600A Service...Long Pull! - Contractor Talk - Professional Construction and Remodeling Forum

mpmacbride · 01-14-2008, 01:59 AM

I have a 120/240 404A load (600A srvc), a 600ft distance (sloped), and (3) 200A subs. If my calcs are right, w/500 mcm, my drop should be around 2.8v. Does that look right? Thanks everyone, I learn more here at this forum than I do in the "Crapper". MAC

Celtic · 01-14-2008, 11:09 AM

I get 12.5% or 5.2v

http://www.electrician2.com/calculat...alculator.html

Magnettica · 01-14-2008, 10:18 PM

Celtic, will he need to use 300 (285 amps) or 350 (310 amps) kcmil, in parallel, assuming he's using equipment rated for 75º?

Does 240.4(B) permit using 300 kcmil for this job?

Celtic · 01-14-2008, 10:57 PM

You could use the 300's (CU)...and the allowance of 240.4(B) for the 600A service....this is, of course, provided the calculated load is under 570A.

The OP could even use 250's...as long as the calculated load is under 510A. This would be a risky proposition...even though the OP has stated the load is calculated at 404A - things change...and I would be plenty PO'ed at paying for 600A and only getting 510A capacity should the need arise for that 90A paid for once already.

(All of the above is taking no notice of any VD)

Magnettica · 01-14-2008, 11:25 PM

Thanks for the info. And I agree, I would want a true 600 amp service if I was paying for it. So if you consider the 12.5% voltage drop (5.2 VAC) he would likely need to use the 350's for a true 600 amp, no?

Celtic · 01-14-2008, 11:34 PM

More than likely....but not having done the math (on account of SEVERE laziness due to multiple bowls of pasta fagioli)...I guess so

mpmacbride · 01-15-2008, 02:31 AM

Glad I could help massage your ego Celtic...and by the way it was "Linguini w/Two Sick & Screaming Bambinos" CAPICHE?!
Yeah I was being lazy, should have blown the dust off the old "On-Line Volt Drop Calculator"...thanks for that link by the way. Fact of the matter is guys is I have not been doing this for a very long time and I do have a lot to learn, but you can make

sure that I am going to do my homework before I start making 50 or 100k mistakes. MAC

Your feedback has been "gratiously appriciated"