How do I hook a generator to its own panel box with it s own receptacles seperate from everything else?

Question

How can i hook a generator to its OWN 100 amp panel box and run emrgency receptacles that will only work when i cut on the generator and then the main breaker in THAT box,,the generator is rated at 125 amps.And also is it best to run 240 to save amps? if so is 12/2 the right cable? And what gauge do i use to hook to the panel box IF i can hook it up that way?

Answer 1

The way I understand your question is you are talking about a whole separate emergency power system so you don't need a transfer switch.

So you would start with a fairly standard service panel with a main breaker of, well, 100 A, and your circuits of 15 or 20 amps each or whatever.

The wire size needed is #2 copper for up to 115A, or #1 aluminum for 100 A, or service entrance cable that is rated for the amps you want.  

You most certainly would run this as a 3-wire circuit, 2 hot legs and neutral, giving you 120/240V service.

BUT, that's a helluva big generator (30 kW), and should be capable of supporting a sizable house, so a transfer switch to your existing panel would seem to be the more flexible, easier, and probably cheaper solution.

With a much smaller generator I can see the idea of just running a few emergency circuits.

Answer 2

Your question is not clear. I guess what you mean is you want to switch over to the generator power when the main power panel is off. Get a motor starter relay with normally closed contacts  which would be used to connect the power from the generator to the panel box and connect the coil of that relay to the main power. So when the main power is ON, the relay contact connections would be OPEN, but when the power goes out the generator power is connected. 240 V power would cut the current by half. The gauge of the wires depends on the distant between the generator and the panel box. If it is only a few feet, 12 gauge wire is OK but longer distant you would require 10/3 .

Answer 3

You need a transfer switch between the main panel and the branch you want to run on the gennie. The transfer switch would kick in either utility from the main panel or from the generator. It's a 'break-before-make' switch that prevents backfeeding to the utility.

You also need to put the isolated outlets on a sub-panel with their own breakers to protect that branch.

Your question about 12/2 leads me to believe that you don't know what you're doing... 125A would need much larger cable than that.

Save yourself some headache and call a licensed electrician....