220v conversion question

[email protected] (Doug Miller) wrote in
news:[email protected]:

*snip*
>
> You don't need a neutral for current to flow; you just need the two
> sides of the circuit to have a voltage difference between them.
>
> The utility company brings somewhere around 4KV to your utility pole,
> connected to the primary windings of a step-down transformer. This
> transformer reduces the 4KV from the utility company to 240V. There
> are *three* wires attached to the secondary windings: one at each end,
> and one in the middle. The two at the ends are 240V apart, and the one
> in the middle is 120V from either of them. Let's color the wires
> connected to the ends of the secondary coil black and red, and the one
> connected to the middle, white. There's 120V between the black and
> white wires, 120V between the red and white, and 240V between the
> black and red. Now tie the white one to a copper rod that's driven
> into the ground, to ensure that it's always at true earth potential.

*snip*

So, for truly instantious table saw start up, we should hook the motor up
to the 4KV, bypassing the transformer. We'd only need a few microamps at
most to power it, therefore all the power we'd need go directly to the
saw.

Better add a cast iron body to the cast iron top, though... The slightest
imbalance might flip the saw over!

Jokingly,

Puckdropper
--
"The potential difference between the top and bottom of a tree is the
reason why all trees have to be grounded..." -- Bored Borg on
rec.woodworking

To email me directly, send a message to puckdropper (at) fastmail.fm

On Sep 2, 4:57=A0am, "J. Clarke" <[email protected]> wrote:
> Leon wrote:
> > "Chris Friesen" <[email protected]> wrote in message
> >news:[email protected]...
> >>>> Huh? =A0Voltage is just potential.
>
> >>> Yes, that's right. That's why the motor will start more quickly with
> >>> higher
> >>> voltage.
>
> >> I hope that's supposed to be a joke.
>
> >> Chris
>
> > Ok, again, I am no electrical expert but in my coloring book world of
> > looking at electricity, =A0You have less resistance up to the motor
> > using 240 vs 120. =A0Each of the 2 wires carrying 120 volts is carrying
> > 1/2 the load up to the motor than the single wire in a 120 volt
> > application.
>
> No, each of the wires in a 220v circuit is carrying the same current, one
> carries it in, one carries it out, just like with 110.

That would suggest a direction to the current flow, and with AC we
know that isn't the case.

On Sep 1, 7:05=A0am, "[email protected]" <[email protected]> wrote:
> > .... I had the electrician put in 2 220 circuits and 2 120 circuits for=
my shop ...
>
> > The question: I plan to switch over my bandsaw to 220 as well. =A0What
> > happens to the gooseneck lamp?
>
> I wired the lamp with one hot line (110v) to the center, and connected
> a neutral to the outside. ( Sorry - I don't know the precise
> terminology.)

In most 240 circuits there is no neutral (certainly not those used for
tools). Wiring it to ground isn't a good idea either.

> As an alternative, you can find 220v lamps on line.

A much better idea.

On Sep 2, 5:40=A0pm, Nova <[email protected]> wrote:
> Chris Friesen wrote:
>
> > Consider a motor that draws 15A at 120V. =A0Let's call it a 90A inrush
> > current, with a wiring length of 30 feet (20 feet from the panel,
> > 10-foot cord) and #12 wiring.
>
> > Power loss in the wiring is:
>
> > Pc =3D I^2 * R
>
> > For 30' of #12 copper, R=3D0.048 ohm
>
> I believe the resistance of the motor's windings figures into the
> formula as well as it's part of the circuit.
>
> --
> Jack Novak
> Buffalo, NY - USA
> [email protected]

The line losses of pushing 1000 watts through a given conductor at a
higher voltage creates less resistance than at a lower voltage. Hence
500KV power lines.
Current is your enemy, voltage is your friend.

Speaking of Watts... Charlie did NOT, I repeat, DID NOT quit he
Rolling Stones.

Slightly OT but relevant.

I am a no nothing in terms of electrical. I can properly wire a plug
or wall sockets but don't understand the flow, grounding, etc. Just
never studied it. But on a related topic, I have always wondered why
my planer and my big sander have a 220 line to run the big moter and a
110 line to run the feed table. I asked on of the Mfg's if there was a
way to wire the 110 from the 220 and they clearly ran and hide, saying
don't ask us.

So I ask here. Is there some way to "properly" do this? Can I put an
onboard converter or something. I would really like to eliminate the
two cords scenario because I am constantly juggling machines because
of my space restrictions and it is a big hassle with two plugs.

On Sep 1, 6:56=A0am, Chris Friesen <[email protected]> wrote:
> On 09/01/2009 05:25 AM, Dave - Parkville, MD wrote:
>
> > I just had an upgrade for my electric service to a 200 Amp panel as
> > part of an HVAC upgrade. =A0At the same time, I had the electrician put
> > in 2 220 circuits and 2 120 circuits for my shop (lights were already
> > separate). =A0Last night I switched over my table saw to 220. =A0Wow,
> > start up is almost instant.
>
> If it makes that much difference, there was probably something wrong
> with the 120V circuit or wire size. =A0If everything was sized properly
> there shouldn't really be any difference.
>
> > The question: I plan to switch over my bandsaw to 220 as well. =A0What
> > happens to the gooseneck lamp? =A0The switch over instructions don't
> > mention it. =A0Rewiring for the motor is pretty straightfoward. =A0Am I
> > missing something?
>
> My bandsaw has a separate plug for the lamp. =A0If it's not mentioned
> they're probably using the safety ground as a neutral which you're not
> really supposed to do.
>
> Chris

On Sep 2, 10:29=A0am, Chris Friesen <[email protected]> wrote:
> On 09/02/2009 06:52 AM, DLB wrote:
>
> > On Sep 1, 7:01 pm, Chris Friesen <[email protected]> wrote:
> >> Technically true. =A0But on a properly designed circuit the NEC requir=
es
> >> at most 5% voltage loss. =A0Even assuming that we got perfect efficien=
cy
> >> at 240V I defy you to notice a tablesaw coming up to speed 5% faster.
>
> >> This is not a "wow, start up is almost instant" sort of difference.
> > I (OP) noticed a difference.
>
> As I mentioned in my first email, if it makes that much difference then
> it's likely the motor itself was not operating optimally at 120V.
>
> Aside from supply losses which have been discussed extensively :) in
> this thread, there's no inherent reason why a motor would operate more
> efficiently at higher voltage.
>
> Chris

I understand what your are saying. When on 120v the saw was on a
circuit with 4 outlets. The only other item plugged in was a cordless
phone charger.

There is a clear difference in start up. I am definitely not an
electrical professional, so I can't explain it.

On Sep 2, 11:31=A0am, Chris Friesen <[email protected]> wrote:
> On 09/01/2009 08:28 PM, Lew Hodgett wrote:
>
> > All other things being equal , the higher the voltage, the more
> > =A0efficient the connected motor will be.
>
> Absolutely. =A0And I actually did know this before the whole discussion
> started.
>
> I chose to ignore the line losses because they're supposed to be small
> to start with on a properly designed circuit, so reducing them further
> should make very little difference--certainly not one that is noticeable
> to the user.

That's where you make your mistake. Line losses are *not* small,
particlarly when the machine is starting. The power lost due to the
line resistance is the square of the voltage lost. It is *not*
insignificant.

> > The resistance value used is totally immaterial since mathematically,
> > it cancels out in the calculations.
>
> The resistance is needed if you want to look at absolute values of line
> loss rather than ratios.
>
> > I long ago standardized on #10AWG for motor conductors.

Expensive, it's a good idea if you're going to stick to 120V. Note
that the difference between #10 and #12 is less than the difference
between 120V and 240V. Going from 120V to 240V takes no more copper;
#12 to #10 does. Of course, there is nothing stopping your from doing
both.

> > Simplifies the distribution and any increased costs go away if you buy
> > 15-25 ft, molded cord sets and chop off the receptacle end, then wire
> > to motor for 240V service.
>
> Surely #10 molded cord sets cost more than #12 or #14?

...harder to find, stiffer, harder to work with...

On Sep 1, 1:03=A0pm, Jack Stein <[email protected]> wrote:
> [email protected] wrote:
> >> I am no electrical =A0expert but iIwould guess it will work OK. =A0If =
you have
> >> normal residental home wiring you will actually have 2- 110 volt lines=
going
> >> to your BS. =A0Add them up and you get 220 volts. =A0The lamp will pro=
bably
> >> continue to have 1 single 110 volt line going to it.
> > It'll work but it's against code and (somewhat) unsafe. =A0To split off
> > 120V you need a neutral.
>
> Just out of dumb curiosity, does this mean if you don't split off 120,
> you don't need a neutral? =A0Normally, with 120 you need 2 wires plus
> ground, hot, common and ground. =A0I don't know zip about 220 but are you
> guys saying 220 can have 2 wires, both hot, plus a ground (no common),
> and you connect one of the hots to the light, and what normally would be
> common or neutral to the ground? =A0

You generally need a ground but only need the neutral if you are using
the split phase (the 120V part). So, 240V will usually have three
wires (if there aren't any 120V loads) or four (with 120V loads).

> I'm in the dark here, just asking.
> Doesn't 220 always need a common ground (neutral?), just like 120?

Be careful, "ground" and "neutral" are different things. "Ground" is
used for safety purposes only. "Neutral" is a current carrying
conductor. If there is no current in the neutral (as is the case in a
purely 240V circuit) there isn't any need for the conductor. ;-)

On Sep 1, 7:01=A0pm, Chris Friesen <[email protected]> wrote:
> On 09/01/2009 02:29 PM, Tom Veatch wrote:
>
> > On Tue, 01 Sep 2009 12:02:53 -0600, Chris Friesen
> > <[email protected]> wrote:
>
> >> Faster startup implies that the mechanical work of spinning up the mot=
or
> >> is done in a shorter amount of time. =A0This means either the motor is
> >> more efficient at 240V or else it's drawing more power. =A0In both cas=
es
> >> this would be due to motor design, not simply higher voltage.
>
> > At 240v there's slightly more power available to the motor because of
> > less power loss in the circuit wiring due to the higher current at
> > 120v. This is especially evident under high current conditions like
> > startup when the motor is temporarily drawing several times it's
> > normal current draw.
>
> Technically true. =A0But on a properly designed circuit the NEC requires
> at most 5% voltage loss. =A0Even assuming that we got perfect efficiency
> at 240V I defy you to notice a tablesaw coming up to speed 5% faster.
>
> This is not a "wow, start up is almost instant" sort of difference.
>
> Chris

I (OP) noticed a difference.

On Sep 1, 9:11=A0am, "Leon" <[email protected]> wrote:
> "Dave - Parkville, MD" <[email protected]> wrote in messagenews:a=
[email protected]...
>
> >I just had an upgrade for my electric service to a 200 Amp panel as
> > part of an HVAC upgrade. =A0At the same time, I had the electrician put
> > in 2 220 circuits and 2 120 circuits for my shop (lights were already
> > separate). =A0Last night I switched over my table saw to 220. =A0Wow,
> > start up is almost instant.
>
> > The question: I plan to switch over my bandsaw to 220 as well. =A0What
> > happens to the gooseneck lamp? =A0The switch over instructions don't
> > mention it. =A0Rewiring for the motor is pretty straightfoward. =A0Am I
> > missing something?
>
> I am no electrical =A0expert but iIwould guess it will work OK. =A0If you=
have
> normal residental home wiring you will actually have 2- 110 volt lines go=
ing
> to your BS. =A0Add them up and you get 220 volts. =A0The lamp will probab=
ly
> continue to have 1 single 110 volt line going to it.
>
> Electric ovens and ranges have the same set up.

