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    line voltage limits

    What are the rms voltage limits for a 120Vac system? And are there specific references as in tech docs? I have the need to prove that a +10% is acceptable...

    #2
    Re: line voltage limits

    Sections 210.19(A)(1) FPN No.4 and 215.2(A)(4) FPN No.2 are the only two areas of the NEC that directly address the problem of voltage drop of current carrying conductors. The reason for voltage drop concerns is that equipment is designed to operate within a certain range of voltage. If a voltage that is outside of that range is applied, damage or poor operation could be the result.

    Reasonable operation of equipment depends on the equipment in question. Some computer equipment is very voltage sensitive while some motors and lights can stand a very large voltage drop. As an example, you will see a voltage drop range from 5% to 13% or greater listed in some ballast electrical data charts. Some motors are designed to operate on either 240 volt or 208 volt circuits. If you intend to supply 240 volts and the drop is excessive, the motor will still be fine.

    The bottom line is that a 10% overvoltage may not be fine.
    Charlie Eldridge, Indianapolis, Utility Power Guy

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      #3
      Re: line voltage limits

      110.4 has voltage specs, but they are not very specific. Specific voltage limit information is going to have to come from the equipment that you are installing. That would be more restrictive than 110.4 as equipment is required to be installed in accordance with it's installation instructions per 110.3.

      +10% is probably acceptable for heating elements, and motors, but not much else in my experience. You may need to move a tap on a transformer somewhere...

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