Adding a sub-panel - wire question

[Chuckster815]

New to the forum, planning to add a compressor to my garage. Researched adding a sub-panel and feel relatively comfortable, having done some wiring before.

What I don't know is how to figure what size wire to run from the main panel to the sub-panel in the garage. Basically one end of the house to the other, approximately 75 feet. For a 100A sub-panel, what would be required?

Chuck

 

[kool55]

Just finished mine. Ended up running 1/0-1/0-1/0-2 AL SER feeder thru 2'' pvc conduit 80' to a 125 amp lug panel. It is fed by a 125 breaker in the main panel and a 50 amp at the sub.8-3 copper in 3/4 conduit from the sub to a disconnect at the compressor.

 

[Chuckster815]

Thank you much, Kool55!

 

[Aceman]

New to the forum, planning to add a compressor to my garage. Researched adding a sub-panel and feel relatively comfortable, having done some wiring before.

What I don't know is how to figure what size wire to run from the main panel to the sub-panel in the garage. Basically one end of the house to the other, approximately 75 feet. For a 100A sub-panel, what would be required?

Chuck

Is this an attached garage? Do you want to run conduit or use cable?

Just finished mine. Ended up running 1/0-1/0-1/0-2 AL SER feeder thru 2'' pvc conduit 80' to a 125 amp lug panel. It is fed by a 125 breaker in the main panel and a 50 amp at the sub.8-3 copper in 3/4 conduit from the sub to a disconnect at the compressor.

Same question, attached or detached garage?

If Alum you need 3 - #2 guage and 1 - #6 for ground, again with green insulation for the ground wire.

#2 AL is not 100 amp wire in this scenario. Depending on the whether he uses conduit with individual wires or cable, it can have a max breaker size anywhere from 70-90 amps.

 

[sberry]

They have number 2 alum quad wire at the box stores just for this, direct burial or pipe. I don't recall which but one of them had a better wire, there is a difference. One store had 2-2-4-6 and one was 2-2-2-6 and priced better to boot. I usually feed them with a 60A as the breaker is cheap.

 

[Chuckster815]

The garage is attached. I do not currently have any conduit, code here does not call for it. If I was to use copper cable would it be 2-2-2-4? I would have a 75' to 80' foot run with 100A sub-panel.

 

[Aceman]

If I was to use copper cable would it be 2-2-2-4? I would have a 75' to 80' foot run with 100A sub-panel.

Yes, that would work for a 100 amp panel. You can price out 1/0 AL SER too, if you get sticker shock on the copper.

You may need to purchase from a supply house to get these sizes. I believe Home Depot usually only carries #2 AL SER cable.

 

[kool55]

Is this an attached garage? Do you want to run conduit or use cable?



Same question, attached or detached garage?



#2 AL is not 100 amp wire in this scenario. Depending on the whether he uses conduit with individual wires or cable, it can have a max breaker size anywhere from 70-90 amps.

Aceman, my shop is detached

 

[Aceman]

Just finished mine. Ended up running 1/0-1/0-1/0-2 AL SER feeder thru 2'' pvc conduit 80' to a 125 amp lug panel. It is fed by a 125 breaker in the main panel and a 50 amp at the sub.8-3 copper in 3/4 conduit from the sub to a disconnect at the compressor.

Aceman, my shop is detached

The reason I asked is that the codebook doesn't allow SER underground. Something like this would of been more appropriate:
http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet15

 

[mad57]

Thats what im going to use now 2-2-2-4 aluminum with a 8 space 100amp breaker sub panel $36 bucks... to go about 70 feet its cheaper than the copper wire from there ill branch off the sub panel to my welder . plasma .. lift.. compressor ..with 6-3 copper... forgot to add i have a 200 amp square d box... all the parts are at the hd and are cheaper than my local elec supply.. although the elec supply priced me .89cents a foot for 6-3 copper where hd was 2.64 a foot by the foot. if you buy there 125 ft roll its $136.00 so some savings there. good luck sounds like your on the right track mike.

The garage is attached. I do not currently have any conduit, code here does not call for it. If I was to use copper cable would it be 2-2-2-4? I would have a 75' to 80' foot run with 100A sub-panel.