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Conductors in Parallel

jar546

jar546

CBO
Joined
Oct 16, 2009
Messages
13,378
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Not where I really want to be
I just had this question asked of me on email.

I have an existing complex that is being renovated the service and gear is 45 years old. Coming out of the disconnect they have 4 under ground conduits feeding a MDP, All of the phases are in separate conduits A Phase in one conduit, B phase in another and so on, no Grounding conductor either. This I feel violates Arts. 366.20 and 250. I mentioned to the EC and Engineer they have to comply with the Art for parallel services and Art. 366.20. The Engineer is telling me they don't have to be replaced. In short of writing about this what is your opinion. Art 366.20 was adopted to the 2017 NEC.
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I would expect any ferrous conduits and the knockouts the wires go through to get very hot. Around here, the conduits underground would be PVC, so your only hot point would be the knockouts. Regardless of the code in place at the time, this could be a serious enough hazard to invoke the nuclear option in the IEBC.

Maybe you could re-identify the conductors and land them accordingly to balance the magnetic fields.
 
If the raceways are non-metallic, and the other requirements of 300.3(B)(1) Exception are met, this is an allowed installation. 366.20 would only apply within an auxilliary gutter; no such equipment was mentioned in the description of the installation.

Cheers, Wayne

P.S. 300.3(B)(1) Exception is redundant, as it provides no allowances not already provided by 300.3(B)(3).
 
jar546 said:
I just had this question asked of me on email.
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What do they mean by “no grounding conductor?” Are they saying the installation doesn’t comply with 250.24(C)? Or are they talking about supply side bonding jumpers? Or no Grounding electrode conductor?
 
jar546 said:
Do you think the original question meant there is no neutral or no EGC? I don't think that was clarified.
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Since the OP refers to isophase and refers to 4 conduits, I infer that the system is 3 phase and the conduits are A, B, C, and N. [I'm excluding the possibility of 2 phase without a neutral.]. So the comment about no grounding conductor would be referring to an EGC or SSBJ. EGCs do not exist on the utility side of the service disconnect, and there's no particular reason to expect the install would require an SSBJ.

Cheers, Wayne
 
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