Good point Leon. I know in a 4 wire 220 supply you can have two hots,
a neutral and a ground. The outlet and plug will only have a 3 wires
(2 hots and ground). I haven't pulled the plate off of the motor yet,
maybe there is more info there. I am a bit shocked (no pun) that
Powermatic's site doesn't have much support.

On 09/01/2009 11:55 AM, SonomaProducts.com wrote:
> Slightly OT but relevant.
>
> I am a no nothing in terms of electrical. I can properly wire a plug
> or wall sockets but don't understand the flow, grounding, etc. Just
> never studied it. But on a related topic, I have always wondered why
> my planer and my big sander have a 220 line to run the big moter and a
> 110 line to run the feed table. I asked on of the Mfg's if there was a
> way to wire the 110 from the 220 and they clearly ran and hide, saying
> don't ask us.
>
> So I ask here. Is there some way to "properly" do this? Can I put an
> onboard converter or something. I would really like to eliminate the
> two cords scenario because I am constantly juggling machines because
> of my space restrictions and it is a big hassle with two plugs.

Sure, but it might not be worth the hassle.

To do it properly you'd need a 3-conductor plus ground cable, with a
4-prong plug. Two hots, neutral, and ground. Bring the main cord into
a junction box mounted to the tool somewhere. In the junction box split
the wires out appropriately to the two motors. The main motor then gets
driven by the two hots, while the feed table gets driven by a hot and
the neutral.

The ampacity of the conductors must be suffient to provide for both the
feed table and the main motor, so you'd probably have to increase the
conductor size. You'll likely need to add a special 4-prong receptacle,
also wired with large enough conductors.

It's probably easier to just zip-tie the two cords together so that they
don't get tangled.

Chris

dpb <[email protected]> writes:
>[email protected] wrote:
>...
>> Just don't do it, and stop telling others to violate safety codes!
>> You're being irresponsible!
>
>I'm not "telling" anybody to do anything--I'm simply pointing out it's
>been common practice until quite recently.
>
>As for your experience, there has always been an external safety ground
>supplied on driers; whether one bothered to hook them up is another matter.

There has not always been a grounded conductor on driers, only a grounding
conductor. Unfortunately, in the olden days, the grounding conductor has
been used as a grounded conductor as well for 120 volt loads, which can
cause the frame (which is attached to the grounding conductor) to have a
potential difference relative to earth. (if they didn't bother to hook up
the "external safety ground" as you call it (NEC calls it the grounding
conductor), the light in the dryer wouldn't work at all, so it's quite
likely that they _did_ bother to hook them up in almost all cases).

Modern NEC requires both a grounding and a grounded conductor on 240v/120v
split loads.

scott

On Sep 2, 9:25=A0am, Chris Friesen <[email protected]> wrote:
> On 09/01/2009 09:50 PM, krw wrote:
>
>
>
> > On Tue, 01 Sep 2009 16:40:47 -0600, Chris Friesen
> > <[email protected]> wrote:
>
> >> On 09/01/2009 01:37 PM, [email protected] wrote:
> >>> On Sep 1, 1:02 pm, Chris Friesen <[email protected]> wrote:
>
> >>>> Huh? =A0Voltage is just potential. =A0You need power to do work, and=
the
> >>>> amount of power (and thus the amount of work that can be done) is th=
e
> >>>> same in each case.
>
> >>> Power is proportional to the *square* of the potential.
>
> >> You forgot the whole "divided by resistance" part. =A0and Potential
> >> divided by resistance is current.
>
> > The resistance of the wire is the same. =A0...unless you're wiring your
> > house with 16AWG.
>
> The resistance of the motor changes when rewired for 240V.

The resistance of the wire does not.

On Tue, 01 Sep 2009 17:01:46 -0600, Chris Friesen
<[email protected]> wrote:

>On 09/01/2009 02:29 PM, Tom Veatch wrote:
>> On Tue, 01 Sep 2009 12:02:53 -0600, Chris Friesen
>> <[email protected]> wrote:
>>
>>> Faster startup implies that the mechanical work of spinning up the motor
>>> is done in a shorter amount of time. This means either the motor is
>>> more efficient at 240V or else it's drawing more power. In both cases
>>> this would be due to motor design, not simply higher voltage.
>>
>> At 240v there's slightly more power available to the motor because of
>> less power loss in the circuit wiring due to the higher current at
>> 120v. This is especially evident under high current conditions like
>> startup when the motor is temporarily drawing several times it's
>> normal current draw.
>
>Technically true. But on a properly designed circuit the NEC requires
>at most 5% voltage loss. Even assuming that we got perfect efficiency
>at 240V I defy you to notice a tablesaw coming up to speed 5% faster.
>
>This is not a "wow, start up is almost instant" sort of difference.

Try it. You *will* notice the difference.

On 09/01/2009 01:02 PM, Doug Miller wrote:
> In article <[email protected]>, Chris Friesen <[email protected]> wrote:
>> On 09/01/2009 11:08 AM, Doug Miller wrote:
>>> In article <[email protected]>, Chris Friesen
>> <[email protected]> wrote:
>>
>>>> I agree it will draw half the current. Assuming properly sized
>>>> conductors such that voltage loss is negligible, why would 6A at 240V
>>>> behave any differently than 12A at 120V? In both cases we're drawing 1440W.
>>>
>>> Higher voltage.
>>
>> Huh? Voltage is just potential.
>
> Yes, that's right. That's why the motor will start more quickly with higher
> voltage.

I hope that's supposed to be a joke.

Chris

On 09/01/2009 01:37 PM, [email protected] wrote:
> On Sep 1, 1:02 pm, Chris Friesen <[email protected]> wrote:

>> Huh? Voltage is just potential. You need power to do work, and the
>> amount of power (and thus the amount of work that can be done) is the
>> same in each case.
>
> Power is proportional to the *square* of the potential.

You forgot the whole "divided by resistance" part. and Potential
divided by resistance is current.

P=(V^2)/R = V*I

As Tom Veatch indicated, in the typical case when you rewire the motor
for 240V you are also increasing the resistance so that the final power
ends up the same.

>> Faster startup implies that the mechanical work of spinning up the motor
>> is done in a shorter amount of time. This means either the motor is
>> more efficient at 240V or else it's drawing more power. In both cases
>> this would be due to motor design, not simply higher voltage.
>
> Not more efficient, but does have more *power* available, all else
> being the same.

Again...why would this be the case? The available electrical power of a
motor drawing 6A at 240V is exactly the same as one drawing 12A at 120V.

Chris

On 09/02/2009 06:52 AM, DLB wrote:
> On Sep 1, 7:01 pm, Chris Friesen <[email protected]> wrote:

>> Technically true. But on a properly designed circuit the NEC requires
>> at most 5% voltage loss. Even assuming that we got perfect efficiency
>> at 240V I defy you to notice a tablesaw coming up to speed 5% faster.
>>
>> This is not a "wow, start up is almost instant" sort of difference.

> I (OP) noticed a difference.

As I mentioned in my first email, if it makes that much difference then
it's likely the motor itself was not operating optimally at 120V.

Aside from supply losses which have been discussed extensively :) in
this thread, there's no inherent reason why a motor would operate more
efficiently at higher voltage.

Chris

On Sep 1, 9:38=A0am, dpb <[email protected]> wrote:
> [email protected] wrote:
>
> ...
>
> > In most 240 circuits there is no neutral (certainly not those used for
> > tools). =A0Wiring it to ground isn't a good idea either.
>
> Well, split-voltage appliances (ranges, dryers, ...) have run that way
> for approaching 100 years w/o any significant issues.

They don't anymore, and for a reason.

> Only w/ a relatively late NEC revision did the requirement for 4-wire
> service come into play.

For a reason.

> While it strictly speaking, isn't up to current Code, for a load no
> larger than the work lamp there's no issue imo.

Your opinion isn't going to matter if someone gets hurt. It's a lot
easier to wire a separate circuit.

> This came up not too long ago and someone noted that between an early
> manual and later the particular manufacturer of his dp had dropped the
> illustration/wiring diagram for the split voltage, undoubtedly to
> maintain strict Code compliance from a liability standpoint. =A0However,
> they hadn't changed the wiring iiuc... :)

Their lawyers are dumber than stumps if they think paperwork is going
to get them out of the inevitable lawsuit. Do they have a compliance
(UL, etc.) mark on them?

> >> As an alternative, you can find 220v lamps on line.
>
> > A much better idea.
>
> Take your choice; I'd just rewire it meself...

You're perfectly within your rights to knowingly violate codes. No
"grandfather" excuse here, either.

"Leon" <[email protected]> wrote in message
news:[email protected]...
>
> "Dave - Parkville, MD" <[email protected]> wrote in message
> news:[email protected]...
>>I just had an upgrade for my electric service to a 200 Amp panel as
>> part of an HVAC upgrade. At the same time, I had the electrician put
>> in 2 220 circuits and 2 120 circuits for my shop (lights were already
>> separate). Last night I switched over my table saw to 220. Wow,
>> start up is almost instant.
>>
>> The question: I plan to switch over my bandsaw to 220 as well. What
>> happens to the gooseneck lamp? The switch over instructions don't
>> mention it. Rewiring for the motor is pretty straightfoward. Am I
>> missing something?
>
> I am no electrical expert but iIwould guess it will work OK. If you have
> normal residental home wiring you will actually have 2- 110 volt lines
> going to your BS. Add them up and you get 220 volts. The lamp will
> probably continue to have 1 single 110 volt line going to it.
>
> Electric ovens and ranges have the same set up.

What he said. I'm in Baltimore and on the same lines as you, Dave.

Ed

On Tue, 1 Sep 2009 10:58:01 -0700 (PDT), "[email protected]"
<[email protected]> wrote:

>> This came up not too long ago and someone noted that between an early
>> manual and later the particular manufacturer of his dp had dropped the
>> illustration/wiring diagram for the split voltage, undoubtedly to
>> maintain strict Code compliance from a liability standpoint.  However,
>> they hadn't changed the wiring iiuc... :)
>
>Their lawyers are dumber than stumps if they think paperwork is going
>to get them out of the inevitable lawsuit. Do they have a compliance
>(UL, etc.) mark on them?

I'm not sure if "dpb" was referring to me, or not, but I found that
with my DP. Motor can be rewired for 240, but the wiring harness has
no provisions for a neutral feed. The "stock" harness connects the
work lamp across the two non-ground leads so that if the DP is plugged
into a 120v circuit, the lamp socket sees 120. And if plugged into a
240v circuit, the socket sees 240v. I'd strongly suspect the OP's band
saw is similar. He'll certainly find out if he rewires the motor for
240 and his work light (with a 120v bulb) burns very brightly for a
very short time.

Several years ago, on the manufacturer's web site, the PDF manual for
the DP, as a part of the diagram for rewiring the tool for 240, showed
the work light socket being changed to connect across one hot lead and
the EGC to provide 120 to the lamp. I went back to the site at a later
date, and that part of the diagram was no longer there. It now shows
only a configuration that connects the lamp socket across the
non-ground leads with no direct connection to the EGC. I suspect the
diagram was deleted as a result of UL requirements.

Using the EGC for an operational conductor does violate the current
NEC. But, the NEC doesn't cover anything beyond the wall plug. It's
only applicable to permanent wiring, so rewiring the DP (or band saw)
to supply 120v from a 2+G 240 circuit doesn't technically violate the
NEC unless the device is hardwired into the facility wiring. That
doesn't mean it's any more or less safe, just that it's not covered by
the NEC. That's according to my understanding of the scope of the NEC.
Even if "plug in" loads was covered by the NEC, compliance would be
impossible to enforce unless you had to pull a permit and get an
inspector out every time you plugged the vacuum cleaner into the
living room wall socket.

