Voltage Drop

[papa]

On a 120 volt circuit, what would be the minimum acceptable voltage for general purpose recp? I have some runs over 500 ft. These recp. will will be on the street for christmas lights and specal events.

 

[Buck Parrish]

I think it's 8% max, I'm not sure where I heard that though.
Check here, if you have not already.

http://www.csgnetwork.com/voltagedropcalc.html

 

[Dennis Alwon]

Remember this is an FPN and is not enforceable by the NEC troppers. However, it is good practice to follow.

210.19 Conductors ? Minimum Ampacity and Size.

FPN No. 4: Conductors for branch circuits as defined in Article 100, sized to prevent a voltage drop exceeding 3 percent at the farthest outlet of power, heating, and lighting loads, or combinations of such loads, and where the maximum total voltage drop on both feeders and branch circuits to the farthest outlet does not exceed 5 percent, provide reasonable efficiency of operation. See FPN No. 2 of 215.2(A)(3) for voltage drop on feeder conductors.

 

[gar]

091129-2015 EST

papa:

If your load is constant and is resistive, then I do not think you care what the voltage drop is if you get the desired end result.

In the case of incandescent Christmas lights you will get longer lamp life if run at reduce voltage. For these if you did not drop below 90 to 100 V, then light output would probably be adequate. Obviously you do not want the wire undersized for the load current.

Put your lights on a Variac and see what you think is a reasonable minimum voltage.

Is any other kind of load going to be on these circuits?

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