split bus panel PV interconnection rules

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jsherwin

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Location
cocoa, fl, usa
I am looking for guidance/reference on a pv interconnection to split bus panel at a residential installation (I understand they are no longer permitted but were used at one time). They were allowed under art 230 and the six handle rule.
 
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jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
I'll add: these can suck.

I saw one once that was a 200A service. We needed to install a 7.6kW inverter which would normally be fine. But the service panel was split bus with two 100A sections with 100A main breakers. I said 'either they upgrade that or we charge them the extra for two 3.8kW inverters.' The project ended up not going forward.
 
romex jockey

romex jockey

Senior Member
Location
Vermont
Occupation
electrician
Yes.....but the HO would hear nothing of it.....HI's having evolved to sit at the right hand of God and all.....:p~RJ~
 
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jsherwin

Member
Location
cocoa, fl, usa
jaggedben said:
What guidance is needed? They are basically two panels in one. Apply the rules for whichever you want to connect to.
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I apologize for my unfamiliarity with this type of panel but they are rare in my area and I don't know much about them. I am not the installer or AHJ, but doing a third party certification of the PV system which includes the interconnection.
I am unsure if there any rules that apply to the bus on the supply side of the connection. Do the breakers (read: disconnects?) need to have the same interrupt rating that a mocpd would have? Am I missing anything regarding the bus bar loading? My first criteria would be to cite 705.12(A) that the ratings of the sum of all the supply side overcurrent devices not exceed the rating of the service (in this case the bus). Just trying to learn and I appreciate any insight the panel can offer.
 
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ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
jsherwin said:
I apologize for my unfamiliarity with this type of panel but they are rare in my area and I don't know much about them. I am not the installer or AHJ, but doing a third party certification of the PV system which includes the interconnection.
I am unsure if there any rules that apply to the bus on the supply side of the connection. Do the breakers (read: disconnects?) need to have the same interrupt rating that a mocpd would have? Am I missing anything regarding the bus bar loading? My first criteria would be to cite 705.12(A) that the ratings of the sum of all the supply side overcurrent devices not exceed the rating of the service (in this case the bus). Just trying to learn and I appreciate any insight the panel can offer.
Click to expand...

There's nothing different on the supply side from a normal panel.
 
synchro

synchro

Senior Member
Location
Chicago, IL
Occupation
EE
Some split bus panels have one bus that is for lighting and other small loads, and this bus is fed from a breaker on a bus connected to the service. As mentioned above the bus connected to service can be treated like any main buss. But a "lighting" bus should not be used for backfeeding photovoltaic power.
 
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ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
synchro said:
Some split bus panels have one bus that is for lighting and other small loads, and this bus is fed from a breaker on a bus connected to the service. As mentioned above the bus connected to service can be treated like any main buss. But a "lighting" bus should not be used for backfeeding photovoltaic power.
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Why not? It's just an embedded sunbpanel. As long as you conform to 705.12 on both buses, I don't see why you couldn't connect to it.
 
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jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
jsherwin said:
I apologize for my unfamiliarity with this type of panel but they are rare in my area and I don't know much about them. I am not the installer or AHJ, but doing a third party certification of the PV system which includes the interconnection.
I am unsure if there any rules that apply to the bus on the supply side of the connection. Do the breakers (read: disconnects?) need to have the same interrupt rating that a mocpd would have? Am I missing anything regarding the bus bar loading? My first criteria would be to cite 705.12(A) that the ratings of the sum of all the supply side overcurrent devices not exceed the rating of the service (in this case the bus). Just trying to learn and I appreciate any insight the panel can offer.
Click to expand...

It might be more useful to share a picture or diagram of the panel and interconnection. Otherwise we're just speculating about what might be relevant. As mentioned, there are no special rules so it's a matter of understanding how to apply the rules to an unusual situation.
 
synchro

synchro

Senior Member
Location
Chicago, IL
Occupation
EE
ggunn said:
Why not? It's just an embedded sunbpanel. As long as you conform to 705.12 on both buses, I don't see why you couldn't connect to it.
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It could be done, but then it's very likely you'd have to give up one of the 2-pole breaker locations on the main bus anyway in order to meet the maximum of 6 disconnects grouped in one location requirement. Unless the AHJ will allow otherwise.
 
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jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
synchro said:
It could be done, but then it's very likely you'd have to give up one of the 2-pole breaker locations on the main bus anyway in order to meet the maximum of 6 disconnects grouped in one location requirement. Unless the AHJ will allow otherwise.
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Huh? If the lighting bus qualifies for your backfeed then that's it, you're done.
 
G

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
synchro said:
It could be done, but then it's very likely you'd have to give up one of the 2-pole breaker locations on the main bus anyway in order to meet the maximum of 6 disconnects grouped in one location requirement. Unless the AHJ will allow otherwise.
Click to expand...

If that's what your AHJ says you have to do it, I guess, but the NEC does not say that. PV connected on the load side of an OCPD does not contribute to the six handle rule.

Really, it doesn't even if it's on the line side, but many AHJ's don't see it that way. That's a battle I actually won with my local AHJ, with some support from some material from Mike Holt.
 
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