Shop wiring

In article <K5seb.471566$Oz4.291108@rwcrnsc54>,
Wm Gardner <[email protected]> wrote:
>
>
[[.. munch ..]]

>#2- The answer to this is hinted at above. Lets explain with an example.....
>#12 conductors are rated at 20 amps. Were you to put 20 amp loads on each of
>these circuits, but have only one return, you would actually be handling 40
>amps through the return line. Definite code violation and unless you are
>running GFCI breaker it would work until the fire started......


WRONGO! the neutral only carries the _difference_ between the load
on the two hot wired.

If the two hot leads are 180 degrees out of phase, and you have equal
110V loads on each leg, the current carried on the neutral will be *ZERO*.

Life is a little more complicated if you have two phases of 3-phase
power. In that scenario, with balanced 110V loads, you will have some
current-flow in the neutral, but it is _substantially_ less than the
flow in the hot wires. Without digging out references, I want to say
that it's like 16% of the flow in the hot wires.

ELA wrote:

<snip>

> Pulling 120VAC off of the 208VAC at the saw is not a good idea. Run a
> separarte 20AMP circuit. The circuit breaker is there to protect the wire
> NOT the device. If you have a 30AMP circuit for your saw, which btw is good
> for about 5HP @ 208VAC, you'll need 10AWG wire.

208 VAC is three phase.

--
Jack Novak
Buffalo, NY - USA

Christopher wrote:

> "Morgans" <[email protected]> wrote in message
> news:[email protected]...
>
>
>>Not a good idea to have portions of two circuits in one box. Keep those
>
> two
>
>>different 110's separate. My gut tells me there are other reasons, too,
>>but I can't think of them all now.
>>
>>Another reason is that you will want to wire the table saw for at least 25
>>amps, and that would be too large for 110 volt devices, and the wires
>
> would
>
>>be too heavy to deal with.
>>
>>Wire for the table saw with the two hot legs, and a neutral and a ground.
>>You could then hook up a 110 outlet on the side of the saw hooked into the
>>magnetic starter for your dust collector.
>>--
>>Jim in NC
>>
>
>
> I thought it was common practice to run two hot wires plus the neutral and
> ground and alternate the circuits as you go down the outlets. I can't
> remember if you have to have two neutral wires as well though. It's seems
> like you would need two or one wire would have to handle current flow for
> two different circuits. I understand DC circuits pretty well but AC
> behavior is not something I know very well.
>
> I don't understand what you mean by 25 amp circuits being "too large" for
> 110volts. That's just the amperage the circuit will provide before the
> breaker trips. A 110V device will not draw more current than it needs no
> matter how many amps the circuit is capable of providing.
>
> -Chris
>
>
Chris,
What you suggest violates code and good wiring practice. The 220v
circuit should only be for 220v devices and have a dedicated breaker
that will trip both sides in the event of an overload. The 110v circuits
should each have a dedicated breaker. If there is not enough room in
the main panel, a subpanel should be used.
I would run #10 wire for the 220v circuit and #12 for the 110v circuits.
Regards
Hank



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Thank-you for clarifying this for everyone. I think there was some confusion
caused by my original response to Christopher. My reference was to 120v
circuits only (no mention of 240v in my post).

