Garage sub panel wiring

[Alcan]

I want to run power to my garage from my house.
I will need (1) 120V, 20 amp circuit for outlets
and (1) 120V, 15 amp circuit for lights.

The total wire run from house main panel
to garage sub panel is 90 feet.

What is the minimum 240V main panel breaker
size that I should use (outlet circuit on
one hot to neutral and lighting circuit on
the other hot to neutral) and what is the minimum
wire size that I should use to keep voltage
drop under 2% ?

Thanks,
Arky

 

[ActionDave]

Just run two circuits on 20A single pole breakers with 12AWG wires.

 

[Sponsor]

 

[JWelectric]

60 amp breaker with a 60 amp main panel in building, 2-#6 THW, 1-#8 THW and 1-#10 THW. Must install two ground rods at building

 

[Alcan]

Just run two circuits on 20A single pole breakers with 12AWG wires.

"Thanks for your reply, since I don't plan on any future upgrades at all,
the plan now is to just run a MWBC (multi wire branch circuit).
From a 2 pole, 20 amp breaker at the main service panel, run (4) 10ga THWN wires
underground through pvc conduit to a junction box in the garage.
One hot to the outlets, the other hot to the lights and garage door opener.
The neutral will be shared since the hots are on different legs of the main buss.
And the 4th wire will go from main panel ground to equipment ground.
12ga would work, but going with 10 for reduced voltage drop,
then from junction box, 12ga to outlets and lights.
I plan on getting a 500' roll of #10 THHN/THWN from Lowes for $75
which is so much cheaper than by the foot for $.49/ft."

The above is what I have now planned, but after your post, I see that I will have
plenty of wire left over, so I could, as you say, just run from (2) 20A single pole
breakers instead of a MWBC. What advantage would that have over the MWBC
or vice-versa ?

 

[Reach4]

Regarding MWBC breakers, a 2 pole independent trip breaker would be best. http://www.schneider-electric.us/do...d-standards/circuit-breaker-markings-iaei.pdf page 60 and 61.

That allows a tied-together breaker to be turned off together for working on the system (required by newer codes) while not automatically turning off both legs in the face of an overload on one.

If you tie two regular breakers together, I don't know how they behave.

 

[Jadnashua]

It somewhat depends on whether you want to have to run back into the house to deal with a tripped breaker or you want to be able to control things locally in the garage. TO do it in the garage, you'd need to install a subpanel there verses just a new breaker(s) in the main and running the wires. Note, that a garage typically requires GFCI (and maybe AFCI), and I'm not sure how well those work on a multiwire branch circuit.

 

[JWelectric]

If you use a #6 or smaller then the neutral will be required to be white from end to end 200.6 and the equipment grounding conductor will be required to be green or bare from end to end 250.119. 225.31 requires that there be a disconnecting means at the building that turns off all hot circuits. This can be accomplished with a no fuse pull out

 

[ActionDave]

60 amp breaker with a 60 amp main panel in building, 2-#6 THW, 1-#8 THW and 1-#10 THW. Must install two ground rods at building

OOOPS! I forgot you can't run two circuits. I was trying to stay away from MWBC. You should have given me a dope slap.

 

[Alcan]

OOOPS! I forgot you can't run two circuits. I was trying to stay away from MWBC. You should have given me a dope slap.

What do you mean ? Is there a code rule about not running two circuits in the same conduit ?

 

[JWelectric]

No problem running two circuits in the same conduit the problem is running two circuits to one building. 225.30 says one branch circuit or one feeder per building being served.