > cost materials. Won't get an electrician or the inspector on the phone
> > until next week.
> >
> > TIA
> >
> >
>
>
"Doug Miller" <[email protected]> wrote in message
news:[email protected]....
>
> Utter nonsense.
>
No, it isn't. Look at my simplified description of the current in a
two-phase circuit for a clue that I know what I'm talking about.
In article <nDKyd.6899$k25.6498@attbi_s53>, "Keith Carlson" <[email protected]> wrote:
>I was just thinking about this on the way to pick up pizza. With 10AWG wire,
>I'd have a circuit capable of 30A, but the cords from all the tools are
>110V/15A. (leaving out the Dust Collector for a moment). Those will plug
>into 20A receptacles, so say I wire 20A receptacles on the 120V outlets. Now
>suppose the planer or whatever manages to load down and wants to pull
>something like 28 amps. The circuit breaker says "no problem". Could run
>that way all day and it wouldn't trip. But what about that receptacle that's
>rated for 20A??
Yep, that's a problem. Hence toller's statement that your 120V circuit isn't
rated for 30A. Technically, that's not exactly correct: there's no reason that
you can't have a 120V 30A circuit, as long as the wire is 10ga copper or
larger. But you're probably not going to find any receptacles that you can
plug a 15A or 20A tool into, that are rated for 30A.
>Are the connections or conductors inside it going to
>overheat?
Not if you don't feed current through it to some downstream load, *and* the
load you have plugged into that outlet never overloads. But if either of those
conditions occurs, yes, there is indeed a risk of overheating and fire.
>Might be some risk there, not to mention the tool itself like you
>say. I should go look at my reference book; NEC probably doesn't allow a 20A
>rated receptacle on a circuit protected to 30A.
Right, it doesn't.
>
>Then there's 120V/30A receptacles. Haven't looked, but probably cost more
>than the 20's. The 110V/15A plugs won't fit in them, so I'd have to change
>plugs on the tools.
Right on both counts.
>Even then I have to consider how likely it is that I'll
>have situations where the tool wants to pull more than its rated current.
Not relevant -- you have the same issue with a 20A rated receptacle on a 20A
circuit.
>
>The 3-wire circuit starts to look like more trouble than it's worth. It
>sounded like a slick idea at first, because I have the breaker, and I'd be
>able to run 3 wires + ground in my conduit. (Finished walls, and I'm not
>going to tear them up, so I'll be running EMT and individual wires inside).
Have you considered that when you rewire the dust collector for 240V, it will
pull only half as many amps? This may enable you to run the DC on a 20A
circuit, which you could wire with 12/3 and then add standard 15A or 20A 120V
receptacles. (Code *does* permit 15A-rated receptacles on 20A circuits.)
--
Regards,
Doug Miller (alphageek-at-milmac-dot-com)
Get a copy of my NEW AND IMPROVED TrollFilter for NewsProxy/Nfilter
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On 4/13/14, 11:00 PM, Leon wrote:
> YOU RESPONDED TO A 10 YEAR OLD POST.
He wanted to reply then, but it took him this long to get his PhD in
electrical engineering. :-)
--
-MIKE-
"Playing is not something I do at night, it's my function in life"
--Elvin Jones (1927-2004)
--
http://mikedrums.com
[email protected]
---remove "DOT" ^^^^ to reply
On 4/13/14 9:53 PM, [email protected] wrote:
> On Thursday, December 23, 2004 10:59:07 AM UTC-8, Keith Carlson wrote:
>> I know I'm going to get the "DAGS" for this question, but I just came from
>> there, and I didn't see this specific information. Lots of debate about how
>> much current the neutral wire carries, though :-)
>>
>> With a 3-wire circuit, is it okay to wire both 120V and 240V outlets on that
>> same circuit? I know it's *possible* by using the two hots for 240 and
>> either hot and neutral for 120, but is it recommended? Maybe this is the
>> main reason for this type of circuit, so I didn't see reference to it on
>> Google. Much of the discussion I read was on balancing the load, which could
>> imply using the 3-wire circuit with all 120V outlets.
>>
>> I've got a dust collector coming soon, and the extra 6-7 continuous amps is
>> going to result in some frequent breaker trips when I start a saw or planer.
