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Default NEC question -- can a circuit have both 220v and 110v outlets

I suspect that the answer is no, but want to double check.

Residential.

Can I have a circuit, protected by a double pole circuit breaker, that
would have a neutral and both 220v, as well as 110v, outlets.
Obviously, wiring would match the breaker's capacity.

thanks

i
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Default NEC question -- can a circuit have both 220v and 110v outlets


"Ignoramus2331" wrote in message
...
I suspect that the answer is no, but want to double check.

Residential.

Can I have a circuit, protected by a double pole circuit breaker, that
would have a neutral and both 220v, as well as 110v, outlets.
Obviously, wiring would match the breaker's capacity.

thanks

i


No


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Default NEC question -- can a circuit have both 220v and 110v outlets

In article , Ignoramus2331 wrote:
Can I have a circuit, protected by a double pole circuit breaker, that
would have a neutral and both 220v, as well as 110v, outlets.


Yes.

"Multiwire branch circuits shall supply only line-to-neutral loads. ...
Exception: Where all ungrounded conductors of the multiwire branch circuit are
opened simulaneously by the branch-circuit overcurrent device." [2005 NEC,
Article 210.4(C)]


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

It's time to throw all their damned tea in the harbor again.
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Default NEC question -- can a circuit have both 220v and 110v outlets

In article , kjpro @ usenet.com wrote:

"Ignoramus2331" wrote in message
m...

Can I have a circuit, protected by a double pole circuit breaker, that
would have a neutral and both 220v, as well as 110v, outlets.


No


Bzzzt! Sorry, but thanks for playing.

Specifically permitted unter NEC 210.4(C), Exception 2.

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

It's time to throw all their damned tea in the harbor again.
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Default NEC question -- can a circuit have both 220v and 110v outlets

On Fri, 03 Aug 2007 14:53:55 GMT, Doug Miller wrote:
In article , Ignoramus2331 wrote:
Can I have a circuit, protected by a double pole circuit breaker, that
would have a neutral and both 220v, as well as 110v, outlets.


Yes.

"Multiwire branch circuits shall supply only line-to-neutral loads. ...
Exception: Where all ungrounded conductors of the multiwire branch circuit are
opened simulaneously by the branch-circuit overcurrent device." [2005 NEC,
Article 210.4(C)]



This is great. I have existing conduit going into my basement
"workshop". It supplies 110v right now. I want to rewire it to supply
20A 220v, with neutral, and will add 110v outlets on both legs, as
well as 220v outlets.

On the main panel, I will use a double pole 220v breaker so that ``all
ungrounded conductors of the multiwire branch circuit are opened
simulaneously by'' that breaker.

The reason for it I want to convert my drill press to three phase with
VFD, mostly for tapping. I need 220v for it.

Also, on the same circuit, outside the basement wall, I want to add
outdoor receptacles (110v and 220v) for my pool's pump. It would be
GFCI protected and I will use outdoor rared hardware.

The above mentioned pump runs a water slide on my inflatable round
pool, which also doubles as a water filter.

i


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Default NEC question -- can a circuit have both 220v and 110v outlets

In article ,
Ignoramus2331 wrote:

On Fri, 03 Aug 2007 14:53:55 GMT, Doug Miller wrote:
In article , Ignoramus2331
wrote:
Can I have a circuit, protected by a double pole circuit breaker, that
would have a neutral and both 220v, as well as 110v, outlets.


Yes.

"Multiwire branch circuits shall supply only line-to-neutral loads. ...
Exception: Where all ungrounded conductors of the multiwire branch circuit
are
opened simulaneously by the branch-circuit overcurrent device." [2005 NEC,
Article 210.4(C)]



This is great. I have existing conduit going into my basement
"workshop". It supplies 110v right now. I want to rewire it to supply
20A 220v, with neutral, and will add 110v outlets on both legs, as
well as 220v outlets.

On the main panel, I will use a double pole 220v breaker so that ``all
ungrounded conductors of the multiwire branch circuit are opened
simulaneously by'' that breaker.

The reason for it I want to convert my drill press to three phase with
VFD, mostly for tapping. I need 220v for it.

Also, on the same circuit, outside the basement wall, I want to add
outdoor receptacles (110v and 220v) for my pool's pump. It would be
GFCI protected and I will use outdoor rared hardware.

