Wire Size For 100 Amp Basement Sub-panel - Electrical - DIY Chatroom Home Improvement Forum

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Old 01-26-2009, 03:14 PM   #1
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Wire size for 100 amp basement sub-panel

Have a 200 amp main in my attached garage. I am adding a 100 amp sub-panel in my basement to run all my basement circuits (2 bedrooms, office, living room, wet bar, bathroom).

I have a panel with breaker set in the basement, and already have the 100 amp breaker to go in the main in the garage, but need to buy the wire to run in between.

I'm planning to call the inspector and just ask him, but looking for any other information first. I'm running it inside a wall, and through an attic space above my garage and back to my panel, so I'm not using conduit.

Is #4 for the hots and neutral enough? Or do I need to use #2? I think I can get a bundle with #4 hots and neutral at Home Depot, but not the bundle with #2 in it.




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Old 01-26-2009, 03:55 PM   #2
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actually you could use a #3 / 3conductor romex (copper) a little price per foot, but the easiest /quickest to install


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Old 02-17-2009, 10:38 AM   #3
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Well, my inspector told me I could run #3 copper or #1 alumimum SER. The suppliers that I contacted here in Minneapolis basically said they only carry the aluminum in a bundle 'cuz that's what everyone buys. So that's what I did. I've got the panel hooked up and am now running my circuits back to it. A lot nicer than running out to the garage to test them all the time!
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Old 02-17-2009, 11:44 AM   #4
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You used the correct cable by choosing SER and the inspector would be correct on the wire size assuming your not on 2008 code however if he told you that it was OK I wouldn't sweat it. You are likely 2005 or earlier code cycle.

You need 4 wires in your cable...2 Hots , a neutral and a ground. A main breaker in the sub panel is fine but was not required... just an FYI. You need to keep neutrals (whites) and all grounds separate in the sub-panel. I'll put up a diagram showing you how it should look. You will not install the main bonding jumper in the sub-panel could be a green screw or some other means. You may have to install a ground bar kit to accomplish the separation of the two.

If you can give us the make and model of your sub-panel we can tell you how to do this most likely.

Any questions get back to us.
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Old 10-25-2009, 09:58 AM   #5
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In other words, the sub panel box is grounded through the main panel, just like anything connected to the subpanel?

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