How Many feed back PV breakers per Panel?

I

ING23

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Las Vegas
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Site Survey Tech
Hi, My PV permit was rejected because AHJ states only one PV breaker is allowed per Service Panel and they mention that only one dedicated output breaker is permitted per 705.12 2017 NEC.

Article 705.12(B)(1) States that ONE or MORE power source shall have its own circuit breaker or fusible disconnect means. ( One per Power source )
Article 705.12(B)(2)(3)(b) or commonly known as 120% rule for back feed breaker at the opposite side of the bus bar specifically mention .......power source(s) ..... referring at the possibility to have more than ONE power source (on our project Two Back feed breaker at the opposite end of the bus bar)

Am I misunderstanding this ?
 

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Normally when multiple PV AC sources are to brought to a service they are first brought to a combiner panel then only one feed would go to the service panel.
 
Fred B said:
Normally when multiple PV AC sources are to brought to a service they are first brought to a combiner panel then only one feed would go to the service panel.
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Maybe that's normal, but it's not required. Plan reviewer's rejection in the OP is incorrect.

Cheers, Wayne
 
wwhitney said:
Maybe that's normal, but it's not required. Plan reviewer's rejection in the OP is incorrect.

Cheers, Wayne
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Not necessarily; some AHJs will only allow a single point of interconnection for a PV system. Austin Energy and CPS (San Antonio) both have this rule.
 
ggunn said:
Not necessarily; some AHJs will only allow a single point of interconnection for a PV system. Austin Energy and CPS (San Antonio) both have this rule.
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The OP references a rejection per 705.12 2017 NEC. That part is incorrect.

If the AHJ is a POCO and has their own rules, then your caveat is applicable.

Cheers, Wayne
 
ING23 said:
Hi, My PV permit was rejected because AHJ states only one PV breaker is allowed per Service Panel and they mention that only one dedicated output breaker is permitted per 705.12 2017 NEC.

Article 705.12(B)(1) States that ONE or MORE power source shall have its own circuit breaker or fusible disconnect means. ( One per Power source )
Article 705.12(B)(2)(3)(b) or commonly known as 120% rule for back feed breaker at the opposite side of the bus bar specifically mention .......power source(s) ..... referring at the possibility to have more than ONE power source (on our project Two Back feed breaker at the opposite end of the bus bar)

Am I misunderstanding this ?
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AHJ is incorrect, although this is a somewhat common misunderstanding as far as I've seen in this forum.

Both breakers arguably need to be at the opposite end, so a side-by-side panel or a quad breaker may be needed.

Ask him where it says there can only be one per service panel. (Note also the rule quoted applies to all panels.) The NEC is a permissive code: unless it clearly prohibits something, or requires something else, then it's allowed.
 
jaggedben said:
AHJ is incorrect, although this is a somewhat common misunderstanding as far as I've seen in this forum.

Both breakers arguably need to be at the opposite end, so a side-by-side panel or a quad breaker may be needed.

Ask him where it says there can only be one per service panel. (Note also the rule quoted applies to all panels.) The NEC is a permissive code: unless it clearly prohibits something, or requires something else, then it's allowed.
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(25+16)*1.25+175=220 (which is less than 200*1.2=240A)

(25+16+175)*1.25=264 (which is more than 200*1.2=240A)

Maybe they were even using the breaker ratings instead of the solar source ratings?

Do you think they were just doing the math wrong? I used to include the main for the longest time because of the confusing wording.

There is also the phrasing "Where two sources, one a primary power source and the other another power source, are located at opposite ends of a busbar", which would imply one solar one utility. Maybe that is what they are pulling from?

So maybe you should just meet (a) and be done? If the bus bar is 225A then you got it.

(1.25*(25+16)) +175 < 225
 
Elect117 said:
(25+16)*1.25+175=220 (which is less than 200*1.2=240A)

(25+16+175)*1.25=264 (which is more than 200*1.2=240A)

Maybe they were even using the breaker ratings instead of the solar source ratings?

Do you think they were just doing the math wrong? I used to include the main for the longest time because of the confusing wording.

There is also the phrasing "Where two sources, one a primary power source and the other another power source, are located at opposite ends of a busbar", which would imply one solar one utility. Maybe that is what they are pulling from?

So maybe you should just meet (a) and be done? If the bus bar is 225A then you got it.

(1.25*(25+16)) +175 < 225
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I just traying to comply with the 120% rule , specific for the opposite end of the bus bar. You are write about where they came out with the two source but the ( s ) on Article 705.12(B)(2)(3)(b) should means more than one also.
 
ING23 said:
I just traying to comply with the 120% rule , specific for the opposite end of the bus bar. You are write about where they came out with the two source but the ( s ) on Article 705.12(B)(2)(3)(b) should means more than one also.
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I was just trying to piece together what the AHJ might be saying so that you can better prepare to debate them or make a revision to get a fast approval.

