PV load side connection without a service main breaker.

[ocoee]

I have a 120 208 three phase MDP. 1200 amp bussing. We could do a supply side connection but would rather not if there is a way around it.

The MDP has no main breaker and is 25 years old and located in a large church. We would like to keep this equipment for the expenses of replacement make this project a non starter.

My back feed breaker will be 300 amps. My buss bar is 1200 but no main breaker exists or is able to be installed. Is there a way to install my backed breaker when no main exists.

Currently, in the MDP there is 700 amp breaker feeding some more distribution equipment. a 200 amp breaker feeding a panel. and 2. 100 amp breakers feeding other equipment. A total of four handles to disconnect the entire service.

My guess is that I can not install a pv breaker in this situation. because..... A total of 1100 amp can be pulled through the bussing before any on the four load breakers would trip. plus the current on the back feed breaker 240 amp MAX I. would exceed the buss bar rating. Plus there is room for more load breakers to be added increasing the total load beyond what is there now.

Thought?

Thanks

 

[jaggedben]

You seem to be saying that the MDP is the service equipment since there is no main upstream. In that case, adding a breaker to the MDP *is* a supply side connection.

A potential complication is that this kind of service equipment configuration is no longer allowed in new installations, since the 2020 NEC. The 2023 NEC contains an exception for services that were compliant when installed. If you are still on the 2017 NEC it's no issue. But if you are one the 2020 NEC you may need to get the AHJ to specially grandfather the installation.

Adding a source breaker to the panel does not increase the amount of current that the existing four breakers can draw. It is perfectly safe and code compliant.

Another option could be to do a tap on the 700A feeder. You would need to protect the feeder on the load side of your tap with another 700A overcurrent device.

 

[ggunn]

I have a 120 208 three phase MDP. 1200 amp bussing. We could do a supply side connection but would rather not if there is a way around it.

The MDP has no main breaker and is 25 years old and located in a large church. We would like to keep this equipment for the expenses of replacement make this project a non starter.

My back feed breaker will be 300 amps. My buss bar is 1200 but no main breaker exists or is able to be installed. Is there a way to install my backed breaker when no main exists.

Currently, in the MDP there is 700 amp breaker feeding some more distribution equipment. a 200 amp breaker feeding a panel. and 2. 100 amp breakers feeding other equipment. A total of four handles to disconnect the entire service.

My guess is that I can not install a pv breaker in this situation. because..... A total of 1100 amp can be pulled through the bussing before any on the four load breakers would trip. plus the current on the back feed breaker 240 amp MAX I. would exceed the buss bar rating. Plus there is room for more load breakers to be added increasing the total load beyond what is there now.

Thought?

Thanks

Well, a couple of things.

What code cycle are you on? Main panels that are MLO and have no main service disconnect with OCP ahead of them are now not compliant; I doubt that an AHJ will permit you to land a PV breaker in one without bringing the service up to code, and for a large service this would be expensive. Maybe very expensive.

But assuming that it would be allowed, the rating of the busbar is irrelevant; it already has a whole lot more current available to it than its rating. You seem to be confabulating 705.12 (load side) with 705.11 (supply side) issues. If you land a PV breaker in an MLO service panel, it is a supply side, not a load side interconnection and all the load breakers are service disconnects.

 

[don_resqcapt19]

Well, a couple of things.

What code cycle are you on? Main panels that are MLO and have no main service disconnect with OCP ahead of them are now not compliant; I doubt that an AHJ will permit you to land a PV breaker in one without bringing the service up to code, and for a large service this would be expensive. Maybe very expensive.

But assuming that it would be allowed, the rating of the busbar is irrelevant; it already has a whole lot more current available to it than its rating. You seem to be confabulating 705.12 (load side) with 705.11 (supply side) issues. If you land a PV breaker in an MLO service panel, it is a supply side, not a load side interconnection and all the load breakers are service disconnects.

That change was made in the 2020 code, but they added an exception in the 2023 code to permit additional breakers to be installed in MLO service equipment that was installed under the 2017 or older code.

 

[ggunn]

That change was made in the 2020 code, but they added an exception in the 2023 code to permit additional breakers to be installed in MLO service equipment that was installed under the 2017 or older code.

Would the exception cover PV breakers or is it left to the discretion of the AHJ that is responsible for enforcing electrical rules?

 

[ocoee]

Well, a couple of things.

What code cycle are you on? Main panels that are MLO and have no main service disconnect with OCP ahead of them are now not compliant; I doubt that an AHJ will permit you to land a PV breaker in one without bringing the service up to code, and for a large service this would be expensive. Maybe very expensive.

But assuming that it would be allowed, the rating of the busbar is irrelevant; it already has a whole lot more current available to it than its rating. You seem to be confabulating 705.12 (load side) with 705.11 (supply side) issues. If you land a PV breaker in an MLO service panel, it is a supply side, not a load side interconnection and all the load breakers are service disconnects .

Sounds about right. I have never considered the buss bar to be an extension of the service lateral, I guess it is. I always connect "supply side" of the bussing either on Parallel main lugs or taps on the entrance conductors.

Would the exception cover PV breakers or is it left to the discretion of the AHJ that is responsible for enforcing electrical rules

rating of the busbar is irrelevant; it already has a whole lot more current available to it than its rating.

Aside from adding more load breakers ,a buss bar without a main OCPD would be limited to the connected loads via the branch circuit breakers. Not necessarily exceeding the buss rating. (often times but but not in this case).

Going to connect to the spare main lugs. and follow the rules for a supply side connection.

 

[don_resqcapt19]

Would the exception cover PV breakers or is it left to the discretion of the AHJ that is responsible for enforcing electrical rules?

In my opinion it covers breakers installed for any reason as they are all service disconnects, even though CMP4 does not like that term.

 

[don_resqcapt19]

Sounds about right. I have never considered the buss bar to be an extension of the service lateral, I guess it is. I always connect "supply side" of the bussing either on Parallel main lugs or taps on the entrance conductors.


rating of the busbar is irrelevant; it already has a whole lot more current available to it than its rating.

Aside from adding more load breakers ,a buss bar without a main OCPD would be limited to the connected loads via the branch circuit breakers. Not necessarily exceeding the buss rating. (often times but but not in this case).

Going to connect to the spare main lugs. and follow the rules for a supply side connection.

This is service equipment and the only limit on adding solar to this is that the rating of the solar breaker cannot exceed the rating of the service.

Not sure why you want to connect to the spare lugs...you are still going to need an OCPD. Seems like adding a breaker could be cheaper than adding a service disconnect downstream from the spare main lugs.

 

[jaggedben]

Would the exception cover PV breakers or is it left to the discretion of the AHJ that is responsible for enforcing electrical rules?

It would cover PV breakers. It should not be up to discretion.

 

[electrofelon]

Aside from adding more load breakers ,a buss bar without a main OCPD would be limited to the connected loads via the branch circuit breakers. Not necessarily exceeding the buss rating. (often times but but not in this case).

Note that it has always been allowed (2017 and prior) for the sum of MLO breakers to exceed the rating of the busbar. The busbar is considered protected by the load calc. 230.90(A) Ex #3.