Wiring new detached garage

[What the?]

Couple questions I'll throw out, it'd be great if someone could lend thier help.

I'm building a new detached garage, and I have buried pvc conduit connecting it to the house (about 75 feet). I have plenty of room in my home's main panel. The garage will have two garage door openers, a couple outlets to run power tools, and a heater rated for 240v/30A.

I'm guessing that I'll need a 15A breaker for the openers, another 15A for the outlets, and a 30A for the heater. So thats a total of 60 amps needed for the garage.

I was thinking about putting a 60amp breaker in the main panel.
Running a single line from the main panel through the conduit.
Wiring a small panel in the garage.
Adding the 15A 15A and 30A breakers in the sub panel and wiring from there.

Is this a good plan?
What are the specs of the line I will need in the conduit?
Should I ground the sub panel?
What am I missing here?

Thanks, Joe

[bkrahmer]

Once you look at the price of two wires versus one, a subpanel might be cost effective, but I don't see it as necessary in this case. I don't think you need seperate circuits for the openers and general purpose outlets. I'd run the garage on one 20A circuit, plus the heater. If the heater actually uses 30A, you need to go to 40A for it, and use 8 ga wire.

With a subpanel, I would run 8/3. It should be UF. Not sure if you can use anything else (i.e. not UF), since you are using conduit. The sub panel should be grounded, but the neutral bar must be separated from the ground bar, and taken back to the main panel neutral bus.

[What the?]

Thanks for the info! The more I think about it, the more I think you are correct that one 20 amp line should be sufficient for the general power and openers. I was concerned that if I ran my air compressor, and opened the garage door, the breaker would trip. But I think it will be OK, those openers don't really suck too much power. Plus, that will not be an everyday occurance, I can just be careful not to do that if it causes a problem.

As for the heater, I was looking at: http://www.heater-home.com/product/G73.aspx

The specs require a 30 amp circuit, but I will probably still need 8/3, you think?

[bkrahmer]

You could surely go 10/3, but if you go 8/3, you'll have room for another circuit or two without further rewiring. It's up to you.

[Sparks]

Just remember that the NEC states that if more than one circuit is run to a building, there must be a grounding electrode system. So just running 2 circuits from main panel in house without a grounding electrode system would be illegal, it would also be a violation to run 2 circuits from house to garage and not have a disconnect for garage. If you're running a big compressor, you may be better off with a sub-panel. Unless, you can make it all work on one 20 amp circuit, using just a 20 amp single pole switch as a disconnect. Being that you have a 30 amp heater, I would go with a sub-panel with a 4 wire feeder and install a grounding electrode system.

[Vector]

Don't run UF in conduit. It's for direct burial. Use THWN instead.

Put in a 60A sub-panel, it's hardly any more work than running a single circuit, and if you're doing shop woprk out there you will appreciate it someday.

Run four 6ga (Sparks please correct me if I'm wrong here) THWN wires from the house to the garage. Two hots, a neutral, and a ground (red, black, white, and green).

In the sub-panel, do not bond the neutral and ground busses together (remove or don't install the green bonding screw). Also run a ground wire off of the ground buss to a grounding rod outside of the garage. Your sub-panel can have a main breaker or main lugs. I personally would want the main breaker just so that I had a way to shut off the whole garage with one throw.

When wiring in the garage, just keep the neutrals and ground on their respective busses rather than mixing them (good practice generally, but some people do mix them).

Any circuits inside the garage will likely require GFI protection.

[Sparks]

Sounds good Vector. I see Romex and UF in conduit so often around here I'm dumbfounded. Why would anyone want to do this when it's unneccesary and is actually a lot harder to do?! Oh well, some people don't know about THHN/THWN I guess. So, either pull a pull string into your PVC when your piping it or just get yourself a 100' fish tape and pull in your 4 conductors and follow everything Vector said. Again, it's your choice as to install a sub with a main breaker or not, as long as the garage has less than 6 disconnects you're OK either way.

[What the?]

Thanks everyone. Since I'm not sure what I will do with this garage yet, I think I'll just put in a 60 or 100 amp sub panel. So I guess I'm looking at pulling four 6 gauge THWN.

Joe

[Sparks]

With a 60 amp yes, obviously with a 100 amp the conductors would have to be upsized. Just making sure we're clear, you will be limited to 60 amps with 6 awg conductors. I've never seen a residential/hobby use garage need more than 60 amps. Of course you could install a 100 amp panel in the garage, but the breaker feeding it must be 60 amps or less.

[rabadger]

If you are going to spend a lot of time in the garage spend the extra money and go with 100 amp. You may deside to put in a small air conditioner some day.

Will you be putting a frig in for the summer months?

[giddonah]

hahahah, I love you Rich. I bet if I started a thread asking about a tree house, you'd make sure I considered the HVAC. :lol:

[rabadger]

Sorry, I was just thinking about other mistakes made by not looking into the future. I would think a little extra service would not hurt. Had a neighbor that built a small bole barn big enough to hold about 3 cars and all his lawn tools. When they sold he ended up giving a allowance for new service so it could be headed. All he had was 3 light bulbs and a few outlets.

[What the?]

You guys crack me up :lol:
No, this garage is not my shop, so really the 60 amp will be more than enough. I just wanted to make sure that if I worked on the car in the winter, I could flip on the heater when I was running an air compressor. I'm raising another building on the property for my workshop, which will be the primary spot for all the fun tools. The garage will not have anything but cars and mechanics tools. The fridge will be in the other building, full of BEvERages :shock:

[Vector]

Regardless, 60A service is more than enough for the vast majority of fairly serious shops.

60A@240V = 120A@120V


You could run a *huge* A/C unit or heater and still have a good 60A of 120V available. How many tools can you run at once? ;)

[rabadger]

Ok fine! Never mind :D

[giddonah]

I'm glad you can take the ribbing Rich :D

[rabadger]

Where I am located the word GARAGE can mean several things. You have to qualify it.