Thanks again,
Bill

--

"Do what you can, with what you have, where you are."
-Theodore Roosevelt


"Al Reid" <[email protected]> wrote in message
news:[email protected]...
> To be clear consider this:
>
> Two (2) 120VAC circuits fed from two independent breakers WILL require a
separate neutral per circuit by code even though, if by
> chance or design, the breakers are installed on different legs of a 240V
panel.
>
> In a single 240VAC 3 wire feeder (2 hots, a neutral and a ground fed from
a 2 pole breaker) with 120V loads attached, the neutral
> will carry only the difference in the currents. That is why the wire size
of the hots and neutral are the same. Worst case, one
> hot is fully loaded and the other is not loaded, the neutral carries 100%
of the return current. Any load subsequently applied to
> the other leg will only reduce the current in the neutral.
>
> Hope this helps.
>
> Al
>
> "Robert Bonomi" <bonomi@c-ns.> wrote in message
news:[email protected]...
> > In article <K5seb.471566$Oz4.291108@rwcrnsc54>,
> > Wm Gardner <[email protected]> wrote:
> > >
> > >
> > [[.. munch ..]]
> >
> > >#2- The answer to this is hinted at above. Lets explain with an
example.....
> > >#12 conductors are rated at 20 amps. Were you to put 20 amp loads on
each of
> > >these circuits, but have only one return, you would actually be
handling 40
> > >amps through the return line. Definite code violation and unless you
are
> > >running GFCI breaker it would work until the fire started......
> >
> >
> > WRONGO! the neutral only carries the _difference_ between the load
> > on the two hot wired.
> >
> > If the two hot leads are 180 degrees out of phase, and you have equal
> > 110V loads on each leg, the current carried on the neutral will be
*ZERO*.
> >
> > Life is a little more complicated if you have two phases of 3-phase
> > power. In that scenario, with balanced 110V loads, you will have some
> > current-flow in the neutral, but it is _substantially_ less than the
> > flow in the hot wires. Without digging out references, I want to say
> > that it's like 16% of the flow in the hot wires.
> >
>
>

In article <[email protected]>,
Al Reid <[email protected]> wrote:
>
>
>To be clear consider this:
>
>Two (2) 120VAC circuits fed from two independent breakers WILL require a
>separate neutral per circuit by code even though, if by
>chance or design, the breakers are installed on different legs of a 240V
>panel.

Got a cite? I just completed an installation using a common neutral w/
independant single-pole breakers (on opposite phases -- wiring color-coded),
which the city inspector _has_ signed off on.

>In a single 240VAC 3 wire feeder (2 hots, a neutral and a ground fed
>from a 2 pole breaker) with 120V loads attached, the neutral
>will carry only the difference in the currents. That is why the wire
>size of the hots and neutral are the same. Worst case, one
>hot is fully loaded and the other is not loaded, the neutral carries
>100% of the return current. Any load subsequently applied to
>the other leg will only reduce the current in the neutral.
>
>Hope this helps.
>
>Al
>
>"Robert Bonomi" <bonomi@c-ns.> wrote in message
>news:[email protected]...
>> In article <K5seb.471566$Oz4.291108@rwcrnsc54>,
>> Wm Gardner <[email protected]> wrote:
>> >
>> >
>> [[.. munch ..]]
>>
>> >#2- The answer to this is hinted at above. Lets explain with an example.....
>> >#12 conductors are rated at 20 amps. Were you to put 20 amp loads on each of
>> >these circuits, but have only one return, you would actually be handling 40
>> >amps through the return line. Definite code violation and unless you are
>> >running GFCI breaker it would work until the fire started......
>>
>>
>> WRONGO! the neutral only carries the _difference_ between the load
>> on the two hot wired.
>>
>> If the two hot leads are 180 degrees out of phase, and you have equal
>> 110V loads on each leg, the current carried on the neutral will be *ZERO*.
>>
>> Life is a little more complicated if you have two phases of 3-phase
>> power. In that scenario, with balanced 110V loads, you will have some
>> current-flow in the neutral, but it is _substantially_ less than the
>> flow in the hot wires. Without digging out references, I want to say
>> that it's like 16% of the flow in the hot wires.
>>
>
>

I seperated the basement into 2 sections, hand tools and machines. Ran one
circuit for each, but put the DC on the hand circuit to cut the load. I am
only one person so can only run 1 machine at a time. All is 12 gage with 20
amp breakers. When I got the 3 hp saw, ran a seperate circuit for it.

