[mudslinger]

Hello, its been a long while since ive visited.
I have a 12/3 w ground existing underground from my house to the garage. The run from the main box to the garage is 80'. I'd like to ask what the best configuration in terms of the most power to the garage, using the existing wire. As it stands I've set it up as 1 20a circuit with the 3rd wire unused. I'm hoping for 2 20a circuits, but am unsure with the single common.
Thanks in advance

 

[jeffmattero76]

Hello, its been a long while since ive visited.
I have a 12/3 w ground existing underground from my house to the garage. The run from the main box to the garage is 80'. I'd like to ask what the best configuration in terms of the most power to the garage, using the existing wire. As it stands I've set it up as 1 20a circuit with the 3rd wire unused. I'm hoping for 2 20a circuits, but am unsure with the single common.
Thanks in advance

I am not an electrician but i do plenty of electrical work. I believe what you a looking to do is create a "multiwire circuit". You can Google that for more information.
At the house end get a double pole 20 amp breaker and hook the red wire to one pole and the black wire to the other pole and install that breaker in the main panel. At the garage end use the black and white for one of your circuits and the red and white for the other circuit.
As i understand it, the shared neutral on this configuration is perfectly legal as long as one handle on the breaker shuts off both circuits. Using a double pole breaker puts each circuit on a different phase so that the neutral will only carry the difference between the two circuits rather than the additive if the two circuits were on the same phase.
I am sure others here can explain it more clearly than i have done. Good luck!

Sent from my LG-D415 using Tapatalk

 

[mudslinger]

Ok. Double pole 20 at the main. Now at the garage sub, I would use 2 20a breakers with a bonded ground and ground rod?
Thanks

 

[rjniles]

Ok. Double pole 20 at the main. Now at the garage sub, I would use 2 20a breakers with a bonded ground and ground rod?
Thanks

You don't need a sub-panel, breakers or ground rods in the garage. With the multiwire circuit you have 2 20 amp circuits.

 

[Jim Port]

With a MWBC feed you do not need a ground rod or subpanel. Just use a two pole switch as a disconnect .

 

[mudslinger]

I over do most things, and wouldnt mind breakers in the garage to save going back to the house in case of overload, I,m dabbling in woodworking and theres a fairly heavy initial draw from the air compressor and saws. Would the breakers and ground rod be a problem? Nothing has tripped the main up to this point, but the lights draw down.

thanks

 

[rjniles]

I over do most things, and wouldnt mind breakers in the garage to save going back to the house in case of overload, I,m dabbling in woodworking and theres a fairly heavy initial draw from the air compressor and saws. Would the breakers and ground rod be a problem? Nothing has tripped the main up to this point, but the lights draw down.

thanks

With a 20 amp breaker in the house and a 20 amp in the garage, the house breaker may trip before the garage. Don't over think this, do as has been suggested.

 

[mudslinger]

Check, thanks again.