The above mentioned pump runs a water slide on my inflatable round
pool, which also doubles as a water filter.

i


Other than the obvious concern about whether your existing conduit has
enough room for the extra wires, I'm curious about your tapping
requirements. We use standard 120 VAC drill presses all the time for
tapping, with Tapmatic or other brand tapping heads. Are you talking
about rigid tapping? Just curious.
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Default NEC question -- can a circuit have both 220v and 110v outlets

On Fri, 03 Aug 2007 08:33:30 -0700, Smitty Two wrote:
Other than the obvious concern about whether your existing conduit has
enough room for the extra wires, I'm curious about your tapping
requirements. We use standard 120 VAC drill presses all the time for
tapping, with Tapmatic or other brand tapping heads. Are you talking
about rigid tapping? Just curious.


I think that a 1/2" conduit has enough room for three 12 gauge
conductors. I would have to double check.

As for the drill press, there are many reasons why I may want my drill
press to go slow, including drilling larger holes in steel, etc.

i
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Default NEC question -- can a circuit have both 220v and 110v outlets

According to Ignoramus2331 :

This is great. I have existing conduit going into my basement
"workshop". It supplies 110v right now. I want to rewire it to supply
20A 220v, with neutral, and will add 110v outlets on both legs, as
well as 220v outlets.

On the main panel, I will use a double pole 220v breaker so that ``all
ungrounded conductors of the multiwire branch circuit are opened
simulaneously by'' that breaker.

The reason for it I want to convert my drill press to three phase with
VFD, mostly for tapping. I need 220v for it.

Also, on the same circuit, outside the basement wall, I want to add
outdoor receptacles (110v and 220v) for my pool's pump. It would be
GFCI protected and I will use outdoor rared hardware.

The above mentioned pump runs a water slide on my inflatable round
pool, which also doubles as a water filter.


That sounds _way_ more than can be supported off a single circuit,
240/120 or otherwise. You'd be better off running multiple circuits,
some dedicated 240, others 120. Or put a subpanel in the basement
and do it from there.
--
Chris Lewis,

Age and Treachery will Triumph over Youth and Skill
It's not just anyone who gets a Starship Cruiser class named after them.
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Default NEC question -- can a circuit have both 220v and 110v outlets

On Fri, 03 Aug 2007 10:22:58 -0500, Ignoramus2331
wrote:

On Fri, 03 Aug 2007 14:53:55 GMT, Doug Miller wrote:
In article , Ignoramus2331 wrote:
Can I have a circuit, protected by a double pole circuit breaker, that
would have a neutral and both 220v, as well as 110v, outlets.


Yes.

"Multiwire branch circuits shall supply only line-to-neutral loads. ...
Exception: Where all ungrounded conductors of the multiwire branch circuit are
opened simulaneously by the branch-circuit overcurrent device." [2005 NEC,
Article 210.4(C)]



This is great. I have existing conduit going into my basement
"workshop". It supplies 110v right now. I want to rewire it to supply
20A 220v, with neutral, and will add 110v outlets on both legs, as
well as 220v outlets.

On the main panel, I will use a double pole 220v breaker so that ``all
ungrounded conductors of the multiwire branch circuit are opened
simulaneously by'' that breaker.

The reason for it I want to convert my drill press to three phase with
VFD, mostly for tapping. I need 220v for it.

Also, on the same circuit, outside the basement wall, I want to add
outdoor receptacles (110v and 220v) for my pool's pump. It would be
GFCI protected and I will use outdoor rared hardware.

The above mentioned pump runs a water slide on my inflatable round
pool, which also doubles as a water filter.

i


Some pumps use a lot of power. The one you are talking about is
probably not as high as some, but you should consider it.

The drill's power consumption could be high too.
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Default NEC question -- can a circuit have both 220v and 110v outlets

In article , Ignoramus2331 wrote:

Also, on the same circuit, outside the basement wall, I want to add
outdoor receptacles (110v and 220v) for my pool's pump. It would be
GFCI protected and I will use outdoor rared hardware.


Now *that* part is a potential problem.You'll want to split the multiwire
circuit into two separate 120V circuits on the LINE (input) side of the GFCI,
or use a double-pole GFCI breaker. Those aren't cheap.

The above mentioned pump runs a water slide on my inflatable round
pool, which also doubles as a water filter.


Good reason for using GFCIs. But why the same circuit?

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

It's time to throw all their damned tea in the harbor again.


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Default NEC question -- can a circuit have both 220v and 110v outlets

On Fri, 03 Aug 2007 15:39:57 -0000, Chris Lewis wrote:
According to Ignoramus2331 :

This is great. I have existing conduit going into my basement
"workshop". It supplies 110v right now. I want to rewire it to supply
20A 220v, with neutral, and will add 110v outlets on both legs, as
well as 220v outlets.