Using the tool's EGC for a neutral return will, as stated, energize
the grounded portions of everything connected to that circuit, as well
as everything on every circuit which has an EGC connected to the
ground bus in the panel that houses that circuit. The voltage on those
energized grounds will be the product of the resistance to ground of
the panel's ground bus times the current flowing from the ground bus
to ground. May or may not be dangerous depending on the amperage and
the resistance to ground.

Incidentally that is the same condition that exists if any device
drawing current through that panel develops a short to ground. Until
the breaker trips (assuming the leakage to ground is enough to trip
the breaker) every grounded item in, or connected to, that panel will
be energized with that amps x resistance voltage.

The use of GFI breakers addresses that condition by tripping anytime
there is a very small difference in the amperage in the two non-EGC
conductors. Otherwise the fault current would have to be on the order
of the breaker rating. A DP or BS rewired to use the EGC as neutral on
a 240v circuit would certainly trip any 240v GFI breaker that
monitored the current in the two hot wires the way a 120v GFI breaker
monitors the current in the hot and neutral wires.

Tom Veatch
Wichita, KS
USA

On Sep 2, 3:33=A0pm, Chris Friesen <[email protected]> wrote:
> On 09/02/2009 01:08 PM, [email protected] wrote:
>
> > On Sep 2, 11:31 am, Chris Friesen <[email protected]> wrote:
> >> I chose to ignore the line losses because they're supposed to be small
> >> to start with on a properly designed circuit, so reducing them further
> >> should make very little difference--certainly not one that is noticeab=
le
> >> to the user.
>
> > That's where you make your mistake. =A0Line losses are *not* small,
> > particlarly when the machine is starting. =A0The power lost due to the
> > line resistance is the square of the voltage lost. =A0It is *not*
> > insignificant.
>
> Consider a motor that draws 15A at 120V. =A0Let's call it a 90A inrush
> current, with a wiring length of 30 feet (20 feet from the panel,
> 10-foot cord) and #12 wiring.
>
> Power loss in the wiring is:
>
> Pc =3D I^2 * R
>
> For 30' of #12 copper, R=3D0.048 ohm
>
> At 120V, assuming 90 A inrush:
> Pc =3D 389W
>
> At 240V the inrush should be half, or 45A:
> Pc =3D 97W
>
> This makes sense, we double the voltage and cut power loss by a factor
> of 2^2.
>
> So for a total inrush power draw of 10800W (90*120 or 45*240), at 120V
> we lose 3.6% of the power to supply losses, while at 240V we lose 0.9%.
>
> We get 2.7% more power delivered to the motor by switching to 240V. =A0I
> wouldn't be able to notice the difference, so I call that "small".
>
> Chris

I agree, small. But noticable to me.

Doug Miller wrote:
>
> Sorry, but that's not correct. At 240V, it will draw half the current that it
> did at 120V. This will provide a much faster start, even if the 120V circuit
> was properly sized.

Woah up a second here!

That's true if the device is built to run off of 240 Volts.

But if the internal resistance is the same as it was in the 120
device, it will draw TWICE the amperage - until it "opens".

On Sep 1, 11:03=A0am, Jack Stein <[email protected]> wrote:
> [email protected] wrote:

> > It'll work but it's against code and (somewhat) unsafe. =A0To split off
> > 120V you need a neutral.

>Just out of dumb curiosity, does this mean if you don't split off 120,
>you don't need a neutral?

220V wired to a three pole socket has HOT1, HOT2, and ground.
Wired to a four-pole socket, it has HOT1, neutral, HOT2, and ground.

While generally considered poor practice, it was normal for many years
in the US for stoves and clothes dryers to have a heavy three-prong
plug for 220V 30A, and a small (fused 10A) auxiliary 110V circuit
that ran from one hot wire to ground. Safety code had an
"appliance exception" for this, and it was done because a 4-wire 30A
circuit and socket would have been excessive and expensive.

Think about it: there's gotta be a 30A ground wire for these items,
and
it carries NO current; to add a 120V 10A convenience socket, do you
want
to add a 30A neutral wire as well?

<[email protected]> wrote in message
news:b8bbef60-47d6-4a10-9f19-8d286e2cd2be@d21g2000vbm.googlegroups.com...
On Sep 1, 8:11 am, "Leon" <[email protected]> wrote:
> "Dave - Parkville, MD" <[email protected]> wrote in
> messagenews:[email protected]...
OK. If you have
> normal residental home wiring you will actually have 2- 110 volt lines
> going
> to your BS. Add them up and you get 220 volts. The lamp will probably
> continue to have 1 single 110 volt line going to it.

It'll work but it's against code and (somewhat) unsafe. To split off
120V you need a neutral.

> Electric ovens and ranges have the same set up.

Electric ovens have a neutral, or at least they do now.


Correct, I was just trying to point out a logical picutre. Absolutely they
have neutral lines.

On 09/02/2009 12:22 PM, Larry W wrote:

> During motor startup the current could be more like 40-60 amps. Breakers
> are designed to allow for momentary inrush currents of that magnitude,
> maybe even higher. What does that 6.8% figure change to when you
> do your calculations on 40 amps instead of 10?

Okay, but let's use a more realistic wiring length of 30 feet. (20 feet
from the panel, 10-foot cord.)

Power loss in the wiring is:

Pc = I^2 * R

For 30' of #12 copper, R=0.048 ohm

At 120V, assuming 60A inrush:
Pc = 173W

At 240V, assuming 30A inrush:
Pc = 43W

So for a total inrush power draw of 7200W (60*120 or 30*240), at 120V we
lose 2.4% of the power to supply losses, while at 240V we lose 0.6%.

We get 1.8% more power delivered to the motor by switching to 240V.

Chris

"Dan Coby" wrote:

> No. The voltage drop in the cable is VC = I * R
>
> The power lost in the cable is Pc = I^2 * R
>

"Duh, Brain Fart Dummy", he says to self.

Thank you for the correction.

Below is the corrected version.

The total voltage drop across a motor consists of the voltage drop
across the motor itself plus the voltage drop across the cable
feeding
the motor.

The voltage drop across the cable is as follows:

VC = I*R

For purposes of explanation, assume:

Case 1: (120V service)
R = 1 Ohm
I = 10 Amps

VC = 10*1 = 10 volts

Case 2: (240V service)
R = 1 Ohm
I = 5 Amps

VC = 5*1 = 5 volts

Increasing the supply voltage from 120V to 240V, all other things
being equal, reduces the line losses by a factor of 2:1 (10/5) which
results in a higher voltage being delivered to the motor.

All other things being equal , the higher the voltage, the more
efficient the connected motor will be.

Note:

The resistance value used is totally immaterial since mathematically,
it cancels out in the calculations.

>Motor starting current may be several times the running current that
> makes the voltage drop in the wire during start up much worse. This
> will
> favor the 240 volt system with if the wire size is the same as the
> 120 volt
> system.

Absolutely.

Being able to handle inrush with out blinking is a great advantage.

> The above calculations also have a built in assumption that the 240
> volt
> system was wired with the same gauge as the 120 volt. That may or
> may not
> be true. If the 240 volt system was wired with smaller wire then it
> may
> have worse voltage drops.

I long ago standardized on #10AWG for motor conductors.

Simplifies the distribution and any increased costs go away if you buy
15-25 ft, molded cord sets and chop off the receptacle end, then wire
to motor for 240V service.

Lew

On 09/01/2009 09:50 PM, krw wrote:
> On Tue, 01 Sep 2009 16:40:47 -0600, Chris Friesen
> <[email protected]> wrote:
>
>> On 09/01/2009 01:37 PM, [email protected] wrote:
>>> On Sep 1, 1:02 pm, Chris Friesen <[email protected]> wrote:
>>
>>>> Huh? Voltage is just potential. You need power to do work, and the
>>>> amount of power (and thus the amount of work that can be done) is the
>>>> same in each case.
>>>
>>> Power is proportional to the *square* of the potential.
>>
>> You forgot the whole "divided by resistance" part. and Potential
>> divided by resistance is current.
>
> The resistance of the wire is the same. ...unless you're wiring your
> house with 16AWG.

The resistance of the motor changes when rewired for 240V.

Chris

Chris Friesen wrote:
> On 09/01/2009 01:37 PM, [email protected] wrote:
>
>>On Sep 1, 1:02 pm, Chris Friesen <[email protected]> wrote:
>
>
>>>Huh? Voltage is just potential. You need power to do work, and the
>>>amount of power (and thus the amount of work that can be done) is the
>>>same in each case.
>>
>>Power is proportional to the *square* of the potential.
>
>
> You forgot the whole "divided by resistance" part. and Potential
> divided by resistance is current.
>
> P=(V^2)/R = V*I
>
> As Tom Veatch indicated, in the typical case when you rewire the motor
> for 240V you are also increasing the resistance so that the final power
> ends up the same.
>
>
>>>Faster startup implies that the mechanical work of spinning up the motor
>>>is done in a shorter amount of time. This means either the motor is
>>>more efficient at 240V or else it's drawing more power. In both cases
>>>this would be due to motor design, not simply higher voltage.
>>
>>Not more efficient, but does have more *power* available, all else
>>being the same.
>
>
> Again...why would this be the case? The available electrical power of a
> motor drawing 6A at 240V is exactly the same as one drawing 12A at 120V.
>
> Chris

Depending on the total wire resistance the voltage drop to the motor
would vary. The power loss formula P = I² R shows that if you double the
voltage you reduce the power loss by a factor of 4. On motors above 2
HP the difference between 120V and 240V is quite noticable.

--
Jack Novak
Buffalo, NY - USA
[email protected]

<[email protected]> wrote:

>...harder to find, stiffer, harder to work with...

Think molded cord set.

Definitely flexible.

Definitely available at all the big box stores.

Lew

In article <a317577e-a0a0-4b1b-a433-5c114f137e77
@s6g2000vbp.googlegroups.com>, [email protected] says...
>
> I just had an upgrade for my electric service to a 200 Amp panel as
> part of an HVAC upgrade. At the same time, I had the electrician put
> in 2 220 circuits and 2 120 circuits for my shop (lights were already
> separate). Last night I switched over my table saw to 220. Wow,
> start up is almost instant.
>

Heh heh, I had that kind of experience when I converted my arc welder
from 230V to 400. No more sticky electrodes! (NB: I'm not in the US,
230V is our 'normal' voltage).

I believe 400V on a thicknesser is a nice thing to have, too. My fairly
light German over and under planer/thicknesser has just about done its
dash; and it doesn't owe me much either after 26 years. I might give
that a second thought.

-P.

DLB wrote:
> On Sep 1, 7:01 pm, Chris Friesen <[email protected]> wrote:
>> On 09/01/2009 02:29 PM, Tom Veatch wrote:
>>
>>> On Tue, 01 Sep 2009 12:02:53 -0600, Chris Friesen
>>> <[email protected]> wrote:
>>>> Faster startup implies that the mechanical work of spinning up the motor
>>>> is done in a shorter amount of time. This means either the motor is
>>>> more efficient at 240V or else it's drawing more power. In both cases
>>>> this would be due to motor design, not simply higher voltage.
>>> At 240v there's slightly more power available to the motor because of
>>> less power loss in the circuit wiring due to the higher current at
>>> 120v. This is especially evident under high current conditions like
>>> startup when the motor is temporarily drawing several times it's
>>> normal current draw.
>> Technically true. But on a properly designed circuit the NEC requires
>> at most 5% voltage loss. Even assuming that we got perfect efficiency
>> at 240V I defy you to notice a tablesaw coming up to speed 5% faster.
>>
>> This is not a "wow, start up is almost instant" sort of difference.
>>
>> Chris
>
> I (OP) noticed a difference.
>

OP: You have gotten a little good advice and a whole lot of very bad
advice. You problem is figuring out which is which. If I someday have
a death wish, I'll have to remember to ask such a question on the wreck.

