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Thread: Service wire size

  1. #1
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    Service wire size

    If you have a 200 amp meter base and 3/0 wire feeding a 200 amp OCPD.
    When you do a line side tap to a 60 amp disconnect for the PV system,do the service conductors need to be rated for 260 amps?


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  2. #2
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    Quote Originally Posted by electricalist View Post
    If you have a 200 amp meter base and 3/0 wire feeding a 200 amp OCPD.
    When you do a line side tap to a 60 amp disconnect for the PV system,do the service conductors need to be rated for 260 amps?


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    No. The PV system is a source, not a load. Output from it reduces the current in the service conductors; it doesn't increase the current.

  3. #3
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    I may be looking at it wrong but it takes 60 amps to power the system I viewed it as a load


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  4. #4
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    Quote Originally Posted by electricalist View Post
    I may be looking at it wrong but it takes 60 amps to power the system I viewed it as a load


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    It will take power to operate a PV system, but nowhere near its full ampere rating This is usually less than 100W per inverter, for typical string inverters.

    The 60A maximum that an inverter will produce, is current that will come from the inverter to the grid. The grid and building loads are the load for the inverter.

    While it is true that there is a section of conductor from your tap point to the building loads main disconnect that could conceivably be subject to 260A, the 200A main OCPD will trip before this happens. This is why if you tap on the load side of the main disconnect, you need an additional OCPD downstream of your tap point.

  5. #5
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    Ty sir


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  6. #6
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    Quote Originally Posted by electricalist View Post
    I may be looking at it wrong but it takes 60 amps to power the system I viewed it as a load


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    It's not a load, it's a source, and current cannot flow both directions at once. If your loads are drawing 200A and your inverter is producing 60A, the current in your service conductors is 140A, not 260A.

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