electrical for new garage

[belvedere]

Just finishing a 28x48 detached garage, and trying to decide what to do for electrical. A neighbor suggested coming right off the meter, and putting a main panel in the garage. An electrician I talked to didn't want to do that, and suggested coming off the main panel in my house and putting a subpanel in the garage. I have a 150A panel in the house.

Any suggestions from your experience? Besides a compressor, I don't have anything that will take alot of juice. Someday, though, I may want to buy a small MIG welder.

Thanks in advance for any replies.

 

[brookscooper]

Well you have a number of choices and the right one for you will be determined by shop usage and cost you can handle.

Best choice - have the garage metered directly. It gets its own feed from the transformer and its own meter. This means the house and garage are completely electrically separate and you can have as much power in your garage as you want. Highest cost, of course. This also means that if you want to pay for you it you can have 3 phase power brought into the garage - only necessary if you are going to be running BIG stationary tools.

Next best choice - upgrade the main box on your house to 200 or 300 capacity. 150 is ludicrously small for a house AND garage. Then run service from the house to the garage with a sub-panel in the garage. For example - if your panel is rated 150 now and you put in a 300 then you can take the extra 150 to the garage. 150 is a bare minimum for a functional garage / shop.

Last choice - run service from your 150 to the garage into a sub. Cheapest - BUT carefully look at your usage now. How much of that 150 is really free? If you have an electrical clothes dryer, electric range, electric water heater you likely have little free space.

Even if you could find an electrician to do the wiring for you do not succumb to the temptation of overloading the panel by saying "oh, I'll only use power in the garage if the range and clothes dryer aren't on, so that capacity can be used for both the house and garage." That's a sure way to have a meeting with your local fire department.

Finally - if the garage is close enough to the house you could certainly use buriable cable and simple run a circuit or two to the garage from the house.

Start with the calculation of the power you'll need in the garage, add 50% and then let that drive your choice of electrical service.

 

[Boones]

I am in the same situation and looking at the various options. I want to go with Option 1 as right now my house panel is older and it has a 60 amp breaker that powers the dryer in the house and is running to the garage (well the one that was there previously), there are two 12-3 (I believe) running from the house panel underground to the garage (about 40 ft away), one was wired directly into a 220 plug for a compressor or dryer and the other went to the fuse panel in the garage that ran 6 overhead lights and about 10 outlets. (it was a large one car garage and a two car carport).

I know that is not enough for my new garage..

can you explain how to determine the amount of power I will need...

 

[Torque1st]

can you explain how to determine the amount of power I will need...

Add up the current draw of all the electrical devices you will have on AT THE SAME TIME. Only count one side of the current draw for a 220 device. Remember things like a compressor, refrigerator, or furnace cycle randomly. When you get that figure multiply by two. Let us know what the total is and post a list of your devices with their individual current draw also.

 

[sberry]

Depends on whats up with the house, most garages do not need 150A, home garages rarely need near 60A service and often are not really even considered added load demands as us is so intermittent.

 

[sberry]

An electrician I talked to didn't want to do that, and suggested coming off the main panel in my house and putting a subpanel in the garage. I have a 150A panel in the house.

I suspect this is why the electrician suggested this route, very practical and sufficient. I do like 90 or 100A wire though. The main consideration is type of home appliances. In all the years I can count on one hand the truly overloaded services I have come across, one being a Bud with all electric house on 60A fuse box, probably services a couple dozen garages with 60A and never, never had a tripped main due to overload including Bud that operates small garage with air comp and even 20A of air cond on occasion.
2 other memorable occasions, both commercial, one a bar/restaurant upgrade overloaded and poorly distributed and another park thing that had 6 wire @ 200 ft and 49A running down one leg and 1 amp down the other.
Excluding large air cond or electric heat you would really need to be screaming to pull 80A in a common home even with electric major appliances. With gas 30A would run most homes, if you were pulling that much current constant your electric bill would be out of site. Welding, air comp, so intermittent. Biggest constant load in residential garages is lighting and next is probably a fridge.

 

[Falcon67]

I came off the meter for mine, mainly because the house has a 100amp panel and I wasn't inclined to upgrade it. I ran #4 from the meter to a 60 amp breaker, then #6 to the shop. As a test, I turned on just about everything - A/C, lathe, drill press, lights, compressor - everything that I could plug in and make go. I think I maxed out at around 22 amps per leg. Later, I noticed I forgot the table saw. But, that gets very little use and I certainly can't run that and the drill press and lathe at the same time. I figure A/C, lights and at least one decent 1~3 hp motor is my typical shop load.

I watch the legs and try to keep the load even. I'm starting to convert anything with a sizable motor over to 220 to help keep the loads even. It's nice to have 220 in the shop - the older 120V "6HP" compressor - really 1 1/2 HP - would cause the flo. lights to chatter just a little bit. The new 3 1/2 HP 60 gallon unit runs on 220 and the lights don't even know when its on. The 5500 BTU 110V window unit in the bedroom of the house causes more electrical "trauma" when it kicks in than the big compressor.

 

[sberry]

Yup, when planning its easy to assume for heavy loads, like you said, put the meter on and its 22. Even adding a saw is another 15,,, and that assumes all that other stuff is running, negligible for the most part.

 

[Falcon67]

Always build in more than you think you need. Hate to sound like a GE salesman but I really like the 8/16 125 amp panel I put in the shop. It replaced a free 6 breaker panel that I was given when I was building the shop. The panel isn't high buck and the thin breakers run $4 for a single and about $8.50 for a double. Makes for a nice compact install with plenty of grow room. I've gone from the original 6 circuits to 6 plug and light circuits with two 220V runs. There is a 3rd 220 coming later and after that I'll still have 4 spots left in the box. I like to break up stuff into bunches, especially plug runs and lights. That way you still have something hot -or some light- close by and still shut off a plug or fixture you might be repairing.

 

[thedoc]

I live a subdivision where the meters are located roadside next to the transformer(underground electrical). The service to the house is 200 amp. My shop is located 205' behind the meter. There was an extra spot already there for a nother breaker. I just bought a 100 amp breaker and ran direct burial line to my shop with a new electrical panel. I talked with the power company and they said that would be more than enough for a typical garage.
Check your panel at the meter, you may have a spot for another breaker that you could use for your shop. I know someone is going to say that you have a 200 amp service with 200 at the house and another 100 at the shop. I figure rarely would I ever have more than 200 amp load between the two. The boiler wont be running in the summer with the air conditioner and the only other major draw would be a compressor. I run that now in the garage on my house with no probs with the a/c, dryer, and washer running at the same time. Just make sure you check for wire size over amp drop for long runs. I had to up my wire size to 1 ot aluminum instead of #4 copper due to a run of 205 feet. Not supposed to have more than 5% drop in voltage. Theres a chart somewhere online for that.
Good luck