>> Looked at my electrical service, and found there's an unused double-pole 30A
>> breaker, feeding an unused dryer outlet (house had a gas dryer when I moved
>> in). That should give me the 2 hots for a 3-wire circuit.
>>
>> My thought on this type of circuit is to wire one outlet at 240V (re-wire DC
>> motor to 220V), and the rest wired at 120V. With that 30A breaker and 10 AWG
>> wire, should have no problem handling the loads from a DC and air cleaner
>> running, and startup surge from another tool.
One problem I see is you are wiring a 110V outlet on a 30A circuit. That
is fine, but you need to get an outlet rated for 30A. The typical 110V
duplex is 20A max (NEMA 5-20), Your outlets will need to be NEMA 5-30
(which may have issues with your 110V plugs on your tools).
-Bruce
>>
>> An electrician would be a good idea, too. Hopefully I can find someone
>> willing to consult with me; I can do the wiring myself.
>> But I'm hoping to get some idea if this is the way I want to go so I can
>> cost materials. Won't get an electrician or the inspector on the phone
>> until next week.
>>
>> TIA
>
> There is a common misconception about watts and volt-amperes. People misunderstands both
>
> the same. But there is a whole different way of calculating the both.
> W and VA are both units of measurement for power, but that's where the similarity ends.
>
> Watts do work or generate heat, while volt-amperes simply provide you with information you
>
> need to size wires, fuses, or circuit breakers. Watts add linearly, while volt-amperes doe
>
> not. And to measure W, you need a special wattmeter. You can calculate VA by using a
>
> standard multimeter to measure VRMS and IRMS and finding the product
> The idea for determining the Real power VS apparent power for ac is uncomplicated,
> We care less of apparent power, its the utilitys problem! it is true true,or CONSIDERED
>
> true for all practical purposes for circuits having motors,etc.
> Electronic products list ac line voltage,frequency, and Amp ratings.
>
> 100Watts = 100 VA
>
> 1 watt
> Watts (W) is calculated by multiplying Volts (V) times Amps (A), so 1W = 1VA
> true true,or CONSIDERED true for all practical purposes
> In reality A pf OF .9 WILL MAKE 1 AMP ABOUT .93 AMPS.
>
>
--- news://freenews.netfront.net/ - complaints: [email protected] ---
In article <[email protected]>, [email protected] wrote:
>Hello Keith,
>I am just passing by and noticed your post , I am an electrician.
>I do not know what level of experiance you have so let me start with
>some warnings, if you know understand what you are doing ignore the
>next few lines ;)
>> (re-wire DC motor to 220V)
>I am not sure what you mean here D.C. is NOT a.c.!
In a woodworking context, "DC" means "dust collector", not "direct current".
He's talking about changing the jumpers on a dual-voltage 120/240 VAC motor on
his dust collector from the current setting of 120VAC operation to 240VAC.
[snip]
>The only real problem that I see is this:
>You have 30 amp double pole breaker.
>You want to use 220 for *whatever*
>You want to use 120 for *whatever else*
>what if the 120v appliance or tool messes up and starts pulling a
>higher load until it burns up ...
>The breaker would stop it huh....Nope not always, not if it didn't
>exceeded the 30 amp breakers capacity.
So what? The breaker is there to protect the circuit wiring, not the
cord-and-plug connected device. Exactly the same risk exists with a 20A
breaker.
--
Regards,
Doug Miller (alphageek-at-milmac-dot-com)
Get a copy of my NEW AND IMPROVED TrollFilter for NewsProxy/Nfilter
by sending email to autoresponder at filterinfo-at-milmac-dot-com
You must use your REAL email address to get a response.
<[email protected]> wrote in message
news:[email protected]...
> Hello Keith,
> I am just passing by and noticed your post , I am an electrician.
> I do not know what level of experiance you have so let me start with
> some warnings, if you know understand what you are doing ignore the
> next few lines ;)
>> (re-wire DC motor to 220V)
> I am not sure what you mean here D.C. is NOT a.c.! Unless there is
Thanks, M.E. Sorry for the confusion. As someone else noted, I meant Dust
Collector, not direct current. Made an assumption about the audience of that
post. The dust collector has a 110/220V motor, pre-wired for 110. I believe
it's a straightforward task to re-wire for 220. I don't believe it comes
with a 220V plug, though; I'd need to add that.
