parallel neutral

[ceb]

Here is a situation I have come upon and need your thoughts on. 14/2 line voltage into box, hot pigtailed to feed two three way switches, two 14/3 leave to go to other box red and blk. on one switch other red and blk. on other switch, both net. tied to line net. same in other box the two net. are tied to load net. they go to one ceiling fan. One controls the light and the other controls the fan. dose any one see a problem with this or should one of the net. be done away with since it serves one common device?

 

[roger]

Re: parallel neutral

Ceb, per the actual wording of 310.4 this may be questionable, but in the real world there would be no problem, just redundancy.

Roger

 

[hbiss]

Re: parallel neutral

I agree with Roger. 310.4 doesn't really address this. I've probably done this myself but, that said, the neutrals from the 14/3's should not be tied together at the second switch location but kept separate and each used to supply their respective loads. That would make more sense than just not using one at all.

 

[karl riley]

Re: parallel neutral

To see whether the Code (310-4) and the real world share the same universe, clamp your ammeter around any part of that circuit. If it does not read zero, the problem is in the real world. You have created a net current magnetic field that can cause a computer monitor screen to jitter, for one example. Try detaching the redundant neutral and see the clamp-on read zero as it should.
I get paid to find these neutral connections and have them corrected.
Karl

 

[don_resqcapt19]

Re: parallel neutral

The code does permit the use of a neutral in only one of the two cables in 300.3(B)(3), but that still results in net current. The best solution is to leave the wiring as is and seperate the two load neutrals at the fan/light.
don

 

[roger]

Re: parallel neutral

Karl, help me out here. These two white conductors are joined together at both ends creating one common conductor to two switch legs.

How is this and the associated readings any different than running one white conductor to the fan/light? I'm not contesting the imbalance from "one" switch leg to the grounded conductor in this portion of the circuit, but measured across both switch legs and grounded conductor back to the switches, the clamp on meter would read zero.


There are literally billions of dual, triple, and quad level switch installations sharing a single grounded conductor in code compliant installations.

Of course maybe I'm missing something in my interpretation of Ceb's post. I only see the paralleled conductor from the switch to the fan/light.

Roger

 

[earlydean]

Re: parallel neutral

IMO I see paralleled neutrals in these switches as no problem. No EMF will result because all the currents are in the same cables. The size of these conductors is sufficient for the OC device. Where is the problem?

 

[don_resqcapt19]

Re: parallel neutral

Roger,
There will be current in both grounded conductors when only one switch is on. There will not be a corresponding hot in one of the cables to cancel the magnetic field from the grounded conductor.
don

 

[roger]

Re: parallel neutral

Don, I see that, but in my visualization of the installation both two conductor cables are from the same box to the fan/light in close proximity (side by side) stapled on the same stud.

Roger

 

[bwyllie]

Re: parallel neutral

Doesn't section 310.4 prohibit the paralleling of conductors below 1/0?

310.4 Conductors in Parallel.

Aluminum, copper-clad aluminum, or copper conductors of size 1/0 AWG and larger, comprising each phase, neutral, or grounded circuit conductor, shall be permitted to be connected in parallel (electrically joined at both ends to form a single conductor).

 

[roger]

Re: parallel neutral

Bwyllie, yes 310.4 prohibits parallel conductors below 1/0 excluding the exceptions.

In an installation where numerous loads and grounded conductors are run grouped together, (stapled or supported closely, not bundled) why would any inadvertent paralleling of grounded conductors be a concern?

Don's earlier post mentioning separation of loads would be a solution to this scenario along with a three conductor cable to the fan/light.

Roger

 

[karl riley]

Re: parallel neutral

I would rather see a graphic at this point, since I may not understand the circuit. The clamp-on reading zero is the bottom line for me.

Karl

 

[hurk27]

Re: parallel neutral

From what I gather there is two 3-ways in a box (two-gain) fed from one end by the same circuit the neutrals are being fed with the travelers on to the opposite 2 3-ways which are also in the same box (two-gain), then a 3 conductor is ran up to the paddle fan/light. one 3-way feeds the light the other feeds the fan but since there is only one neutral coming from the fan both neutrals are put together with the neutral coming from the fan/lite. this allows for both neutrals to share the return load no matter which set of travelers are being used. so unless these cables are ran right next to each other there will be a little magnetic field produced. but to say they would cause harm I couldn't see that. and as others have said, It's not uncommon to find this way of using up an unneeded neutral. but if they are fed from different circuits then it would be a problem.

 

[paul32]

Re: parallel neutral

That last comment says a single neutral comes from the fan and light, which means you either have to tie the neutrals together or just use one of them. If the fan and light were in separate locations and had their own cables and separate neutrals, I would say they should be kept separate.

The question I have is should the grounds be kept separate for this latter case, or be tied together? If the answer is tied together, how about when it is two different branch circuits? I'm inclined to keep them separate, which makes we wonder if they still only get one conductor of box fill. The only thing I could find in the code was isolated grounds needing an extra box fill count. This made me wonder if the grounds need to be tied together or have extra box fill.

 

[hurk27]

Re: parallel neutral

Paul Grounds are non-current carrying conductors and are not subject to paralleling as the only time they will have current on them is in a fault condition. then the extra wire would help in the opening of the OCP. also in a metal box how would you keep the bare copper from touching the box? keeping it from incidental contact and becoming paralleled.

 

[paul32]

Re: parallel neutral

After I posted that I realized it wouldn't be practical to keep the bare wires separate, even in a non-metallic box. I see a case in my house where separate circuits grounding wires are tied together.