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Thread: PV System Interconnection in the Main Service Panel

  1. #1
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    PV System Interconnection in the Main Service Panel

    Hey Guys,

    We have this site, where the load from the solar is 1800A, and I am planning to use 5 sets of 500 CU. The interconnection is in the electrical room and ahead of the meter in the main service panel. The problem is there is no space for 5 sets of 500s in the bus (See Attached). There is already 8 sets of 500 AL in the bottom and 4 sets on top. The idea is to connect it on the top, since we have some space, but still not enough for 5 Sets of 500 CU. From the picture, is there a way we could extend the bus (by contacting the manufacturer)? and even if we extend it, will the weight of the wire damage the bus?

    Has anyone here dealt with such issue in their past?
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    Good Luck

    I did some digging for various lugs and connectors and do not see any easy way to make room for 5 more conductors, it looks like all the spare room has been used up. I think you are looking at a custom bus expansion, working with the manufacturer may be the only solution.
    e^(i pi) = -1

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    Yeah that's a tough one. The only ideas I can come up with:

    1. Combine one or more of those existing feeds into one larger conductor to free up space. Assuming most of those are parallel conductors you have to be careful to terminate them all the same way, but it looks like two are smaller so maybe those?

    2. If you look at those busbars that drop down from above, those very likely have nema standard bolt pattern so you could add a lug to that joint.

    3. Crimped on lugs can be stacked, so maybe there is a combination that will work. If you took off the existing lugs and put on a nema pattern plate and could get 4 lugs, 2 on each side, of a hole pair....or some game like that.

    Of course any of those could open you up to a "modification violation" depending on how strict your AHJ is. Some places I work I could just do whatever I needed with listed parts and no one would care, but YMMV.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

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    Couldn’t you just change out the top lugs to the same type as the bottom lugs?

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    Quote Originally Posted by five.five-six View Post
    Couldn’t you just change out the top lugs to the same type as the bottom lugs?
    He would still be one Port short.

    I have another idea. Maybe use a 1600 amp 100% rated breaker to ditch the 125% factor, which would drop the number of needed sets down to 4? 1600/4 is 400 which is 4 sets of 500.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

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    Do you have room on the back of the bus for 4 750's and stack crimps?

    Sent from my LGL157BL using Tapatalk
    Some people are like slinkies. They serve absolutely no useful purpose. But still put a smile on your face when pushed down a flight of stairs.

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    Quote Originally Posted by electrofelon View Post
    He would still be one Port short.

    I have another idea. Maybe use a 1600 amp 100% rated breaker to ditch the 125% factor, which would drop the number of needed sets down to 4? 1600/4 is 400 which is 4 sets of 500.
    Does this work? Don't conductors still have to be rated 125%?

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    Quote Originally Posted by jaggedben View Post
    Does this work? Don't conductors still have to be rated 125%?
    No, see 215.2(A)(1) Exception 1 and 210.19(A)(1) Exception. The circuit breaker is the only weak link; the conductors are already "100% rated."

    Cheers, Wayne

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    The usual use of 100% breakers is to reduce conductor costs. There are often situations where the increased cost of the breaker and enclosure are more than offset by the conductor savings. There was a good article that gave an example or case study of this, but I can't find it. Here is a general article:

    https://iaeimagazine.org/magazine/20...ocpd-solution/

    Also there may be situations like the OP's where there is a compelling reason to reduce the quantity of conductors. Add in the cost of the accessories for the equipment to make this work (if even available) and a potential UL field evaluation, or a wholesale equipment change, and it may turn out to be an attractive option.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

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    Replace the top lugs with the type of lugs used at the bottom (Ilsco PBHD2-750 or something similar) and then combine the two smaller conductors per phase into a single conductor using Burndy Clear Taps or Polaris connectors. That will get you 5 empty ports per phase.

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