> The only real problem that I see is this:
> You have 30 amp double pole breaker.
> You want to use 220 for *whatever*
> You want to use 120 for *whatever else*
> what if the 120v appliance or tool messes up and starts pulling a
> higher load until it burns up ...
I was just thinking about this on the way to pick up pizza. With 10AWG wire,
I'd have a circuit capable of 30A, but the cords from all the tools are
110V/15A. (leaving out the Dust Collector for a moment). Those will plug
into 20A receptacles, so say I wire 20A receptacles on the 120V outlets. Now
suppose the planer or whatever manages to load down and wants to pull
something like 28 amps. The circuit breaker says "no problem". Could run
that way all day and it wouldn't trip. But what about that receptacle that's
rated for 20A?? Are the connections or conductors inside it going to
overheat? Might be some risk there, not to mention the tool itself like you
say. I should go look at my reference book; NEC probably doesn't allow a 20A
rated receptacle on a circuit protected to 30A.
Then there's 120V/30A receptacles. Haven't looked, but probably cost more
than the 20's. The 110V/15A plugs won't fit in them, so I'd have to change
plugs on the tools. Even then I have to consider how likely it is that I'll
have situations where the tool wants to pull more than its rated current.
The 3-wire circuit starts to look like more trouble than it's worth. It
sounded like a slick idea at first, because I have the breaker, and I'd be
able to run 3 wires + ground in my conduit. (Finished walls, and I'm not
going to tear them up, so I'll be running EMT and individual wires inside).
I am going to ask a local electrician, but starting to think about the
original plan of a simple 2-wire 20A circuit. Then go with 220V, on a
separate circuit, on the dust collector if it's needed.
On Sat, 25 Dec 2004 01:33:37 +0000, LRod wrote:
> The single phase current is transformed from a fairly high voltage off the
> feeders to 240V from the output of a center tapped transformer up on the
> pole. With regard to that 240V, there is no neutral. The 240V comes from
> the two secondaries of the transformer. And there is no + or -. This is
> AC, not DC. It is 240V across the two poles.
It is 240VAC, but it is similar to differential signaling (each wire wioth
equal but opposite instaneous voltage & current) as in twisted pair
ethernet vs. AC with a ground reference as in coax TV cable (the ground
stays at a zero volt reference and the voltage on the center conductor
varies symetrically positive and negative in relation to the ground).
- Doug
--
To escape criticism--do nothing, say nothing, be nothing." (Elbert Hubbard)
On Sat, 25 Dec 2004 09:52:23 -0500, Roy Smith wrote:
> "Todd Fatheree" <[email protected]> wrote:
>> Well, I'm not an EE, but where I went to engineering school, sqrt(-1) =
>> i.
>
> If you had been an EE, you would have learned that sqrt(-1) = j. In
> electrical engineering, the symbol i was already taken (it means current).
> So, electrical engineers just break with tradition and use j for sqrt(-1)
> instead of i. It looks a little weird at first, but you get used to it.
>
> When I was in school, the EE courses used j and the math and physics
> courses used i. You just learn to shift mental gears depending on which
> class you're in.
...and the reason it's "i" in mathematics is that it stands for the
"imaginary" number = sqrt(-1).
- Doug
--
To escape criticism--do nothing, say nothing, be nothing." (Elbert Hubbard)
There is no argument at all. In a two-wire 115V circuit, the current
carried by the neutral is exactly the same as that carried by the hot wire.
In a three-wire 230V circuit, there is a property called phase angle or
J-factor. This results in current flowing in both directions at the same
time (this is not exactly a true statement but a convenient way to consider
current flow in a three-wire circuit). As the current on one phase
increases from zero to some positive value, the current in the other phase
is decreasing from its positive value to zero. The vector sum of the
currents on the neutral is exactly the same as the total of both phases.
Because of the phase angle, however, that does not mean twice the current.
It never exceeds the total current of each phase individually.
Confusing? Yes. One has to study alternating current and understand plane
geometry and simple trigonometry to comprehend it.
"Keith Carlson" <[email protected]> wrote in message
news:%zEyd.245829$V41.11293@attbi_s52...
