Wiring plan

[billd6]

I'd like to run my wiring plan past the electricians in the group.

I want to run a 220 V 100 amp line to the garage from my house. The run is appx. 45 ft, is 2-2-2 aluminum pulled through 2 1/2 inch conduit buried at 18 inches. The main panel in the house is 200 amp with the ground and neutral wires tied together via a common bus.

The subpanel in the garage has the neutral bus floating and isolated from the ground bus.

Two of the wires will go to the main breaker switch in the subpanel and the aluminum braid will get twisted and connected to the floating neutral bus.

The ground bus is connected to the subpanel frame. # 6 copper wire will go from the ground bus to 2 8 foot copper ground rods placed 6 feet apart.

Is this plan valid?


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[pattenp]

Wrong type of wire for the sub-panel feed. You need to use 4 conductor such as 2-2-2-4 MHF (Mobile Home Feeder) or individual THHN/THWN or RHH/RHW wires. The wire you described with braided neutral sounds like SEU which is not allowed under ground. And #2 aluminum is good only to 90 amps as a branch feed. And 2" PVC conduit is fine, you don't need 2.5". And trench needs to be 20+" because 18" is the needed cover.

 

[billd6]

So where do I hook the 4th wire on the main panel if neutral and ground are tied together on the main panel???


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[pattenp]

The neutral and ground are bonded at the main service panel so they can land on the same bar. The neutral is isolated in a sub-panel so the neutral bar is insulated from the panel and ground bar.

See diagram....
View media item 16967

 

[billd6]

Thanks for the quick responses!

 

[wyliesdiesels]

The neutral/groun bond in the main panel is important. Its there so breakers can properly sense ground faults. Without the bond, metal in buildings(pipe,building steel, lath/chicken wire in plaster[dont ask me about that]) can become energized and the breaker on the offending circuit wont trip!

PS: About the chicken wire, cause i know youve got to be curious. I was shocked once when i was drilling a hole for coax in a house i use to rent. It was an old Victorian with mostly ****** knob and tube wiring. Someone had illegally installed 3 prong receptacles. Another ***** had taken an outlet out of a j box and snagged the hot terminal with the chicken wire when they reinstalled it.

Because the outlet(metal j box) nor the chicken wire was grounded, the entire lath grid as well as some plumbing was energized and had been for almost 2 years. Until i came along and started grounding outlets for my computer equipment(weeks after i installed the coax). I finally found the offending outlet once the wall started smoking(the arc wasnt sustaining and the ground connection to the lath was across the room and thus high impedance at the offending outlet. Told the ******* lanlord and he didnt care. So i threatened to report him and fixed it myself and took it outta rent!