"Chris Friesen" wrote:

> Again...why would this be the case? The available electrical power
> of a
> motor drawing 6A at 240V is exactly the same as one drawing 12A at
> 120V.

The above is known as "Chris' Therom" which is false.

The total voltage drop across a motor consists of the voltage drop
across the motor itself plus the voltage drop across the cable feeding
the motor.

The voltage drop across the cable is as follows:

VC = I^2*R

For purposes of explanation, assume:

Case 1: (120V service)
R = 1 Ohm
I = 10 Amps

VC = 10^2*1 = 100 volts

Case 2: (240V service)
R = 1 Ohm
I = 5 Amps

VC = 5^2*1 = 25 volts

Increasing the supply voltage from 120V to 240V, all other things
being equal, reduces the line losses by a factor of 4:1 (100/25) which
results in a higher voltage being delivered to the motor.

All other things being equal , the higher the voltage, the more
efficient the connected motor will be.

Lew

"Chris Friesen" wrote:

> Surely #10 molded cord sets cost more than #12 or #14?

You would be surprised.

Don't forget to include the cost of the male plug in your cost
comparisons.

Lew

Chris Friesen wrote:

>
> Consider a motor that draws 15A at 120V. Let's call it a 90A inrush
> current, with a wiring length of 30 feet (20 feet from the panel,
> 10-foot cord) and #12 wiring.
>
> Power loss in the wiring is:
>
> Pc = I^2 * R
>
> For 30' of #12 copper, R=0.048 ohm

I believe the resistance of the motor's windings figures into the
formula as well as it's part of the circuit.

--
Jack Novak
Buffalo, NY - USA
[email protected]

"Chris Friesen" <[email protected]> wrote in message
news:[email protected]...
>>> Huh? Voltage is just potential.
>>
>> Yes, that's right. That's why the motor will start more quickly with
>> higher
>> voltage.
>
> I hope that's supposed to be a joke.
>
> Chris


Ok, again, I am no electrical expert but in my coloring book world of
looking at electricity, You have less resistance up to the motor using 240
vs 120. Each of the 2 wires carrying 120 volts is carrying 1/2 the load up
to the motor than the single wire in a 120 volt application.

On 09/02/2009 01:08 PM, [email protected] wrote:
> On Sep 2, 11:31 am, Chris Friesen <[email protected]> wrote:

>> I chose to ignore the line losses because they're supposed to be small
>> to start with on a properly designed circuit, so reducing them further
>> should make very little difference--certainly not one that is noticeable
>> to the user.
>
> That's where you make your mistake. Line losses are *not* small,
> particlarly when the machine is starting. The power lost due to the
> line resistance is the square of the voltage lost. It is *not*
> insignificant.

Consider a motor that draws 15A at 120V. Let's call it a 90A inrush
current, with a wiring length of 30 feet (20 feet from the panel,
10-foot cord) and #12 wiring.

Power loss in the wiring is:

Pc = I^2 * R

For 30' of #12 copper, R=0.048 ohm

At 120V, assuming 90 A inrush:
Pc = 389W

At 240V the inrush should be half, or 45A:
Pc = 97W

This makes sense, we double the voltage and cut power loss by a factor
of 2^2.

So for a total inrush power draw of 10800W (90*120 or 45*240), at 120V
we lose 3.6% of the power to supply losses, while at 240V we lose 0.9%.

We get 2.7% more power delivered to the motor by switching to 240V. I
wouldn't be able to notice the difference, so I call that "small".

Chris

On Sep 1, 5:22=A0pm, dpb <[email protected]> wrote:
> [email protected] wrote:
>
> ...
>
> > Just don't do it, and stop telling others to violate safety codes!
> > You're being irresponsible!
>
> I'm not "telling" anybody to do anything--I'm simply pointing out it's
> been common practice until quite recently.

But you are. By your saying that it's perfectly safe (it isn't) and
just the "committies" doing something just to do _something_, you're
telling anyone here who will listen to violate code.

> As for your experience, there has always been an external safety ground
> supplied on driers; whether one bothered to hook them up is another matte=
r.

Not always used, nor useful.

> I stand by my contention the 3-wire split circuit existed in such
> numbers for so long that if it were truly a dangerous practice it would
> have taken far less time than it did for it to finally percolate its way
> to the radar screen.

So you think it's alright to tell people to perform unsafe acts?
They're "safe enough", even though they clearly are not, in the eyes
of thoese with jurisdiction over such things.

> I'll also reassert given my experience on Standards committees there is
> that aforementioned need to find _something_ to modify...they finally
> got to the bottom of the barrel where this became one thing they could
> find to change.

So your lousy experience in some unnamed committee trumps all safety
rules?

> again, imo, ymmv, etc., etc., etc., ...

Ah, the disclaimer, where you tell people that its not your fault when
their kid gets electrocuted.

> And, yes, Code now mandates 4-wire connections; others make your own
> determination, I'm not advocating you violate Code willy-nilly but the
> subject of a work light on a drill press...

As much as you may think so, fire/electrical codes are not there so
"others can make their own determination".

On Sep 1, 1:02=A0pm, Chris Friesen <[email protected]> wrote:
> On 09/01/2009 11:08 AM, Doug Miller wrote:
>
> > In article <[email protected]>, Chris Fri=
esen <[email protected]> wrote:
> >> I agree it will draw half the current. =A0Assuming properly sized
> >> conductors such that voltage loss is negligible, why would 6A at 240V
> >> behave any differently than 12A at 120V? =A0In both cases we're drawin=
g 1440W.
>
> > Higher voltage.
>
> Huh? =A0Voltage is just potential. =A0You need power to do work, and the
> amount of power (and thus the amount of work that can be done) is the
> same in each case.

Power is proportional to the *square* of the potential.

> Faster startup implies that the mechanical work of spinning up the motor
> is done in a shorter amount of time. =A0This means either the motor is
> more efficient at 240V or else it's drawing more power. =A0In both cases
> this would be due to motor design, not simply higher voltage.

Not more efficient, but does have more *power* available, all else
being the same.

Thanks guys. This is my home shop but I don't want to do the 4 wire
work so I guess I'll live with it. It just seems kind of silly. Maybe
I can find some 220 fractional hp motors to run my feed tables.

On Sep 1, 10:55=A0am, "SonomaProducts.com" <[email protected]> wrote:
> Slightly OT but relevant.
>
> I am a no nothing in terms of electrical. I can properly wire a plug
> or wall sockets but don't understand the flow, grounding, etc. Just
> never studied it. But on a related topic, I have always wondered why
> my planer and my big sander have a 220 line to run the big moter and a
> 110 line to run the feed table. I asked on of the Mfg's if there was a
> way to wire the 110 from the 220 and they clearly ran and hide, saying
> don't ask us.
>
> So I ask here. Is there some way to "properly" do this? Can I put an
> onboard converter or something. I would really like to eliminate the
> two cords scenario because I am constantly juggling machines because
> of my space restrictions and it is a big hassle with two plugs.
>
> On Sep 1, 6:56=A0am, Chris Friesen <[email protected]> wrote:
>
>
>
> > On 09/01/2009 05:25 AM, Dave - Parkville, MD wrote:
>
> > > I just had an upgrade for my electric service to a 200 Amp panel as
> > > part of an HVAC upgrade. =A0At the same time, I had the electrician p=
ut
> > > in 2 220 circuits and 2 120 circuits for my shop (lights were already
> > > separate). =A0Last night I switched over my table saw to 220. =A0Wow,
> > > start up is almost instant.
>
> > If it makes that much difference, there was probably something wrong
> > with the 120V circuit or wire size. =A0If everything was sized properly
> > there shouldn't really be any difference.
>
> > > The question: I plan to switch over my bandsaw to 220 as well. =A0Wha=
t
> > > happens to the gooseneck lamp? =A0The switch over instructions don't
> > > mention it. =A0Rewiring for the motor is pretty straightfoward. =A0Am=
I
> > > missing something?
>
> > My bandsaw has a separate plug for the lamp. =A0If it's not mentioned
> > they're probably using the safety ground as a neutral which you're not
> > really supposed to do.
>
> > Chris- Hide quoted text -
>
> - Show quoted text -

On Sep 2, 9:29=A0am, Chris Friesen <[email protected]> wrote:
> On 09/02/2009 06:52 AM, DLB wrote:
>
> > On Sep 1, 7:01 pm, Chris Friesen <[email protected]> wrote:
> >> Technically true. =A0But on a properly designed circuit the NEC requir=
es
> >> at most 5% voltage loss. =A0Even assuming that we got perfect efficien=
cy
> >> at 240V I defy you to notice a tablesaw coming up to speed 5% faster.
>
> >> This is not a "wow, start up is almost instant" sort of difference.
> > I (OP) noticed a difference.
>
> As I mentioned in my first email, if it makes that much difference then
> it's likely the motor itself was not operating optimally at 120V.
>
> Aside from supply losses which have been discussed extensively :) in
> this thread, there's no inherent reason why a motor would operate more
> efficiently at higher voltage.

...and it is exactly the supply losses that make the difference, so...

On Sep 1, 8:11=A0am, "Leon" <[email protected]> wrote:
> "Dave - Parkville, MD" <[email protected]> wrote in messagenews:a=
[email protected]...
>
> >I just had an upgrade for my electric service to a 200 Amp panel as
> > part of an HVAC upgrade. =A0At the same time, I had the electrician put
> > in 2 220 circuits and 2 120 circuits for my shop (lights were already
> > separate). =A0Last night I switched over my table saw to 220. =A0Wow,
> > start up is almost instant.
>
> > The question: I plan to switch over my bandsaw to 220 as well. =A0What
> > happens to the gooseneck lamp? =A0The switch over instructions don't
> > mention it. =A0Rewiring for the motor is pretty straightfoward. =A0Am I
> > missing something?
>
> I am no electrical =A0expert but iIwould guess it will work OK. =A0If you=
have
> normal residental home wiring you will actually have 2- 110 volt lines go=
ing
> to your BS. =A0Add them up and you get 220 volts. =A0The lamp will probab=
ly
> continue to have 1 single 110 volt line going to it.

It'll work but it's against code and (somewhat) unsafe. To split off
120V you need a neutral.

> Electric ovens and ranges have the same set up.

Electric ovens have a neutral, or at least they do now.

