Latest Discussions : Electrical & Lighting


04:16AM | 07/07/06
Member Since: 07/05/06
2 lifetime posts
I am wanting to put a 100 amp sub panel in my detached garage that is about 30 feet from the house. I have a 200 amp main panel in the house. What size underground cable should I use? also, what is the difference between #4 wire and 4/0 wire?


02:13PM | 07/08/06
Member Since: 04/25/05
1915 lifetime posts
Wire sizes are measured by the American Wire Gauge, where smaller number indicate large wire diameters.

They are mostly even numbers until you get to the large sizes. 8, 6, 4, 3, 2, 1.

The next size larger is zero or Ougth, but indicated is 1/0. The next bigger sizes are two ought or 2/0, then 3/0, and 4/0. After 4/0 they are measured in circular mils.

For your 100 amp sub-panel if you use USE cable or THHW, THHN, THWN wire then you can use #3 copper or #1 AL.

If you use UF you need to #2 copper or 1/0 AL.

For a detached structure without any other metalic connections (water, gas pipe, phone or cable) you can use a 3 wire connection and treat the sub-panel as an service entrance (bond neutral and ground). However, some local codes don't allow for this.

Other wise you need to run 4 wires and keep the ground and neutral isolated at the sub-panel.


03:40PM | 07/08/06
Member Since: 07/05/06
2 lifetime posts
Thanks a lot Handyman. You cleared things up just fine for me. I really appreciate it.


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