1600 amps switchgear

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SAP

Senior Member
Location
Fresno Ca
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
 

Ingenieur

Senior Member
Location
Earth
I would be ok with that
is it buried? Can an ambient temp adjustment be made?

std size 1200 then 1600 iirc
you used the next std size

you can get adjustable trip breakers
1600 frame
1400 or 1500 trip if that makes you more comfortable
 
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don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
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
Location
Georgia
Occupation
Former Child
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.

It reads like they are secondary conductors.

I'd send an RFI to clarify this was the engineer's intent.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
It reads like they are secondary conductors.

I'd send an RFI to clarify this was the engineer's intent.
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.
 

Ingenieur

Senior Member
Location
Earth
it looks like it is the primary (semantics? the primary is usually the side power is delivered to, the secondary the load side) of a transformer putting solar power into the grid
so the cb is actually the primary protection?

what are the xfmr specs?
 

Carultch

Senior Member
Location
Massachusetts
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.

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

Senior Member
Location
Massachusetts
it looks like it is the primary (semantics? the primary is usually the side power is delivered to, the secondary the load side) of a transformer putting solar power into the grid
so the cb is actually the primary protection?

what are the xfmr specs?

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.
 

Carultch

Senior Member
Location
Massachusetts
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

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
Location
Massachusetts
you can get adjustable trip breakers
1600 frame
1400 or 1500 trip if that makes you more comfortable

: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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