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How much power is needed here?

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  • How much power is needed here?

    I'm trying to figure out what size fused enclosed safety switch and what Amp fuses are needed for this. Below is the info I have to work with.

    Volts: 230
    Watts: 50,000
    Phase: 3 delta

    This is for a boiler in a commercial building. Please remember this is a three phase setup. Also, being resistive heating elements I don't see where we need to get into power factor and the like. Figure on unity 0.0 power factor, please.

    I need to know the Ampere draw and the correct fused safety switch and fuses to use for this. Remember this will be in use 24/7 and the boiler will see a heavy load so the elements will be pretty much a continuous load.

    The boiler wiring will be 3 conductors with ground. L1, L2, L3 and ground. There is no need to think about a control circuit. Everything is self contained as far as controls go. It is a hot water and not a steam boiler for what that matters.
    Last edited by Woussko; 07-13-2009, 01:30 AM.

  • #2
    Re: How much power is needed here?

    Ohms law= Watts devided by volts= 218amps.
    info for all: http://www.hoistman.com http://www.freeyabb.com/phpbb/index....wwtoolinfoforu --- "I like long walks, especially when they are taken by people who annoy me."

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    • #3
      Re: How much power is needed here?

      218 A is correct for line current but phase current will be 218 / √3 =125.8 A, add the saftey factor of 125% and you have 157.3 A
      I believe the next common size of breaker is 175A so the wire size would be 00.

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      • #4
        Re: How much power is needed here?

        Phase and line current have always thrown me off.

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        • #5
          Re: How much power is needed here?

          Originally posted by papadan View Post
          Ohms law= Watts devided by volts= 218amps.
          But we need to remember this is 3 phase power we are dealing.
          Last edited by Woussko; 07-13-2009, 11:15 PM.

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          • #6
            Re: How much power is needed here?

            60a
            "When we build let us think we build forever. Let it not be for present delight nor for present use alone. Let it be such work that our descendants will thank us for, and let us think, as we lay stone upon stone, that a time is to come when these stones will be held sacred because our hands have touched them, and that men will say, as they look upon the labor and wrought substance of them, "See! This our fathers did for us."
            John Ruskin (1819 - 1900)

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            • #7
              Re: How much power is needed here?

              wbrooks's has it

              50,000 divided by 230 divided by 1.732

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