On Sep 2, 10:38=A0am, Mike <[email protected]> wrote:
> DLB wrote:
> > On Sep 1, 7:01 pm, Chris Friesen <[email protected]> wrote:
> >> On 09/01/2009 02:29 PM, Tom Veatch wrote:
>
> >>> On Tue, 01 Sep 2009 12:02:53 -0600, Chris Friesen
> >>> <[email protected]> wrote:
> >>>> Faster startup implies that the mechanical work of spinning up the m=
otor
> >>>> is done in a shorter amount of time. =A0This means either the motor =
is
> >>>> more efficient at 240V or else it's drawing more power. =A0In both c=
ases
> >>>> this would be due to motor design, not simply higher voltage.
> >>> At 240v there's slightly more power available to the motor because of
> >>> less power loss in the circuit wiring due to the higher current at
> >>> 120v. This is especially evident under high current conditions like
> >>> startup when the motor is temporarily drawing several times it's
> >>> normal current draw.
> >> Technically true. =A0But on a properly designed circuit the NEC requir=
es
> >> at most 5% voltage loss. =A0Even assuming that we got perfect efficien=
cy
> >> at 240V I defy you to notice a tablesaw coming up to speed 5% faster.
>
> >> This is not a "wow, start up is almost instant" sort of difference.
>
> >> Chris
>
> > I (OP) noticed a difference.
>
> OP: You have gotten a little good advice and a whole lot of very bad
> advice. =A0You problem is figuring out which is which. =A0If I someday ha=
ve
> a death wish, I'll have to remember to ask such a question on the wreck.-=
Hide quoted text -
>
> - Show quoted text -

I will probably just wire a separate cord for the 120v lamp. I do
like reading all the comments and thank everyone for posting. It all
helps me understand more than I did. It makes sense that once running
the motor has the same power (one hot leg at 15amps vs. two hot legs
at 7.5amps each).

On Tue, 01 Sep 2009 10:48:17 -0600, Chris Friesen
<[email protected]> wrote:

>Now it's possible that the motor itself could be designed such that it
>runs more efficiently at 240V than at 120V. This isn't necessarily the
>case here, but if it is it would be due to the motor design, not the
>higher voltage as such.

Not likely. Typical dual voltage motors are set up such that two
windings are in series for 240v and in parallel for 120v. So
regardless of the supplied voltage, the voltage drop and current in
each of the windings is the same in either case. In other words, the
working parts of the motor don't know the difference between the motor
being connected to 240v or 120v.

Tom Veatch
Wichita, KS
USA

I really don't even understand electrical concepts to know how to
determine what the load would be. If I can string a few wires together
to get juice where I need it I am capable but only venture into such
issues when there is no question of how to proceed. Swapping out a
switch, changing a plug to match a socket, etc.

No worries, just a curiosity for now. Would like a better solution but
the best solution is to get a bigger shop and be able to leave
machines in place, pulg in once and forget.

On Sep 1, 7:21=A0pm, dpb <[email protected]> wrote:
> SonomaProducts.com wrote:
> > Thanks guys. This is my home shop but I don't want to do the 4 wire
> > work so I guess I'll live with it. It just seems kind of silly. Maybe
> > I can find some 220 fractional hp motors to run my feed tables.
>
> ...
>
> How large _are_ the 110 loads? =A0To keep the one particular individual
> off my back note I'm _NOT_ telling you to do this but there still _is_
> the unmentionable solution... :)
>
> --

On Sep 1, 1:00=A0pm, dpb <[email protected]> wrote:
> [email protected] wrote:
> > On Sep 1, 9:38 am, dpb <[email protected]> wrote:
> >> [email protected] wrote:
>
> >> ...
>
> >>> In most 240 circuits there is no neutral (certainly not those used fo=
r
> >>> tools). =A0Wiring it to ground isn't a good idea either.
> >> Well, split-voltage appliances (ranges, dryers, ...) have run that way
> >> for approaching 100 years w/o any significant issues.
>
> > They don't anymore, and for a reason.
>
> ...
>
> Yes, that reason is Code. =A0Having worked on various Standards groups
> over the years, there's a definite tendency to continue to make
> modifications simply for the purpose of appearing to continue to do
> something and thereby justify the existence of the body.

The NFPA is known to write the "code in blood". Someone was injured
or killed before the code was modified. Sure, you'll likely get away
with it but it is *NOT* smart to knowingly flaunt the electrical
code. Lawyers love it, even if you don't kill anyone.

> In the 100 years before, where's the overwhelming evidence it was ever a
> problem????

Depends on your definition of "overwhelming". It was never a good
idea to tie a current carrying conductor to the case of a device.
That's essentially what you're advocating.

> As I said, one can choose but it's certainly not a major actual problem
> or there wouldn't have been the history of successful applications (and
> lord knows how many still existing appliances????) w/o any issues.

Absolute nonsense! There are many dangerous practices that are no
longer acceptable. This is one.

> When's the last time you _EVER_ heard of it being the cause of anything?

When I was *nailed* off my MIL's dryer (after she'd been complaining
for months I took a look at it). Had it a safety ground it would
never have shocked anyone. The code wasn't changed for this one
instance (that they never knew about).

Just don't do it, and stop telling others to violate safety codes!
You're being irresponsible!

On Sep 2, 2:50=A0pm, "Lew Hodgett" <[email protected]> wrote:
> "Chris Friesen" wrote:
> > Consider a motor that draws 15A at 120V. =A0Let's call it a 90A inrush
> > current, with a wiring length of 30 feet (20 feet from the panel,
> > 10-foot cord) and #12 wiring.
>
> The inrush current can easily be in the order of 8-10 times the FLA.
>
> Using your example above, a 15 FLA motor could easily have 120A-150A
> inrush.

In fact, since the motor is an inductor, the inrush is only limited by
the resistance. The lower the source impedance the higher the inrush,
for a shorter time. Shorter time =3D> faster start. QED.

> I was under the impression we were talking about reconfiguring a dual-voltage
> 120/240 motor from 120 to 240. I don't think anybody was suggesting operating
> a 120V motor at 240V.

Dual voltage motor - correct.

On 09/01/2009 05:25 AM, Dave - Parkville, MD wrote:
> I just had an upgrade for my electric service to a 200 Amp panel as
> part of an HVAC upgrade. At the same time, I had the electrician put
> in 2 220 circuits and 2 120 circuits for my shop (lights were already
> separate). Last night I switched over my table saw to 220. Wow,
> start up is almost instant.

If it makes that much difference, there was probably something wrong
with the 120V circuit or wire size. If everything was sized properly
there shouldn't really be any difference.

> The question: I plan to switch over my bandsaw to 220 as well. What
> happens to the gooseneck lamp? The switch over instructions don't
> mention it. Rewiring for the motor is pretty straightfoward. Am I
> missing something?

My bandsaw has a separate plug for the lamp. If it's not mentioned
they're probably using the safety ground as a neutral which you're not
really supposed to do.

Chris

> .... I had the electrician put in 2 220 circuits and 2 120 circuits for m=
y shop ...
>
> The question: I plan to switch over my bandsaw to 220 as well. =A0What
> happens to the gooseneck lamp?

I wired the lamp with one hot line (110v) to the center, and connected
a neutral to the outside. ( Sorry - I don't know the precise
terminology.)

As an alternative, you can find 220v lamps on line.

On Sep 1, 10:55=A0am, "SonomaProducts.com" <[email protected]> wrote:
> Slightly OT but relevant.
>
> .... I asked on of the Mfg's if there was a
> way to wire the 110 from the 220 and they clearly ran and hide, saying
> don't ask us.
>
> So I ask here. Is there some way to "properly" do this?

Two ways. First, you can use a 220/110V transformer (do the voltage
conversion the hard way). Second, you can note that the motor
may have series-connected windings for 220V, one of the
motor internal wiring taps has 110V on it when the motor is
operating. That means your light goes off when the motor is
switched off, of course...

My preference would be to use a 12V halogen worklight, and get
the 220 to 12V version of transformer for it. The 12V lamps are
more vibration-resistant, and you have to have the transformer
anyhow (no real difference in cost, though some suppliers might
not price it that way).

On Tue, 01 Sep 2009 12:02:53 -0600, Chris Friesen
<[email protected]> wrote:

>Faster startup implies that the mechanical work of spinning up the motor
>is done in a shorter amount of time. This means either the motor is
>more efficient at 240V or else it's drawing more power. In both cases
>this would be due to motor design, not simply higher voltage.

At 240v there's slightly more power available to the motor because of
less power loss in the circuit wiring due to the higher current at
120v. This is especially evident under high current conditions like
startup when the motor is temporarily drawing several times it's
normal current draw.

If the 120v circuit had half the resistance of the 240v circuit, there
would likely be little or no difference in the behavior of the motor.
But that's typically not the case. A 20 amp 120v circuit would
typically be wired with 12ga wire. A 20 amp 240v circuit would also
typically be wired with 12ga wire. Therefore, all other things being
the same, the 120v and the 240v circuits would have roughly the same
resistance. I'd expect the motor running on 240 under those conditions
to have faster startup characteristics as well as being slightly
harder to stall.

Tom Veatch
Wichita, KS
USA

On Tue, 01 Sep 2009 13:03:42 -0500, Jack Stein <[email protected]>
wrote:

>Doesn't 220 always need a common ground (neutral?), just like 120?

No. Speaking in the context of "normal" residential, single phase
120v/240v service, circuits that supply only 240v do not need or use
the neutral. Only the 120v circuits use the neutral wire. Multiwire
circuits that supply both 240 and 120 do need the neutral to support
the 120v loads.

Tom Veatch
Wichita, KS
USA

In article <[email protected]>, Chris Friesen <[email protected]> wrote:
>On 09/01/2009 05:25 AM, Dave - Parkville, MD wrote:
>> I just had an upgrade for my electric service to a 200 Amp panel as
>> part of an HVAC upgrade. At the same time, I had the electrician put
>> in 2 220 circuits and 2 120 circuits for my shop (lights were already
>> separate). Last night I switched over my table saw to 220. Wow,
>> start up is almost instant.
>
>If it makes that much difference, there was probably something wrong
>with the 120V circuit or wire size. If everything was sized properly
>there shouldn't really be any difference.

Sorry, but that's not correct. At 240V, it will draw half the current that it
did at 120V. This will provide a much faster start, even if the 120V circuit
was properly sized.
>
>> The question: I plan to switch over my bandsaw to 220 as well. What
>> happens to the gooseneck lamp? The switch over instructions don't
>> mention it. Rewiring for the motor is pretty straightfoward. Am I
>> missing something?
>
>My bandsaw has a separate plug for the lamp. If it's not mentioned
>they're probably using the safety ground as a neutral which you're not
>really supposed to do.

More than "not supposed to do". It's unsafe, because it energizes the ground
conductor, thus energizing the chassis of *everything* that's plugged into
that circuit. Remember that electricity does not "follow the path of least
resistance" as many people believe; rather, it follows all possible paths.
That includes the path that goes through the grounding conductor to the
chassis of the saw to the saw table to the hands of the operator.

[email protected] wrote:
...
> In most 240 circuits there is no neutral (certainly not those used for
> tools). Wiring it to ground isn't a good idea either.

Well, split-voltage appliances (ranges, dryers, ...) have run that way
for approaching 100 years w/o any significant issues.

Only w/ a relatively late NEC revision did the requirement for 4-wire
service come into play.

While it strictly speaking, isn't up to current Code, for a load no
larger than the work lamp there's no issue imo.

This came up not too long ago and someone noted that between an early
manual and later the particular manufacturer of his dp had dropped the
illustration/wiring diagram for the split voltage, undoubtedly to
maintain strict Code compliance from a liability standpoint. However,
they hadn't changed the wiring iiuc... :)

>> As an alternative, you can find 220v lamps on line.
>
> A much better idea.

Take your choice; I'd just rewire it meself...

--

[email protected] wrote:

>> I am no electrical expert but iIwould guess it will work OK. If you have
>> normal residental home wiring you will actually have 2- 110 volt lines going
>> to your BS. Add them up and you get 220 volts. The lamp will probably
>> continue to have 1 single 110 volt line going to it.

> It'll work but it's against code and (somewhat) unsafe. To split off
> 120V you need a neutral.

