Announcement

Collapse
No announcement yet.

Conductor Sizing for Solar Sub Panel Output

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • ggunn
    replied
    Originally posted by iwire View Post
    Yes, same in many places

    The AHJ makes written changes that everyone know about, they cant simply decide on the spot.
    That's what I meant; sorry if I wasn't clear.

    Leave a comment:


  • iwire
    replied
    Originally posted by ggunn View Post
    The city passed an ordinance that declares what is the electric code for the city. It references the 2014 NEC but adds stuff that is not in the NEC. They don't make stuff up on the spot but they enforce their code, which is mostly the NEC but has some differences. The NEC is not law but their ordinance is.
    Yes, same in many places

    The AHJ makes written changes that everyone know about, they cant simply decide on the spot.

    Leave a comment:


  • ggunn
    replied
    Originally posted by iwire View Post
    I doubt that is true in your area and it certainly is not the case in most places.

    That would be the same as a judge making up laws on the spot.
    The city passed an ordinance that declares what is the electric code for the city. It references the 2014 NEC but adds stuff that is not in the NEC. They don't make stuff up on the spot but they enforce their code, which is mostly the NEC but has some differences. The NEC is not law but their ordinance is.

    Leave a comment:


  • Smart $
    replied
    Originally posted by jaggedben View Post
    Yes, but still not the breaker for the feeder. Some AHJs will apply it to all busses and conductors, and some will apply it to none if the bus is in a combiner panel dedicated to inverters. Most the AHJs I encounter will not apply it to the feeder even under the 2011 code.
    You are correct. Got to thinking about it after I posted. Figured I'd wait until you replied to 'fess up.

    Leave a comment:


  • electrofelon
    replied
    Originally posted by ggunn View Post
    The AHJ can adopt the NEC or not, and it can selectively enforce it as well as amend it as they see fit. My local AHJ has adopted the 2014 NEC but is not yet enforcing rapid shutdown. The AHJ is the last word.
    Are they just not enforcing it, or is there an amendment stating that 690.12 shall be deleted/not adopted?

    Leave a comment:


  • iwire
    replied
    Originally posted by ggunn View Post
    The AHJ can adopt the NEC or not, and it can selectively enforce it as well as amend it as they see fit. My local AHJ has adopted the 2014 NEC but is not yet enforcing rapid shutdown. The AHJ is the last word.
    I doubt that is true in your area and it certainly is not the case in most places.

    That would be the same as a judge making up laws on the spot.

    Leave a comment:


  • ggunn
    replied
    Originally posted by Carultch View Post
    . The AHJ is not supposed to make up their own rules. Any violation claim needs to be based on a specific code requirement.
    The AHJ can adopt the NEC or not, and it can selectively enforce it as well as amend it as they see fit. My local AHJ has adopted the 2014 NEC but is not yet enforcing rapid shutdown. The AHJ is the last word.

    Leave a comment:


  • jaggedben
    replied
    Originally posted by Smart $ View Post
    Some interpret the 120% rule of earlier editions as applying to all buses and feeders between PV inverter and service.
    Yes, but still not the breaker for the feeder. Some AHJs will apply it to all busses and conductors, and some will apply it to none if the bus is in a combiner panel dedicated to inverters. Most the AHJs I encounter will not apply it to the feeder even under the 2011 code.

    Leave a comment:


  • GoldDigger
    replied
    Originally posted by jaggedben View Post
    That's only true for calculating the 120% rule. The code never said that the breaker for a feeder supplying an AC combiner has to be done that way.
    True.
    In exactly the same way that you do not add up load breakers to get the load on a feeder.

    Leave a comment:


  • Smart $
    replied
    Originally posted by jaggedben View Post
    That's only true for calculating the 120% rule. The code never said that the breaker for a feeder supplying an AC combiner has to be done that way.
    Some interpret the 120% rule of earlier editions as applying to all buses and feeders between PV inverter and service.

    Leave a comment:


  • jaggedben
    replied
    Originally posted by GoldDigger View Post
    Pre 2014 (e.g. 2011) the code specifically says to add up the values of the first breaker on each inverter output.
    That's only true for calculating the 120% rule. The code never said that the breaker for a feeder supplying an AC combiner has to be done that way.

    Leave a comment:


  • GoldDigger
    replied
    Pre 2014 (e.g. 2011) the code specifically says to add up the values of the first breaker on each inverter output.

    Leave a comment:


  • Carultch
    replied
    Originally posted by roblsmith3 View Post
    Thank you all for replying! I originally had 1 AWG and wanted to be sure it was still good to use. JaggedBen, i hear you on the 125A MCB thing.....That's what I would like to do but a lot of the AHJs around here don't see it that way and want us to add up the breakers.....I've been fighting it for years! Anyways, thank you all again for replying. Till next time!
    Do they ever provide a code reference on why they want you to add up the breakers, and accumulate all the rounding errors? Instead of adding up the current, and applying a master 1.25 factor. The AHJ is not supposed to make up their own rules. Any violation claim needs to be based on a specific code requirement.

    I can understand accumulating rounding errors, if you are sizing conductors for use with an MLO panel with no master OCPD anywhere within the main output circuit. But once you have a master OCPD, the master OCPD should only need to be as large as 125% of the total maximum continuous current, and the wire should only need to be as large as needed for the load and to be protected by the master OCPD.

    Leave a comment:


  • roblsmith3
    replied
    Thank you all for replying! I originally had 1 AWG and wanted to be sure it was still good to use. JaggedBen, i hear you on the 125A MCB thing.....That's what I would like to do but a lot of the AHJs around here don't see it that way and want us to add up the breakers.....I've been fighting it for years! Anyways, thank you all again for replying. Till next time!

    Leave a comment:


  • Carultch
    replied
    Originally posted by jaggedben View Post
    I'm curious why you say the wire ampacity must be a millionth of an amp over the breaker rating, instead of a thousandth or a billionth.
    It was arbitrary. I just held the zero key down a random amount of time, and it happened to coincide with a millionth. I'm exaggerating to make my point about the next size up rule, in the sense that the ampacity of the conductor cannot be an exact match to the previous standard OCPD rating, and that it has to be able to exceed the previous and round up to the next. The rule doesn't specify just how much it needs to exceed the previous standard size.

    I've been in situations where after adjustment and correction factors, the ampacity of the conductor is small fractions (less than 0.5A) of amperes above a standard breaker size. It can also depend on how you calculate the temperature correction, whether you use the square root formula, or the rounded values based on the 5C temperature ranges.

    Leave a comment:

Working...
X