"Christopher" <[email protected]> wrote in message
news:[email protected]...
> I'm about to run some conduit and wiring in my garage for additional AC
> outlets. I'm fine with the basics but I want to allow for a 220V outlet
for
> that new tablesaw I hope to have one of these days. I want to run hot
wires
> from two different breakers and alternate 110 outlets between the two
> circuits but is it OK to end the run with the two hot wires going to the
220
> volt outlet? It seems like it should be just fine but I thought I would
ask
> before going out to buy the stuff. Is there any problem with using one of
> the 110 outlets at the same time I use the tablesaw connected across both
of
> them? Assuming I don't draw more amps than the individual circuit can
> handle, of course.
>
> Another question I have is whether there is any type of gadget available
> that will turn power on to my dust collector (shopvac) when I use the
table
> saw and is there any special wiring I should consider in advance for
> something like that.
>
> I know this isn't an electrical forum but I also know many here have done
> this before.
>
> Thanks!
>
> -Chris
>
>

In article <[email protected]>, bonomi@c-ns. (Robert Bonomi) wrote:
>In article <[email protected]>,
>Al Reid <[email protected]> wrote:
>>To be clear consider this:
>>
>>Two (2) 120VAC circuits fed from two independent breakers WILL require a
>>separate neutral per circuit by code even though, if by
>>chance or design, the breakers are installed on different legs of a 240V
>>panel.
>
>Got a cite? I just completed an installation using a common neutral w/
>independant single-pole breakers (on opposite phases -- wiring color-coded),
>which the city inspector _has_ signed off on.
>

This is prohibited, at least in homes, by Article 210-4(b): "In dwelling
units, a multiwire branch circuit supplying more than one device or equipment
on the same yoke shall be provided with a means to disconnect simultaneously
all ungrounded conductors at the panelboard where the branch circuit
originated." [1993 NEC]


--
Regards,
Doug Miller (alphageek-at-milmac-dot-com)

Christopher,

It depends on how you are wiring. When I wired the receps in my garage I ran
two complete circuits through the conduit runs. Meaning that I also had two
"neutral" or "return" conductors. There are two reasons to do this with 110v
circuits.
#1- I had to as I am using GFCI breakers. They would trip instantly if I ran
only one common as there would be a difference in current between the supply
and the return.
#2- The answer to this is hinted at above. Lets explain with an example.....
#12 conductors are rated at 20 amps. Were you to put 20 amp loads on each of
these circuits, but have only one return, you would actually be handling 40
amps through the return line. Definite code violation and unless you are
running GFCI breaker it would work until the fire started......

While I agree with your statement that a device will only pull the amount of
current it actually needs, I believe Jim was referring to the fact that you
would need to use fairly heavy (#10 or better) conductors to handle this
load. Were you to connect lighter wire (#12 or #14) to a 25 amp breaker you
have committed a NEC violation. #12 is rated for 20 amps, #14 is rated for
15 amps. That you do not intend to draw 25 amps down that line does not
matter. The potential is there, it could happen. An additional thing to
consider is how difficult it will be to find 110v receps rated for above 20
amps. Again, draw more than the rated amperage from a recep and..........

I hope this helps. Absolutely no offense is intended but if these
explanations do not make sense then it may be time to consult a
professional. Electricity is not something to mess around with. If you have
other questions you could try the Taunton book "Wiring a House" by Rex
Cauldwell. It is a really good resource. Your local library probably has it
but it is worth the $15 to buy your own copy that reflects the 2002 NEC
changes.

