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Faunsdale, AL | Yes, if you’re using this generator for backing up
a normal mix of loads that includes lots of 120 volt circuits IN A PANEL THATS NORMALLY SUPPLIED BY THE UTILITY, you want the neutral to be the same size as the lines. Ground can normally be smaller.
If you’re setting up panels at bin sites that do not have utility power or a portable panel that will travel with the generator, I can’t see how it would matter what you do as long as the conductors are big enough not to get hot.
For example if you want a single 15 amp circuit to run a light, you would need a 14 gauge neutral at a minimum. That might be short sighted and it make more sense to use a #6, but the 14 gauge would be perfectly adequate as long as you only ever use that one 15 amp circuit.
One thing that might become important is protecting the wiring between the generator and the panels or transfer switch. If there is a main breaker in the panel and the connecting wires from the generator are short, the main breaker in the panel can protect it. I’ve seen a figure for how long is too long and I’m thinking it was like 15 feet. However I like to have a breaker on the generator output. A big one is expensive, so I can see the rationale for letting the main breaker in the panel do the duty.
I have a 75 kW 3 phase generator hooked to a manual transfer switch at a dairy. There is no main breaker anywhere in the multiple panels fed by this transfer switch. Welding cables were used to make the connections and have deteriorated over the decades to the point that one day when a thunderstorm blew up and we were running on the generator the old welding cables started arcing.
I had a 200 amp breaker on generator output but as impressive as the arcing was, it wasn’t enough to trip that breaker. I really didn’t want to approach it to switch it off but I was glad it was there so I could disconnect the generator. Switched off breaker, arcing stopped and fire went out. generator was fine and all I had to do was replace the old welding cable. It was replaced with THHN stranded wire in conduit since the generator was bolted down vs the pto generator on a trailer that had been used when the transfer switch was installed.
Edited by ccjersey 3/28/2025 08:46
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220 volt 3 wire question
