Need Garage Sub Panel Advice

[cwood3]

My house is 22 years old. The garage is attached. The main breaker panel is outside on the back of the house. The previous owner had some mods made. He ran a conduit (about 1/2", maybe 3/4") out the bottom of the box straight down into the ground, along the foundation, around the corner to the side of the garage, up out of the ground about 12", and into the garage. The wires come off of 2 110V/20A breakers on the main panel to provide 220V in the garage. My main panel is "full". I would like to have 220V in the garage as I have an air compressor, a lathe, a mill, and some welding machines. I would like to have a new panel installed inside the garage that would support my 220V needs and a few 110 circuits for lighting and some more outlets. I know I need big wire to get the proper amount of current to the new sub panel. The only time I have two 220V loads going at the same time would be if the air compressor kicked on while another machine was on. Never two machines simultaneously. My real question is, does code allow the wiring from the existing main panel to the new sub panel to be run underground in buried conduit? What is the preferred method? I am going to hire a licensed electrician to do the sub panel install, but I want to be able to discuss it with him intelligently with some degree of knowledge/confidence.

(On a side note, I'd love nothing better than to eliminate the old breaker panel and go all new, but that outdoor panel really irks me.)

Thanks.

 

[madstat]

It's ok to run wire for a sub-panel through conduit underground. If you verify the correct depth and its the correct size and type of conduit for burial then you may be able to just use what's already buried and save you a lot of work. If it is only 1/2" this is likely too small to run a sub-panel off of. If it's 3/4" conduit then you are probably good to run new (larger) gauge wire through the existing for a small sub-panel.

The electrician should be able to remove the two existing 120v breakers and replace them with a new 240v breaker feeding your sub without needing a more space in the existing panel. He can also verify weather your existing conduit is at the right depth and is the correct type. If he's able to reuse the conduit then he can simply pull the new wires (2-hot 1-neutral 1-ground) through the existing conduit, using the old wire as a pull wire.

 

[cwood3]

As I've been doing some more reading, I am resolved to dig up the old stuff and toss. If I use a sub panel that is 60A or greater, I may as well have it run with the big wire (2-2-2-4...?) Doesn't that require like 1.5" or 2" conduit with "sweeps" for direction changes...?

 

[pattenp]

Can you access the garage through an attic area? If you can run wire from outside panel box up the wall into the the attic area you could use SER cable and only need conduit from main panel to where the wire enters the attic. As long as the SER cable is in the attic and inside a wall you can get by with out conduit. Where conduit is needed I would use 2" for 2-2-2-4 SER. It's just a lot easier to pull through.

 

[blasto9000]

Ditto on replacing the two 120 volt lines with a proper 240 volt breaker. The way I did it at my place was to swap the regular 240 breaker for the household air conditioning with a "duplex" 240 volt breaker that fed both the a/c and the new garage sub-panel. (The duplex breaker is the same size as a normal breaker, so in essence you get two circuits from a single breaker space.)

For the sub-panel, I suggest using a main breaker panel (the type without the meter hole) with a pre-installed "backfed" breaker. You wire the 240 input wires to the backfed breaker, and the backfed breaker powers the bus bars in the panel. That way the sub panel has its own on/off main in addition to the breaker feeding it from your main panel.

One thing I wish I could do over with my panel was to use a larger one... much larger. Mine has 8 positions and were instantanteously filled with just my nominal shop load. Now I want to add more lighting and it will an exercise in creativity.

 

[pattenp]

May be just a misuse of terms but if buying a new panel buy a Main Breaker Panel do not buy a Main Lug Panel and use a back fed breaker as a disconnect.

Ditto on replacing the two 120 volt lines with a proper 240 volt breaker. The way I did it at my place was to swap the regular 240 breaker for the household air conditioning with a "duplex" 240 volt breaker that fed both the a/c and the new garage sub-panel. (The duplex breaker is the same size as a normal breaker, so in essence you get two circuits from a single breaker space.)

For the sub-panel, I suggest using a main entry panel (the type without the meter hole) with a pre-installed "backfed" breaker. You wire the 240 input wires to the backfed breaker, and the backfed breaker powers the bus bars in the panel. That way the sub panel has its own on/off main in addition to the breaker feeding it from your main panel.

One thing I wish I could do over with my panel was to use a larger one... much larger. Mine has 8 positions and were instantanteously filled with just my nominal shop load. Now I want to add more lighting and it will an exercise in creativity.

 

[Charles (in GA)]

You must live out west somewhere. Outside panels are common out there.

Charles

 

[jeff000]

Ok, first off I am a Canadian Electrician, So the CEC is a little different then the NEC, but close.

If you don't like the main panel that is outside, and want lager anyways, I would do it all at the same time. I'm going to assume you live in a modest size home, with average loads, and have a 100+ amp service already (if not upgrade).

If you are leaving the existing main panel, and the existing PVC is 3/4" then you can run your three #6 copper wires to the garage for a 60amp sub panel. I really like the Square D 100amp 20 space load centers.
Just feed it with a 60amp breaker from the main box.

If you can't reuse the conduit then NMWU will be the best bet to drop into a trench of adequate depth.

That's the short of it anyways.

 

[cwood3]

Thanks all. I think new panels are in order.

 

[6768rogues]

Take the old wire to the scrap yard. Insulated copper wire is worth about $1.50/lb.