> I know I'm going to get the "DAGS" for this question, but I just came from
> there, and I didn't see this specific information. Lots of debate about
how
> much current the neutral wire carries, though :-)
>
> With a 3-wire circuit, is it okay to wire both 120V and 240V outlets on
that
> same circuit? I know it's *possible* by using the two hots for 240 and
> either hot and neutral for 120, but is it recommended? Maybe this is the
> main reason for this type of circuit, so I didn't see reference to it on
> Google. Much of the discussion I read was on balancing the load, which
could
> imply using the 3-wire circuit with all 120V outlets.
>
> I've got a dust collector coming soon, and the extra 6-7 continuous amps
is
> going to result in some frequent breaker trips when I start a saw or
planer.
> Looked at my electrical service, and found there's an unused double-pole
30A
> breaker, feeding an unused dryer outlet (house had a gas dryer when I
moved
> in). That should give me the 2 hots for a 3-wire circuit.
>
> My thought on this type of circuit is to wire one outlet at 240V (re-wire
DC
> motor to 220V), and the rest wired at 120V. With that 30A breaker and 10
AWG
> wire, should have no problem handling the loads from a DC and air cleaner
> running, and startup surge from another tool.
>
> An electrician would be a good idea, too. Hopefully I can find someone
> willing to consult with me; I can do the wiring myself.
> But I'm hoping to get some idea if this is the way I want to go so I can
> cost materials. Won't get an electrician or the inspector on the phone
> until next week.
>
> TIA
>
>
On Fri, 24 Dec 2004 22:47:19 GMT, "toller" <[email protected]> wrote:
>
>>I think one of the problems in this thread is the confusion of using
>> "phase" to refer to both true phases as in 3-phase versus the 180-deg
>> phase difference between the two hot legs of a single-phase AC circuit.
>>
>> I don't know when it became prevelant or popular (if it actually is or
>> whether it's still fairly isolated) to refer to the two hots as two
>> "phases"
>
>As I understand it, everything is pretty much the same whether you have true
>240v (one 240v hot and a 0v neutral)...
In the U.S. I don't believe there is any such thing. Household supply
is obtained from a single phase of a three phase system. For all
intents and purposes, when the power grid appears in your
neighborhood, forget about two of those phases. You will never be
involved with them. Only single phase is getting into your house.
The single phase current is transformed from a fairly high voltage off
the feeders to 240V from the output of a center tapped transformer up
on the pole. With regard to that 240V, there is no neutral. The 240V
comes from the two secondaries of the transformer. And there is no +
or -. This is AC, not DC. It is 240V across the two poles.
Our well known 120V supply comes, as you know, from one hot leg and
the center tap of the transformer. Either hot leg will work.
Here is the most important thing: ALL of this; the 240V, and each 120V
is developed from the same single phase of the three phase system. It
is single phase power. There is no "two phase" power.
>...or "2 phase" 240v (two 120v hots 180 degrees out of phase).
There is no "two phase" power. The two legs or poles are 180° out of
phase, as you say, because they come off the opposite legs of the
secondary of the transformer. They are NOT two phases of the three
phase system. It is single phase. All of the current in your house
comes from the same, SINGLE phase of the three phase system.
>However 3 phase electricity is very different. Or so I have heard.
Yes and no, but I will leave that discussion to those with experience
with it. I have none.
>I think that is why 240v is not called "2 phase"; it can be thought of as 1
>phase,
It IS single phase. There's no "thinking" about it.
>but is completely different than 3 phase.
Sigh. Yes, you have stated a tautology.
- -
LRod
Master Woodbutcher and seasoned termite
Shamelessly whoring my website since 1999
http://www.woodbutcher.net
"Matthew" <[email protected]> wrote:
> My tablesaw and jointer have 3 prongs on their plugs (L1, L2, and G) -- no
> neutral is needed, since only the 240V motor is used. My bandsaw has 3
> prongs (L1, N, and G) If, however, I wanted to add a 120V light bulb at a
> 240V tool, 4 prongs would be needed (L1 L2 N & G). I would need to add the
> neutral wire to carry the 120V current. That's a hassle, which is why most
> people would just run a separate plug. :)
Or a step-down transformer inside the machine. Not that that's not a
hassle in its own way.
The best suggestion I ever saw was just put two bulbs in series.
Or, I suppose, find a source for 240V bulbs (they must exist).
