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fdilley · Oct 1, 2007, 03:32 PM

I have a 30KW 3 phase generator I purchased from government surplus. After repairing the generator it runs fine and I will only be using 2 of the phases. Now my question. I have a new Cutler-Hamer model DT224URK-NPS 200 amp transfer switch which I have mounted above where my service enters my home. The switch is after my meter and main cut off breaker. The service to my home is 4/0 aluminum with 2/0 neutral and 4AWG ground. I can disconnect and pull the wire back from my main breaker box and feed the transfer switch with not much problem. The feed is long enough. What I want to know is can I use 2/0 copper feed, 2/0 neutral and 4AWG ground from the switch back into my breaker box or do I have to use the 4/0 aluminum feed wire? This would make the job much more easy.

Thanks much

Forrest

tkrussell · Oct 2, 2007, 02:27 AM

The load side can be copper wire.

What you need to watch out for is any 240 volt loads in your home. They will not run to full operational power due to the 208 volt that will be delivered by the generator. Esp motors, which probably you don't have many, maybe a well pump.

Also, need to be careful of the generator, It will not like being loaded only on two phases.

Keep in mind, that a main breaker must be first in line before feeding the transfer switch, otherwise there will be no short circuit protection for the switch.

fdilley · Oct 2, 2007, 01:49 PM

Thanks tkrussell. The other phase is to be used by my neighbors. All the loads in the house are resistive (hot water tank, range etc.) I don't think I should have a problem with a loss of 32 volts. And the meter and disconnect breaker is before the switch. One other question, should I bond the ground and neutral at the generator or just ground the generator? I have an 8ft ground rod at the generator.

Thanks again.

Forrest

tkrussell · Oct 2, 2007, 02:32 PM

Oh I now I have heard everything, the neighbor will use the third phase! I don't even want to know how he will wire that. La La La I hear nothing...

Do not connect the neutral to the equipment ground at the genset. The transfer switch will not break the neutral, so you will have a non-separately derived system.

You may notice a loss of heating time with the electric elements in the appliances. No harm will be done to anything other than slower heating.
You may drive the rod to ground the frame and equipment ground, but not necessary.