Parallel Neutrals

[don_resqcapt19]

I don't see any danger with paralleling conductors of any size, or even of multiple sizes, as long as the rating of the OCPD does not except the ampacity of the smallest conductor, but that is clearly a code violation unless you meet one of the limited exceptions.

The following words, "to supply control power to indicating instruments, contactors, relays, solenoids, and similar control devices, or for frequencies of
360 Hz and higher," should be removed from Exception #1. As long as the smallest conductor is protected, there is no safety issue.

 

[infinity]

I don't see why this as a debatable issue. The NEC provides the definition of conductors in parallel and limits their minimum size. If you connect 2-#12's together at both ends it a violation whether it's a safety issue or not.

(H) Conductors in Parallel.
(1) General. Aluminum, copper-clad aluminum, or copper
conductors, for each phase, polarity, neutral, or grounded cir-
cuit shall be permitted to be connected in parallel (electrically
joined at both ends) only in sizes 1/0 AWG and larger where
installed in accordance with 310.10(H)(2) through (H)(6).

 

[kwired]

Exception No. 1: Conductors in sizes smaller than 1/0
AWG shall be permitted to be run in parallel to supply
control power to indicating instruments, contactors, relays,
solenoids, and similar control devices, or for frequencies of
360 Hz and higher, provided all of the following apply:

(a) They are contained within the same raceway or
cable.

(b) The ampacity of each individual conductor is sufficient
to carry the entire load current shared by the parallel
conductors.

(c) The overcurrent protection is such that the ampacity
of each individual conductor will not be exceeded if one
or more of the parallel conductors become inadvertently
disconnected.

It is very common in control schemes to not follow the requirements in (a) above, unless attachment to a switch means the conductors in question are no longer in parallel. But then that changes the whole issue of defining what is "in parallel", which is what has been debated in length in the past.

As I said, IMO NEC does not clearly define what they mean with certain conductors to not be installed in parallel. Multiple conductors installed for the purpose of increasing the overall ampacity really is a different application than incidental control conductors that end up connected in parallel paths

 

[DBoone]

I don't see why this as a debatable issue. The NEC provides the definition of conductors in parallel and limits their minimum size. If you connect 2-#12's together at both ends it a violation whether it's a safety issue or not.

It seems that most people here agree it is a violation but also there is no real danger in the OP scenerio. Do you think the rule should be changed to allow parallel conductors smaller than 1/0 serving the same circuit?

 

[iwire]

It is very common in control schemes to not follow the requirements in (a) above, unless attachment to a switch means the conductors in question are no longer in parallel. But then that changes the whole issue of defining what is "in parallel", which is what has been debated in length in the past.

As I said, IMO NEC does not clearly define what they mean with certain conductors to not be installed in parallel. Multiple conductors installed for the purpose of increasing the overall ampacity really is a different application than incidental control conductors that end up connected in parallel paths

Common or not it is in fact a clear violation.

If you choose to ignore it is up to you.

 

[infinity]

It seems that most people here agree it is a violation but also there is no real danger in the OP scenerio. Do you think the rule should be changed to allow parallel conductors smaller than 1/0 serving the same circuit?

I agree in case this isn't a safety hazard but I see no reason for a change the NEC to a smaller parallel conductor threshold to accommodate an incorrect installation. It's possible to configure this installation in a code compliant manner without the need to rewrite the NEC.

 

[ggunn]

Multiple conductors installed for the purpose of increasing the overall ampacity really is a different application than incidental control conductors that end up connected in parallel paths.

I think that "...for the purpose of increasing the overall ampacity..." is an important distinction. Another reason to do it would be to reduce voltage drop; if that were the only reason for the parallel runs, if one of the paralleled connections were to fail, the ampacity of the remaining conductor(s) could still be sufficient to safely carry the current.

 

[kwired]

Common or not it is in fact a clear violation.

If you choose to ignore it is up to you.

so if you are running multiple control devices parallel to one another (using an OR logic) do you run two conductors out to each side of a switch that is in a remote location - kind of like a supervised fire alarm circuit in a way? I bet not unless the supervised monitoring is a part of the design of the control ciruit.


I don't choose to ignore the issue, but I also don't think the NEC has clarified the intent of exactly what parallel installations it is talking about in 300.3. It all makes good sense when talking about conductors paralleled with the intent of increasing the ampacity or possibly for lowering voltage drop, but throw in a section of a control circuit and it becomes clouded. If sub part a in that exception wouldn't mention all of the conductors being in same raceway or cable then it would be a lot more clear on the control circuits, but putting all them in same raceway kind of changes the entire installation - every switch of an OR function would need two wires per terminal run to it to comply.

