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Thread: Pretty simple wire sizing question but want to be sure

  1. #1
    Join Date
    Mar 2016
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    Washington State
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    Pretty simple wire sizing question but want to be sure

    So I will be installing (3) Solaredge 7600 inverters (32 amp continuous output). All of their AC outputs will land in a combiner panel before heading to the main panel. So (3) 40 amp breakers in the combiner panel.

    So.......32 amps+32+ 32= 96 amps. Muliplied by 1.25 and get 120 amps. This is my full inverter output adjusted for continuous load.

    Now to size wire. Looks like if I use THWN-2 or THHN I can go safely with #2 conductors (good to 130 amps) with a 125 amp breaker in the main panel.

    Does this look right?

    Thanks

  2. #2
    Join Date
    May 2013
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    Massachusetts
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    Quote Originally Posted by bbartmasse r View Post
    So I will be installing (3) Solaredge 7600 inverters (32 amp continuous output). All of their AC outputs will land in a combiner panel before heading to the main panel. So (3) 40 amp breakers in the combiner panel.

    So.......32 amps+32+ 32= 96 amps. Muliplied by 1.25 and get 120 amps. This is my full inverter output adjusted for continuous load.

    Now to size wire. Looks like if I use THWN-2 or THHN I can go safely with #2 conductors (good to 130 amps) with a 125 amp breaker in the main panel.

    Does this look right?

    Thanks
    Read 110.14(C), and then realize that more often than not, you need to satisfy the 75C column, even if using 90C wire.

  3. #3
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    Mar 2016
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    Right. I new there was a reason I asked. So, likely the enclosures, lugs, etc are going to be rated at 75 so I need to use 75?

  4. #4
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    Quote Originally Posted by bbartmasse r View Post
    Right. I new there was a reason I asked. So, likely the enclosures, lugs, etc are going to be rated at 75 so I need to use 75?
    Yes, you need to use #1.

    #2 ampacity is 130A@90 and 115A@75. Continuous use @75 = (0.8)(115A) = 92A; 92A < 96A

  5. #5
    Join Date
    May 2013
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    Quote Originally Posted by bbartmasse r View Post
    Right. I new there was a reason I asked. So, likely the enclosures, lugs, etc are going to be rated at 75 so I need to use 75?
    Yes. Even if the lug itself is marked AL9CU or similar, indicating that when separately installed, it's rated for 90C. What matters is what termination temperature the manufactured equipment is rated for as a whole assembly.

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