Multiwire circuit on 208v?
 

I want to add a circuit to a 208 panel, but there are no holes and I really
don't want to go at it with a hole saw.

There is a circuit consisting of one outlet connected to the box by 1/2"
conduit. If multiwire circuits are allowed on 208v, I could put the outlet
on one leg of the multiwire circuit and put my new circuit on the other.
That way I can just put my new MC cable to the bottom of the outlet box,
which does have a hole.

Seems to me that it should be pretty much the same as 240v, except that some
current will always be returning over the neutral; but there is no harm to
that. But maybe I am overlooking something (which, given my knowledge of
208v, is not unlikely)

If I can't use a multiwire circuit, can I simply attach the MC cable to the
bottom of the outlet box and run it up through the conduit to the panel box?
I think 1/2" will take 6 #12 wires.

Thanks.

Multiwire circuit on 208v?
 

On Jul 22, 12:09*am, "jack" wrote:
I want to add a circuit to a 208 panel, but there are no holes and I really
don't want to go at it with a hole saw.

There is a circuit consisting of one outlet connected to the box by 1/2"
conduit. *If multiwire circuits are allowed on 208v, I could put the outlet
on one leg of the multiwire circuit and put my new circuit on the other.
That way I can just put my new MC cable to the bottom of the outlet box,
which does have a hole.

Seems to me that it should be pretty much the same as 240v, except that some
current will always be returning over the neutral; but there is no harm to
that. *But maybe I am overlooking something (which, given my knowledge of
208v, is not unlikely)

If I can't use a multiwire circuit, can I simply attach the MC cable to the
bottom of the outlet box and run it up through the conduit to the panel box?
I think 1/2" will take 6 #12 wires.

Thanks.

Do not split a 240V circuit.
If you need an extra knockout, why don't you use a duplex BX connector
like this:

http://www.acehardware.com/product/i...entPage=family

Multiwire circuit on 208v?
 

"jack" wrote in message
...
I want to add a circuit to a 208 panel, but there are no holes and I really
don't want to go at it with a hole saw.

There is a circuit consisting of one outlet connected to the box by 1/2"
conduit. If multiwire circuits are allowed on 208v, I could put the
outlet on one leg of the multiwire circuit and put my new circuit on the
other. That way I can just put my new MC cable to the bottom of the outlet
box, which does have a hole.

Seems to me that it should be pretty much the same as 240v, except that
some current will always be returning over the neutral; but there is no
harm to that. But maybe I am overlooking something (which, given my
knowledge of 208v, is not unlikely)

If I can't use a multiwire circuit, can I simply attach the MC cable to
the bottom of the outlet box and run it up through the conduit to the
panel box? I think 1/2" will take 6 #12 wires.

Thanks.


What you're proposing is fine. Bring your cable into the outlet box, splice
the two neutral wires together with a pigtail to the outlet, as the neutrals
of a multiwire circuit cannot be dependent upon a device, and run your new
hot leg for the new circuit to a circuit breaker adjacent to the one feeding
the outlet circuit

Multiwire circuit on 208v?
 

Do not split a 240V circuit.
If you need an extra knockout, why don't you use a duplex BX connector
like this:

http://www.acehardware.com/product/i...entPage=family

=====================

If I had known that existed I would have used it. But now the multiwire
idea just seems more elegant.
Do you know of any reason not to use a multiwire circuit?

Multiwire circuit on 208v?
 

What you're proposing is fine. Bring your cable into the outlet box,
splice the two neutral wires together with a pigtail to the outlet, as the
neutrals of a multiwire circuit cannot be dependent upon a device, and run
your new hot leg for the new circuit to a circuit breaker adjacent to the
one feeding the outlet circuit

I was planning on taking the neutral off the outlet, so I appreciate you
pointing out that it is improper. Pigtailing is almost as easy.

I guess what you don't want is the neutral connection to the box breaking.
With a pigtail you lose everything or nothing, so you can't get a floating
neutral; is that the idea?

Multiwire circuit on 208v?
 

RBM wrote:
"jack" wrote in message
...
I want to add a circuit to a 208 panel, but there are no holes and I really
don't want to go at it with a hole saw.

There is a circuit consisting of one outlet connected to the box by 1/2"
conduit. If multiwire circuits are allowed on 208v, I could put the
outlet on one leg of the multiwire circuit and put my new circuit on the
other. That way I can just put my new MC cable to the bottom of the outlet
box, which does have a hole.

Seems to me that it should be pretty much the same as 240v, except that
some current will always be returning over the neutral; but there is no
harm to that. But maybe I am overlooking something (which, given my
knowledge of 208v, is not unlikely)

If I can't use a multiwire circuit, can I simply attach the MC cable to
the bottom of the outlet box and run it up through the conduit to the
panel box? I think 1/2" will take 6 #12 wires.

That works. Normally you would add 2 wires to the conduit and splice to
MC at the outlet box. In both cases the outlet box needs to be big enough.

You have 4 conductors in the conduit. The wire ampacity has to be
derated to 80% (4-6 wires). If you are using #12 THHN the ampacity is
30A which derates to 24A (and can only be used at 20A).


What you're proposing is fine. Bring your cable into the outlet box, splice
the two neutral wires together with a pigtail to the outlet, as the neutrals
of a multiwire circuit cannot be dependent upon a device, and run your new
hot leg for the new circuit to a circuit breaker adjacent to the one feeding
the outlet circuit

I agree except the 2008 NEC wants a common disconnect on multiwire
branch circuits (210.4). Could be a breaker handle tie. (The change
should make multiwires much less attractive.)

--
bud--

Multiwire circuit on 208v?
 

wrote in message
...
On Tue, 22 Jul 2008 11:02:09 -0400, "Wade Lippman"
wrote:

Do you know of any reason not to use a multiwire circuit?

Harmonics ... what kind of load is it

One circuit is a small water heater, the other a convenience outlet next to
the panel box. I suppose a light or a radio occasionally.

Multiwire circuit on 208v?
 

On Tue, 22 Jul 2008 12:36:22 -0400, wrote:

On Tue, 22 Jul 2008 11:02:09 -0400, "Wade Lippman"
wrote:

Do you know of any reason not to use a multiwire circuit?

Harmonics ... what kind of load is it

Unless he answers........a bank of computers. What have we learned
here?

I have never heard a situation of harmonics being a problem in
residential wiring. Maybe someone can give us an example.

Multiwire circuit on 208v?
 

"Wade Lippman" wrote in message
...


What you're proposing is fine. Bring your cable into the outlet box,
splice the two neutral wires together with a pigtail to the outlet, as
the neutrals of a multiwire circuit cannot be dependent upon a device,
and run your new hot leg for the new circuit to a circuit breaker
adjacent to the one feeding the outlet circuit

I was planning on taking the neutral off the outlet, so I appreciate you
pointing out that it is improper. Pigtailing is almost as easy.

I guess what you don't want is the neutral connection to the box breaking.
With a pigtail you lose everything or nothing, so you can't get a floating
neutral; is that the idea?

That is the idea, exactly, and as Bud correctly points out, the 08' NEC
requires the breakers of the two circuits to be tied. This may or may not
apply, as I know in my area we're still using the 05' code, but it's a good
practice to get into, to prevent Edison circuits from accidentally getting
screwed up