Switchgear with no main breaker

[CMEFAY]

I have a solar installation here in northern Illinois that the solar installer wants to connect 1000A onto a 1600A bus in a switchgear with no main breaker. The gear already has 2000A of load with three breakers (800, 600, 600) on the bus.

His response to my concern is as follows:

At this particular site, we do not have a single main breaker, and we are using the 6 disconnecting means rule. The interconnection is line side of the existing disconnecting means/devices and would be interconnected under 705.12(A), allowing per 230.82(6) to be interconnected line side, and that the sum of all “Power Production Sources” (i.e. solar) do not exceed the rating of the service. In our case, this is 1000A of Solar compared to the 1600A service.

References:

705.12(A) Supply Side. An electric power production source shall be permitted to be connected to the supply side of the service disconnecting means as permitted in 230.82(6). The sum of the ratings of all overcurrent devices connected to power production sources shall not exceed the rating of the service.

230.82(6) – Solar photovoltaic systems, fuel cell systems, wind electric systems, energy storage systems, or interconnected electric power production sources


This seems like a violation to me because there is no single service disconnecting means to protect the bus.

I welcome any comments and am always open to learning!

Thanks, Lori

 

[ggunn]

I have a solar installation here in northern Illinois that the solar installer wants to connect 1000A onto a 1600A bus in a switchgear with no main breaker. The gear already has 2000A of load with three breakers (800, 600, 600) on the bus.

His response to my concern is as follows:

At this particular site, we do not have a single main breaker, and we are using the 6 disconnecting means rule. The interconnection is line side of the existing disconnecting means/devices and would be interconnected under 705.12(A), allowing per 230.82(6) to be interconnected line side, and that the sum of all “Power Production Sources” (i.e. solar) do not exceed the rating of the service. In our case, this is 1000A of Solar compared to the 1600A service.

References:

705.12(A) Supply Side. An electric power production source shall be permitted to be connected to the supply side of the service disconnecting means as permitted in 230.82(6). The sum of the ratings of all overcurrent devices connected to power production sources shall not exceed the rating of the service.

230.82(6) – Solar photovoltaic systems, fuel cell systems, wind electric systems, energy storage systems, or interconnected electric power production sources


This seems like a violation to me because there is no single service disconnecting means to protect the bus.

I welcome any comments and am always open to learning!

Thanks, Lori

Your installer is correct, although some AHJs will not allow a connection like this, and the service is not 2023 NEC compliant; you need to make sure the AHJ is not enforcing the 2023 code yet or it will likely be "you touch it, you fix it", which will not be cheap.

The "rating of the service" is ambiguous in the version of the NEC he is quoting, but you want to make sure that the bus and service conductors can handle 1000A and that the kVA rating of the utility transformer is not less than the AC kW rating of the PV system; none of that should be a problem on a 1600A service. In this system, since there is no OCPD ahead of the bus, the load breakers are all service disconnects and the PV is a supply side connection. The fact that there is no OCPD ahead of the bus means that the bus already has access to the full load current from the utility transformer, which is typically more than the rating of the bus. The ratings of the load breakers on the bus are not relevant.

 

[jaggedben]

This seems like a violation to me because there is no single service disconnecting means to protect the bus.

I welcome any comments and am always open to learning!

Thanks, Lori

First, see 230.90 Exception 3 with respect to the 2000A of breakers on a 1600A bus. This certainly could be compliant. A load calculation or documentation from the time of installation could verify that. The solar is not a load and does not increase the calculated load, so only the calculated load on the existing disconnects needs to be considered.

As for a single disconnecting means, it is not a violation to have multiple service disconnects. But compare 230.71 in the 2017 NEC to the 2020 NEC, and take note of the exception in the 2023 NEC. The 2020 NEC prohibited multiple service disconnects in the same enclosure, but before that it was allowed. The 2023 NEC contains an exception grandfathering older installations.
So it matters a lot which code cycle you're enforcing here, as well as your willingness to grandfather the existing installation if you are enforcing the 2020 NEC.

If the solar installers are taking their 1000A feed to a disconnect in a separate enclosure, I would argue that it's compliant with the 2020 NEC.

 

[jaggedben]

Your installer is correct, although some AHJs will not allow a connection like this, and the service is not 2023 NEC compliant; ...

Under the 2023 NEC the service could be compliant if it was compliant when installed. The 2020 NEC did not have that exception. (230.71)

 

[ggunn]

Under the 2023 NEC the service could be compliant if it was compliant when installed. The 2020 NEC did not have that exception. (230.71)

You are correct, sir. I thought that the separate enclosure rules came in in 2023, but I see that they are in the 2020 NEC (thanks for citing the article). I haven't designed a system connected like the one described here in several years. If the OP's AHJ is on the 2020 NEC and doesn't want to grandfather it in, there may be a problem.

 

[electrofelon]

Not part of your question, but FYI it may be of concern how this bus tap is made. A real picky AHJ may only allow connections to existing or factory approved lugs, or lugs bolted to existing holes marked "tap", see this article. They may insist on a field evaluation for other methods. Of course they might not be picky about this at all, you never know what you're going to get.

Tapping Busbar Considerations - Code Authorities https://code-authorities.ul.com/wp-content/uploads/2014/04/ul_TappingBusbarConsiderations.pdf

 

[CMEFAY]

Thank you all for your help and clarifying the situation. I am the AHJ, and we are under the 2014 code right now. I did assume that the original installation allowed for the exception to allow for engineering load calculations.

My enforcement style allows for the belief that most installations can utilize the newer codes, and often look ahead when making a decision in a difficult situation to see if it may be allowed in newer codes. They did the taps on the factory tap locations.

To summarize the situation, would you say that if there was a main breaker, the connection would have to be made either before the main breaker or on the opposite end of the bus as a load side tap, but because there is no main breaker this is considered a supply side tap and can be connected anywhere before or after the multiple disconnects?

Thanks and have a great day!

Lori

 

[ggunn]

To summarize the situation, would you say that if there was a main breaker, the connection would have to be made either before the main breaker or on the opposite end of the bus as a load side tap, but because there is no main breaker this is considered a supply side tap and can be connected anywhere before or after the multiple disconnects?

In essence, yes, but if the panel had a 1600A breaker on a 1600A bus, the most inverter output current you could connect to a backfed breaker at the opposite end of the busbar would be (0.2)(1600A)(0.8) = 256A.

 

[jaggedben]

...

To summarize the situation, would you say that if there was a main breaker, the connection would have to be made either before the main breaker or on the opposite end of the bus as a load side tap,

That's not a complete description of options, but it's a start. The opposite end thing is a rule for one of the load side connection options, yes.

but because there is no main breaker this is considered a supply side tap and can be connected anywhere before or after the multiple disconnects?

Yes.

 

[ggunn]

That's not a complete description of options, but it's a start. The opposite end thing is a rule for one of the load side connection options, yes.

But also note that the OP said that the PV connection is 1000A. That is too much for a backfed breaker in a 1600A panel with a 1600A MCB.

 

[CMEFAY]

Thank you for all for your help. I refer to this forum often to research and clarify code questions. Since Illinois doesn't have licensing, we are on our own here.

 

[electrofelon]

But also note that the OP said that the PV connection is 1000A. That is too much for a backfed breaker in a 1600A panel with a 1600A MCB.

A few nitpicks, since after all this is the MH forum . Panelboards only go up to 1200A so this would be a switch board not a panelboard. Switchboards are likely to have a bus rating higher than the main breaker, although doubtfully enough to meet the 120% rule with a 1000A back feed.

And finally, does the multiple ampacity busbar with engineering supervision provision still exist? I've lost track