Just out of dumb curiosity, does this mean if you don't split off 120,
you don't need a neutral? Normally, with 120 you need 2 wires plus
ground, hot, common and ground. I don't know zip about 220 but are you
guys saying 220 can have 2 wires, both hot, plus a ground (no common),
and you connect one of the hots to the light, and what normally would be
common or neutral to the ground? I'm in the dark here, just asking.
Doesn't 220 always need a common ground (neutral?), just like 120?

--
Jack
Using FREE News Server: http://www.eternal-september.org/
http://jbstein.com

In article <[email protected]>, Chris Friesen <[email protected]> wrote:
>On 09/01/2009 08:35 AM, Doug Miller wrote:
>> In article <[email protected]>, Chris Friesen
> <[email protected]> wrote:
>>> On 09/01/2009 05:25 AM, Dave - Parkville, MD wrote:
>>>> I just had an upgrade for my electric service to a 200 Amp panel as
>>>> part of an HVAC upgrade. At the same time, I had the electrician put
>>>> in 2 220 circuits and 2 120 circuits for my shop (lights were already
>>>> separate). Last night I switched over my table saw to 220. Wow,
>>>> start up is almost instant.
>>>
>>> If it makes that much difference, there was probably something wrong
>>> with the 120V circuit or wire size. If everything was sized properly
>>> there shouldn't really be any difference.
>>
>> Sorry, but that's not correct. At 240V, it will draw half the current that it
>
>> did at 120V. This will provide a much faster start, even if the 120V circuit
>> was properly sized.
>
>I agree it will draw half the current. Assuming properly sized
>conductors such that voltage loss is negligible, why would 6A at 240V
>behave any differently than 12A at 120V? In both cases we're drawing 1440W.

Higher voltage.
>
>Now it's possible that the motor itself could be designed such that it
>runs more efficiently at 240V than at 120V. This isn't necessarily the
>case here, but if it is it would be due to the motor design, not the
>higher voltage as such.
>
>>>> The question: I plan to switch over my bandsaw to 220 as well. What
>>>> happens to the gooseneck lamp? The switch over instructions don't
>>>> mention it. Rewiring for the motor is pretty straightfoward. Am I
>>>> missing something?
>>>
>>> My bandsaw has a separate plug for the lamp. If it's not mentioned
>>> they're probably using the safety ground as a neutral which you're not
>>> really supposed to do.
>>
>> More than "not supposed to do". It's unsafe, because it energizes the ground
>> conductor, thus energizing the chassis of *everything* that's plugged into
>> that circuit. Remember that electricity does not "follow the path of least
>> resistance" as many people believe; rather, it follows all possible paths.
>> That includes the path that goes through the grounding conductor to the
>> chassis of the saw to the saw table to the hands of the operator.
>
>It's true that electricity will follow all possible paths, but the
>higher the resistance of a particular path relative to the other paths
>the less electricity will flow through it. The safety ground is a
>low-resistance path, so most of the electricity will flow through it
>rather than through the operator.

Quite true; OTOH, at 120VAC 60Hz, it takes only a few tens of milliamperes to
interfere with heart rhythms, thus *any* current flowing through the operator
is a potential hazard.

In article <[email protected]>, cavelamb <[email protected]> wrote:
>Doug Miller wrote:
>>
>> Sorry, but that's not correct. At 240V, it will draw half the current that it
>
>> did at 120V. This will provide a much faster start, even if the 120V circuit
>> was properly sized.
>
>Woah up a second here!
>
>That's true if the device is built to run off of 240 Volts.
>
>But if the internal resistance is the same as it was in the 120
>device, it will draw TWICE the amperage - until it "opens".
>
I was under the impression we were talking about reconfiguring a dual-voltage
120/240 motor from 120 to 240. I don't think anybody was suggesting operating
a 120V motor at 240V.

In article <[email protected]>, Jack Stein <[email protected]> wrote:
>[email protected] wrote:
>
>>> I am no electrical expert but iIwould guess it will work OK. If you have
>>> normal residental home wiring you will actually have 2- 110 volt lines going
>>> to your BS. Add them up and you get 220 volts. The lamp will probably
>>> continue to have 1 single 110 volt line going to it.
>
>> It'll work but it's against code and (somewhat) unsafe. To split off
>> 120V you need a neutral.
>
>Just out of dumb curiosity, does this mean if you don't split off 120,
>you don't need a neutral?

Exactly so. Pure 240V circuits (in North America) don't have, or need, a
neutral.

>Normally, with 120 you need 2 wires plus
>ground, hot, common and ground. I don't know zip about 220 but are you
>guys saying 220 can have 2 wires, both hot, plus a ground (no common),

Yes.

>and you connect one of the hots to the light, and what normally would be
>common or neutral to the ground?

No. It will work, but it's unsafe, and violates both the U.S. and Canadian
electrical codes.

> I'm in the dark here, just asking.
>Doesn't 220 always need a common ground (neutral?), just like 120?

It's 240, not 220. And no, it doesn't need a neutral. 120 needs a neutral; so,
if an appliance has both 240V and 120V loads (e.g. electric stove: 240V
heating elements, 120V control circuits; electric dryer: 240V heating
elements, 120V motor) then it needs a four wires: two hots, neutral (for the
120V) and equipment (safety) ground. Pure 240V loads (e.g. a table saw or
welder) need only three: two hots and equipment ground. No neutral.

[email protected] wrote:
> On Sep 1, 9:38 am, dpb <[email protected]> wrote:
>> [email protected] wrote:
>>
>> ...
>>
>>> In most 240 circuits there is no neutral (certainly not those used for
>>> tools). Wiring it to ground isn't a good idea either.
>> Well, split-voltage appliances (ranges, dryers, ...) have run that way
>> for approaching 100 years w/o any significant issues.
>
> They don't anymore, and for a reason.
...

Yes, that reason is Code. Having worked on various Standards groups
over the years, there's a definite tendency to continue to make
modifications simply for the purpose of appearing to continue to do
something and thereby justify the existence of the body.

In the 100 years before, where's the overwhelming evidence it was ever a
problem????

As I said, one can choose but it's certainly not a major actual problem
or there wouldn't have been the history of successful applications (and
lord knows how many still existing appliances????) w/o any issues.

When's the last time you _EVER_ heard of it being the cause of anything?

--

Jack Stein wrote:
...
> Just out of dumb curiosity, does this mean if you don't split off 120,
> you don't need a neutral? Normally, with 120 you need 2 wires plus
> ground, hot, common and ground. I don't know zip about 220 but are you
> guys saying 220 can have 2 wires, both hot, plus a ground (no common),
> and you connect one of the hots to the light, and what normally would be
> common or neutral to the ground? I'm in the dark here, just asking.
> Doesn't 220 always need a common ground (neutral?), just like 120?

By NEC it now does to be Code-compliant.

For roughly 100 years, split-voltage appliances such as ranges, dryers,
etc., used (and were Code-compliant!!!!) the ground as neutral for the
110V side.

Only w/ a relatively recent Code revision was this changed to require
the 4-wire connection in all cases.

While granted it's not current Code, there are zillions of appliances
still in service and certainly a fair number of drill presses and other
machine tools wired the same way. There's absolutely no evidence they
have been a major safety issue in that time period.

Hence, while granted it's no longer within _current_ Code, there's
little real justification for that change being a big deal.

$0.02, etc., etc., ...

--

SonomaProducts.com wrote:
> Slightly OT but relevant.
>
> I am a no nothing in terms of electrical. I can properly wire a plug
> or wall sockets but don't understand the flow, grounding, etc. Just
> never studied it. But on a related topic, I have always wondered why
> my planer and my big sander have a 220 line to run the big moter and a
> 110 line to run the feed table. I asked on of the Mfg's if there was a
> way to wire the 110 from the 220 and they clearly ran and hide, saying
> don't ask us.
>
> So I ask here. Is there some way to "properly" do this? Can I put an
> onboard converter or something. I would really like to eliminate the
> two cords scenario because I am constantly juggling machines because
> of my space restrictions and it is a big hassle with two plugs.
...
They say "don't ask us" because of the the revised NEC Code requirements
discussed in the upthread subthread sidebar discussion.

In all likelihood previously they would have simply used the three-wire
appliance-style arrangement and all would have been happy; now they
can't do that and as Chris explains the hassle of the four-wire
connections they result was they probably decided simply the two-cord
solution was the easiest for them and still meet current Code.

As for what to do; depends in large part on whether you're in a
situation where your shop does have to be current-Code-compliant or this
is a personal shop. I gather your situation is probably the former so
you probably don't want to take the expedient way out and so the only
real choice is probably to either live with it as is or rewire to the
four-conductor supply.

How much of a pain and what you would have to do physically is dependent
on the shop wiring extant now as well as the sizes of the various motors
involved.

In short, as Chris says, you can but it may not be worth the hassles
despite the other existing hassle.

--

In article <0e510de3-eff9-4a0e-9e56-99fc54e6fd62@y10g2000prg.googlegroups.com>, "SonomaProducts.com" <[email protected]> wrote:
>Slightly OT but relevant.
>
>I am a no nothing in terms of electrical. I can properly wire a plug
>or wall sockets but don't understand the flow, grounding, etc. Just
>never studied it. But on a related topic, I have always wondered why
>my planer and my big sander have a 220 line to run the big moter and a
>110 line to run the feed table. I asked on of the Mfg's if there was a
>way to wire the 110 from the 220 and they clearly ran and hide, saying
>don't ask us.
>
>So I ask here. Is there some way to "properly" do this? Can I put an
>onboard converter or something. I would really like to eliminate the
>two cords scenario because I am constantly juggling machines because
>of my space restrictions and it is a big hassle with two plugs.

Yes, there is. How easy it will be depends on whether the 240V circuit (not
"220") supplying the machine has a neutral or not. If not, you'll need a new
circuit.

Assuming that you have a four-wire 240V circuit available (two hot legs,
neutral, and ground), install a 4-conductor receptacle on that circuit, and a
4-conductor plug and cord on the machine. Connect the planer motor to the two
hot wires; connect the feed-table motor to one of the hot wires (it doesn't
matter which one) and the neutral wire. Connect the ground wire to the frame
of the unit.

In article <[email protected]>, Chris Friesen <[email protected]> wrote:
>On 09/01/2009 11:08 AM, Doug Miller wrote:
>> In article <[email protected]>, Chris Friesen
> <[email protected]> wrote:
>
>>> I agree it will draw half the current. Assuming properly sized
>>> conductors such that voltage loss is negligible, why would 6A at 240V
>>> behave any differently than 12A at 120V? In both cases we're drawing 1440W.
>>
>> Higher voltage.
>
>Huh? Voltage is just potential.

Yes, that's right. That's why the motor will start more quickly with higher
voltage.

Another alternative is to add a second lamp of identical wattage
and wire them in series.


--
There is always an easy solution to every human problem -- neat,
plausible, and wrong." (H L Mencken)

Larry Wasserman - Baltimore Maryland - lwasserm(a)sdf. lonestar. org

In article <[email protected]>, dpb <[email protected]> wrote:
>Jack Stein wrote:
>....
>> Just out of dumb curiosity, does this mean if you don't split off 120,
>> you don't need a neutral? Normally, with 120 you need 2 wires plus
>> ground, hot, common and ground. I don't know zip about 220 but are you
>> guys saying 220 can have 2 wires, both hot, plus a ground (no common),
>> and you connect one of the hots to the light, and what normally would be
>> common or neutral to the ground? I'm in the dark here, just asking.
>> Doesn't 220 always need a common ground (neutral?), just like 120?
>
>By NEC it now does to be Code-compliant.

