Sub panel wiring?

ELMO67 · Feb 3, 2003

I have just added an attached garage, and now need to add electricity to it. I have a 125 amp subpanel mounted in the basement of the garage, it is approximately 40-45 feet from the main panel. My question is - what size cable do I need to run from panel to panel. I'd prefer to use copper, and does the subpanel need it's own ground cable/ ground rod? I hope this was the correct forum to post this question to ,I apologize if it isn't.

WVBill · Feb 3, 2003

Is the garange a detached building or in the same building as the main panel?

Inspector507 · Feb 3, 2003

Attached garage does not need a ground rod, but yes needs a grounding conductor from the main panel. Decide if you want 125A, 100A, 90A....then make your wire selection . (We'll help) /forums/images/graemlins/grin.gif

ELMO67 · Feb 3, 2003

Thanks for the replies, so far! The garage is attached to the house by way of a 10'x 12' mudroom. The house, mudroom and garage all have basements, which is where the main panel ( house), and subpanel (garage) are located. The subpanel I have mounted in the garage basement is rated at 125 amp capacity; I would like to have that full capacity available. I think that the most I'll be drawing at one time would be 60 amps, but that may not allow for a start up draw.

TWINKLE_TOES · Feb 3, 2003

<font color="blue"> (We'll help) </font>

You just did /forums/images/graemlins/smile.gif I have had the ground rod on my to-do list for 5 years. Amazing how time solves problems, thanks

Inspector507 · Feb 3, 2003

For 125A feed to the garage, you’ll need to keep the following in mind.
Assuming all your terminations are rated at 75°C, you can use #2AWG Cu to feed the sub-panel. The #2 is rated at 115A at 75°C, but then you can “round up” to the next standard fuse size, which is 125A.
Run 3-#2Cu, one of them being marked white in some fashion. AND include a #6 bare or green for the grounding conductor.

The above is all based the premise you want to run Copper, sizes must be changed accordingly if you use Aluminum.

Jerry

ELMO67 · Feb 3, 2003

Thanks for the info, guys, now when I get the wiring done I won't have to keep dragging an extension cord all over the place!

bky · Feb 3, 2003

Remember to keep the neutral bar isolated from the panel and keep all neutral (white) wires on it and add a ground bar and put all the ground (bare or green) wires on it and bond (connect the ground bar to the metal breaker box

yooperdave · Feb 4, 2003

BKY-

I was told by an electrical engineer and a electrical inspector that you only use the bonding screw to bond the main box and not the sub box.

Please verify.

Thanks

Yooper Dave