Kind Sirs and Madams, please educate me about running electricity to a detached garage

So my garage is a 24x24 detached garage with no real electricity. I have overhead lights and some outlets run, and my current set up is running an extension cord with a home-made male to male adapter from the house to one of the outlets in the garage. This is not ideal.

The garage is probably 20' from the house, and the breaker box is probably 20' from the back of the house, so I'd probably need to run at least 50' of wire. I have an older fuse box that a neighbor gave me that I can use in the garage, or I can buy new if need be. I don't really need 220v in the garage, but it might be nice for future upgrades. I do plan on running a large-ish air compressor and a small welder (both are currently 110v, but the compressor can be switched to 220v), so keep that in mind.

The breaker box in the house is a 100 amp unit with only one empty breaker slot. I don't actually know that all the breakers are being used, but there is only one empty slot. I'd almost be surprised if they all are in use, as it seems that when on trips, 90% of the house turns off, but who knows.

What's the best way to go about it? Assuming that I only have one unused breaker spot, do I need to get a bigger box? Is one 20amp circuit big enough? What size wire/conduit should I use? Assume that I'm a complete moron and need it all spelled out in detail please! Thanks in advance!

I did find this http://diy.stackexchange.com/questions/48408/wiring-to-a-detached-garage , which helps quite a bit, but I'm wondering if the welder or the compressor (not too worried about running them at the same time) is too much of a strain on a single pole 20amp circuit. And if I did have enough room for a double pole breaker, could they be combined to make a 220v outlet?

run 220 now

as to wire for the purpose I'd recommend a 10 gauge UF cable inside a plastic conduit, I'd run the conduit underground.

You're not going to like this, but 100A service is already pretty marginal on a residence. You can't even get FHA financing on it. The seller of the house I live in was forced to upgrade it to 200A to make the sale.

You honestly need 50A to your garage. If you're going to bother with 220V, you want at least 30A. Then you need a 20A 110V service for lights and normal outlets.

Honestly, I'd call an Electrician in for advice. Estimates/bids are always free. It's a bit jerk-ish if you have no intention of actually hiring them, but you wouldn't be the first.

Here's how "220v" household wiring works, you have 3 wires coming into the house, two hots and a neutral (and a ground, but the neutral and ground are bonded at the panel), each hot is 120 volts (give or take 5). You get "220"(more like 240), because the two hots have their AC waveforms 180* out of synch, so the potential between the two 120 volt wires is 240 volts. So yes, double pole breaker=220 service.

Kenny_McCormic wrote: Here's how "220v" household wiring works, you have 3 wires coming into the house, two hots and a neutral (and a ground, but the neutral and ground are bonded at the panel), each hot is 120 volts (give or take 5). You get "220"(more like 240), because the two hots have their AC waveforms 180* out of synch, so the potential between the two 120 volt wires is 240 volts. So yes, double pole breaker=220 service.

Excellent, that's exactly what I thought. I guess I'm not a total moron after all.

You should upgrade service as some one has pointed out however you could run say 40-60 amps to the garage. Here's what I'd do.

Run a 8 cuircut 60 amp sub panel in the house. Remove 1-3 circuits from the main panel and move them to the sub. Install 60amp 220V breaker in the main panel. Run 2 hots to the 60amp sub panel, run a ground and a neutra . It is required that the subpanel "float" and not have the ground and nuetral be tied together. You now have extra circuits in the house in your new sub panel.

You basically repeat this from the sub panel to the garage. You need to be careful with the cable you run to the garage. Cable jackets are rated for different uses. They make special "triple rate" cable that can run free-air, in wall, and in buried conduit. You will need this so you don't have to splice outside. You put the new panel in the garage and leave it floating (unbonded) as well. You will have 5 wires running to this panel. 2 hots, a nuetral, ground from your house sub panel, and a ground from a ground rod. I would run either a 40 or 50 amp garage panel.
You would then run your garage wireing using normal methods. Put whatever panel size you want in with at least 1 220v circuit for fun.