 

[Stevareno]

I didn't see this mentioned. What would be the harm if the extra white wire was just capped off at both ends and not used?

 

[iwire]

I didn't see this mentioned. What would be the harm if the extra white wire was just capped off at both ends and not used?

Depending on the wiring methods used that could be a 300.3(B) violation.

 

[DBoone]

I didn't see this mentioned. What would be the harm if the extra white wire was just capped off at both ends and not used?

I don't see any harm either way, capped off or connected and in parallel. Let's run another rabbit while we have everyone participating. A 20 amp 12 awg circuit and a 15 amp 14 awg circuit share a double gang box. By tying all EGCs together if there is a bad connection at some point of the 12 awg EGC you now have a 14 awg EGC on a 20 amp circuit. Thoughts?

 

[infinity]

I don't see any harm either way, capped off or connected and in parallel. Let's run another rabbit while we have everyone participating. A 20 amp 12 awg circuit and a 15 amp 14 awg circuit share a double gang box. By tying all EGCs together if there is a bad connection at some point of the 12 awg EGC you now have a 14 awg EGC on a 20 amp circuit. Thoughts?

Thoughts? You're derailing the thread because non-CCC's, like EGC's can be connected in parallel regardless of size.

 

[jaggedben]

I don't see any harm either way, capped off or connected and in parallel. Let's run another rabbit while we have everyone participating. A 20 amp 12 awg circuit and a 15 amp 14 awg circuit share a double gang box. By tying all EGCs together if there is a bad connection at some point of the 12 awg EGC you now have a 14 awg EGC on a 20 amp circuit. Thoughts?

Same situation. Technically a violation but I don't see a safety issue.

The failure mode you mentioned is irrelevant to me, because this is equipment grounding. Only the 12 awg EGC is required to be there, but you could have a bad connection on an EGC if it was the only one there. Also in most situations having a 14awg EGC on a 20A circuit will be better than having no EGC.

 

[iwire]

I don't see any harm either way, capped off or connected and in parallel.

I don't see the harm, what I do see are code violations which should be considered.

 

[jaggedben]

Thoughts? You're derailing the thread because non-CCC's, like EGC's can be connected in parallel regardless of size.

Where does it say that?

 

[GoldDigger]

Same situation. Technically a violation but I don't see a safety issue.

The failure mode you mentioned is irrelevant to me, because this is equipment grounding. Only the 12 awg EGC is required to be there, but you could have a bad connection on an EGC if it was the only one there. Also in most situations having a 14awg EGC on a 20A circuit will be better than having no EGC.

Somehow I do not see the various parallel rules applying to EGCs in the first place, since I believe that the rules only refer to current carrying conductors. Ungrounded conductors and grounded conductors are both mentioned separately, but not EGCs.

 

[iwire]

Somehow I do not see the various parallel rules applying to EGCs in the first place, since I believe that the rules only refer to current carrying conductors. Ungrounded conductors and grounded conductors are both mentioned separately, but not EGCs.

I agree and if the rules did apply to EGC virtually every installation would have violations.

 

[Dennis Alwon]

I understand the issue but if you take the 2- 12/2 nm cables in box 1 and tie them through then the 3 way is a dead end. Neutral is there so just tie everything together in Box 2.

Is this thread more about why it can't be done the way it is? The biggest objection I see to the install as the OP has it is that you have created electromagnetic field's that one probably doesn't want. I agree it is a code violation.

 

[jaggedben]

Somehow I do not see the various parallel rules applying to EGCs in the first place, since I believe that the rules only refer to current carrying conductors. Ungrounded conductors and grounded conductors are both mentioned separately, but not EGCs.

That's what I would have thought. But then I look at 310.10(H)(2) and I see the specific inclusion of EGCs. Granted, they are not included in 310.10(H)(1). It's confusing.

And as far as non-current carrying conductors, I certainly don't see an exception for MWBC neutrals.

 

[infinity]

That's what I would have thought. But then I look at 310.10(H)(2) and I see the specific inclusion of EGCs. Granted, they are not included in 310.10(H)(1). It's confusing.

And as far as non-current carrying conductors, I certainly don't see an exception for MWBC neutrals.

A MWBC neutral is a current carrying conductor by definition. It may or may not be one for derating purposes.