On the main panel, I will use a double pole 220v breaker so that ``all
ungrounded conductors of the multiwire branch circuit are opened
simulaneously by'' that breaker.

The reason for it I want to convert my drill press to three phase with
VFD, mostly for tapping. I need 220v for it.

Also, on the same circuit, outside the basement wall, I want to add
outdoor receptacles (110v and 220v) for my pool's pump. It would be
GFCI protected and I will use outdoor rared hardware.

The above mentioned pump runs a water slide on my inflatable round
pool, which also doubles as a water filter.


That sounds _way_ more than can be supported off a single circuit,
240/120 or otherwise. You'd be better off running multiple circuits,
some dedicated 240, others 120. Or put a subpanel in the basement
and do it from there.


Right now, the pump is 1 honest HP and draws about 10A 110V. I do not
think that it will be a big deal for a 20A circuit.

i
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Default NEC question -- can a circuit have both 220v and 110v outlets

On Fri, 03 Aug 2007 11:42:48 -0400, Terry wrote:
On Fri, 03 Aug 2007 10:22:58 -0500, Ignoramus2331
wrote:

On Fri, 03 Aug 2007 14:53:55 GMT, Doug Miller wrote:
In article , Ignoramus2331 wrote:
Can I have a circuit, protected by a double pole circuit breaker, that
would have a neutral and both 220v, as well as 110v, outlets.

Yes.

"Multiwire branch circuits shall supply only line-to-neutral loads. ...
Exception: Where all ungrounded conductors of the multiwire branch circuit are
opened simulaneously by the branch-circuit overcurrent device." [2005 NEC,
Article 210.4(C)]



This is great. I have existing conduit going into my basement
"workshop". It supplies 110v right now. I want to rewire it to supply
20A 220v, with neutral, and will add 110v outlets on both legs, as
well as 220v outlets.

On the main panel, I will use a double pole 220v breaker so that ``all
ungrounded conductors of the multiwire branch circuit are opened
simulaneously by'' that breaker.

The reason for it I want to convert my drill press to three phase with
VFD, mostly for tapping. I need 220v for it.

Also, on the same circuit, outside the basement wall, I want to add
outdoor receptacles (110v and 220v) for my pool's pump. It would be
GFCI protected and I will use outdoor rared hardware.

The above mentioned pump runs a water slide on my inflatable round
pool, which also doubles as a water filter.

i


Some pumps use a lot of power. The one you are talking about is
probably not as high as some, but you should consider it.

The drill's power consumption could be high too.


The pump is 1 HP, about 10 amps or even a little less (I should look at
the nameplate). It is a lawn sprinkler pump by Wayne.

i
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Default NEC question -- can a circuit have both 220v and 110v outlets

In article , Ignoramus2331 wrote:
On Fri, 03 Aug 2007 08:33:30 -0700, Smitty Two
wrote:
Other than the obvious concern about whether your existing conduit has
enough room for the extra wires, I'm curious about your tapping
requirements. We use standard 120 VAC drill presses all the time for
tapping, with Tapmatic or other brand tapping heads. Are you talking
about rigid tapping? Just curious.


I think that a 1/2" conduit has enough room for three 12 gauge
conductors. I would have to double check.


Electrically, it depends on the conduit and the type of wire. For most
combinations of the two, you're good, but (for example) with type RHH or RHW
wire in Sched. 80 rigid PVC conduit, you're limited to two 12ga conductors
total. Obviously if there are other wires there already, you need to take that
into account as well when calculating the conduit capacity.

Physically, you may find it awkward to pull three conductors through 1/2
conduit, especially if there are already conductors in it.

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

It's time to throw all their damned tea in the harbor again.
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Default NEC question -- can a circuit have both 220v and 110v outlets

On Fri, 03 Aug 2007 15:49:42 GMT, Doug Miller wrote:
In article , Ignoramus2331 wrote:

Also, on the same circuit, outside the basement wall, I want to add
outdoor receptacles (110v and 220v) for my pool's pump. It would be
GFCI protected and I will use outdoor rared hardware.


Now *that* part is a potential problem.You'll want to split the multiwire
circuit into two separate 120V circuits on the LINE (input) side of the GFCI,
or use a double-pole GFCI breaker. Those aren't cheap.


I would do the former (protect the outdoor outlets with an outlet
GFCI, separate GFCI for 110v and 220v outlets).

