Neutral necessary in three phase combiner panel?

[ggunn]

A colleague is designing a PV system which has 6 inverters wired phase to phase at 208VAC going into a three phase AC combiner panel. No conductors from the inverters touch neutral. Is there any reason why he would need to run the neutral from the service out to the combiner panel? The case of the panel will of course be grounded.

I told him that I didn't think so.

 

[augie47]

There are folks here far better qualified to answer and hopefully they will do so, however, since none have so far I will give an opinion. Since you have service conductors terminating in the box I would think 250.24(C) would require a neutral conductor. (again, just an opinion but worth considering)

 

[GoldDigger]

There are folks here far better qualified to answer and hopefully they will do so, however, since none have so far I will give an opinion. Since you have service conductors terminating in the box I would think 250.24(C) would require a neutral conductor. (again, just an opinion but worth considering)

But if there is OCPD on the service side, the combiner box would not be service equipment and the incoming conductors would not be service conductors.
Is the combiner also serving as the OCPD and PV disconnect?
If the wiring on the POCO facing side of the combiner is just a feeder, then IMHO the neutral need not be brought in.

 

[augie47]

But if there is OCPD on the service side, the combiner box would not be service equipment and the incoming conductors would not be service conductors.
Is the combiner also serving as the OCPD and PV disconnect?
If the wiring on the POCO facing side of the combiner is just a feeder, then IMHO the neutral need not be brought in.

agree,,,if it's a feeder... I was basing my answer on the OP mentioning "service conductors".

 

[GoldDigger]

agree,,,if it's a feeder... I was basing my answer on the OP mentioning "service conductors".

Actually what he said was the conductors "from the service out to the combiner panel"

Tapatalk!

 

[jaggedben]

I agree that if the conductors supplying the combiner are a feeder, then no neutral is required.

If the conductors are service conductors, then it may be a highly debatable question. One of the first large solar installations that I worked on (my role being minor) got hung up on this question and it delayed AHJ approval for weeks if not months. The electrical engineer who had consulted on the job eventually convinced the AHJ it was not necessary to have a neutral because the grounding wire run with the conductors provided the effective ground fault path. I'm not sure how they designated that grounding conductor (EGC, GEC, and/or bonding jumper). It was a high stakes discussion because running the neutral would have involved another shut-down by the utility and running another expensive copper conductor inside a raceway that may not have been large enough. My advice would be to make the raceway big enough to carry the neutral in case you can't convince the AHJ of your interpretation of 250.24(C).

 

[ggunn]

But if there is OCPD on the service side, the combiner box would not be service equipment and the incoming conductors would not be service conductors.
Is the combiner also serving as the OCPD and PV disconnect?
If the wiring on the POCO facing side of the combiner is just a feeder, then IMHO the neutral need not be brought in.

The conductors from the panel will be connected to the service though a disco and a meter. I'm not sure if the interconnect will be done through a backfed breaker or a supply side tap, but in either case there will be OCPD at the service end of the conductors between the panel and the service. So no, the combiner will serve as neither OCPD (except for the individual conductors from the inverters) nor PV disco.

The utility will likely want a neutral run through the PV meter, but it seems to me that it could terminate in the disco and not be pulled to the combiner panel. Nothing in the panel would touch the neutral and single phase loads will not be allowed in the panel. They wouldn't work, anyway, if there were no neutral in the panel.