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  1. #1
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    Default RPC Wiring question

    Hey guys with the help of the forums and a few different designs i have put together a 10hp RPC. I have a question in regards to the neutral line and the ground line.

    my setup consists of:
    my main 240v single phase panel has the neutral line and grounds separated. the bare ground goes to a rod in the ground.

    i have 240v single phase going into my RPC box to power everything. I brought the Neutral line and ground line into the RPC box and are separated still. i use the neutral because my 2 contactor coils are 120 single phase.

    then i send the 3 phase legs from the RPC box to a 3 phase panel which has the breakers for the different machines. what i noticed i did was i brought the neutral line down into the 3 phase panel instead of the ground line.

    what should i bring into the 3 phase panel? neutral or the bare ground? and why?

    i have 3 things running on this RPC. i only run 1 at a time. 1st is a forklift battery charger, 2nd is a makino rmc55 mill which power goes through a transformer to go from 230v to 200v and 3rd is a hurco mill which also goes through a 230v to 208 transformer.

    thanks for the help in advance

  2. #2
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    Your 3 phase lines should have a safety ground (green wire).

    A small control transformer would allow for 240vac to 120vac, neutral not needed.

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    Quote Originally Posted by rons View Post
    Your 3 phase lines should have a safety ground (green wire).

    A small control transformer would allow for 240vac to 120vac, neutral not needed.
    +1

    If any of the downstream loads need a neutral, then bring both. But the green wire
    groundING conductor always needs to be there.

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    Quote Originally Posted by alienturtle View Post
    Hey guys with the help of the forums and a few different designs i have put together a 10hp RPC. I have a question in regards to the neutral line and the ground line.

    my setup consists of:
    my main 240v single phase panel has the neutral line and grounds separated. the bare ground goes to a rod in the ground.

    i have 240v single phase going into my RPC box to power everything. I brought the Neutral line and ground line into the RPC box and are separated still. i use the neutral because my 2 contactor coils are 120 single phase.

    then i send the 3 phase legs from the RPC box to a 3 phase panel which has the breakers for the different machines. what i noticed i did was i brought the neutral line down into the 3 phase panel instead of the ground line.

    what should i bring into the 3 phase panel? neutral or the bare ground? and why?

    i have 3 things running on this RPC. i only run 1 at a time. 1st is a forklift battery charger, 2nd is a makino rmc55 mill which power goes through a transformer to go from 230v to 200v and 3rd is a hurco mill which also goes through a 230v to 208 transformer.

    thanks for the help in advance
    Neutral and ground are connected together in you panel unless you have ground fault. But neutral and ground are not the same though they are connected at the same place. You asked WHY? OK ground can NOT carry current. Neutral can. Reason why as you noticed the ground is bare though it don't have to be and is usually a green insulated wire. It is intended to provide safety if it is carrying current and all the machinery frames are connected to the ground and for some reason the conductor is broken then all grounded items before the break will be hot to ground and become a shock hazard. If you already have a neutral then tape it with green tape and use it as ground but not to carry current such as a 120VAC light on the machine.


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