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z-man99 07-17-2009 05:35 PM

Adding a sub panel 250ft away from the main
Forum newbie here. I ran a search but didn't see a thread that quite matched what I was looking for.

I'm planning on adding an electrical sub panel to a garage approximately 250 feet away from the main panel. I already have 2 inch conduit with 2 ft sweeps running underground from the main to the garage. The main panel is a 200 amp breaker box with 4 empty spaces. My plan was to add a 100 amp breaker into the main box, use 2/0 triplex wire with two hot wires and one neutral and ground the sub panel at its location. There aren't any other services connecting the house to the garage. Inside the new shop I'd like to have the ability to run a 230 volt air compressor along with a dozen fluorescent lights and have a couple of breakers worth of 120 outlets. Should I proceed as planned?

thanks for your help...

220/221 07-17-2009 05:51 PM

Triplex leave you one wire short.

You need Hot, Hot, Neutral, Ground for this installation in most areas.

What I call Triplex has Hot, Hot, Neutral/ground

You also need a couple ground rods at the garage attached to the ground bus with a #6 wire.

You also need a main breaker at the garage.

z-man99 07-17-2009 07:25 PM

So I add a bare ground wire to the triplex and tie it into the ground terminal on the main and the sub boxes?

bobimperial 07-18-2009 09:35 PM

No. The triplex has two insulated wires, and a bare wire, but the sub-panel requires a separate isolated neutral bus bar along with an insulated wire. That way the return sees only one path back to the pole transformer. So you need four wires, 3 insulated and one bare. Sub-panels have two bus bars.

220/221 07-19-2009 01:56 AM

Typically we don't pull triplex. We use individual wires, usually THWN, XHHW etc..

The power company uses triplex for their service conductors.

Feeders after the service generally need to be a 4 wire system with the hots and neutral insulated.

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