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Thread: 208 3ph to 230-240 Y transformer

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    208 3ph to 230-240 Y transformer

    Wondering if it's OK to connect a 208 3ph 230-240Y 112kva transformer to a 3phase subpanel the input current is 100amps

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    Quote Originally Posted by Bill 12 View Post
    Wondering if it's OK to connect a 208 3ph 230-240Y 112kva transformer to a 3phase subpanel the input current is 100amps



    Whats the 240Y for? Your source is 208 volts and the secondary is 240Y?
    I'm in over my head...

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    I'm curious, why that large of a transformer for a 100-amp circuit?

    If you have the proper OCP in place, I don't believe the NEC has a problem in under using a transformer's rating. I have heard that transformers might waste more energy when lightly loaded.

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    It will feed a 3ph sub panel that is powering a bunch of 240 3ph equipment one is a 100amp welder.

    https://www.larsonelectronics.com/p-...BoCQuwQAvD_BwE

    This is the transformer they want me to get. Sorry it a 75kva not 112 that was wrong

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    Quote Originally Posted by Bill 12 View Post
    It will feed a 3ph sub panel that is powering a bunch of 240 3ph equipment one is a 100amp welder.

    https://www.larsonelectronics.com/p-...BoCQuwQAvD_BwE

    This is the transformer they want me to get. Sorry it a 75kva not 112 that was wrong
    That transformer is single phase. You won't be able to power 240 3ph equipment with it.


    Maybe the wrong link?

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    Quote Originally Posted by Bill 12 View Post
    It will feed a 3ph sub panel that is powering a bunch of 240 3ph equipment one is a 100amp welder.

    https://www.larsonelectronics.com/p-...BoCQuwQAvD_BwE

    This is the transformer they want me to get. Sorry it a 75kva not 112 that was wrong
    So I'm guessing that this will be a 3Ø, 3wire, 240 volt system without a neutral? If you need to supply any 120 volt loads then a 3Ø,4W Delta secondary might be better. A 240 volt Wye system has a phase to neutral voltage of 139 volts.
    Last edited by infinity; 03-14-19 at 04:09 PM. Reason: Spelling
    Rob

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    All responses based on the 2014 NEC unless otherwise noted

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    Larson gave me 2 quotes here is the other one
    https://www.larsonelectronics.com/p-147482-.aspx

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    So we are trying to keep from running a new service which would entail changing a main panel to a 400amp and doing a hot tap and 200ft of new wire

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    Quote Originally Posted by Bill 12 View Post
    Larson gave me 2 quotes here is the other one
    https://www.larsonelectronics.com/p-147482-.aspx
    112.5kva is the correct one.


    Yes it can be done- make sure your sub panel has straight rated breakers only and no 120 volt loads.
    I'm in over my head...

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    OK cool. So if they wanted 120 also could I get a transformer that would do that also?

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