Good luck,
Bill

--

"Do what you can, with what you have, where you are."
-Theodore Roosevelt


"Christopher" <[email protected]> wrote in message
news:[email protected]...
> "Morgans" <[email protected]> wrote in message
> news:[email protected]...
>
> > Not a good idea to have portions of two circuits in one box. Keep those
> two
> > different 110's separate. My gut tells me there are other reasons,
too,
> > but I can't think of them all now.
> >
> > Another reason is that you will want to wire the table saw for at least
25
> > amps, and that would be too large for 110 volt devices, and the wires
> would
> > be too heavy to deal with.
> >
> > Wire for the table saw with the two hot legs, and a neutral and a
ground.
> > You could then hook up a 110 outlet on the side of the saw hooked into
the
> > magnetic starter for your dust collector.
> > --
> > Jim in NC
> >
>
> I thought it was common practice to run two hot wires plus the neutral and
> ground and alternate the circuits as you go down the outlets. I can't
> remember if you have to have two neutral wires as well though. It's seems
> like you would need two or one wire would have to handle current flow for
> two different circuits. I understand DC circuits pretty well but AC
> behavior is not something I know very well.
>
> I don't understand what you mean by 25 amp circuits being "too large" for
> 110volts. That's just the amperage the circuit will provide before the
> breaker trips. A 110V device will not draw more current than it needs no
> matter how many amps the circuit is capable of providing.
>
> -Chris
>
>

Wade Lippman wrote:
> In residential electrical, you never run more than one device off a 240v
> circuit. I don't know if there is a specific code against it, or if it is
> just a matter of what is practical; all the wiring on the circuit (including
> the outlets) has to be capable of handling the current the breaker is rated
> at, so it might not even be possible.
>

You can run multiple outlets on a 240 circuit. There are no
more US Electrical code restriction on that than there are
on a 120 circuit.

The majority of the world except North America and Japan has
homes wired 220-240 volt with multiple outlets on nominal
240v circuits.

Some countries even run three phase to residences.

Dick



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My courses in electrical engineering are many years behind me, will research
what you have added here. However, this does not change the fact that
Christopher's plan is a clear NEC violation.....

Thanks,
Bill

--

"Do what you can, with what you have, where you are."
-Theodore Roosevelt


"Robert Bonomi" <bonomi@c-ns.> wrote in message
news:[email protected]...
> In article <K5seb.471566$Oz4.291108@rwcrnsc54>,
> Wm Gardner <[email protected]> wrote:
> >
> >
> [[.. munch ..]]
>
> >#2- The answer to this is hinted at above. Lets explain with an
example.....
> >#12 conductors are rated at 20 amps. Were you to put 20 amp loads on each
of
> >these circuits, but have only one return, you would actually be handling
40
> >amps through the return line. Definite code violation and unless you are
> >running GFCI breaker it would work until the fire started......
>
>
> WRONGO! the neutral only carries the _difference_ between the load
> on the two hot wired.
>
> If the two hot leads are 180 degrees out of phase, and you have equal
> 110V loads on each leg, the current carried on the neutral will be *ZERO*.
>
> Life is a little more complicated if you have two phases of 3-phase
> power. In that scenario, with balanced 110V loads, you will have some
> current-flow in the neutral, but it is _substantially_ less than the
> flow in the hot wires. Without digging out references, I want to say
> that it's like 16% of the flow in the hot wires.
>

"Wade Lippman" <[email protected]> wrote in message
news:[email protected]...
> In residential electrical, you never run more than one device off a 240v
> circuit.

Small correction: it is allowed to run more than one room air conditioner
on a 240v circuit, but the circuit must be at least twice as large as what
the AC requires. There might be other instance where it is done, but I
expect the "twice" rule applies there also.

On Tue, 30 Sep 2003 20:53:31 -0500, Christopher wrote:


> I know this isn't an electrical forum but I also know many here have done
> this before.
>

One word: subpanel

DAGS (Do A Google Search - tmLJ)

-Doug

On Tue, 30 Sep 2003 20:53:31 -0500, "Christopher"
<[email protected]> wrote:

>I'm about to run some conduit and wiring in my garage for additional AC
>outlets. I'm fine with the basics but I want to allow for a 220V outlet for
>that new tablesaw I hope to have one of these days. I want to run hot wires
>from two different breakers and alternate 110 outlets between the two
>circuits but is it OK to end the run with the two hot wires going to the 220
>volt outlet? It seems like it should be just fine but I thought I would ask
>before going out to buy the stuff. Is there any problem with using one of
>the 110 outlets at the same time I use the tablesaw connected across both of
>them? Assuming I don't draw more amps than the individual circuit can
>handle, of course.
>
>Another question I have is whether there is any type of gadget available
>that will turn power on to my dust collector (shopvac) when I use the table
>saw and is there any special wiring I should consider in advance for
>something like that.
>
>I know this isn't an electrical forum but I also know many here have done
>this before.
>
>Thanks!
>
>-Chris
>

Run a separate wire for the 220 circuit. Install at least two 220
receptacles. There should not be any 110 receptacles connected the
the 220 circuit.

