Will 40A service be sufficient for detached garage

stevens1920

9 years ago

Hello all, new to the forum. So here goes my first post.
I have a 1728 sq foot house with 100 amp service and a detached 24x24 garage with 10 ft ceilings and an attic. The garage is 35 ft from the main panel, and I already have the proper schedule 40 pvc run under ground and ready to run a 4 wire setup. Is 40 amp service to the garage sufficient? I want at least one 240v circuit to run a compressor for basic mechanical work and possibly another for a heater (I also have natural gas run). I imagine a garage door opener and three runs of outlets including lighting, with one of them being a 20a 120v limited to 3 or 4 outlets for occasional use of power tools. In my house I have a gas furnace, hot water heater, central air, electric range (switching to gas within a year),and brand new high efficiency washer and dryer (electric 240v on a 30 amp circuit) and two adults, and two college students home for the usual breaks. What do you think? Should I consider 50 or 60? There will be no more expansion or addition to this property and I do not intend to upgrade my main service. Thank you for any input.

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Comments (8)

joefixit2
9 years ago
What kind of wire are you running? #8 THWN is what you need for 40 amps but it will also carry 50.
stevens1920
Original Author
9 years ago
Yes, #8 THWN is the initial plan, unless I determine I need to up it to #6 for more capacity.
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OK, based on what you stated the oven needs a 40A circuit and the cooktop a 30A circuit. You can use the current range circuit for the new induction cooktop. The central air will likely need a 30A circuit. If you run all three appliances at the same time at maximum rating (unlikely), you will draw an additional 70A to what you are using now. However all additional circuits in your home must be considered and it wouldn't take much to push your demand over 100A I would recommend you put in a new service with 200A capacity. Be aware that this will cost at least several thousand dollars, maybe more. Get more than 1 quote and references unless you know your electrician already. Also, make sure everything is inspected and all permits are acquired.
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Indeed you have alot of circuits but dont be concerned with the quantity nor the total of all the beaker amps added. example being those 4 water heater @ 40 A will only draw initiaily at startup and would probably never all run together ever again. The suggestion that induction cooking draws alot is incorrect as it is extremely efficient and draws uses much less energy than a conventional cooktop (just look as the amp rating) youll likely need two panels for the breaker space. The unknown factor you havent detailed is whats going on in those outbuilings. If they sre for blown woodworking shops lets say, then all bets are off. At that point you might consider just bringing in a separate service to the outbuidings. Its done all the time at would be less costly. Just food for thought.
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User
9 years ago
With only a 100 main, you need to upgrade your main service. Especially with power outlet seeking college students ever in search of a free outlet for their device chargers.
joefixit2
9 years ago
"With only a 100 main, you need to upgrade your main service. Especially with power outlet seeking college students ever in search of a free outlet for their device chargers."

How can you possibly know the OP needs an upgrade with the information given? And just how much power do you think cell phone and lap top chargers take??

This post was edited by joefixit2 on Sun, May 11, 14 at 0:52
joefixit2
9 years ago
I ran a 100 amp service to my 1,200 sq foot garage 3 years ago, but I didn't have a 100 amp QO breaker on hand so I put in a 50. I have a big compressor, grinders, 3 welders, drill press, 2 chop saws,1,300 watts of overhead lighting and two evaporative coolers. Haven't had a problem yet with 50 amps. Unless you plan on electric heat I think you'll be fine. Of course only one or two people working at a time keeps the demand down.
lee676
9 years ago
If you're in the city or suburbs, may want to keep the electric or plug-in hybrid car option available for the future, when these will likely become more common. If so you'll want a 240v/40a outlet available just for charging..
petey_racer
9 years ago
I don't get this concept of "you should have provisions for an electric car", like everyone in the future will have electric cars.
Right now, and in coming years, they are a fad. We will NOT be an electric vehicle society for a long time.
IF you do happen to get an electric car, deal with it then. They do not all require the same thing, so WHY bother with prepping for it before hand???
Ron Natalie
9 years ago
I don't know Petey, the fad is getting bigger. While a lot of manufacturers are only doing it to appease certain states that are mandating a percentage of EEV's, they're becoming more popular. I've got a Volt and the dealerships (including the caddy dealer across the street) have a hand full of cars on the lot even here in Virginia. Charging stations are popping up all over the area (my favorite is in front of my local bar/restaurant).

Still, unless one was really considering an electric car in the next two or three years, I'm not there's any economy in putting in the additional capacity in the "hope" it might be needed. Though It was less costly because I did the labor myself, adding my 30A (the Volt charger is a bit anemic) circuit to my garage wasn't a big thing.

Will 40A service be sufficient for detached garage

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joefixit2

stevens1920
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Will 40A service be sufficient for detached garage

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stevens1920Original Author

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stevens1920
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