In article <[email protected]>,
"David G. Sizemore" <[email protected]> wrote:
> Roy Smith wrote:
> > I don't know much about the NEC, but I do understand polyphase
> > circuits (4 years of EE in college). I don't think I've ever heard
> > the term J-factor. What is it?
>
> The "J" factor is the square root of -1. No, really.
We called that "j". Always lower-case, and never with a "-factor" on
the end.
> If you have a generator, and you
> place 3 "brushes" equidistant around the amature, those 3 "phases" will
> be 120deg "out of phase" with each of their neighbors. if you increase
> the brushes to four, and place them equidistant, each will be 90deg out
> of phase to its neighbor, and 180deg out of phase with its diametric
> opposite cousin.
It is interesting that you mention that. It certainly is possible to
build a 4-phase generator. I've never seen or heard of one, but it
would be no big deal to build one. You would really have 4 windings,
not four brushes, but that's a detail.
Now, let's try an experiment. Label the 4 phases A, B, C, and D, in
order. Assume the windings are star-connected, so there's a common
neutral, which we'll label N. Let's further assume that the leg-neutral
voltage of each phase is 120 VAC.
I'm going to give you two panels, each having three terminals on it.
One both panels, the terminals are labeled X, Y, and N. One one panel,
X and Y are connected to phases A and C from our 4-phase generator, and
N is connected to the neutral. On the other, X and Y are connected to
L1 and L2 from a typical center-tapped 240V residential pole drop, and N
is connected to the center tap. On both panels, N is tied to earth at
the panel.
Can you describe a measurement that you can make, which will tell you
which panel is connected to the 4-phase generator and which is connected
to the pole drop? You can use voltmeters, ammeters, power meters, phase
meters, oscilloscopes, or any other tool or instrument you desire.
Assume, however, that both are ideal voltage sources, i.e. you can't
draw enough current from them to significantly load them down.
My claim is that you can't tell the difference.
"Todd Fatheree" <[email protected]> wrote:
> Well, I'm not an EE, but where I went to engineering school, sqrt(-1) = i.
If you had been an EE, you would have learned that sqrt(-1) = j. In
electrical engineering, the symbol i was already taken (it means
current). So, electrical engineers just break with tradition and use j
for sqrt(-1) instead of i. It looks a little weird at first, but you
get used to it.
When I was in school, the EE courses used j and the math and physics
courses used i. You just learn to shift mental gears depending on which
class you're in.
The only other place I've seen j used for sqrt(-1) is in the Python
programming language (http://docs.python.org/lib/typesnumeric.html)
In article <XiLyd.552464$wV.437490@attbi_s54>, "Keith Carlson" <[email protected]> wrote:
>Hmm. I do have trouble tripping the breaker on the current (present) 15A
>circuit. Could be that the breaker is old and trips easier? From what you're
>saying, starting up a TS or planer shouldn't draw a high current long enough
>to trip the breaker.
Yes, that could very easily be the case. Breakers are cheap; replace it and
see what happens.
--
Regards,
Doug Miller (alphageek-at-milmac-dot-com)
Get a copy of my NEW AND IMPROVED TrollFilter for NewsProxy/Nfilter
by sending email to autoresponder at filterinfo-at-milmac-dot-com
You must use your REAL email address to get a response.
This type of setup is common on a stove, right? 240 for the stove heating
elements, and 110 for the lights/clock?
Personally, I'm thinking of this for my tablesaw/router (router built into
tablesaw wing). It would be handy to just have one cordt to trip over,
rather than two. But I don't know if you can get 4 wire extension cables.
Haven't switched my saw over to 240 yet, so that hasn't been a problem. And
since I'm wiring my garage up with 20 amp circuits, I might not bother.
Clint
"Greg" <[email protected]> wrote in message
news:[email protected]...
> If the breaker is double pole and the cable is 4 wire you can do it.
> Don't share the neutral and ground!
> They even make a combo 120/240v duplex receptacle for this.
