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Supplying 208V rated equipment from 240V power supply

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    Supplying 208V rated equipment from 240V power supply

    Is this kosher if the 208V load can tolerate higher voltage? In this example, it would be a resistive load. Would I have to check the cut sheets for the product to determine if it can be fed from a 240V, 3 phase source?

    Thanks!

    #2
    Shorter life of the heating elements, possible overheating, tripping of over temp control if so equipped. Buck/boost transformers could be used to lower voltage.

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      #3
      It certainly won’t hurt to investigate. Your heaters will get hotter.
      Tom
      TBLO

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        #4
        As a heater rated for operation on 240v will run at almost exactly 75% power, I imagine a heater rated for 208v would run at the reciprocal, or 133% rated power.
        Master Electrician
        Electrical Contractor
        Richmond, VA

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          #5
          Originally posted by FaradayFF View Post
          Is this kosher if the 208V load can tolerate higher voltage? In this example, it would be a resistive load. Would I have to check the cut sheets for the product to determine if it can be fed from a 240V, 3 phase source?

          Thanks!
          Each load you might encounter may have a different answer to this question.

          When it comes to heaters, many are designed for 240 volts, but also have a marked 208 volt rating.

          I know of one particular line of cove heaters I use that sells 208 volt ,240 volt and 277 volt units - same watts per foot, different input volts. They are designed to operate at a certain optimal temp and overtemp may destroy them.Their warranty is no good if there is any evidence a unit is connected to a higher voltage than rated for and they state that in the instructions. I have had a couple warranty cases and first thing they ask is what voltage it is connected to.
          I live for today, I'm just a day behind.

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            #6
            Whether it would be safe and whether it would even work at all are separate issues. But unless the manufacturer's documentation declares that the equipment is rated for both voltages, it would be a violation of 110.4 to install it the way you describe.
            Charles E. Beck, P.E., Seattle
            Comments based on 2017 NEC unless otherwise noted.

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