In this case, it would be easier to verify the panel's busbar rating of 225A and then just use (a). Then you could see if the AHJ approves it. I think they are just interpreting the 120% rule incorrectly or differently than usual. It might be more difficult to get them to see it your way than it would be to adapt and move on.

If the busbar is not 225A, then I would just put in a PV combiner breaker panel next to the service panel. It shouldn't add much of a cost.
 
Elect117 said:
It might be more difficult to get them to see it your way than it would be to adapt and move on.
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This. I have learned to choose my battles.
Elect117 said:
If the busbar is not 225A, then I would just put in a PV combiner breaker panel next to the service panel. It shouldn't add much of a cost.
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I am not sure what you mean by this, but if the 120% rule won't allow the PV interconnection in the main panel, just putting into a subpanel and connecting it via a breaker in the main panel won't help.
 
ggunn said:
I am not sure what you mean by this, but if the 120% rule won't allow the PV interconnection in the main panel, just putting into a subpanel and connecting it via a breaker in the main panel won't help.
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Maybe I misunderstood.

705.12(B)(2)(3)(b) - "Where two sources, one a primary power source and the other another power source, are located at opposite ends of a busbar that contains loads, ..."

I was under the impression the AHJ's comments might have to do with (b) saying the line above. Or they were doing the calculation wrong.

By adding a combiner panel it makes the interconnection only two sources. One solar (since you had a combiner panel upstream) and one utility. You could also argue that it is only one disconnect per interconnection if they land on a breaker in the service panel. The combiner panel wouldn't contain loads. I thought it might be a work around on both AHJ comments.
 
Elect117 said:
Maybe I misunderstood.

705.12(B)(2)(3)(b) - "Where two sources, one a primary power source and the other another power source, are located at opposite ends of a busbar that contains loads, ..."

I was under the impression the AHJ's comments might have to do with (b) saying the line above. Or they were doing the calculation wrong.

By adding a combiner panel it makes the interconnection only two sources. One solar (since you had a combiner panel upstream) and one utility. You could also argue that it is only one disconnect per interconnection if they land on a breaker in the service panel. The combiner panel wouldn't contain loads. I thought it might be a work around on both AHJ comments.
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It would indeed combine the PV into one interconnection point on the main panel bus; we do that frequently. Some people, though, incorrectly believe that when you do this it gets around the 120% rule requirements in the main panel, which it does not. I thought that you might be suggesting landing the PV in a combiner panel for that reason. BTW, 705.12(B)(3) in the 2023 NEC (aka the "sum of all breakers" rule - it moves around in 705.12) does allow loads in the combiner panel.
 
Reviewing 2023 NEC 705.12(B)(2) afresh, I am afraid that there is strong support for the idea that as written it permits only one non-primary power source output connection (per busbar). The full text (minus warning label text) is below, with the relavent portions bolded. Commenting on those bolded portions in order:

(1) Two means two and excludes three or more
(2) One power source connection may carry the current from multiple power sources if those currents are first combined separately
(3) "The" is singular and implies only one back-fed breaker.

Cheers, Wayne

2023 NEC 705.12(B)(2)

Where two sources, one a primary power source and the other another power source, are located at opposite ends of a busbar that contains loads, the sum of 125 percent of the power-source(s) output circuit current and the rating of the overcurrent device protecting the busbar shall not exceed 120 percent of the busbar ampere rating. The busbar shall be sized for the loads connected in accordance with Article 220. A permanent warning label shall be applied to the distribution equipment adjacent to the back-fed breaker from the power source that displays the following or equivalent wording:
 
My rewrite of 705.12(B)(2) to allow multiple non-primary connections:

Where two or more sources, one of them primary, are located so that all non-primary sources are at the opposite end of a busbar from the primary source, the sum of 125 percent of the non-primary power-source(s) output circuit current and the rating of the primary overcurrent device protecting the busbar shall not exceed 120 percent of the busbar ampere rating. The busbar shall be sized for the loads connected in accordance with Article 220. A permanent warning label shall be applied to the distribution equipment adjacent to each back-fed breaker from the non-primary power source(s) that displays the following or equivalent wording:
 
ggunn said:
This. I have learned to choose my battles.

I am not sure what you mean by this, but if the 120% rule won't allow the PV interconnection in the main panel, just putting into a subpanel and connecting it via a breaker in the main panel won't help.
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Agree, l am going to use a Load Center to combine the Old and the New PV system ending in One PV breaker at the Main Panel .
Just some thoughts I think , regardless of how many subpanel you have down string from the Main panel , you have to comply with the 120% rule as you mention before . Thanks for the advise (choose my battles.)
 
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