The "Long Ranger" comes in 110v or 220v models. It plugs into a
receptacle then you plug in your DC. A remote turns it on/off.

A shopvac doesn't have the necessary cfm nor capacity for proper dust
collection of most woodworking machines.

In residential electrical, you never run more than one device off a 240v
circuit. I don't know if there is a specific code against it, or if it is
just a matter of what is practical; all the wiring on the circuit (including
the outlets) has to be capable of handling the current the breaker is rated
at, so it might not even be possible.

You can run a 240v circuit to put the each 120v outlet on a box on a
separate circuit. It is called a multiwire circuit, and it commonly done in
kitchens; though I personally think it is a poor practice. I have never
heard of mixing 240 outlets with 120v outlets on the same circuit; you
probably run into the same problems mentioned above. You can check with
your local building department, but it seems like a mistake even if not
forbidden.

"Christopher" <[email protected]> wrote:
> I'm about to run some conduit and wiring in my garage for additional AC
> outlets. I'm fine with the basics but I want to allow for a 220V outlet for
> that new tablesaw I hope to have one of these days. I want to run hot wires
> from two different breakers and alternate 110 outlets between the two
> circuits but is it OK to end the run with the two hot wires going to the 220
> volt outlet?

You don't run a 220V outlet off "two different breakers". You run it
off one double-pole breaker. The difference is that if one side trips,
it opens the other side as well.

"Christopher" <[email protected]> wrote in message
news:[email protected]...
> I'm about to run some conduit and wiring in my garage for additional AC
> outlets. I'm fine with the basics but I want to allow for a 220V outlet
for
> that new tablesaw I hope to have one of these days. I want to run hot
wires
> from two different breakers and alternate 110 outlets between the two
> circuits but is it OK to end the run with the two hot wires going to the
220
> volt outlet? It seems like it should be just fine but I thought I would
ask
> before going out to buy the stuff. Is there any problem with using one of
> the 110 outlets at the same time I use the tablesaw connected across both
of
> them? Assuming I don't draw more amps than the individual circuit can
> handle, of course.
>
> Another question I have is whether there is any type of gadget available
> that will turn power on to my dust collector (shopvac) when I use the
table
> saw and is there any special wiring I should consider in advance for
> something like that.
>
> I know this isn't an electrical forum but I also know many here have done
> this before.
>
> Thanks!
>
> -Chris
>
>

Not a good idea to have portions of two circuits in one box. Keep those two
different 110's separate. My gut tells me there are other reasons, too,
but I can't think of them all now.

Another reason is that you will want to wire the table saw for at least 25
amps, and that would be too large for 110 volt devices, and the wires would
be too heavy to deal with.

Wire for the table saw with the two hot legs, and a neutral and a ground.
You could then hook up a 110 outlet on the side of the saw hooked into the
magnetic starter for your dust collector.
--
Jim in NC

"Roy Smith" <[email protected]> wrote in message
news:[email protected]...
> "Christopher" <[email protected]> wrote:
> > I'm about to run some conduit and wiring in my garage for additional AC
> > outlets. I'm fine with the basics but I want to allow for a 220V outlet
for
> > that new tablesaw I hope to have one of these days. I want to run hot
wires
> > from two different breakers and alternate 110 outlets between the two
> > circuits but is it OK to end the run with the two hot wires going to the
220
> > volt outlet?
>
> You don't run a 220V outlet off "two different breakers". You run it
> off one double-pole breaker. The difference is that if one side trips,
> it opens the other side as well.