That is incorrect. Pure 240V circuits do *not* need a neutral conductor.
>
>For roughly 100 years, split-voltage appliances such as ranges, dryers,
>etc., used (and were Code-compliant!!!!) the ground as neutral for the
>110V side.
>
>Only w/ a relatively recent Code revision was this changed to require
>the 4-wire connection in all cases.

No, only in those cases where the circuit supplies both 240V and 120V loads.

[email protected] wrote:
...
> Just don't do it, and stop telling others to violate safety codes!
> You're being irresponsible!

I'm not "telling" anybody to do anything--I'm simply pointing out it's
been common practice until quite recently.

As for your experience, there has always been an external safety ground
supplied on driers; whether one bothered to hook them up is another matter.

I stand by my contention the 3-wire split circuit existed in such
numbers for so long that if it were truly a dangerous practice it would
have taken far less time than it did for it to finally percolate its way
to the radar screen.

I'll also reassert given my experience on Standards committees there is
that aforementioned need to find _something_ to modify...they finally
got to the bottom of the barrel where this became one thing they could
find to change.

again, imo, ymmv, etc., etc., etc., ...

And, yes, Code now mandates 4-wire connections; others make your own
determination, I'm not advocating you violate Code willy-nilly but the
subject of a work light on a drill press...

--

Doug Miller wrote:
...
> That is incorrect. Pure 240V circuits do *not* need a neutral conductor.

You misread what I was talking about--I was talking of the split
volatage circuit...

...

>> Only w/ a relatively recent Code revision was this changed to require
>> the 4-wire connection in all cases.
>
> No, only in those cases where the circuit supplies both 240V and 120V loads.

Again, that "all" was specifically the "all" I was speaking of.

--

In article <[email protected]>, dpb <[email protected]> wrote:
>Doug Miller wrote:
>....
>> That is incorrect. Pure 240V circuits do *not* need a neutral conductor.
>
>You misread what I was talking about--I was talking of the split
>volatage circuit...

But you were responding to a question that did not involve dual-voltage
circuits.

Sounds like we're on the same page, though, just neither of us completely
clear on who was talking about what.

Tom Veatch wrote:
...
> I'm not sure if "dpb" was referring to me, or not, but I found that
> with my DP. Motor can be rewired for 240, but the wiring harness has
> no provisions for a neutral feed. ...
> Several years ago, on the manufacturer's web site, the PDF manual for
> the DP, as a part of the diagram for rewiring the tool for 240, showed
> the work light socket being changed to connect across one hot lead and
> the EGC to provide 120 to the lamp. I went back to the site at a later
> date, and that part of the diagram was no longer there. It now shows
> only a configuration that connects the lamp socket across the
> non-ground leads with no direct connection to the EGC. I suspect the
> diagram was deleted as a result of UL requirements.

...

Yes, it was you, Tom; that's the description I recalled, just couldn't
recall who...

I'm willing to bet that's the same scenario OP has--a machine built
before the change and documentation of same removed to avoid the issue
from their end.

--

Doug Miller wrote:
> In article <[email protected]>, dpb <[email protected]> wrote:
>> Doug Miller wrote:
>> ....
>>> That is incorrect. Pure 240V circuits do *not* need a neutral conductor.
>> You misread what I was talking about--I was talking of the split
>> volatage circuit...
>
> But you were responding to a question that did not involve dual-voltage
> circuits.

Not the way I read it--the whole thread was about split voltage circuits
and the question was about when needed a neutral as well as ground (or
at least that's what I thought (and still think) the question was)...

--

SonomaProducts.com wrote:
> Thanks guys. This is my home shop but I don't want to do the 4 wire
> work so I guess I'll live with it. It just seems kind of silly. Maybe
> I can find some 220 fractional hp motors to run my feed tables.
...

How large _are_ the 110 loads? To keep the one particular individual
off my back note I'm _NOT_ telling you to do this but there still _is_
the unmentionable solution... :)

--

Scott Lurndal wrote:
...
> There has not always been a grounded conductor on driers, only a grounding
> conductor. ...

Read what I wrote instead of looking for an axe to grind and to try to
show how shumart thou art... :(

I didn't write "grounded conductor" I wrote "external safety
ground"--two different things but the latter solves a large portion of
the problems (but they were often never connected or to an adequate
ground in practice)...

--

In article <[email protected]>, dpb <[email protected]> wrote:
>Doug Miller wrote:
>> In article <[email protected]>, dpb <[email protected]>
> wrote:
>>> Doug Miller wrote:
>>> ....
>>>> That is incorrect. Pure 240V circuits do *not* need a neutral conductor.
>>> You misread what I was talking about--I was talking of the split
>>> volatage circuit...
>>
>> But you were responding to a question that did not involve dual-voltage
>> circuits.
>
>Not the way I read it--the whole thread was about split voltage circuits
>and the question was about when needed a neutral as well as ground (or
>at least that's what I thought (and still think) the question was)...
>
OK, maybe I got mixed up, but I thought you were responding to the guy who
asked if 240V circuits needed a neutral, as a general question, not in
reference to any specific equipment.

Anyway, we agree about the wiring requirements.

Leon wrote:
> "Chris Friesen" <[email protected]> wrote in message
> news:[email protected]...
>>>> Huh? Voltage is just potential.
>>>
>>> Yes, that's right. That's why the motor will start more quickly with
>>> higher
>>> voltage.
>>
>> I hope that's supposed to be a joke.
>>
>> Chris
>
>
> Ok, again, I am no electrical expert but in my coloring book world of
> looking at electricity, You have less resistance up to the motor
> using 240 vs 120. Each of the 2 wires carrying 120 volts is carrying
> 1/2 the load up to the motor than the single wire in a 120 volt
> application.

No, each of the wires in a 220v circuit is carrying the same current, one
carries it in, one carries it out, just like with 110.

Doug Miller wrote:
> Jack Stein wrote:

>> Just out of dumb curiosity, does this mean if you don't split off 120,
>> you don't need a neutral?

> Exactly so. Pure 240V circuits (in North America) don't have, or need, a
> neutral.

Doug, thanks for your clear reply. I use the same coloring book Leon
uses when it comes to electricity so any enlightenment is welcome. I
know enough to wire 120 circuits in my sleep, without killing me, or
anyone else so far, but

>> Normally, with 120 you need 2 wires plus
>> ground, hot, common and ground. I don't know zip about 220 but are you
>> guys saying 220 can have 2 wires, both hot, plus a ground (no common),

> Yes.

OK, but in my 120 coloring book, electricity comes in the hot wire, and
goes out the neutral wire, thus the circuit, or loop is completed. How
does this work with 220?

>> and you connect one of the hots to the light, and what normally would be
>> common or neutral to the ground?

> No. It will work, but it's unsafe, and violates both the U.S. and Canadian
> electrical codes.

It sounds unsafe to me to be connecting a common ground to the safety
ground. In my small world, most of the time the safety ground is a bare
copper wire, not even insulated. In a 120 circuit, it would seem
anytime the load is hot, the common wire is carrying current back to
ground? Also, the motor frame, electrical box etc is connected to the
safety ground, would this mean the box/motor frame is hot whenever the
the load is on if you used the safety ground as a neutral wire?

In Somona's instance, he has his 240 motor hooked up, plus he has a 120
motor running the feed rollers. Assuming a 3 wire 240 hookup, he could
(unsafely, but common in the past?) hook one hot wire to the 120 motor,
and use the safety ground as the neutral wire for the 120 motor. If he
did this, the safety ground would always be carrying juice when the
motor was running, and ergo, anything hooked up to the safety ground,
the motor frame, wiring boxes and so on, would also be carrying juice?
Is that correct? If so, it sure sounds too dangerous to have been done
routinely for 100 years? I'm sure I'm missing something here, but hey,
I'm just trying to color in some of the pages:-)

>> I'm in the dark here, just asking.
>> Doesn't 220 always need a common ground (neutral?), just like 120?
>
> It's 240, not 220.

I'm glad you said that. I was thinking damn, I don't even know if my
service is 110, 115 or 120? I see all sorts of things on electrical
devices. Even this thread is stating 220, or 2 110 lines? You are the
only one to correct it so far. No wonder I'm so confused... still alive
though:-)

And no, it doesn't need a neutral. 120 needs a neutral;

Again, this confuses me. How is the circuit completed in a 240 circuit?
2 120 lines come from the source to the motor, then what? Where does it
go? I bet it has something to do with phase? Each line takes turns
being the neutral? If not, I'm lost, if so, still lost:-)

--
Jack
Using FREE News Server: http://www.eternal-september.org/
http://jbstein.com

In article <[email protected]>,
Chris Friesen <[email protected]> wrote:
>
>As Dan Coby pointed out, with a 314ft run of 12awg you'd have 6.8% more
>power available due to reduced supply losses if drawing 10A at 120V.
>With a typical shop wiring configuration the difference would be less.
>
>There's no way that the reduction in supply losses results in a "wow,
>start up is almost instant" sort of difference when switching to 240V
>unless the 120V circuit was way undersized.
>
>Chris
>
>
>

During motor startup the current could be more like 40-60 amps. Breakers
are designed to allow for momentary inrush currents of that magnitude,
maybe even higher. What does that 6.8% figure change to when you
do your calculations on 40 amps instead of 10?


--
There are no stupid questions, but there are lots of stupid answers.

Larry Wasserman - Baltimore Maryland - lwasserm(a)sdf. lonestar. org

In article <[email protected]>, Jack Stein <[email protected]> wrote:
>Doug Miller wrote:
>> Jack Stein wrote:
>
>>> Just out of dumb curiosity, does this mean if you don't split off 120,
>>> you don't need a neutral?
>
>> Exactly so. Pure 240V circuits (in North America) don't have, or need, a
>> neutral.
>
>Doug, thanks for your clear reply. I use the same coloring book Leon
>uses when it comes to electricity so any enlightenment is welcome. I
>know enough to wire 120 circuits in my sleep, without killing me, or
>anyone else so far, but
>
>>> Normally, with 120 you need 2 wires plus
>>> ground, hot, common and ground. I don't know zip about 220 but are you
>>> guys saying 220 can have 2 wires, both hot, plus a ground (no common),
>
>> Yes.
>
>OK, but in my 120 coloring book, electricity comes in the hot wire, and
>goes out the neutral wire, thus the circuit, or loop is completed. How
>does this work with 220?

Same way. Really. Only difference is that the two wires have a 240V potential
between them, not 120V, and neither one is grounded.
>
>>> and you connect one of the hots to the light, and what normally would be
>>> common or neutral to the ground?
>
>> No. It will work, but it's unsafe, and violates both the U.S. and Canadian
>> electrical codes.
>
>It sounds unsafe to me to be connecting a common ground to the safety
>ground. In my small world, most of the time the safety ground is a bare
>copper wire, not even insulated. In a 120 circuit, it would seem
>anytime the load is hot, the common wire is carrying current back to
>ground?

Right -- but let's use some different terminology. The common-usage term for
what you call "common ground" is "neutral", and for what you call "safety
ground", "ground". The official terms as used in the National Electrical Code
(NEC) are "grounded conductor" and "equipment grounding conductor"
respectively.

> Also, the motor frame, electrical box etc is connected to the
>safety ground, would this mean the box/motor frame is hot whenever the
>the load is on if you used the safety ground as a neutral wire?

