OK, an electrical question..

[JohnnyB]

On another thread, I can't remember the one, we were talking about figuring voltage drop on length of wire and wolf dog was so kind as to provide us with his resources. I had mentioned the parking lot pole lighting job I got. Well, I got another couple of questions...

Can I just run #10 out to the poles. I have 243vac at the panel and 240 at the outlet on the building. If I run #10 to the furthest pole I should have about 210vac. I though I could do this and change the lights to multi tap ballasts and use the low voltage tap, like the 208 tap. I'm pretty sure most of the lights don’t work anyway. These are HID lights watts unknown but I measured 1.5 amp draw from the only functional one. Loosing 30-40 vac due to the R of the run shouldn’t cause any problem, heat I mean, right?

[Pegleg Smith]

How many times do you want to do this job?
If your theory doesn't work then what?
Are you prepared to do the job over using a larger gauge wire?

I think you should really consider all aspects of this situation. It is far better to use a larger wire than actually needed that to do the whole job over again because you tried to save the customer some money.
The second time is paid out of your pocket.

[wolfdog]

The 3% maximum voltage drop is not a code requirement. It is a FPN (fine print note). Some size things for less drop and some size things for more voltage drop to save money on materials.


Remeber that the 30 - 40 volts you are losing is turned to heat in the wire and is electricity being used that will show up at the meter.

[JohnnyB]

I suspect this may have been done originally because I dug up some of the old wireing and its all #10 out to the poles. I only got 3/4 emt from the panel to the outside of the building. I told my boss that in order to not have an apriechable VD that # 4 would be required to the outside of the building. I dont belive I could get 250' of #4 through the 3/4" so now he wants to run a new run to the outside through the building, OK,. fine, but the grade is 4' higher than the electrical room where he wants to come out and the lot is another 3' and their is one of those block retaining walls and like all the utility feeds, FU@%!

[Pegleg Smith]

sounds as if you are about to get a profitable job going!

[JohnnyB]

http://www.electrician.com/articles/advanced_voltage_drop_calculator.html

score!

[condenseddave]

350 MCM should do it. Your pipe is getting bigger and bigger, Johnny!:D:p