On Fri, 18 Apr 2014 08:20:12 -0600, Brewster <[email protected]> wrote:
>On 4/13/14 9:53 PM, [email protected] wrote:
>> On Thursday, December 23, 2004 10:59:07 AM UTC-8, Keith Carlson wrote:
>>> I know I'm going to get the "DAGS" for this question, but I just came from
>>> there, and I didn't see this specific information. Lots of debate about how
>>> much current the neutral wire carries, though :-)
>>>
>>> With a 3-wire circuit, is it okay to wire both 120V and 240V outlets on that
>>> same circuit? I know it's *possible* by using the two hots for 240 and
>>> either hot and neutral for 120, but is it recommended? Maybe this is the
>>> main reason for this type of circuit, so I didn't see reference to it on
>>> Google. Much of the discussion I read was on balancing the load, which could
>>> imply using the 3-wire circuit with all 120V outlets.
>>>
>>> I've got a dust collector coming soon, and the extra 6-7 continuous amps is
>>> going to result in some frequent breaker trips when I start a saw or planer.
>>> Looked at my electrical service, and found there's an unused double-pole 30A
>>> breaker, feeding an unused dryer outlet (house had a gas dryer when I moved
>>> in). That should give me the 2 hots for a 3-wire circuit.
>>>
>>> My thought on this type of circuit is to wire one outlet at 240V (re-wire DC
>>> motor to 220V), and the rest wired at 120V. With that 30A breaker and 10 AWG
>>> wire, should have no problem handling the loads from a DC and air cleaner
>>> running, and startup surge from another tool.
>
>One problem I see is you are wiring a 110V outlet on a 30A circuit. That
>is fine, but you need to get an outlet rated for 30A. The typical 110V
>duplex is 20A max (NEMA 5-20), Your outlets will need to be NEMA 5-30
>(which may have issues with your 110V plugs on your tools).
>
>-Bruce
>
>>>
>>> An electrician would be a good idea, too. Hopefully I can find someone
>>> willing to consult with me; I can do the wiring myself.
>>> But I'm hoping to get some idea if this is the way I want to go so I can
>>> cost materials. Won't get an electrician or the inspector on the phone
>>> until next week.
>>>
>>> TIA
>>
>> There is a common misconception about watts and volt-amperes. People misunderstands both
>>
>> the same. But there is a whole different way of calculating the both.
>> W and VA are both units of measurement for power, but that's where the similarity ends.
>>
>> Watts do work or generate heat, while volt-amperes simply provide you with information you
>>
>> need to size wires, fuses, or circuit breakers. Watts add linearly, while volt-amperes doe
>>
>> not. And to measure W, you need a special wattmeter. You can calculate VA by using a
>>
>> standard multimeter to measure VRMS and IRMS and finding the product
>> The idea for determining the Real power VS apparent power for ac is uncomplicated,
>> We care less of apparent power, its the utilitys problem! it is true true,or CONSIDERED
>>
>> true for all practical purposes for circuits having motors,etc.
>> Electronic products list ac line voltage,frequency, and Amp ratings.
>>
>> 100Watts = 100 VA
>>
>> 1 watt
>> Watts (W) is calculated by multiplying Volts (V) times Amps (A), so 1W = 1VA
>> true true,or CONSIDERED true for all practical purposes
>> In reality A pf OF .9 WILL MAKE 1 AMP ABOUT .93 AMPS.
>>
>>
>
>
>--- news://freenews.netfront.net/ - complaints: [email protected] ---
Really simple to get around the 30 amp problem. Install a fused
outlet. In the UK they are common devices, but not here, so you would
install a fused (or breaker protected) disconnect on the 30 amp
circuit, and connect the 115 volt outlets to that "sub panel"
"David G. Sizemore" <[email protected]> wrote in message
news:[email protected]...
>
> If you try to make up a home-brewed solution to
> allow them to co-exist, it would be a good idea to get advice not from a
> newsgroup, or the web itself.
Very sound advice. Newsgroups, while full of very good advice are also full
of wive's tales and anecdotal experiences which get stretched to become
trueisms.
> Consulting with a live electrician, an
> electrical inspector, AND your homeowner's insurance carrier is a must!
> Insurance will not cover incidents caused by wiring not done to code.
> DAMHIKT!
The insurance company part of this statement is one of those truisms.
Insurance companies pay off every single day on house fires that the Cause
and Origin Team has determined started with faulty wiring. Bad wiring, not
simply wiring that mice worked on, etc. In most, if not all states,
insurance companies have to pay against acts of stupidity. Check with an
adjuster.
--
-Mike-
[email protected]