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3 Phase Question

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  1. #1
    Join Date
    Apr 2007

    Default 3 Phase Question

    I am currently doing a long term reno on my house, which has 3 phase power to drive my ducted air con.

    My mains are 63amps, and according to the electrician he has spread the house over all three phases.

    My question is given that many new houses are apparently 100 Amp. Is there any point in me attempting to upgrade my mains? I believe that the cable running to the house is 16mm (?? - which would have to be replaced in order to go to 100 amp?).

    Am i getting any advantage here by having three phase? If so what?

    Am I getting potentially 63 Amp on each phases therefore negating any need to go to 100 amp?

  2. #2
    Senior Member
    Join Date
    Dec 2005
    Huntington Beach, CA USA


    How much current do you expect to use at one time. If that mumber if over 63 amps on each of the phases (all at the same time) then you may need to upgrade.

    BTW - During a remodel or our home, I added a 100 amp sub-panel to the shop (errr garage) with a like upgrade to the main panel to 200 amps and my local utility didn't think that increasing the size of the mains (house to pole) was necessary. I have run the cabinet saw and dust collector while SWMBO was cooking (electric oven and electric cook top) with the A/C running. Not a big deal. Although I think that if the clothes dryer was electric and also running there might be a problem with the main tripping.

    Help! I've dropped my nail gun and can't glue up.

  3. #3
    2K Club Member chrisp's Avatar
    Join Date
    May 2004
    Melbourne, Australia


    Quote Originally Posted by mdfdust View Post
    Am i getting any advantage here by having three phase? If so what?

    Am I getting potentially 63 Amp on each phases therefore negating any need to go to 100 amp?
    You have already answered your first question - you can run three-phase equipment such as a 3-phase air conditioner.

    If you have 3 phase at 63 amp per phase, it is the equivalent of 3 x 63 = 189 A single phase. It is hardly worthwhile going to 100A single phase (which is what most new houses would have). You would have to have an awful lot of electrical stuff to need 100A 3-phase supply.

  4. #4
    Senior Member
    Join Date
    Dec 2006


    Just to clarify what crisp said,

    You have 63 amps available per phase, not 189 amps single phase. If you are mainly running single phase items in your garage, ensuring that the load is spread over the three phases in the shed, you wouldnt need 100amps per phase for your property.

    If you are worried about the load being drawn in the shed, spread the load over the seperate phases. Im assuming you have 3 phases in the shed?


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