Voltage Drop

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sfav8r

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San Francisco Bay Area
We are installing a few pole lights. The lights are 150w each and there are three lights. The power is 208v. The distance is 400' and we were planning on running #10. The plans call for #4. Am I out of line thinking this is overkill? The load will draw just over 2 amps. Their logic is that the circuit will have a 20a breaker so the voltage drop should be calculated on a 20a load. I suggested we could solve that problem (which I don't even consider a real problem) by using a smaller breaker, fusing etc.

Upsizing to #4 for some POSSIBLE future load that isn't in any kind of plan for the foreseeable future seems a little crazy to me. There is plenty of room to do another pull in the future if they do add another load.
 
Since the NEC does not require us to account for voltage drop, it is really up to the owner to decide what they are willing to pay for. Are there any specs for this project? If so, do they talk about VD? I agree that #4 is overkill for the present situation, and that #10 would answer for the three 150 watt lights.
 
It should be noted that the NEC does provide the following FPN:
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.

It is not binding as being a part of the code of course but I believe it could be considered an industry standard and good practice.
 
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