Exhaust Fan Switch Leg

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DBoone

DBoone

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Location
Mississippi
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General Contractor
We are installing a Panasonic heater-light-exhaust combo and the supply house doesn't have 12-4. Would I be okay running two 12-2 cables and using one of the neutrals (identified on both ends as an ungrounded conductor) as a switch leg?

Or do I need to run one 12-2 and one 12-3 so I will have a neutral in each cable.
 
DBoone said:
We are installing a Panasonic heater-light-exhaust combo and the supply house doesn't have 12-4. Would I be okay running two 12-2 cables and using one of the neutrals (identified on both ends as an ungrounded conductor) as a switch leg?
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If I understand your installation correctly, then the change to 200.7(C)(1) for the 2011 code would prohibit that. The new wording only permits the re-identified conductor to be used as the supply to the switch and not as the switch leg.
 
DBoone said:
We are installing a Panasonic heater-light-exhaust combo and the supply house doesn't have 12-4. Would I be okay running two 12-2 cables and using one of the neutrals (identified on both ends as an ungrounded conductor) as a switch leg?

Or do I need to run one 12-2 and one 12-3 so I will have a neutral in each cable.
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I won't say I have never done that, but it probably shouldn't pass inspection either. How about using some ENT or other flexible raceway between the switch and the unit? Of course you probably need a different switch box than what you were going to use also. 12-4 NM cable may or may not be something you want to purchase, though the code has changed enough to make it more favorable then it used to be, but then again 12-2-2 is even more likely to be desired than 12-4. I myself don't want to stock these items if I am not going to use them all that much, and the ENT is a little more universally usable for many things and will not remain in stock as long.
 
kwired said:
I won't say I have never done that, but it probably shouldn't pass inspection either. How about using some ENT or other flexible raceway between the switch and the unit? Of course you probably need a different switch box than what you were going to use also. 12-4 NM cable may or may not be something you want to purchase, though the code has changed enough to make it more favorable then it used to be, but then again 12-2-2 is even more likely to be desired than 12-4. I myself don't want to stock these items if I am not going to use them all that much, and the ENT is a little more universally usable for many things and will not remain in stock as long.
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You're right about the switch box. It's installed and cables going in today. Looks like I will go the way of 12-2 and 12-3.

Just wondering, why can a white be re-identified and used as the feed to a switch but not as a switch leg as Don mentioned.
 
Why do you need 12/4 if you have a heater/fan/light. Is there a night light? I just don't wire them. If you need 12/4 then you could run a 12/3 and a 12/2 so the neutrals are together and there wont be any unwanted emf's
 
DBoone said:
You're right about the switch box. It's installed and cables going in today. Looks like I will go the way of 12-2 and 12-3.

Just wondering, why can a white be re-identified and used as the feed to a switch but not as a switch leg as Don mentioned.
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In your case it probably doesn't quite meet the circumstances of what the intent was, but as worded would still apply.

I think they just don't want two white wires being left in a outlet box as the connecting points to a luminaire was the main concern.
 
Dennis Alwon said:
Why do you need 12/4 if you have a heater/fan/light. Is there a night light? I just don't wire them. If you need 12/4 then you could run a 12/3 and a 12/2 so the neutrals are together and there wont be any unwanted emf's
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Customer wants a switch for each one. The 12-2/12-3 was my second suggestion so I could have a neutral in each cable a you suggested. That's the route we are going.
 
DBoone said:
Customer wants a switch for each one. The 12-2/12-3 was my second suggestion so I could have a neutral in each cable a you suggested. That's the route we are going.
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Just don't tie all the whites together or you create other violations, keep the neutral load in the same cable as the ungrounded conductor supplying the particular component.
 
DBoone said:
Parallel conductors smaller than 1/0?
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That is one violation. You can also cite 300.3(B)- all conductors of the same circuit need to be in the same raceway or cable, which would also be a violation in the OP's suggestion of using two 12-2 cables.
 
DBoone said:
You're right about the switch box. It's installed and cables going in today. Looks like I will go the way of 12-2 and 12-3.

Just wondering, why can a white be re-identified and used as the feed to a switch but not as a switch leg as Don mentioned.
Click to expand...

If you use a re-identified white as a power source to a switch, it will be hot unless the circuit feed is off. Thus it won't be confused as a neutral if you test it with a meter or non-contact voltage tester.

If you use a re-identified white as a switch leg, then if the switch is off, it is de-energized and more likely to be confused with a neutral.
 
DBoone said:
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Just wondering, why can a white be re-identified and used as the feed to a switch but not as a switch leg as Don mentioned.
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I think it is a "left over" rule from the days before you were required to re-identify the white conductor used in a switch loop. You were permitted to use the white as the hot for the switch without re-identifying it in the older codes.

It had the same wording as now...that is the white could only be used as the supply to the switch. This made sure that the white wire at the light fixture was the grounded conductor and helped prevent the installer from connecting the screw shell of the lamp socket to the hot conductor. Have the screw shell connected to the hot conductor it a potential shock hazard as lamps are often changed with the power on.
 
Dennis Alwon said:
If you need 12/4 then you could run a 12/3 and a 12/2 so the neutrals are together and there wont be any unwanted emf's
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The amount of EMF you are talking about is directly related to how far apart the conductors are from each other. Assuming you run two cables side by side EMF should not be a problem even with conductors of the same circuit run in separate cables.
 
iwire said:
The amount of EMF you are talking about is directly related to how far apart the conductors are from each other. Assuming you run two cables side by side EMF should not be a problem even with conductors of the same circuit run in separate cables.
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That is true if it is wired that way
 
IIRC, the Panasonic instructions call for an individual circuit for the heater which would make the whole thing clear. I always run a 12/2 for the heater and a 14/3 for the rest. For the one customer I had that wanted the night light hooked up, I ran a separate 14/2 since I can't get 14/4 easily around here.
 
kwired said:
That is what I meant to say, somehow it didn't all get there.
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I think we are having a communication break down. :)

300.3(B)(3) allows the conductors of a circuit to be run separately under the conditions indicated.

Basically, NM and plastic boxes will get it done.
 
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