I am putting together a bid on a home renovation. Included in it is to run power to a barn. I called my electrical sub and he said I would have to run 3- #2cables and 1-#4 cables to deliver enough power for the 60 amp breaker in the barn. I have been a builder for a while and I am just starting to dable in contracting so I have no idea whathe is talking about. Is that 4 seperate wires? Any help would be great thanks.
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Sounds like hot + hot + neutral + ground, but, you'ld have to ask him to be sure.
How far is it between panels?
SamT
It is about 250' between
" 3- #2cables and 1-#4 cables "
No you would run one cable that has those wire in it, or you would run conduit with 3 #2 wires and 1 #4 wire.
Thank You bill that will help.
Did you mention the 250 feet to your electrician ? Using #2 AWG Aluminum conductors, I get a voltage drop of 7.5 volts at 50 amps (which, hopefully, will be double checked by someone else).
Or could he have said "2 ought" wire ? Usually written as "00". ("1 ought" is thicker than #1 AWG. "2 ought" is thicker than "1 ought". etc.
#2 copper is fine or #1 Al.http://www.elec-toolbox.com/calculators/voltdrop.htmhttp://www.electrician.com/vd_calculator.html
I use the formula: E = (K X I X L X 2) / CMA where E is the voltage drop, K is resistance in ohms per circular mil foot (20 for AL), I is current, L is length of circuit (one way), and CMA is cross sectional area in circular mils (66,360 for #2 AWG)
E = (20 X 50 X 250 X 2) / 66,360 = 7.5 volts And, of course, there is additional voltage drop in the circuit from the panel to the tool itself.
Voltage drops are mentioned as FPNs (and as such aren't enforceable parts of the code) in the 1999 NEC, so unless the code has changed you can have any voltage drop you want. I was just saying that 7.5 volts is more than I would want (especially on a hot afternoon like today where the utility supplied voltage is already close to 10 volts lower than usual at my house).
Around here, a feed to a garage/shop subpanel would be individual direct-burial conductors in a trench not less than 24" deep. The wires must be inside conduit if less than 24" deep, so the electrician runs a conduit riser starting 24" deep and then up onto/into the building.