Voltage drop calculations... - Electrician Talk - Professional Electrical Contractors Forum

waco · 06-29-2009, 12:29 PM

Playing with the Southwire Calculator linked by somebody here, it still won't perform calculations for 4/0 Al at 200 amps or 1/0 Al at 200 amps, saying only that 4/0 and 1/0 can't carry 200 amps. Of course, they both CAN carry 200 amps.

I wonder what I'm missing or are there all sorts of such "sources" out there that misinform us or are we the victims of our own assumptions?

InPhase277 · 06-29-2009, 12:38 PM

Quote:

Originally Posted by waco

Playing with the Southwire Calculator linked by somebody here, it still won't perform calculations for 4/0 Al at 200 amps or 1/0 Al at 200 amps, saying only that 4/0 and 1/0 can't carry 200 amps. Of course, they both CAN carry 200 amps.

I wonder what I'm missing or are there all sorts of such "sources" out there that misinform us or are we the victims of our own assumptions?

In an NEC compliant installation, 4/0 aluminum cannot be used for 200 A, except in the case of a residential service. A 200 A feeder using aluminum would be required, by T310.16, to be at least 250 kcmil.

drsparky · 06-29-2009, 12:50 PM

Read 310.15 (B) (6) and table 310-16.

waco · 06-29-2009, 12:57 PM

Quote:

Originally Posted by InPhase277

In an NEC compliant installation, 4/0 aluminum cannot be used for 200 A, except in the case of a residential service. A 200 A feeder using aluminum would be required, by T310.16, to be at least 250 kcmil.

Of course, you are right, "except in the case of residential service" which is a reality and in the case of the wire simply "carrying" 200 amps regardless of code.

Here is another calculator which seems more realistic: http://www.electrical-designer-guide...wire-size.html