We have a pretty big solar ground mount comming, We are installing a new 1600 amp 480 volt solar loads only service ,with new transformer from poco, no rule 16 yet from paco (rule 16 distribution line extensions) Plans call for 5 3" conduit using 300 mcm copper for each conductor run in parallel from Xfmr to switchgear . 300 mcm ampicity is 285 at 75c, 5 times 285 =1485. I'm guessing 1485 amps is the max that the photovoltaic system will produce shouldn't we be basing it on the 1600 main OCPD, I'm I missing something, I'm thinking 300 mcm is to small
1600 amps switchgear
- Thread starter SAP
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- Illinois
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- retired electrician
Where is the service point? If these conductors are on the line side of the service point, the conductors are not under the NEC rules. If they are on the load side of the service point, I would expect that 230.90(A) would apply and they are too small.
brantmacga
Señor Member
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- Georgia
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- Former Child
It reads like they are secondary conductors.
I'd send an RFI to clarify this was the engineer's intent.
- Location
- Illinois
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- retired electrician
Yes, they are on the secondary side of the transformer, but that does not tell us where the service point is as the transformer appears to be a utility transformer. Around here, the service point would be the secondary terminals of that transformer. In other places the service point would be the line side connection to the service disconnect.
Carultch
Senior Member
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- Massachusetts
It is common in stand-alone solar applications to have a customer-owned transformer with the point of common coupling at a primary medium voltage meter. Look for terms like customer-owned, utility-owned, and point of common coupling on the plans, to determine where the service point is.
Carultch
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- Massachusetts
It is a semantics issue, when you have backfed transformers, and the primary/secondary nomenclature is ambiguous. In my experience, the convention in applications like this, is that the utility side is still the primary.
brantmacga
Señor Member
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- Georgia
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- Former Child
I see..... I didn't know that was the case in some places.
Carultch
Senior Member
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- Massachusetts
If these classify as "transformer secondary conductors" per 240.21(C), then you need as much wire as you have OCPD. Doesn't matter what the operating current is. Also, over 800A, the 240.4(B) "next size up rule" doesn't apply.
You are correct to think that 5 x 300 kcmil is insufficient. The minimum size for 5 sets is 400 kcmil Cu.
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Carultch
Senior Member
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- Massachusetts
:thumbsup: Exactly!
The OP does need to confirm what 1.25* inverter current is, and set the setting to at least that. This is something that should to be indicated on the plan set.
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