Any electricians or electrical engineers out there?

Discussion in 'Community Discussion' started by brunetmj, Aug 30, 2010.

  1. brunetmj macrumors member

    Joined:
    Jul 9, 2010
    Location:
    Upstate, NY
    #1
    In order to use my 5000 Watt generator properly I recently bought a 6 circuit reliance transfer switch along with a 10 gauge (3) wire for use with the switch. Anyway I wired this cable directly into the transfer switch box. The other end of this cable runs into a wall mounted electrical box.
    My older generator has a single 20 AMP 4 prong connector (3 wire) and a 30 AMP 3 prong (2 wire) connector. I have an existing 20 foot length of 10 gauge (2 wire) cable.
    I was considering using this 10 gauge wire with the 30 AMP circuit and running it into the electrical box. Here I would pig tail the black wire *to both the black and red wires already in the box that run to the transfer switch (and of course connect white to white and ground to ground). Note that I have no need to for 220 volt circuit.
    Can I get away with this? Or would I be better off getting a new 20 AMP*NEMA 4 prong plug and
    3 wire cable.?
    *
    *
     
  2. djjclark macrumors regular

    Joined:
    Feb 17, 2008
    #2
    Well in case someone with more knowledge then me doesn't post I have to say NO. It sounds like you are trying to run generator power back in to the switch via the Line input and the generator output via the switch.

    Go hire an electrician and you will sleep better at night.
     
  3. brunetmj thread starter macrumors member

    Joined:
    Jul 9, 2010
    Location:
    Upstate, NY
    #3
    Well thanks for the input but what I planned is generally ok.
    It would end up being a simple branch circuit with one branch feeding 3 circuits and the other branch feeding the other three. What I actually don't know is how it would effect the amp and wattage distribution.
    I think your right as this question is better suited for an electrical forum. I was at work at the time with limited Internet access when I posted and thought - what the heck there might be some electrical people here
     
  4. samiwas macrumors 65816

    Joined:
    Aug 26, 2006
    Location:
    Atlanta, GA
    #4
    Am I reading correct that you want to use your existing piece of 10-gauge 2-wire cable to power both the black and red side of your electrical box, by splitting the black 10-gauge wire to both sides of the electrical box. And you'd be running this from a 5000-watt generator?

    Note that 10-gauge wire cannot handle anywhere NEAR 5000 watts, closer to 2500 watts of constant feed. You do not want to use a single 10-gauge wire to power your entire transfer panel. It doesn't matter if you need to power 220 volt appliances or not. You either need to upgrade to a much higher gauge cable, or use three-wire 10-gauge (assuming the generator can split it.

    In the end, I would absolutely call in an electrician if you have even the slightest question about what you're doing.
     
  5. Giuly macrumors 68040

    Giuly

    #5
    If I get it right, 5000 Watt on 110V equals about 45 Ampere max - you want to use 5-gauge wiring then, and NEMA 5-50 connectors for 125V or NEMA 14-50 for 125/250V.

    And don't forget to ground the whole thing.
     
  6. millertime021 macrumors 6502a

    millertime021

    Joined:
    Jan 28, 2010
    Location:
    AZ
    #6
    Go big or go home. Just do it.

    Report back, let us know how it goes. :cool:



    Haha no, don't do that. ^^^ listen to these people. I'd call someone if you don't know what you're doing. Better safe than sorry.
     
  7. jeffy.dee-lux macrumors 6502a

    Joined:
    Nov 19, 2003
    Location:
    montreal
    #8
    where do you guys get your wire ratings? Everything I've seen says gauge 10 is good for about 55 amps continuous.
     
  8. Giuly macrumors 68040

    Giuly

    #9
    Handbook of Electronic Tables and Formulas.

    10-gauge is fine inside the switch box, but the cable that connects the box to the generator has to be 5-gauge.
     
  9. brunetmj thread starter macrumors member

    Joined:
    Jul 9, 2010
    Location:
    Upstate, NY
    #10
    Thanks everyone- here is a response that I got from an electrical forum. I will use 20Amp 3 wire cable.
    "If you dont have any 240V circuits in your generator subpanel, then hooking it up the way you describe would be acceptable. Does your generator have a 120/240 switch? If it doesnt then you would be only using half the windings in the generator head to power your transfer panel. In the worst case scenario, you could burn out the generator by trying to pull the full rated power of the genny out of only half of the windings. Another thing to consider is that 30A * 120V = 3600 watts while 20A * 240V = 4800 watts."
     

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