I did this in my detached and can take some pics if you'd like. Mine is 200amp house, 100amp sub, 90 amp garage.

Also, if you want I don't think there is anything against the rules to put in conduit and pull 4 #10(30 amp) or bigger wires and only connecting three for a 20 amp branch circuit to the garage until you do a panel upgrade in the house and put a 220 subpanel in the garage.

I am in the midst of upping the service to the house from 100A to 200A. A new panel is in the existing attached garage (new mast through the roof as well, new meter soon), 100A will continue to feed the existing house, and 100A will be available for my fictitious garage. I have hired an electrician for this.

Trenching the electrical around the magical unknown septic field will be fun.

Regardless of what you have currently (pun, hah-hah) in use in the garage, run a heavy wire out there to cover future growth. You may be able to use aluminum service entrance cable (cheaper than copper) but check with someone who knows more than me.

Not sure if it legal or not, but were is your meter in relation to the garage? You could tap in there on the house side. (not the "hot&cheaty" side ahead of the meter). This would bring 220 to the garage without affecting the house box at all. Add proper box to the garage and let there be amps!

I don't mean to brag, but my builder put two 200-amp panels in my house, and 50 amps to the detached garage, along with a 220-volt outlet.

Okay, it's possible that I wanted to brag a little bit.

In reply to Kenny_McCormic:

I'm not sure what you are suggesting? Are you saying he cab run garage circuits directly off the house panel? As in the breaker for outlets in the garage are in a seoerate building? If so I don't believe that is allowed and even if it is its a bad idea. If you needed to cut power for whatever reason you would need to go into a different building. It is safer and better to have a main breaker in the garage to disconnect all garage circuits that all voltage to the building is coming from a single breaker in the house.

If you mean running a 30 amp sub panel in the garage off 110v only I think its allowed but you would risk overloading 1 leg of your main panel and having an unbalanced load. Its really not any more complicated to run 220V to a small box with 2 outlet circuits, a light circuit, and a 220v circuit.

I'm going to have a 3 way switch in the house garage that will control exterior lights on the house. I pulled an extra 12/3 Romex through my conduit (which I highly recommend, I wish I I had burried a cat 5). I will feed this Romex from the garage so that if I need to kill power to it I can either just kill the whole garage from the house or kill its circuit from the garage. If I feed it from the house my garage box would not be able to kill it and I would have 2 feeds to the garage.

In reply to nocones:

I mean running the whole garage off one 20 amp 120 volt beaker, in the house's box, just using very heavy duty wire to future proof it. If you did this, you'd obviously want some sort of disconnect in the garage, a $10 air conditioner disconnect should be fine, or even a 20 amp light switch on the hot wire.

This thread is relevant to my interests, but reading it has made my head explode.

I have what I think is 110v running from the breaker panel in the house to a single pole 20A breaker in the garage. I can't run my air compressor and anything else without throwing the breaker.

I'll have to have someone who knows what the hell they're doing to take a look.

This page has a pretty good tutorial on wiring up a detached garage: http://www.selfhelpandmore.com/home-wiring-usa/accessory-structures-to-dwellings/wiring-a-detached-garage-2002.php It was written some time ago, to the 2002 edition of the National Electric Code, so there may be some minor changes but it will give you somewhere to start.

And for the record, the voltages in the US are 120vac and 240vac - we haven't used 110 and 220 for about 50 years now.

Gotta run subpanel- go 220/50A. Gotta ground the garage separate. Definitely worth it. It's what I did for my detached, and I love it- lots of 20A outlets, couple of 220 outlets. No shortage of powa.

Extension cords: Nature's rope.

