busbar rating and breaker size

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  • vlz
    Junior Member
    • Sep 2009
    • 1
    #1

    busbar rating and breaker size

    We are installing a 10.5 Kw solar PV system on a residence. The inverter requires a 60 amp breaker. My main panel is 200, and I cannot find information about the busbar rating. My understanding is that I can only use a 40 amp breaker (20% of 200) unless the busbar is rated higher than 200. If there is no spec sheet, how can I find out if the busbar is rated higher than 200?

    Any suggestions?
    Tags: None
    • Mike90250
      Moderator
      • May 2009
      • 16020
      #2
      You could find the Mfg's label in the box, and call or write them with the model #

      You may be better off with a sub-panel if you need 60A for the PV. I'd also consider using 2 5KW inverters, instead of 1 monster inverter, then you only need 30 A breakers, and you might break even on the price, vs swapping out a panel.

      I don't really know the household electrical code, so run this past a code book, don't trust me on it. 120% this, 125% that, 90C this 75C that, 600V, or 600V??

      Mike
      Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
      || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
      || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

      solar: http://tinyurl.com/LMR-Solar
      gen: http://tinyurl.com/LMR-Lister

        Comment

        • Vern2
          Junior Member
          • Sep 2009
          • 78
          #3
          Viz,

          What my install company is doing is reducing the 200 amp breaker (two screws) to 150 to meet this spec. That way the 8.6k breakers are legal. I'll never hit 150 amps in my box at any one time.

          Where's all that smoke coming from!
          Last edited by Vern2; 10-01-2009, 11:26 PM.
          Vern
          --------------
          [URL="http://www.enichesoftware.com"]Home projects:[/URL]

            Comment

            • solar_geoff
              Member
              • Jan 2009
              • 49
              #4
              ...Or go to a 175A main so your de-rate is not as severe. With a 60A backfeed breaker you will still be under 240A (200x1.2). Or NEC 690.64(A) allows you to connect supply (line) side of the main breaker which gets around te 20% rule and derating your main breaker... Of course you need conductors that are exposed enought to tap or somewhere to attach some lugs.

                Comment

                • AES
                  Junior Member
                  • Oct 2009
                  • 5
                  #5
                  Derating the main breaker is certainly 1 option. However you should do a load calculation to make sure you have enough ampacity for existing circuits.
                  I like supply side connections. Parallel taps are a good option for this type of hook-up. Ideal & brundy both make these type of connectors.

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