I should have thought of that. I think I would have caught it before it was
too late but thanks.

-Chris

"Morgans" <[email protected]> wrote in message
news:[email protected]...

> Not a good idea to have portions of two circuits in one box. Keep those
two
> different 110's separate. My gut tells me there are other reasons, too,
> but I can't think of them all now.
>
> Another reason is that you will want to wire the table saw for at least 25
> amps, and that would be too large for 110 volt devices, and the wires
would
> be too heavy to deal with.
>
> Wire for the table saw with the two hot legs, and a neutral and a ground.
> You could then hook up a 110 outlet on the side of the saw hooked into the
> magnetic starter for your dust collector.
> --
> Jim in NC
>

I thought it was common practice to run two hot wires plus the neutral and
ground and alternate the circuits as you go down the outlets. I can't
remember if you have to have two neutral wires as well though. It's seems
like you would need two or one wire would have to handle current flow for
two different circuits. I understand DC circuits pretty well but AC
behavior is not something I know very well.

I don't understand what you mean by 25 amp circuits being "too large" for
110volts. That's just the amperage the circuit will provide before the
breaker trips. A 110V device will not draw more current than it needs no
matter how many amps the circuit is capable of providing.

-Chris

"Christopher" <[email protected]> wrote >
> I thought it was common practice to run two hot wires plus the neutral and
> ground and alternate the circuits as you go down the outlets.

No, with 110, you go with one hot (black, or color) and one neutral, and one
ground. To get 220, you use two hots and a ground. They are installed in
breaker slots above and right next to each other in the breaker box. As has
been posted, they will have a common handle. The only reason to run a
neutral with your 220 circuit, is if you are going to use a 110 circuit as
well as the 220. A welder, or table saw with only 220, would have three
prong plugs. A stove will have 4 prongs, because it uses 220, and 110, for
the timer and light bulb.

>I can't
> remember if you have to have two neutral wires as well though. It's seems
> like you would need two or one wire would have to handle current flow for
> two different circuits. I understand DC circuits pretty well but AC
> behavior is not something I know very well.

Do some research. It looks like you have a bit to learn.
>
> I don't understand what you mean by 25 amp circuits being "too large" for
> 110volts. That's just the amperage the circuit will provide before the
> breaker trips. A 110V device will not draw more current than it needs no
> matter how many amps the circuit is capable of providing.

Some will argue this, but in my view, the device (recepticle) is only rated
at 15 or 20 amps. It is not guaranteed not to fry at higher amps. Also,
the # 10 wire for a 25 amp circuit is so stiff, it is very difficult to work
with, getting it all bent up and stuffing two cables in a box.

--
Jim in NC

20 amp circuts are normal for 120VAC and requires12AWG wire. 15 amp
circuits, 14AWG. It is perfectly fine to wire the top and bottom of duplex
outlets to different circuits, just pull a separate hot & neutral leg for
each circuit. A common ground is acceptable (deep boxes are a good idea).
Pulling 120VAC off of the 208VAC at the saw is not a good idea. Run a
separarte 20AMP circuit. The circuit breaker is there to protect the wire
NOT the device. If you have a 30AMP circuit for your saw, which btw is good
for about 5HP @ 208VAC, you'll need 10AWG wire.

