Paralleling a single neutral conductor with a 3/C tray cable 1

[bdn2004]

The manufacturer's recommended wire size for input and output wiring to a UPS is for a 200% rated neutral. If we installed a a 4-wire #1/0, is there any reason we can't parallel in another #1/0?

 

[dpc]

As long as they are all in the same conduit or tray, it should be acceptable. The two neutrals should be as close together as possible so that they share the neutral current equally. If one conductor is inside a ferrous conduit and the other is outside the conduit, that would be a problem.

This assumes you are covered by the NEC. #1/0 is the smallest size for which conductors can be put in parallel.

Other codes may be different.

"The more the universe seems comprehensible, the more it also seems pointless." -- Steven Weinberg

 

[resqcapt19]

Assuming that the four 1/0s are in the form of a cable and you are installing per the NEC, it would be my opinion that the adding an exteral 1/0 for the parallel grounded conductor would be a violation of 300.3(B). That being said, as long as you make the installation as suggested by dpc, I don't see any actual problems...just a code violation.

 

[bdn2004]

resqcapt19,

Is there a hint of sarcasm in your response? but I agree and thanks for pointing it out. However, I work for a utility where the NEC, although adhered to most of the time, has no real jurisdiction and actual science can prevail.

 

[resqcapt19]

bdn,
There are a number of NEC rules that can't be supported by science, but none the less they are enforced by the AHJ, at least most of the time.

 

[capuchi]

dpc,

your advise quite interest me. you mentioned that two neutral wire can be paralleled provided that they are as close to each other and must be in the same conduit. my query is . . . what would be the adverse effect if one in inside ferrous conduit while the other is inside non-metallic conduit (PVC). Really would appreciate your reply. thanks,

capuchi

 

[dpc]

Not quite sure I understand your question, but if one neutral is inside a steel conduit and the other is outside, the two conductors will not share load equally, with the inside conductor carrying more than half the current, due to lower inductive reactance.

"The more the universe seems comprehensible, the more it also seems pointless." -- Steven Weinberg