What size neutral with paralleld conductors

[mull982]

If I have (2) parallel sets of 4/0 cables running in two seperate conduits on a 4-wire system do I need to pull a neutral with each one of the feeders.

This feed is between the inverter and main connection panel I have referenced in another thread. I was going to size the neutral based on 250.122 and pull one with each feeder however I dont know if I need to pull both? Any recommendations?

In conjunction with my other post I'm assuming that these neutral conductors would be seperatge from the combined grounding electrode conductor (GEC) that I need however would the neutral be bonded to the GEC at the main panel?

Thanks.

 

[Dennis Alwon]

If you need a neutral then you must pull them in both conduits but it may be size as small as 250.122 if the calculated load permits. No neutral is necessary if there are no 120V loads.

 

[mull982]

If you need a neutral then you must pull them in both conduits but it may be size as small as 250.122 if the calculated load permits. No neutral is necessary if there are no 120V loads.

This is actually kind of an odd one. The inverter output has a delta output transformer however the main panel that it is tying into is a 4-wire system. The inverter manufacturer says that the neutral if pulled to the inverter is connected to ground inside the inverter and is only used for voltage sensing/reference.

So in this case if a neutral is pulled it would only be used for voltage reference and not as a current carrying conductor.

 

[Dennis Alwon]

I see....IMO, it still cannot be smaller than T. 250.122 for the feeder ocpd. If there is a neutral to hot short you have to ensure the breaker will trip so it cannot be smaller than the required egc. 215.2(A)(2).

 

[augie47]

This is actually kind of an odd one. The inverter output has a delta output transformer however the main panel that it is tying into is a 4-wire system. The inverter manufacturer says that the neutral if pulled to the inverter is connected to ground inside the inverter and is only used for voltage sensing/reference.

So in this case if a neutral is pulled it would only be used for voltage reference and not as a current carrying conductor.

"connected to the ground"... does this mean it would connect to the same potential as the equipmemt ground ?
If so, you would be violating 250.24(A)(5).
Sounds to me as if the neutral is not needed, but what do I know