Running two 10-2 NM-B for electric dryer

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iwire said:
One UL listing = one piece of equipment.
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So what do you do when the manufacturer's instructions state to use two NMs?

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Note please that the unit is wired with separate neutrals for the two load groups. There is no connection between them at the fan (so no parallel wiring) and each neutral carries only the return current for its load.
If you chose to tie the two white wires of the fan unit together at the fan j box it would create a violation.

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GoldDigger said:
Note please that the unit is wired with separate neutrals for the two load groups. There is no connection between them at the fan (so no parallel wiring) and each neutral carries only the return current for its load.
If you chose to tie the two white wires of the fan unit together at the fan j box it would create a violation.
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:thumbsup:
 
iwire said:
You are right, it could be if you jump through all the needed hoops to do so.

And then the inspector looks at it when you are not there, makes a mistake, fails the job and things are delayed

Run the numbers on that and see if it makes sense to do so vs a 10/3.
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There's "code-compliant" and "something you don't mind attaching your name to".

This is an instance where I don't care if I wind up driving two hours, don't care how technically correct I am, and don't care if I am walking with the inspector to explain or not, and don't care if the inspector is sharp enough to understand that it's legal; 10-3 goes in the wall. You don't need condoning or executing something as hack as this following you around for years to come.
 
GoldDigger said:
The violation is that not all of the conductors are in the same cable.
An exception for running separate conductors in two or more non-ferrous raceways does not directly apply to cable wiring methods.
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I agree with wwhitney, 300.3(B)(3) allows running NM away from ferrous metals in separate cables. Two-wire threeways would be a more common application for it.
 
George Stolz said:
There's "code-compliant" and "something you don't mind attaching your name to".

This is an instance where I don't care if I wind up driving two hours, don't care how technically correct I am, and don't care if I am walking with the inspector to explain or not, and don't care if the inspector is sharp enough to understand that it's legal; 10-3 goes in the wall. You don't need condoning or executing something as hack as this following you around for years to come.
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Except when it's 3:15 on a Friday.
 
I get that the fan/heat/light/night light is one "unit", but I still think it's different because each component has it's own hot and neutral leads.

Unless the dryer has a 120v rotary motor and all associated controls on one phase and the heater on the other phase, splitting up the wiring into two separate cables is dangerous.

Otherwise why don't we just go back to knob and tube and feed whatever with whatever?
 
talk them out of the dang night lite
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Now that I am older and my irises are slower than there once were, those night lights are WONDERFUL!:)

No more blind night visits to the bathroom. But I digress from the original question.

Around here a gas dryer is quite rare. The fault is on the GC not telling you what the house needed in the first place. Looks like 10/3 to get your inspection at this point. :(
 
pkelectrical, what did you have to do? Is the inspector allowing 2 10/2 (after you un-parallel the neutrals), or making you run 10/3? I still say 2 10/2 NM is legal by 300.20(B) provided you dont have paralleled conductors. Ugly, but legal.
 
Frank DuVal said:
The fault is on the GC not telling you what the house needed in the first place. Looks like 10/3 to get your inspection.
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If it's not on the original contract then it's additional work and may involve a seperate trip charge if additional materials are required. What's the problems with a trip to the supply house?

This way the EC gets to eat all the additional time required to pass inspection.
 
GoldDigger said:
Apparently, did you look at the thread I referenced? By CMP 3:

Recommendation:




Delete the following:


Exception: Conductors installed in nonmetallic raceways run underground
shall be permitted to be arranged as isolated phase installations. The raceways
shall be installed in close proximity, and the conductors shall comply with the
provisions of 300.20(B).
Substantiation:




The exception is not required. Such installations are permitted


by 300.3(B)(3) in all locations, not just underground locations.
Panel Meeting Action: Reject
Panel Statement: This exception is necessary to permit installations where
nonmetallic raceways are installed in close proximity with all of Phase A in one
raceway, all of Phase B in another raceway, all of Phase C in another, and all
the grounded conductors in another raceway. Where this is useful is between
underground manholes so the phase conductors can exit the raceways and be
easily racked within the manhole, taking up less space, and making it easier to
do testing and maintenance on the installation. This would not be permissible
without this exception.
Number Eligible to Vote: 13
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Looks to me like the submitter was trying to get an exception specifically for underground non metallic raceways, the CMP simply mentioned that those are already covered by current wording.

It does not say this rule only applies to raceways, and neither does the CMP substantiation.
 
This exception is necessary to permit installations where
nonmetallic raceways are installed in close proximity with all of Phase A in one
raceway,....
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That says to me that the CMP felt that the exception for underground duct, which the proposer wanted to see removed, is necessary because no other section covered that case.

You may read that language differently.
 
GoldDigger said:
Apparently, did you look at the thread I referenced? By CMP 3:
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So, you are of the opinion that the text of 300.3(B)(3), which is adopted into legal statute, is over-ridden by a phrase by the CMP directed to isolated phase grouping underground in nonmetallic raceways ???

To me, the CMP is saying that if the text pertaining to isolated phase grouping is deleted, the isolated phase raceways could be run without regard to being grouped. . . . which is what 300.3(B)(3) says in the broad sense.

That's all the CMP is saying. They are not saying that 300.3(B)(3) doesn't mean what it says, because the CMP is talking about the Proposal, not 300.3(B)(3). It is really that simple.

I agree with Wayne, et. al., that a pair of 10/2 NMB cables that are an Electric Clothes Dryer 30 Amp 240 / 120 Volt branch circuit meeting the requirements of 300.20(B) IS a Code compliant installation and the inspector is wrong.
 
GoldDigger said:
Not if you parallel the neutrals, for sure.
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:roll: Well, yeah. . . 310.10(H) absolutely applies to this installation, but it does not prohibit two 10/2 NMBs. And neither does the CMP comment about deleting the Exception.
 
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