The above mentioned pump runs a water slide on my inflatable round
pool, which also doubles as a water filter.


Good reason for using GFCIs. But why the same circuit?


All slots taken on the panel.

i
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Default NEC question -- can a circuit have both 220v and 110v outlets

In article , Ignoramus2331 wrote:
On Fri, 03 Aug 2007 15:49:42 GMT, Doug Miller wrote:
In article , Ignoramus2331

wrote:

Also, on the same circuit, outside the basement wall, I want to add
outdoor receptacles (110v and 220v) for my pool's pump. It would be
GFCI protected and I will use outdoor rared hardware.


Now *that* part is a potential problem.You'll want to split the multiwire
circuit into two separate 120V circuits on the LINE (input) side of the GFCI,


or use a double-pole GFCI breaker. Those aren't cheap.


I would do the former (protect the outdoor outlets with an outlet
GFCI, separate GFCI for 110v and 220v outlets).

The above mentioned pump runs a water slide on my inflatable round
pool, which also doubles as a water filter.


Good reason for using GFCIs. But why the same circuit?


All slots taken on the panel.


Half-height breakers are a good solution to that, if your panel supports them.

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

It's time to throw all their damned tea in the harbor again.


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Default NEC question -- can a circuit have both 220v and 110v outlets

On Fri, 03 Aug 2007 15:56:47 GMT, Doug Miller wrote:
In article , Ignoramus2331 wrote:
On Fri, 03 Aug 2007 08:33:30 -0700, Smitty Two
wrote:
Other than the obvious concern about whether your existing conduit has
enough room for the extra wires, I'm curious about your tapping
requirements. We use standard 120 VAC drill presses all the time for
tapping, with Tapmatic or other brand tapping heads. Are you talking
about rigid tapping? Just curious.


I think that a 1/2" conduit has enough room for three 12 gauge
conductors. I would have to double check.


Electrically, it depends on the conduit and the type of wire. For most
combinations of the two, you're good, but (for example) with type RHH or RHW
wire in Sched. 80 rigid PVC conduit, you're limited to two 12ga conductors
total. Obviously if there are other wires there already, you need to take that
into account as well when calculating the conduit capacity.

Physically, you may find it awkward to pull three conductors through 1/2
conduit, especially if there are already conductors in it.


Well, I would pull out the existing wires and pull new ones in. It is
not that long. Just one bend from the panel. My conduit is steel.

i
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Default NEC question -- can a circuit have both 220v and 110v outlets

In article , Ignoramus2331 wrote:
On Fri, 03 Aug 2007 15:56:47 GMT, Doug Miller wrote:


Electrically, it depends on the conduit and the type of wire. For most
combinations of the two, you're good, but (for example) with type RHH or RHW
wire in Sched. 80 rigid PVC conduit, you're limited to two 12ga conductors
total. Obviously if there are other wires there already, you need to take that
into account as well when calculating the conduit capacity.

Physically, you may find it awkward to pull three conductors through 1/2
conduit, especially if there are already conductors in it.


Well, I would pull out the existing wires and pull new ones in. It is
not that long. Just one bend from the panel. My conduit is steel.


Rigid or flexible? Thickwall, intermediate, or thinwall? What type of
conductors?

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

It's time to throw all their damned tea in the harbor again.
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Default NEC question -- can a circuit have both 220v and 110v outlets

On Fri, 03 Aug 2007 16:10:13 GMT, Doug Miller wrote:
In article , Ignoramus2331 wrote:
On Fri, 03 Aug 2007 15:56:47 GMT, Doug Miller wrote:


Electrically, it depends on the conduit and the type of wire. For most
combinations of the two, you're good, but (for example) with type RHH or RHW
wire in Sched. 80 rigid PVC conduit, you're limited to two 12ga conductors
total. Obviously if there are other wires there already, you need to take that
into account as well when calculating the conduit capacity.

Physically, you may find it awkward to pull three conductors through 1/2
conduit, especially if there are already conductors in it.


Well, I would pull out the existing wires and pull new ones in. It is
not that long. Just one bend from the panel. My conduit is steel.


Rigid or flexible? Thickwall, intermediate, or thinwall? What type of
conductors?


thinwall, rigid, 12 gauge THHN

i
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Default NEC question -- can a circuit have both 220v and 110v outlets

In article , Ignoramus2331 wrote:

thinwall, rigid, 12 gauge THHN


Code permits up to 9 (!!) 12AWG THHN conductors in 1/2" thinwall ("electrical
metallic tubing" or EMT), so you're perfectly good with three or four. Even
though Code permits using the conduit as the equipment grounding conductor, I
prefer to pull a separate wire when possible.

