Voltage Drop/wire size

[c_picard]

Gentlemen,

I was hoping for a little proofreading from y'all...

I have a 125A subpanel to be installed in a workshop
125' from a single family dwelling. I will run PVC and 4 wires
out to the shop. I would like to keep Voltage drop to
a minimum knowing that I will be installing a welding outlet.

#1/0 copper, table 8 value of .122 ohm/kFT and table 9 value 0.12ohm/kFT
so AC and DC resistance are nearly the same, with 12.9 being the constant for copper
(2x12.9x125Ax125')/105600=3.82volts/240=1.6%

I can't know for sure just yet what the neutral load will be, so should I run a full sized
grounded conductor, can I only downsize if I know the load?

Would it be more practical/economical to use Aluminum conductors, in your opinion?

I'm another one of those guys who is only accustomed to spending other peoples'
money on commercial jobs....

Another question would be the disconnecting means, a 125A main breaker panel should
cover this right?

Thanks,
Charles

 

[augie47]

Gentlemen,

I was hoping for a little proofreading from y'all...

I have a 125A subpanel to be installed in a workshop
125' from a single family dwelling. I will run PVC and 4 wires
out to the shop. I would like to keep Voltage drop to
a minimum knowing that I will be installing a welding outlet.

#1/0 copper, table 8 value of .122 ohm/kFT and table 9 value 0.12ohm/kFT
so AC and DC resistance are nearly the same, with 12.9 being the constant for copper
(2x12.9x125Ax125')/105600=3.82volts/240=1.6%

If you go to Mike Holt's homepage under "Free stuff" you can download a voltage drop calculator and "play" with various loads, wire sizes, etc.,

I can't know for sure just yet what the neutral load will be, so should I run a full sized
grounded conductor, can I only downsize if I know the load?

By "the rules", yes, but you know part of your load will be the welder with no neutral. Normally downsizing in this situation would not be problem.

Would it be more practical/economical to use Aluminum conductors, in your opinion?

Yes

I'm another one of those guys who is only accustomed to spending other peoples'
money on commercial jobs....

Another question would be the disconnecting means, a 125A main breaker panel should
cover this right?

Should See Art 225 Part II

Thanks,
Charles

 

[lakee911]

I always like full size nuetrals, but I often design work that others will pay for. :grin: You never know what someone is going to do with it in the future.

Go with the aluminum. For large wire sizes, the old problems have for the most part been taken care of. It's cheaper and easier to work with. Throw some antiox compound on the connections if it makes you feel better (or if the manufacturer calls for it).

 

[SG-1]

I like this volt drop calculator because it will also give you the temperature of the conductor under load.

http://www.electrician2.com/calculators/vd_calculatoradv.htm