ELA

"Christopher" <[email protected]> wrote in message
news:[email protected]...
> "Morgans" <[email protected]> wrote in message
> news:[email protected]...
>
> > Not a good idea to have portions of two circuits in one box. Keep those
> two
> > different 110's separate. My gut tells me there are other reasons,
too,
> > but I can't think of them all now.
> >
> > Another reason is that you will want to wire the table saw for at least
25
> > amps, and that would be too large for 110 volt devices, and the wires
> would
> > be too heavy to deal with.
> >
> > Wire for the table saw with the two hot legs, and a neutral and a
ground.
> > You could then hook up a 110 outlet on the side of the saw hooked into
the
> > magnetic starter for your dust collector.
> > --
> > Jim in NC
> >
>
> I thought it was common practice to run two hot wires plus the neutral and
> ground and alternate the circuits as you go down the outlets. I can't
> remember if you have to have two neutral wires as well though. It's seems
> like you would need two or one wire would have to handle current flow for
> two different circuits. I understand DC circuits pretty well but AC
> behavior is not something I know very well.
>
> I don't understand what you mean by 25 amp circuits being "too large" for
> 110volts. That's just the amperage the circuit will provide before the
> breaker trips. A 110V device will not draw more current than it needs no
> matter how many amps the circuit is capable of providing.
>
> -Chris
>
>

Thanks to everyone for the replies. I have a much better understanding of
what I need to do now.

-Chris

To be clear consider this:

Two (2) 120VAC circuits fed from two independent breakers WILL require a separate neutral per circuit by code even though, if by
chance or design, the breakers are installed on different legs of a 240V panel.

In a single 240VAC 3 wire feeder (2 hots, a neutral and a ground fed from a 2 pole breaker) with 120V loads attached, the neutral
will carry only the difference in the currents. That is why the wire size of the hots and neutral are the same. Worst case, one
hot is fully loaded and the other is not loaded, the neutral carries 100% of the return current. Any load subsequently applied to
the other leg will only reduce the current in the neutral.

Hope this helps.

Al

"Robert Bonomi" <bonomi@c-ns.> wrote in message news:[email protected]...
> In article <K5seb.471566$Oz4.291108@rwcrnsc54>,
> Wm Gardner <[email protected]> wrote:
> >
> >
> [[.. munch ..]]
>
> >#2- The answer to this is hinted at above. Lets explain with an example.....
> >#12 conductors are rated at 20 amps. Were you to put 20 amp loads on each of
> >these circuits, but have only one return, you would actually be handling 40
> >amps through the return line. Definite code violation and unless you are
> >running GFCI breaker it would work until the fire started......
>
>
> WRONGO! the neutral only carries the _difference_ between the load
> on the two hot wired.
>
> If the two hot leads are 180 degrees out of phase, and you have equal
> 110V loads on each leg, the current carried on the neutral will be *ZERO*.
>
> Life is a little more complicated if you have two phases of 3-phase
> power. In that scenario, with balanced 110V loads, you will have some
> current-flow in the neutral, but it is _substantially_ less than the
> flow in the hot wires. Without digging out references, I want to say
> that it's like 16% of the flow in the hot wires.
>

"Wade Lippman" <[email protected]> wrote in message
news:[email protected]...
> In residential electrical, you never run more than one device off a 240v
> circuit. I don't know if there is a specific code against it, or if it is
> just a matter of what is practical; all the wiring on the circuit
(including
> the outlets) has to be capable of handling the current the breaker is
rated
> at, so it might not even be possible.
>
> You can run a 240v circuit to put the each 120v outlet on a box on a
> separate circuit. It is called a multiwire circuit, and it commonly done
in
> kitchens; though I personally think it is a poor practice. I have never
> heard of mixing 240 outlets with 120v outlets on the same circuit; you
> probably run into the same problems mentioned above. You can check with
> your local building department, but it seems like a mistake even if not
> forbidden.
>
>

Code says that each electric motor should have its own circuit. Probably
one of the most overlooked and ignored items.
--
Jim in NC

I will get you the section of the NEC when I get home (I don't have it with
me). This was obviously an oversight by the inspector. What is to stop you
from now moving the second leg to a breaker on the same leg (inadvertently
or purposely). As a degreed electrical engineer with over 20 years of
experience, I would never condone such an installation and I would certainly
not install a circuit like that for myself.

Another concern I have is that if one circuit is turned off w/o the other,
the neutral may still be carrying current and can present a shock hazard.

I will follow up later.

