Anyone familiar with 3 phase power?

Old 03-04-15, 04:36 PM
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Anyone familiar with 3 phase power?

I'm trying to set up 3 electric heaters in a system plugged into 240V/3phase arranged in a delta. Each heater draws 30A. A diagram of what I want to build can be seen at:

Will the amp draw on each leg be 60A? I think it will be but want to check. Thanks!
Old 03-04-15, 05:26 PM
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First check what you really have - measure it. It could be 208.

Playing with numbers show draw would be 51.96 amps -

You really just multiply by the square root of 3.
Old 03-04-15, 06:11 PM
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Yes, measure it, but technically if it is described as 240 volt 3 phase then it should have 240 volts from any phase line to any other phase line. Any type of single phase 240 volt only equipment may be connected to any two of the phases subject to the size (amperes rating) of the service although some effort should be made to balance the loads over all three phases.

Arranged in a delta means that there is no assumed position for a neutral although a neutral may be provided, usually with 120 volts from the "A" phase to neutral and with 120 volts from the "C" phase to neutral.

You should assume that 208 volt equipment may not be operated on 240 volts or vice versa unless the instructions or name plate for the equipment states that such operation is permitted. Those with a reasonable amount of electrical experience can determine additional exceptions for specific makes and models of equipment.

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