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Thread: Going to re-wire the shop

  1. #1
    Join Date
    Mar 2015
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    Default Going to re-wire the shop

    Currently running 12/2 metal shielded wire around the shop for single phase 240v.
    I am interested in a more professional looking installation using plastic conduit and maybe boxes? Going to hook the RPC control panel to the wall next to the main circuit breaker panel. Going to replace all the outlets with 3phase sockets, all the 220v tools will be given three phase plugs as well.
    My RPC panel passes two legs straight through so there is always single phase present. The single phase tools simply won't have the 3rd leg which is the manufactured leg wired to its 3 phase plug. Does this all sound good?
    Next question, what size conduit to run? The entire circuit is running off a 20 amp CB Pbuilt into the RPC panel. Will run 12 gauge. Can I run nomex house wiring inside the conduit, or does it have to be individual strands?
    Will run 10 or 8 gauge from Main Circuit Breaker Panel to the RPC panel, off a 50 amp breaker. It's a 10hp RPC.
    It's a one man shop with no big air compressor. Only one tool will ever be running at a time.

    Another idea, should I also run a common for 120v in the same conduit?
    Last edited by RB211; 08-03-2019 at 06:05 PM.

  2. #2
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    Do you care about doing this "to code"? About Insurance implications? The answers will likely depend on this. The questions you're asking (that you even have to ask...) suggest that you don't.
    "A machinist's (WHAP!) best friend (WHAP! WHAP!) is his hammer. (WHAP!)" - Fred Tanner, foreman, Lunenburg Foundry and Engineering machine shop, circa 1979

  3. #3
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    No, I see a problem with the plan. The rotophase circuit should disconnect both single phase lines when the rotophase is off. That means the entire 3 phase receptacle should be dead unless the rotophase is running. You don't want the rotophase running all the time when you are only using single phase tools.

    Romex is not code approved for surface installation in a garage, it must be under the drywall or "protected from physical damage" as phrased in the code. Romex should not be installed in conduit.

    Single strands are probably the best bet in conduit. Another point to keep in mind is that more than 3 current carrying wires in the conduit requires the wires current rating to be derated. The more wires the more the derating. There is a chart in the code, the chart can be found online. Conduit size must also be to code for the number and size of wires, there is a chart again.

    Metal Clad cable, type MC, is a good easy solution for machine wiring in garages BUT not the prettiest looking thing.

  4. #4
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    Depends on code and insurance, etc. Up here in NY the code requires individual strand in conduit jobs, and I doubt 3-phase is allowable with Romex. The electrician at work uses mostly 12-ga individual stranded wires inside steel conduit, but that is with 480-v low-amp plugs.

  5. #5
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    Quote Originally Posted by Sparky_NY View Post
    Romex is not code approved for surface installation in a garage, it must be under the drywall or "protected from physical damage" as phrased in the code. Romex should not be installed in conduit.
    Funny that in here "code" is opposite:
    "Romex" is ok for surface installation(also garage) but not inside walls. Conduit+Romex would be also ok if you manage to pull it trough somehow.

  6. #6
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    Here is a decent review of the allowed usage of NM-B (romex) wire. https://www.thespruce.com/romex-and-...ations-1821529

    You can use conduit for physical protection BUT trying to get romex through conduit is a BEAR! Its both cheaper and easier to use single strands.

    There is nothing code wise that prohibits romex use for 3 phase circuits.

  7. #7
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    Quote Originally Posted by MattiJ View Post
    Funny that in here "code" is opposite:
    "Romex" is ok for surface installation(also garage) but not inside walls. Conduit+Romex would be also ok if you manage to pull it trough somehow.
    LOL Different rules on the other side of the pond. In the US, pretty much everywhere goes by the National Electric Code, aka NEC, aka NFPA 70. Some localities have a few local rules that exceed the NEC but its fairly rare.

  8. #8
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    Quote Originally Posted by Sparky_NY View Post
    No, I see a problem with the plan. The rotophase circuit should disconnect both single phase lines when the rotophase is off. That means the entire 3 phase receptacle should be dead unless the rotophase is running. You don't want the rotophase running all the time when you are only using single phase tools.

    Romex is not code approved for surface installation in a garage, it must be under the drywall or "protected from physical damage" as phrased in the code. Romex should not be installed in conduit.

    Single strands are probably the best bet in conduit. Another point to keep in mind is that more than 3 current carrying wires in the conduit requires the wires current rating to be derated. The more wires the more the derating. There is a chart in the code, the chart can be found online. Conduit size must also be to code for the number and size of wires, there is a chart again.

    Metal Clad cable, type MC, is a good easy solution for machine wiring in garages BUT not the prettiest looking thing.
    American Rotary actually sells this as a feature. When the RPC is off, only single phase is present. The RPC only runs when needing 3 phase.

  9. #9
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    Perhaps I will just stick to metal clad for simplicity sake

  10. #10
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    Quote Originally Posted by Sparky_NY View Post
    Romex is not code approved for surface installation in a garage, it must be under the drywall or "protected from physical damage" as phrased in the code.
    Guess who just rewired his shop, and guess where the romex is sitting...

    Oooops

    Good thing this is Appalachia.

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