Correct. Sort of. It *is* energized, but since it's also connected to ground,
there's not nearly the same danger in touching it as there would be in
touching the hot wire. The danger comes from the fact that electricity will
follow all possible paths, and a person touching such an energized case forms
a second, parallel path to ground through his body. Such a path has a much
higher resistance than the copper wire, and thus passes only a fraction of the
current that the wire does. The problem is that 20 or 30 milliamps can stop a
heart.
>
>In Somona's instance, he has his 240 motor hooked up, plus he has a 120
>motor running the feed rollers. Assuming a 3 wire 240 hookup, he could
>(unsafely, but common in the past?) hook one hot wire to the 120 motor,
>and use the safety ground as the neutral wire for the 120 motor. If he
>did this, the safety ground would always be carrying juice when the
>motor was running, and ergo, anything hooked up to the safety ground,
>the motor frame, wiring boxes and so on, would also be carrying juice?
>Is that correct?

Yes, that is correct, but as I noted above, the level of current that passes
through the body is much lower than in the copper wire.

> If so, it sure sounds too dangerous to have been done
>routinely for 100 years? I'm sure I'm missing something here, but hey,
>I'm just trying to color in some of the pages:-)

It's nowhere nearly as dangerous as having the hot wire connected to the
equipment chassis. But it's also certainly less than fully safe.

>
>>> I'm in the dark here, just asking.
>>> Doesn't 220 always need a common ground (neutral?), just like 120?
>>
>> It's 240, not 220.
>
>I'm glad you said that. I was thinking damn, I don't even know if my
>service is 110, 115 or 120? I see all sorts of things on electrical
>devices. Even this thread is stating 220, or 2 110 lines? You are the
>only one to correct it so far. No wonder I'm so confused... still alive
>though:-)
>
>And no, it doesn't need a neutral. 120 needs a neutral;
>
>Again, this confuses me. How is the circuit completed in a 240 circuit?

Same way it's completed in any other circuit: by connecting together two
points that have a voltage difference between them.

>2 120 lines come from the source to the motor, then what? Where does it
>go? I bet it has something to do with phase? Each line takes turns
>being the neutral? If not, I'm lost, if so, still lost:-)

You don't need a neutral for current to flow; you just need the two sides of
the circuit to have a voltage difference between them.

The utility company brings somewhere around 4KV to your utility pole,
connected to the primary windings of a step-down transformer. This transformer
reduces the 4KV from the utility company to 240V. There are *three* wires
attached to the secondary windings: one at each end, and one in the middle.
The two at the ends are 240V apart, and the one in the middle is 120V from
either of them. Let's color the wires connected to the ends of the secondary
coil black and red, and the one connected to the middle, white. There's 120V
between the black and white wires, 120V between the red and white, and 240V
between the black and red. Now tie the white one to a copper rod that's driven
into the ground, to ensure that it's always at true earth potential.

There's your 240/120 North American residential electrical service.

The U.S., Canada, and Mexico use substantially the same system. Almost nobody
else does.

In article <[email protected]>, Tom Veatch <[email protected]> wrote:
[...]
>And to pick another nit, those are RMS
>values, not the actual instantaneous voltages. RMS = the square root
>of the integral of the square of the instantaneous voltage with
>respect to time over one cycle. Not sure of the actual maximum
>instantaneous voltage, but seem to recall it's somewhere in the
>neighborhood of 140 to 150 volts on each hot line.)

120V * sqrt(2) = 169.7V

Doug, again thanks for taking the time to explain all this for me. Very
helpful and informative.

Jack

Doug Miller wrote:
> In article <[email protected]>, Jack Stein <[email protected]> wrote:
>> Doug Miller wrote:
>>> Jack Stein wrote:
>>>> Just out of dumb curiosity, does this mean if you don't split off 120,
>>>> you don't need a neutral?
>>> Exactly so. Pure 240V circuits (in North America) don't have, or need, a
>>> neutral.
>> Doug, thanks for your clear reply. I use the same coloring book Leon
>> uses when it comes to electricity so any enlightenment is welcome. I
>> know enough to wire 120 circuits in my sleep, without killing me, or
>> anyone else so far, but
>>
>>>> Normally, with 120 you need 2 wires plus
>>>> ground, hot, common and ground. I don't know zip about 220 but are you
>>>> guys saying 220 can have 2 wires, both hot, plus a ground (no common),
>>> Yes.
>> OK, but in my 120 coloring book, electricity comes in the hot wire, and
>> goes out the neutral wire, thus the circuit, or loop is completed. How
>> does this work with 220?
>
> Same way. Really. Only difference is that the two wires have a 240V potential
> between them, not 120V, and neither one is grounded.
>>>> and you connect one of the hots to the light, and what normally would be
>>>> common or neutral to the ground?
>>> No. It will work, but it's unsafe, and violates both the U.S. and Canadian
>>> electrical codes.
>> It sounds unsafe to me to be connecting a common ground to the safety
>> ground. In my small world, most of the time the safety ground is a bare
>> copper wire, not even insulated. In a 120 circuit, it would seem
>> anytime the load is hot, the common wire is carrying current back to
>> ground?
>
> Right -- but let's use some different terminology. The common-usage term for
> what you call "common ground" is "neutral", and for what you call "safety
> ground", "ground". The official terms as used in the National Electrical Code
> (NEC) are "grounded conductor" and "equipment grounding conductor"
> respectively.
>
>> Also, the motor frame, electrical box etc is connected to the
>> safety ground, would this mean the box/motor frame is hot whenever the
>> the load is on if you used the safety ground as a neutral wire?
>
> Correct. Sort of. It *is* energized, but since it's also connected to ground,
> there's not nearly the same danger in touching it as there would be in
> touching the hot wire. The danger comes from the fact that electricity will
> follow all possible paths, and a person touching such an energized case forms
> a second, parallel path to ground through his body. Such a path has a much
> higher resistance than the copper wire, and thus passes only a fraction of the
> current that the wire does. The problem is that 20 or 30 milliamps can stop a
> heart.
>> In Somona's instance, he has his 240 motor hooked up, plus he has a 120
>> motor running the feed rollers. Assuming a 3 wire 240 hookup, he could
>> (unsafely, but common in the past?) hook one hot wire to the 120 motor,
>> and use the safety ground as the neutral wire for the 120 motor. If he
>> did this, the safety ground would always be carrying juice when the
>> motor was running, and ergo, anything hooked up to the safety ground,
>> the motor frame, wiring boxes and so on, would also be carrying juice?
>> Is that correct?
>
> Yes, that is correct, but as I noted above, the level of current that passes
> through the body is much lower than in the copper wire.
>
>> If so, it sure sounds too dangerous to have been done
>> routinely for 100 years? I'm sure I'm missing something here, but hey,
>> I'm just trying to color in some of the pages:-)
>
> It's nowhere nearly as dangerous as having the hot wire connected to the
> equipment chassis. But it's also certainly less than fully safe.
>
>>>> I'm in the dark here, just asking.
>>>> Doesn't 220 always need a common ground (neutral?), just like 120?
>>> It's 240, not 220.
>> I'm glad you said that. I was thinking damn, I don't even know if my
>> service is 110, 115 or 120? I see all sorts of things on electrical
>> devices. Even this thread is stating 220, or 2 110 lines? You are the
>> only one to correct it so far. No wonder I'm so confused... still alive
>> though:-)
>>
>> And no, it doesn't need a neutral. 120 needs a neutral;
>>
>> Again, this confuses me. How is the circuit completed in a 240 circuit?
>
> Same way it's completed in any other circuit: by connecting together two
> points that have a voltage difference between them.
>
>> 2 120 lines come from the source to the motor, then what? Where does it
>> go? I bet it has something to do with phase? Each line takes turns
>> being the neutral? If not, I'm lost, if so, still lost:-)
>
> You don't need a neutral for current to flow; you just need the two sides of
> the circuit to have a voltage difference between them.
>
> The utility company brings somewhere around 4KV to your utility pole,
> connected to the primary windings of a step-down transformer. This transformer
> reduces the 4KV from the utility company to 240V. There are *three* wires
> attached to the secondary windings: one at each end, and one in the middle.
> The two at the ends are 240V apart, and the one in the middle is 120V from
> either of them. Let's color the wires connected to the ends of the secondary
> coil black and red, and the one connected to the middle, white. There's 120V
> between the black and white wires, 120V between the red and white, and 240V
> between the black and red. Now tie the white one to a copper rod that's driven
> into the ground, to ensure that it's always at true earth potential.
>
> There's your 240/120 North American residential electrical service.
>
> The U.S., Canada, and Mexico use substantially the same system. Almost nobody
> else does.


--
Jack
Using FREE News Server: http://www.eternal-september.org/
http://jbstein.com

On Tue, 01 Sep 2009 16:40:47 -0600, Chris Friesen
<[email protected]> wrote:

>On 09/01/2009 01:37 PM, [email protected] wrote:
>> On Sep 1, 1:02 pm, Chris Friesen <[email protected]> wrote:
>
>>> Huh? Voltage is just potential. You need power to do work, and the
>>> amount of power (and thus the amount of work that can be done) is the
>>> same in each case.
>>
>> Power is proportional to the *square* of the potential.
>
>You forgot the whole "divided by resistance" part. and Potential
>divided by resistance is current.

The resistance of the wire is the same. ...unless you're wiring your
house with 16AWG.

>P=(V^2)/R = V*I
>
>As Tom Veatch indicated, in the typical case when you rewire the motor
>for 240V you are also increasing the resistance so that the final power
>ends up the same.

No, you're not. The house wiring resistance is the same. Any drop in
the house wiring will shop up in the motor power (squared).

>>> Faster startup implies that the mechanical work of spinning up the motor
>>> is done in a shorter amount of time. This means either the motor is
>>> more efficient at 240V or else it's drawing more power. In both cases
>>> this would be due to motor design, not simply higher voltage.
>>
>> Not more efficient, but does have more *power* available, all else
>> being the same.
>
>Again...why would this be the case? The available electrical power of a
>motor drawing 6A at 240V is exactly the same as one drawing 12A at 120V.

Wire resistance.

"J. Clarke" <[email protected]> wrote in message
news:[email protected]...
> Leon wrote:
>> "Chris Friesen" <[email protected]> wrote in message
>> news:[email protected]...
>>>>> Huh? Voltage is just potential.
>>>>
>>>> Yes, that's right. That's why the motor will start more quickly with
>>>> higher
>>>> voltage.
>>>
>>> I hope that's supposed to be a joke.
>>>
>>> Chris
>>
>>
>> Ok, again, I am no electrical expert but in my coloring book world of
>> looking at electricity, You have less resistance up to the motor
>> using 240 vs 120. Each of the 2 wires carrying 120 volts is carrying
>> 1/2 the load up to the motor than the single wire in a 120 volt
>> application.
>
> No, each of the wires in a 220v circuit is carrying the same current, one
> carries it in, one carries it out, just like with 110.
>

It was a coloring book explanation.

On 09/02/2009 09:34 AM, [email protected] wrote:
> On Sep 2, 9:29 am, Chris Friesen <[email protected]> wrote:

>> Aside from supply losses which have been discussed extensively :) in
>> this thread, there's no inherent reason why a motor would operate more
>> efficiently at higher voltage.
>
> ...and it is exactly the supply losses that make the difference, so...

As Dan Coby pointed out, with a 314ft run of 12awg you'd have 6.8% more
power available due to reduced supply losses if drawing 10A at 120V.
With a typical shop wiring configuration the difference would be less.

There's no way that the reduction in supply losses results in a "wow,
start up is almost instant" sort of difference when switching to 240V
unless the 120V circuit was way undersized.

Chris