NEC 225.31 for PV system at separate structure

[efrntzl]

I am working on system that has PV panels on a detached garage, from which the DC output is run back to main house where the inverters are. Inspector wants all ungrounded DC circuits to have disconnects at garage per 225.31. In this case, the strings are not combined, and it is an ungrounded PV system. There are 7 strings, so 14 ungrounded conductors. Using 2-pole disconnects for each string, that's 7 disconnects, which as I understand exceeds the max allowed of 6 per 690.14(C)(4).

So, my questions are:
Does 225.31 apply to DC source circuits for a separate structure, and if not, how can I prove this to inspector?; and,
If disconnects are required, can anyone suggest equipment, multi-pole disconnects I suppose, that can get total number of disconnects under 6?

Thanks.

 

[GoldDigger]

Is there a strong reason not to use combiners?

Tapatalk!

 

[efrntzl]

Well, that is one thing I was thinking. Although in this case, the inverters have an integrated combiner, and we are trying to have as little additional equipment as possible. May have to go this route though. Thanks.

 

[ggunn]

I am working on system that has PV panels on a detached garage, from which the DC output is run back to main house where the inverters are. Inspector wants all ungrounded DC circuits to have disconnects at garage per 225.31. In this case, the strings are not combined, and it is an ungrounded PV system. There are 7 strings, so 14 ungrounded conductors. Using 2-pole disconnects for each string, that's 7 disconnects, which as I understand exceeds the max allowed of 6 per 690.14(C)(4).

So, my questions are:
Does 225.31 apply to DC source circuits for a separate structure, and if not, how can I prove this to inspector?; and,
If disconnects are required, can anyone suggest equipment, multi-pole disconnects I suppose, that can get total number of disconnects under 6?

Thanks.

Do your DC conductors enter the house? If so, you need disconnecting means on all ungrounded connectors before they enter.

But the six handle rule may be covered by your AC disco(s) at your point of interconnection as long as there are 6 or fewer of them. If you are using an AC combiner one handle rules them all.

Also, look at these Eaton DC discos http://www.eaton.com/Eaton/Products...chesandDisconnects/SolarDisconnects/index.htm. You can have one handle break three ungrounded DC circuits.

 

[efrntzl]

Thanks for link, that could be very helpful.

At the house, I think we are fine because the DC disconnects of the inverters would cover that, but inspector wants the DC disconnects at the garage, where the PV panels are, before they go underground and run back to house - and that's what is confusing, because it's not a separate structure that is being fed - it's more like a source circuit, and in that the case the DC disconnects in the inverter at the house would cover the disconnect rule. As I understand, the inverter would never feed a voltage back to the PV panels.

 

[ggunn]

Thanks for link, that could be very helpful.

At the house, I think we are fine because the DC disconnects of the inverters would cover that, but inspector wants the DC disconnects at the garage, where the PV panels are, before they go underground and run back to house - and that's what is confusing, because it's not a separate structure that is being fed - it's more like a source circuit, and in that the case the DC disconnects in the inverter at the house would cover the disconnect rule. As I understand, the inverter would never feed a voltage back to the PV panels.

The way 225.31 has been interpreted by the AHJ's I have worked in is that if DC goes into a building you need a disconnecting means before it does so. If it supplies DC to an inverter outside the building without passing through the building, the DC disco at or integral to the inverter is sufficient. Whether the PV array is on the building, on another building, or ground mounted is irrelevant; the DC conductors are neither passing through nor supplying power to the building. The inverter may be supplying power to the building, but there is at least one disconnecting means between it and any circuits in the building.

I think your AHJ is off base on this one, at least as far as 225.31 is concerned.

 

[efrntzl]

Thanks again. I think this is the argument we'll try. If not, then those Eatons should be fine.