1988RedT2 wrote: I don't mean to brag, but my builder put two 200-amp panels in my house, and 50 amps to the detached garage, along with a 220-volt outlet. Okay, it's possible that I wanted to brag a little bit.

meh. my dad has 2 200 amp main panels and a 100 amp main in the garage. and real service disconnect boxes in house and garage so you can kill the main panel without pulling the meter to work.

my house has a 100 amp service(we got an fha loan 5 years ago just fine, did that change?). i intend to upgrade to 200 when time permits and $ is there to run the new service line and meter socket and have the electric bastards come hook it up. when i bought the house there was a 12-2 interior grade romex running to the garage, and we found it 6" under ground in no conduit. they put the plastic conduit elbows into the ground to fake like they ran the whole wire through it. when digging the garage trench we also found a pair of orange 10 gauge stranded wires running 2" under the grass to the light post by the driveway. fun times when you buy an old house that was originally built by an old autoworker and his drinking buddies to be the "let's get away from the broads and kids for the weekend" poker shack.

step one is get your buddy with a backhoe to come dig you a trench, step two is run 2" conduit from house to garage in that trench. step 3 involves a trio of 4 gauge wires and lots of lube to shove them through the conduit from garage to house. i have a 60 amp breaker in the house taking 220 to the garage, and out there i have a 60 amp redundant main breaker box and a sub panel with my garage circuits in it. separate ground rod for garage.

and for the record i've read anywhere from 108-125 on 110(120) and 215-248 on 220(240) lines at various homes and businesses testing things with a high end multimeter. 110/120 and 220/240 are pretty much interchangable terms. it's when someone says 115 or 230 that i kinda chuckle inside.

This thread is horribly dangerous.

I am giving up on looking carefully at the details, but it is not possible that not a single post is in keeping with the National Electric Code. .

Corey, whatever you do, PLEASE get rid of that male-male cord right away. It's a great way to get electrocuted.

Power to you garage- copper is expensive, conduit is cheap. Put in a conduit, and worry about the upgrade later if you have to. You do not have to stick in a big wire right now "just because".

Don't run a sub panel off a 20A breaker in the main panel. Add a disconnect at the service entrance, and feed a sub-panel in the garage. That way you KNOW what wiring is run for the ENTIRE circuit, and how well it is grounded, etc. You can upgrade the service later.

What did I suggest that is "horribly dangerous"? I ask because it is how my garage is wired and if it is wrong I will fix it.

In reply to nocones:

I didn't call anyone out individually.

I said the thread was horribly dangerous. There are enough bad ideas here that I stopped reading, and am not looking carefully at ANYONE'S details, including yours.

I am not interested in spending an afternoon trying to correct all this stuff.

But, we start with a house with a guy running an extension cord with 2 male ends from an overloaded panel to a garage (wet area, grounding??, flammables, etc), then have everybody make posts about how to load the panel more in various illegal ways, with no knowledge whatsoever of any details at all. What's the current load? Age of house? Condition of wiring? Current grounding? Proposed load? etc. etc. etc.

This has bad idea written all over it.

But no, I wasn't talking about you, nocones (or anyone else in particular).

In reply to nocones:

What you wrote may make sense to you, but it's difficult to understand... I have a pretty good idea after reading it a few times... and designing these systems is what I do for a living. All day, every day.

To the OP: Actually running power out to your garage is fairly straight forward. Buy a copy of the NEC (Handbook version preferred). It describes these systems very well.

Be aware that quite often any sort of new panel in a residence or outbuilding may require a permit and be inspected. This may or may not require a licensed electrician to install. Contact your twp code official and ask. Can you get away with doing under the radar? Sure. But it may very well create a lot of hassle for you if/when you need to sell your house.

Copper wire is expensive. Aluminum wire is cheap. 9 times out of 10, a high amperage feed to a sub-panel in a residence is done with AL wire. Typically anything #6 and larger. This kind a of wire is also available as a direct-burial type, although a minimum trenching depth is required (in the NEC). While copper is better (can carry more current using a smaller wire), AL is always cheaper.

IMHO, if going through the hassle of trenching an electrical feed to a garage, look into running a cold water and sanitary line as well, providing your inverts allow it. Having a hand sink in a garage is nice.

The issue with so many of these discussions is there are no simple "do this" answers. While every design will need to follow the general requirements of the NEC, each design will have aspects unique to each application. Unless you can give me accurate drawings and pictures of your house, then I can't really say what you can or can't do.