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Thread: "neutral conductor" sizing of the inverter

  1. #11
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    May 2011
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    Isn't this that UL 1741 thing, where the inverter is supposed to monitor the neutral if there is one? IOW, you can hook it up to a delta system with no neutral, but if you hook it up to a wye you're supposed to connect a neutral.

  2. #12
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    Oct 2009
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    Austin, TX, USA
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    Quote Originally Posted by jaggedben View Post
    Isn't this that UL 1741 thing, where the inverter is supposed to monitor the neutral if there is one? IOW, you can hook it up to a delta system with no neutral, but if you hook it up to a wye you're supposed to connect a neutral.
    I've seen nothing about that in the installation manuals for the SMA Tripower inverters that can go either way. The manual just says the inverter can be configured to run with or without a neutral.

  3. #13
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    Nov 2015
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    CA, USA
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    681
    Quote Originally Posted by jaggedben View Post
    Isn't this that UL 1741 thing, where the inverter is supposed to monitor the neutral if there is one? IOW, you can hook it up to a delta system with no neutral, but if you hook it up to a wye you're supposed to connect a neutral.
    You are correct. From what I have seen over the years inverter manufacturers sometimes get around the neutral by requiring the inverter to be interconnected only to a grounded 4 wire service. Then they use the EGC as the reference for the line to neutral voltage measurements. This only works if the neutral is not needed as a current carrying conductor. It makes some sense since in the PV industry it is standard to use an EGC conductor and not the conduit as the EGC. So the reduced size neutral and the EGC are the same size going from the inverter to the POCC and basically just creating a redundant parallel conductor.

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