Nine would be pretty tough to pull, though. g

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

It's time to throw all their damned tea in the harbor again.
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Default NEC question -- can a circuit have both 220v and 110v outlets

On Fri, 03 Aug 2007 16:54:22 GMT, Doug Miller wrote:
In article , Ignoramus2331 wrote:

thinwall, rigid, 12 gauge THHN


Code permits up to 9 (!!) 12AWG THHN conductors in 1/2" thinwall ("electrical
metallic tubing" or EMT), so you're perfectly good with three or four. Even
though Code permits using the conduit as the equipment grounding conductor, I
prefer to pull a separate wire when possible.

Nine would be pretty tough to pull, though. g


And seriously derated in ampacity.

--
Art Greenberg
artg at eclipse dot net



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Default NEC question -- can a circuit have both 220v and 110v outlets

On Fri, 03 Aug 2007 16:54:22 GMT, Doug Miller wrote:
In article , Ignoramus2331 wrote:

thinwall, rigid, 12 gauge THHN


Code permits up to 9 (!!) 12AWG THHN conductors in 1/2" thinwall ("electrical
metallic tubing" or EMT), so you're perfectly good with three or four. Even
though Code permits using the conduit as the equipment grounding conductor, I
prefer to pull a separate wire when possible.

Nine would be pretty tough to pull, though. g


OK... So, my plans are solidifying, then. I am going to make it a 20A,
220V, circuit, protected by a double pole breaker. For the outdoor
receptacle, I will have two outlets: one double 110v GFCI outlet on
one of the legs, and one 20A, 220v outlet, protected by its own
GFCI. I hope that such a thing exists.

The outdoor 20a outlet, would be for the purposes of maybe upgrading
the pool pump one day or adding a pool heater.

i
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Default NEC question -- can a circuit have both 220v and 110v outlets

In article ,
Ignoramus2331 wrote:

On Fri, 03 Aug 2007 16:54:22 GMT, Doug Miller wrote:
In article , Ignoramus2331
wrote:

thinwall, rigid, 12 gauge THHN


Code permits up to 9 (!!) 12AWG THHN conductors in 1/2" thinwall
("electrical
metallic tubing" or EMT), so you're perfectly good with three or four. Even
though Code permits using the conduit as the equipment grounding conductor,
I
prefer to pull a separate wire when possible.

Nine would be pretty tough to pull, though. g


OK... So, my plans are solidifying, then. I am going to make it a 20A,
220V, circuit, protected by a double pole breaker. For the outdoor
receptacle, I will have two outlets: one double 110v GFCI outlet on
one of the legs, and one 20A, 220v outlet, protected by its own
GFCI. I hope that such a thing exists.

The outdoor 20a outlet, would be for the purposes of maybe upgrading
the pool pump one day or adding a pool heater.

i


Are you going to make your own three-phase in the basement?
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Default NEC question -- can a circuit have both 220v and 110v outlets

On Fri, 03 Aug 2007 12:19:20 -0700, Smitty Two wrote:
In article ,
Ignoramus2331 wrote:

On Fri, 03 Aug 2007 16:54:22 GMT, Doug Miller wrote:
In article , Ignoramus2331
wrote:

thinwall, rigid, 12 gauge THHN

Code permits up to 9 (!!) 12AWG THHN conductors in 1/2" thinwall
("electrical
metallic tubing" or EMT), so you're perfectly good with three or four. Even
though Code permits using the conduit as the equipment grounding conductor,
I
prefer to pull a separate wire when possible.

Nine would be pretty tough to pull, though. g


OK... So, my plans are solidifying, then. I am going to make it a 20A,
220V, circuit, protected by a double pole breaker. For the outdoor
receptacle, I will have two outlets: one double 110v GFCI outlet on
one of the legs, and one 20A, 220v outlet, protected by its own
GFCI. I hope that such a thing exists.

The outdoor 20a outlet, would be for the purposes of maybe upgrading
the pool pump one day or adding a pool heater.

i


Are you going to make your own three-phase in the basement?


I will use a VFD, which "sort of" makes three phase.

