I recently bought a 12 kw generator that supplies 50 amps at 240 volts. I plan to run three THHN copper lines for the two hot legs and the neutral (plus a ground). One electrician said the legs need to be #6 to handle 50 amps each and another electrician says the legs need to be #2 to handle up to 100 amps of 120 volts. Who’s right?
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If by "running" you mean in conduit, and copper THHN, #6 will be plenty. #6 is good to 75A. What did your installation manual recommend? Is it a Guardian?
Yes, in PVC conduit. The generator is a Kohler and the manual simply says to make sure it’s wired to NEC specifications. I chose it because, for it's size and cost, it has the most advanced electronic control system of all of the generator's I evaluated. I have a lot of computers and electronics, and it's very important to have accurate voltage and frequency regulation. I have a portable Honda 6.5 kw and my APC UPS’s refuse to come on-line when it’s running my office.<!----><!----><!---->
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So you are saying that the second electrician in incorrect when he said that the legs had to be #2 to handle 100 amps of 120 volts each?<!----><!---->
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"are saying that the second electrician in incorrect when he said that the legs had to be #2 to handle 100 amps of 120 volts each?"
I am.
Each leg only has 50 amps max. There's no reason to add them together.
If you want your spouse to listen and pay strict attention to every word you say, talk in your sleep.
The second sparky may be confused by some verbage I tripped across once in a code book (not sure it's even in the current NEC) -- you need to double any shared neutrals if you rig a house that's wired 240V to run off a 120V genset. But that's not what's going on here.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
If it's wired as 120/240 single phase, two hots and a neutral, then #6 is the right answer.
If it's possible to re-tap the jenny for 120 volt two wire use, then you'd need to go to #2. There should be a wiring diagram on the machine showing how if it can be wired that way. But unless you need to run a 120 volt load over 6 kw, like say a 10k lamp, you're better off going the three wire route. You use less copper that way. In fact, that's why it's been done that way for over a century.
So, the question comes down to whether you have one of these around:
http://extranet.mole.com/public/index.cgi?cmd=view_item&parent=-1899-1900-1905-1914-1931&id=9840
-- J.S.
I am not any kind of a electrician. barely know spit from sparks.
That said, I am a GC and my sparkies install a lot of gnerators. Part of the answer depends on the distance from the switch too, but for that size unit, I have never seen anything larger than a #6 used.
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That's what I thought. Thanks, guys.