Maximum breaker size - Commercial applications

Batikikik
Batikikik Solar Expert Posts: 141 ✭✭✭✭✭
in General Solar Power Topics #1
NEC code fro Residential applications.
For 200A main service maximum feedback circuit breaker size is 40A(If main breaker is 200A).
What about commercial applications ? Is that same 20% apply for commercial applications ?
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  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    #2
    Re: Maximum breaker size - Commercial applications
    Batikikik wrote: »
    NEC code fro Residential applications.
    For 200A main service maximum feedback circuit breaker size is 40A(If main breaker is 200A).
    What about commercial applications ? Is that same 20% apply for commercial applications ?

    For 2008 NEC yes. Older NEC, no.

    125% load exception is still residential only.
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  • Batikikik
    Batikikik Solar Expert Posts: 141 ✭✭✭✭✭
    #3
    Re: Maximum breaker size - Commercial applications

    What was in old NEC ?? 30%??
    So by new NEC code if you have 600Amp Busbur, and you have load connected 575A maximum breaker size will be 145A ?
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  • Jburgess
    Jburgess Solar Expert Posts: 130 ✭✭✭
    #4
    Re: Maximum breaker size - Commercial applications
    Batikikik wrote: »
    What was in old NEC ?? 30%??
    So by new NEC code if you have 600Amp Busbur, and you have load connected 575A maximum breaker size will be 145A ?

    To understand your question better, is there a breaker or fuse between the meter and the 600 amp buss bar or is connecter directly to the meter?
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  • Batikikik
    Batikikik Solar Expert Posts: 141 ✭✭✭✭✭
    #5
    Re: Maximum breaker size - Commercial applications

    No , there is a main breaker 600A
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  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    #6
    Re: Maximum breaker size - Commercial applications
    Batikikik wrote: »
    What was in old NEC ?? 30%??
    So by new NEC code if you have 600Amp Busbur, and you have load connected 575A maximum breaker size will be 145A ?

    Old NEC was 100% - no exception for commercial, only residential.

    Now there is a 120% exception for commercial and residential SUPPLY breakers, and a 125% exception for LOAD breakers for residential only.

    LOAD breakers connected doesn't matter to calculate solar supply - only SUPPLY breakers connected. If you have a 600a bus bar, and a 600a SUPPLY breaker, then you can add up to 120a breaker for solar to SUPPLY that bus.
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  • Batikikik
    Batikikik Solar Expert Posts: 141 ✭✭✭✭✭
    #7
    Re: Maximum breaker size - Commercial applications

    dwp respect ! smart post, can you tell me number of article about that ?
    And what is the solution if you have 600A supply brecker and 600 Busbur and you want to connect 140 A solar breaker ? voltage is 120/208v
    Only downgrading 600A to 400A (if load calculation allows you)??
    And except that there is one project which has 3000A and requires 750A solar breaker . In that project max you can connect is 600A ? voltage is 277/480Y

    thanks
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  • Jburgess
    Jburgess Solar Expert Posts: 130 ✭✭✭
    #8
    Re: Maximum breaker size - Commercial applications

    705.12 (D) (2)

    What year code are you working under?
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  • Batikikik
    Batikikik Solar Expert Posts: 141 ✭✭✭✭✭
    #9
    Re: Maximum breaker size - Commercial applications

    We are in 2011 and there is a new code and you cannot go with old codes i think :) I am going with new codes
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  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    #10
    Re: Maximum breaker size - Commercial applications
    Batikikik wrote: »
    We are in 2011 and there is a new code and you cannot go with old codes i think :) I am going with new codes

    Not all places use the new code. You have to check with local authorities which code to use.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #11
    Re: Maximum breaker size - Commercial applications

    Definitely check with your local building inspector--They (and their bosses) control which version of code is acceptable to them. Some do not even use NEC.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Batikikik
    Batikikik Solar Expert Posts: 141 ✭✭✭✭✭
    #12
    Re: Maximum breaker size - Commercial applications

    Its Fresno, I did check they use new codes, but even if they use old codes still you can connect 500A Solar breaker to existing service which has 600A busbar and 600A main right ? there is some limits
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