Al

"Robert Bonomi" <bonomi@c-ns.> wrote in message news:[email protected]...
> In article <[email protected]>,
> Al Reid <[email protected]> wrote:
> >
> >
> >To be clear consider this:
> >
> >Two (2) 120VAC circuits fed from two independent breakers WILL require a
> >separate neutral per circuit by code even though, if by
> >chance or design, the breakers are installed on different legs of a 240V
> >panel.
>
> Got a cite? I just completed an installation using a common neutral w/
> independant single-pole breakers (on opposite phases -- wiring color-coded),
> which the city inspector _has_ signed off on.
>
> >In a single 240VAC 3 wire feeder (2 hots, a neutral and a ground fed
> >from a 2 pole breaker) with 120V loads attached, the neutral
> >will carry only the difference in the currents. That is why the wire
> >size of the hots and neutral are the same. Worst case, one
> >hot is fully loaded and the other is not loaded, the neutral carries
> >100% of the return current. Any load subsequently applied to
> >the other leg will only reduce the current in the neutral.
> >
> >Hope this helps.
> >
> >Al
> >
> >"Robert Bonomi" <bonomi@c-ns.> wrote in message
> >news:[email protected]...
> >> In article <K5seb.471566$Oz4.291108@rwcrnsc54>,
> >> Wm Gardner <[email protected]> wrote:
> >> >
> >> >
> >> [[.. munch ..]]
> >>
> >> >#2- The answer to this is hinted at above. Lets explain with an example.....
> >> >#12 conductors are rated at 20 amps. Were you to put 20 amp loads on each of
> >> >these circuits, but have only one return, you would actually be handling 40
> >> >amps through the return line. Definite code violation and unless you are
> >> >running GFCI breaker it would work until the fire started......
> >>
> >>
> >> WRONGO! the neutral only carries the _difference_ between the load
> >> on the two hot wired.
> >>
> >> If the two hot leads are 180 degrees out of phase, and you have equal
> >> 110V loads on each leg, the current carried on the neutral will be *ZERO*.
> >>
> >> Life is a little more complicated if you have two phases of 3-phase
> >> power. In that scenario, with balanced 110V loads, you will have some
> >> current-flow in the neutral, but it is _substantially_ less than the
> >> flow in the hot wires. Without digging out references, I want to say
> >> that it's like 16% of the flow in the hot wires.
> >>
> >
> >
>
>

In article <[email protected]>,
Christopher <[email protected]> wrote:
>
>
>"Morgans" <[email protected]> wrote in message
>news:[email protected]...
>
>> Not a good idea to have portions of two circuits in one box. Keep those
>two
>> different 110's separate. My gut tells me there are other reasons, too,
>> but I can't think of them all now.
>>
>> Another reason is that you will want to wire the table saw for at least 25
>> amps, and that would be too large for 110 volt devices, and the wires
>would
>> be too heavy to deal with.
>>
>> Wire for the table saw with the two hot legs, and a neutral and a ground.
>> You could then hook up a 110 outlet on the side of the saw hooked into the
>> magnetic starter for your dust collector.
>> --
>> Jim in NC
>>
>
>I thought it was common practice to run two hot wires plus the neutral and
>ground and alternate the circuits as you go down the outlets. I can't
>remember if you have to have two neutral wires as well though. It's seems
>like you would need two or one wire would have to handle current flow for
>two different circuits.

One neutral wire. and it only has to be capable of handling the maximum
load that will be on _one_ hot wire.

> I understand DC circuits pretty well but AC
>behavior is not something I know very well.
>
>I don't understand what you mean by 25 amp circuits being "too large" for
>110volts. That's just the amperage the circuit will provide before the
>breaker trips. A 110V device will not draw more current than it needs no
>matter how many amps the circuit is capable of providing.

you mis-understood. it's the _wire_ that's the problem. Gotta use at
least #10 wire to get the 25A handling capability for the saw. That's
'oversize' for the fittings on typical 110 outlats -- they're designed
for attaching wire that is no bigger than #12.