I do make real three phase in the garage, however.

i
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Default NEC question -- can a circuit have both 220v and 110v outlets

Art Greenberg wrote:
On Fri, 03 Aug 2007 16:54:22 GMT, Doug Miller wrote:
In article , Ignoramus2331 wrote:

thinwall, rigid, 12 gauge THHN

Code permits up to 9 (!!) 12AWG THHN conductors in 1/2" thinwall ("electrical
metallic tubing" or EMT), so you're perfectly good with three or four. Even
though Code permits using the conduit as the equipment grounding conductor, I
prefer to pull a separate wire when possible.

Nine would be pretty tough to pull, though. g


And seriously derated in ampacity.


That is an interesting point.

Say you have 4 circuits - hot and neutral - plus a ground wire - 9 wires
all #12.

The ground wire does not count for derating.

For 8 wires (up to 9 wires) the derating is 70%.

The ampacity of THHN is 30A (but it must in general be protected at 20A).

70% of 30A is 21A. The 4 circuits may be used at 20A.

THHN is wonderful stuff.

--
bud--


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Default NEC question -- can a circuit have both 220v and 110v outlets

Ignoramus2331 wrote:
On Fri, 03 Aug 2007 16:54:22 GMT, Doug Miller wrote:
In article , Ignoramus2331 wrote:

thinwall, rigid, 12 gauge THHN

Code permits up to 9 (!!) 12AWG THHN conductors in 1/2" thinwall ("electrical
metallic tubing" or EMT), so you're perfectly good with three or four. Even
though Code permits using the conduit as the equipment grounding conductor, I
prefer to pull a separate wire when possible.

Nine would be pretty tough to pull, though. g


OK... So, my plans are solidifying, then. I am going to make it a 20A,
220V, circuit, protected by a double pole breaker. For the outdoor
receptacle, I will have two outlets: one double 110v GFCI outlet on
one of the legs, and one 20A, 220v outlet, protected by its own
GFCI. I hope that such a thing exists.

The outdoor 20a outlet, would be for the purposes of maybe upgrading
the pool pump one day or adding a pool heater.


Easiest (not necessarily least expensive) might be two-phase GFCI
breaker. Then the whole circuit is protected.

Yours aye,
W. Underhill


--
"Take sides! Always take sides! You may sometimes be wrong - but the man
who refuses to take sides must *always* be wrong! Heaven save us from
poltroons who fear to make a choice!" R.A. Heinlein, "Double Star"
--
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SCA homepage: http://members.shaw.ca/uilliam/
LiveJournal: http://www.livejournal.com/users/jackytar/
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Default NEC question -- can a circuit have both 220v and 110v outlets

wrote:
On Sat, 04 Aug 2007 03:10:59 -0500, bud--
wrote:

Art Greenberg wrote:
On Fri, 03 Aug 2007 16:54:22 GMT, Doug Miller wrote:
In article , Ignoramus2331 wrote:

thinwall, rigid, 12 gauge THHN
Code permits up to 9 (!!) 12AWG THHN conductors in 1/2" thinwall ("electrical
metallic tubing" or EMT), so you're perfectly good with three or four. Even
though Code permits using the conduit as the equipment grounding conductor, I
prefer to pull a separate wire when possible.

Nine would be pretty tough to pull, though. g
And seriously derated in ampacity.

That is an interesting point.

Say you have 4 circuits - hot and neutral - plus a ground wire - 9 wires
all #12.

The ground wire does not count for derating.

For 8 wires (up to 9 wires) the derating is 70%.

The ampacity of THHN is 30A (but it must in general be protected at 20A).

70% of 30A is 21A. The 4 circuits may be used at 20A.

THHN is wonderful stuff.



Just remember when THHN/THWN is used in a wet location it assumes the
THWN ampacity (75c column)
This is a fairly obscure point and a lot of inspectors will not catch
it. This is in the U/L listing standard.




I never figured out why the same wire, when wet, has a lower ampacity.
Any clue?


------------------
Another scheme (which you've seen but some people may not have) is to
run 3 multiwire branch circuits - A, B, neutral - 9 THWN #12 wires.

The neutrals do not count (unless high harmonic load).

Wire count 6, derating 80%.

The ampacity of THWN is 25A.

80% of 25A is 20A. The 6 circuits can be used at 20A.

--
bud--
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Default NEC question -- can a circuit have both 220v and 110v outlets

On 2007-08-06, bud-- wrote:

I never figured out why the same wire, when wet, has a lower ampacity.
Any clue?


Since the ampacity is based on the temperature at which the insulation
will start to break down, presumably when wet the insulation will
break down at a lower temperature. Just a WAG.

Cheers, Wayne
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