Behind the meter interconnection

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kaveenkw123

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Im new to solar design so wanted to get a second opinion on this.

Existing Service is 800A @ 208V 3ph and the main service disconnect is 800A as well. Looking at the utility data from last three years the peak was 70kW and the average was 47.2kW. Taking the peak kW that comes down to about 200A of usage.

So is it right to reduce the service disconnect fuse down from 800A to 600A to comply with 705.12 and add a 200A PV disconnect?
Thankyou.
 
kaveenkw123 said:
Im new to solar design so wanted to get a second opinion on this.

Existing Service is 800A @ 208V 3ph and the main service disconnect is 800A as well. Looking at the utility data from last three years the peak was 70kW and the average was 47.2kW. Taking the peak kW that comes down to about 200A of usage.

So is it right to reduce the service disconnect fuse down from 800A to 600A to comply with 705.12 and add a 200A PV disconnect?
Thankyou.
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I have done that with the support/permission of the utility.
 
electrofelon said:
Just curious what say does the utility have in that (other than possibly getting a shutdown to do the work)?
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The PV systems I have interconnected that way are commercial systems in AHJ territories where there is a plan review. One in particular was an 800A fused service that we wanted to downgrade with 700A fuses. The utility gave us the demand data which showed the maximum load for the past three years was about 400A, so they greenlighted the downgrade.
 
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ggunn said:
The PV systems I have interconnected that way are commercial systems in AHJ territories where there is a plan review. One in particular was an 800A fused service that we wanted to downgrade with 700A fuses. The utility gave us the demand data which showed the maximum load for the past three years was about 400A, so they greenlighted the downgrade.
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But what difference does this make to the utility, presuming they don't own/maintain the service disconnect, which is kind of what electrofelon asked? Most utilities probably won't even have conductors sized per NEC 310 if utility is responsible for the conductors.
 
You can make a line side connection and not have to make any changes to the existing service equipment.
 
kwired said:
But what difference does this make to the utility, presuming they don't own/maintain the service disconnect, which is kind of what electrofelon asked? Most utilities probably won't even have conductors sized per NEC 310 if utility is responsible for the conductors.
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Around here utility would not care. They may require an inspection to reenergize after a shutdown , but they would not question my sizing or engineering of anything . It's a fused disco, I would just replace the fuses as needed and not even involve the POCO (other than the interconnect agreement of course).
 
kaveenkw123 said:
Im new to solar design so wanted to get a second opinion on this.

Existing Service is 800A @ 208V 3ph and the main service disconnect is 800A as well. Looking at the utility data from last three years the peak was 70kW and the average was 47.2kW. Taking the peak kW that comes down to about 200A of usage.

So is it right to reduce the service disconnect fuse down from 800A to 600A to comply with 705.12 and add a 200A PV disconnect?
Thankyou.
Click to expand...

Yes it's fine. The relevant code section is 220.87. The data is supposed to be the utility 'demand data' or meet the exception. Sounds like you got that.
Your peak calculation is what's relevant. The average is irrelevant.

The rest of this thread is our forever explaining to ggunn that outside of the Texas jurisdictions he works in the utility and the AHJ (building department) typically aren't closely related entities and the utility doesn't enforce the NEC.
 
don_resqcapt19 said:
You can make a line side connection and not have to make any changes to the existing service equipment.
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That's kind of contradictory. I mean it's basically just different changes. Of course it depends on details but the OPs proposal could very well be less expensive and or easier to make compliant.
 
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