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Thread: Use of 120% Rule (Solar Breaker Position) 705.12.D.2.3.b

  1. #11
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    Quote Originally Posted by APS Solar View Post
    We always try to land the solar breaker on the opposite side of the bus from the Main. However there are times due to wire limitations in the main that we can't put the solar breaker in the bottom slot but very near it. My chief building inspector who always passed jobs before is now telling me that the 120% rule will not apply if we can't get it into the far slot so now he wants me to downsize the Mains breaker (to 175A) for a 5KW system with a 30A solar breaker. Does this seem ridiculous? What can be done here? He will listen if I can point to code to justify my position. Also he told me that if the panel has a center fed main breaker then this 120% rule would not apply. Again we've been doing this for years with no problems.

    Advise plz.
    If you cannot place breaker opposite the feed.....120% allowance will not apply.
    The AHJ really has been lenient prior.

    BTW - downsizing the main breaker is my favorite strategy. I use it all the time.

    Now hold on......you still cannot feed 30A of solar! Assuming a 200 rated panel with a new 175A main breaker. That adds up to 205A which exceeds the 100% rule.
    (I, per se, don't see a big problem, with 30A + 175A = 205A on a 200A bus......if your solar breaker really is immediately adjacent to end position on bus......but it is in fact not to Code. If inspector says fine, you are still lucky.)

  2. #12
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    Quote Originally Posted by Zee View Post

    Now hold on......you still cannot feed 30A of solar! Assuming a 200 rated panel with a new 175A main breaker. That adds up to 205A which exceeds the 100% rule.
    (I, per se, don't see a big problem, with 30A + 175A = 205A on a 200A bus......if your solar breaker really is immediately adjacent to end position on bus......but it is in fact not to Code. If inspector says fine, you are still lucky.)
    This is right. The AHJ is still being lenient with suggesting 175 instead of 150. But I'd also need more information to be convinced that it's not much easier to move the breaker to the opposite end, anyway.

  3. #13
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    Wire-nuts are allowed in a service panel.


  4. #14
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    Quote Originally Posted by APS Solar View Post
    We always try to land the solar breaker on the opposite side of the bus from the Main. However there are times due to wire limitations in the main that we can't put the solar breaker in the bottom slot but very near it. My chief building inspector who always passed jobs before is now telling me that the 120% rule will not apply if we can't get it into the far slot so now he wants me to downsize the Mains breaker (to 175A) for a 5KW system with a 30A solar breaker. Does this seem ridiculous? What can be done here? He will listen if I can point to code to justify my position. Also he told me that if the panel has a center fed main breaker then this 120% rule would not apply. Again we've been doing this for years with no problems.

    Advise plz.
    Your inspector has been passing systems which have a code violation. Just because he used to do it doesn't mean he has to continue doing it. Maybe he was reprimanded for it.

  5. #15
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    Quote Originally Posted by ggunn View Post
    Your inspector has been passing systems which have a code violation. Just because he used to do it doesn't mean he has to continue doing it. Maybe he was reprimanded for it.
    AHJ passes something that the contractor thinks might be a code violation, either because the AHJ missed it, does not understand why it is incorrect, or just doesn't care about that one thing, etc. Contractor spends the next 30 years arguing with every AHJ that flags the same thing as being non-compliant saying the way they did it is code compliant because an AHJ approved it once. "I've been doing it this way for 30 years and you are the first AHJ to say I can't do this."

  6. #16
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    Quote Originally Posted by pv_n00b View Post
    AHJ passes something that the contractor thinks might be a code violation, either because the AHJ missed it, does not understand why it is incorrect, or just doesn't care about that one thing, etc. Contractor spends the next 30 years arguing with every AHJ that flags the same thing as being non-compliant saying the way they did it is code compliant because an AHJ approved it once. "I've been doing it this way for 30 years and you are the first AHJ to say I can't do this."
    And it's made even more complicated by the fact that every AHJ has its own special idiosyncrasies that may or may not have any basis in the NEC. We have a constantly evolving document that's now up to 5 pages long with AHJ's listed along with what makes them special.

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