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Discuss Wiring a garage subpanel with a packed house panel. Simple answer (I think). in the American Professional Electrical Advice Forum area at ElectriciansForums.net

JonathanB

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I have charged ahead with a small subpanel installation in a detached garage I am converting to a light-duty shop. The setup is simple, but I have been stymied by a final step. Hoping someone can help.

Old setup was a buried 12-2 wire from a 20a breaker in the house panel (100A) connecting to one circuit (no breaker) powering two outlets, a light bulb, and a garage door opener.
In the house main panel, there is one and only one available opening in the box for a new breaker.

The new garage panel has three circuits: one 15A for LED lights and the door opener, and (2) 20A for two separate runs of outlets (5 outlets per run in three boxes)

The new wire to the garage is in conduit and is 8-2. Within the garage sub-panel, and since I am not running 220, I connected the hot to both sides of the bus using s short black jumper wire. This allowed me to mount the three breakers side-by-side rather than separated by knockouts and made both sides of the bus hot.

The neutral is connected to a neutral bus bar and and I installed a separate ground bus, which has a 4ga wire running to a fully buried grounding rod.

I have temporarily (waiting for the right breaker) wired the house-panel wires to a 20A breaker, which has the black wire in the load terminal. The white wire (8ga) is on the neutral bus, and the ground on the ground bus.

My idea was a 40A breaker in the house. But if I want full amperage connected through the wiring to the garage panel, what is the correct way to install (wire) the breaker in the house? A two-gang 40A breaker takes two spaces, but I think I can't connect the white wire to one of the load terminals on that, or that will connect to the neutral bus in the garage panel. I also have a tandem breaker, but that seems to have the same issue. I think I run the black wire to a single-gang, single-pole 40A breaker and connect the white wire to the neutral bus in the house panel, yes? That will run the entirety of the circuit (40A) through a single black wire.

Related, what amperage should the breaker you suggest be? Single pole 40A?

Notes:

I do have space in the panel for either a single-gang or two-gang (two pole?) breaker in the main panel.
I have a twin (duplex?) (tandem?) breaker that is two poles and 20a per pole. I also have a two-gang, two pole 40a per pole. Do either of these work?
All of the outlets test out properly using a plug in tester, including the proper functioning of GFIs.

Thanks in advance!

Signed,

ALMOST THERE in Connecticut.
 

Megawatt

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Arms
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1,014
I have charged ahead with a small subpanel installation in a detached garage I am converting to a light-duty shop. The setup is simple, but I have been stymied by a final step. Hoping someone can help.

Old setup was a buried 12-2 wire from a 20a breaker in the house panel (100A) connecting to one circuit (no breaker) powering two outlets, a light bulb, and a garage door opener.
In the house main panel, there is one and only one available opening in the box for a new breaker.

The new garage panel has three circuits: one 15A for LED lights and the door opener, and (2) 20A for two separate runs of outlets (5 outlets per run in three boxes)

The new wire to the garage is in conduit and is 8-2. Within the garage sub-panel, and since I am not running 220, I connected the hot to both sides of the bus using s short black jumper wire. This allowed me to mount the three breakers side-by-side rather than separated by knockouts and made both sides of the bus hot.

The neutral is connected to a neutral bus bar and and I installed a separate ground bus, which has a 4ga wire running to a fully buried grounding rod.

I have temporarily (waiting for the right breaker) wired the house-panel wires to a 20A breaker, which has the black wire in the load terminal. The white wire (8ga) is on the neutral bus, and the ground on the ground bus.

My idea was a 40A breaker in the house. But if I want full amperage connected through the wiring to the garage panel, what is the correct way to install (wire) the breaker in the house? A two-gang 40A breaker takes two spaces, but I think I can't connect the white wire to one of the load terminals on that, or that will connect to the neutral bus in the garage panel. I also have a tandem breaker, but that seems to have the same issue. I think I run the black wire to a single-gang, single-pole 40A breaker and connect the white wire to the neutral bus in the house panel, yes? That will run the entirety of the circuit (40A) through a single black wire.

Related, what amperage should the breaker you suggest be? Single pole 40A?

Notes:

I do have space in the panel for either a single-gang or two-gang (two pole?) breaker in the main panel.
I have a twin (duplex?) (tandem?) breaker that is two poles and 20a per pole. I also have a two-gang, two pole 40a per pole. Do either of these work?
All of the outlets test out properly using a plug in tester, including the proper functioning of GFIs.

Thanks in advance!

Signed,

ALMOST THERE in Connecticut.
My friend first off you need 8/3 with ground wiring and it should be installed on a 40 amp double pole breaker in your main panel. The wire should have a black, red, white, and a ground wire. The black needs to hook to one screw and the red hooks to the other screw on the 40 amp double pole breaker. The white and ground have to be separated at this point so in your sub panel you will probably have to add a ground bar. You do not need the ground bar at the garage, that’s why by code you have to have a 4 wire cable not 3 a wire cable. You are going to need help with this project from an experienced electrician. Good luck
 

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