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-   -   Wiring a sub panel (http://www.diychatroom.com/f18/wiring-sub-panel-159586/)

shotout1234 10-09-2012 09:37 PM

Wiring a sub panel
 
I am running new service to a garage. I have a 200 amp panel in the house and wish to install 100 amps in garage. I am assuming that I install a 100 amp breaker in the house and run to the garage. I have a 110 ft run of underground cable to install. I am told that I need to run 4 wire cable to the new panel. Is 2ga. 4 wire the proper cable to run? Do I need a main breaker in the sub panel or is the 100 amp in the main box sufficient? There will only be 110 volt in the garage with no major power draws, just portable tools and lighting. Any additional ingo would be appreciated.

k_buz 10-09-2012 09:40 PM

If you only have 120V loads and nothing that large, why install such a large sub? You could easily get away with a 40A panel and save alot of money.

shotout1234 10-09-2012 09:58 PM

Only because I already have a 100 amp panel that I took out of house and replaced with the 200. How about the feeder cable size? Can you help me with that?

k_buz 10-09-2012 10:03 PM

You can still use the old panel and just fuse it lower.

If you have less than 7 breakers in the panel, you will not need A main disco.

I don't use AL very often, but I believe you would need #1 al or #3 cu for a full 100 amp sub.

Missouri Bound 10-09-2012 10:08 PM

Wire Size Calculator Try this.

The panel you want to use...does it have a main breaker? I believe if you have a panel with more than 6 breakers you HAVE to have a main breaker in a sub panel. If that's not accurate I am sure someone will chime in with the proper info. In addition to the 4 wires there will be some grounding and neutral issues you will need to address. And you will need a couple of grounding rods at the garage. There's a lot of info available...just ask as you get closer to the project.:thumbsup:

shotout1234 10-09-2012 10:17 PM

I had intended to run about 21 inside outlets, 3 outdoor outlets, 6 flourescent 8' lights and 2 exterior lights total. Therefore I will have 5 outlet circuits, 4 light circuits, and 1 for the exterior lights. I am trying to get a difinitive answer on the wire guage for the feeder cable. This can be run on less than a 100 amp feed?

Dan101 10-09-2012 10:34 PM

Based on the information you provided. Yes 2ga. 4 wire will be sufficient for feeder. Just make sure it is listed for direct burial.

Missouri Bound 10-09-2012 10:41 PM

I'd suggest burying conduit rather than "just cable" And I would bury a second conduit as well, for telephone, intercom, cable tv and whatever else you want there....maybe alarm wiring. Not sure it will save you any money, but it will prevent any wiring decay from nicked wires and allow you future changes if you want or need.

k_buz 10-10-2012 05:38 AM

Quote:

Originally Posted by shotout1234 (Post 1027844)
I had intended to run about 21 inside outlets, 3 outdoor outlets, 6 flourescent 8' lights and 2 exterior lights total. Therefore I will have 5 outlet circuits, 4 light circuits, and 1 for the exterior lights. I am trying to get a difinitive answer on the wire guage for the feeder cable. This can be run on less than a 100 amp feed?

4 circuits for lighting is way overkill. You may need 2 depending on the draw of the 8' lamps, but I suspect 1 lighting circuit is all you would need. The problem comes in when you go to switch 4 circuits of lighting. If you want all the lights to come on together you would need a contactor.

You will need a main disconnect.

As stated above, you will also need 2 ground rods.

electures 10-10-2012 06:57 AM

Quote:

Originally Posted by k_buz (Post 1027834)
You can still use the old panel and just fuse it lower.

If you have less than 7 breakers in the panel, you will not need A main disco.

I don't use AL very often, but I believe you would need #1 al or #3 cu for a full 100 amp sub.

Quote:

Originally Posted by Missouri Bound (Post 1027838)
Wire Size Calculator Try this.

The panel you want to use...does it have a main breaker? I believe if you have a panel with more than 6 breakers you HAVE to have a main breaker in a sub panel. If that's not accurate I am sure someone will chime in with the proper info. In addition to the 4 wires there will be some grounding and neutral issues you will need to address. And you will need a couple of grounding rods at the garage. There's a lot of info available...just ask as you get closer to the project.:thumbsup:

Which ever way the op decides to go, the panel has to be "suitable for use as service equipment". Before the "six motions of the hand" rule can be used, the panel instructions have to be reviewed. Some MLO panels will require a main breaker w/ retention clip be installed in order to be "suitable for use as service equipment". Also, the panels listing labelling may require a main as well.


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