Wiring a panel from existing 220v outlet...

[raney]

Hi all,

Been poking around here for a week or so and learning a LOT here - GREAT forum.

Here's the 'quick' version of my plan, which I could use some advice and/or confirmation on:

My garage is currently all wired on a single circuit that also carries a bedroom, and all the outside lighting in my house. Needless to say, I've tripped a breaker once or twice since setting up a router table and the TS. Pulling new cable is a nightmare for a variety of reasons, but I think I've found a pretty simple solution:

My laundry room (shares a wall with the garage) has an unused 220v outlet, wired with 10/3. My plan is to knock through from the garage side and install a small load panel using the wire from this outlet, as I have no foreseeable use for 240 in this location.

At the main panel, I plan to install a 30A double-pole breaker to feed the panel. In the local panel I want two single-pole 20A breakers to feed two 20A 120v lines. One of these will feed a GCFI for the router table/TS (I never use both at once) and the shop-Vac. The other circuit will feed a GCFI and then a strip of outlets for "other tools" - the only thing of any size is a 6-gal pancake compressor I use almost exclusively for a brad nailer.
Both 110 lines will be wired with 12/2.

I've done a reasonable amount of basic' wiring, but never done a panel like this.
Questions: Is it acceptable to have a shared return on the two local breakers to the main panel since they are on different phases?
Is a 30A at the main too much increase over the local 20A breakers?
Am I missing something important?

Thanks for any suggestions/help.

[ChrisL]

Don't use a shared return. You should be alright with a double 30 at the main and 2 20's at the sub. I'm not an electrician but that's my gut right there. I wouldn't use GFCI's. They nuisance-trip too often. One thing I would do is use double gang boxes so you have 4 receptacles at each outlet. Since you are using 20 amp wire, you need 20 amp receptacles.

[ChrisL]

Oh, the other thing you might want to do is run 12/3 wire into your double gang boxes and have each gang box have 2 circuits in it -- one for each receptacle in the gang box.

[LJR]

Raney, the "shared neutral" on the 240 volt circuit is fine. The load on the neutral wire will be the imbalance between the hot legs of the 240 volt lines. So, if you have one side of the 240 volt loaded up to 30 amps the neutral will also be carrying 30 amps. If you have both hot legs of the 240 volt circuit carrying 30 amps the neutral wire will be carrying 0 amps.

Breakers are meant to protect the wire. 30 amp breaker with #10 wire feeding a subpanel is fine. Then, in the subpanel you set 20 amp breakers and run #12 wire. You're still fine. All wire is protected correctly (the number 12 won't pull more than 20 amps and the #10 won't pull more than 30 amps).

GFCI receptacles in a garage are probably a good idea ( and may be required by code in your area ). I have had my share of "nuisance" trips with those receptacles and have found that if I change the receptacle out to a high quality one it will usually fix that problem. They're not cheap but I've been using "Hubbell" GFCI's and been far happier with them.

[sbs]

GFCI are required for accessible garage outlets almost anywhere in the US.

You do not need to use 20A receptacles, except in the case where there is only one receptacle on an entire 20A branch.


There is often a lot of wrong information given on this forum regarding shop wiring. I suggest you check out the FAQ at http://ths.gardenweb.com/forums/wiring/ and ask followup questions over there.

[raney]

Thanks for all the replies...

I wound up skipping the panel for now - I just put a 20A fuse in the main panel, wired two 20A circuits with GFCIs. I'll probably upgrade to a panel down the line, but this will solve the immediate problem.

Thanks for the replies - especially the gardenweb link. That was a VERY helpful link.