Electric service for stand-alone garage

last year

I'm having a new garage built and plan to have electric service to charge up to two EVs, as well as other purposes. I'm having a local contractor install the breaker box and run the service to it, but I plan to do the rest of the wiring. My questions are 1) how much power should I get?, and 2) what load center should I get?

I'm thinking 100A should be plenty - two 50A charging ports plus a couple of lighting and utility circuits. But maybe I should get 125A or more.

I would like Square-D QO series load center (that's what my house has), and I understand they are better than the Homeline series. I saw them both in a BB store the other day and there wasn't a significant difference in price.

Of course, I will discuss these with the electric contractor, but I just wanted an independent opinion.

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3onthetree

last year

Type it, then add ".com"

Browse a bit and post if you want some specific advice for your garage.

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Comments (9)

3onthetree
last year
Jump over to DIYChatroom, there are a couple active and very recent threads on EVs. A bunch of licensed electricians and 1 really smart dude contributing to those. There's certainly knowledge here, but it doesn't seem like any licensed electricians.
mtvhike
Original Author
last year
What's the DIYChatroom?
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Good for you for looking out for your Mom. Your menu sounds delicious too. I have nearly always made the traditional holiday meals myself, from Easter to Thanksgiving to Christmas to New Year's Day. Guests can be anywhere from 10 to 40. This year we had three "Christmas" celebrations. One was at my son in law's, who lives three hours away and everyone brought something. The second was with my family, about 30 people, it was at the town hall and everyone brought a dish to pass, I provide the main dish and dessert. The third was yesterday with my girls and their families and I made everything. I've found that baked goods can be made a day ahead, I baked cheese rolls and made the cheesecake and the peanut butter pie the day before, as well as the pie crust for banana cream pie. I did assemble the banana cream the morning of the meal so the bananas didn't turn black. I made hoppin john the day before as well and sweet and sour greens two days before because my husband is from Tennessee and says you can't overcook greens, LOL. I had the steak marinating and stuffed and rolled it the night before so it was ready to pop into the oven. The mashed potatoes got done first thing in the morning and were put into the crockpot to stay warm, and the gravy was made a day ahead of time from beef stock which I'd canned the day before that. I just kept some in the fridge for gravy and didn't can it. I have a big Nesco roaster, a small Nesco and a crockpot. While the steak was baking, the potatoes were in the crockpot and the greens were in the small Nesco. The gravy and the green beans were in containers in the big Nesco and the rolls got wrapped in foil and put on top of those for warming. The hoppin John was in the microwave and the pies were in my "second refrigerator", which is my garage. It's Michigan and it's plenty cold, the only problem is that it might freeze. All cold drinks are also kept there. I have a very old freezer-on-the-top 17 CF refrigerator, so I just don't have usable space to spare, if it's not cold enough in the garage I use coolers for things like drinks and meat. I set the table the night before and always have a checklist of things that need to be done so I don't leave the sweet potatoes in the microwave or the fruit salad in the garage. This year's "casualty" was the fruit salad mother brought. She stuck it in the garage and it wasn't on my "list", so we both forgot it. (shrug) Many things freeze well, including unbaked cookie dough, so when I do 30 dozen cookies at Christmas I often make dough weeks in advance, portion it out and freeze it on sheet trays, then package in ziplock bags. That way I can take them out a dozen at a time and bake them as I want them. Everyone helps clean up, kind of. My husband will wash dishes left after my dishwasher is full. My girls clean the table, scrape plates, pick up glasses and coffee cups. That way I get to spend time visiting instead of hours in the kitchen cleaning up. At the end of the day I toss the tablecloth and napkins into the washer, have a cup of coffee and start planning the next time, what to do differently, what stays the same, while successes, failures and ideas are still fresh in my mind. Annie
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200Amp would be the way to go when you upgrade the service. I know from my own experiences that other people I work with have no clue what the code is because they either A)have never dealt with it or B) it's been some time since and does not remember. Also a few of the guys will give a higher number because they don't want the job & if the person agrees to it they laugh because they've "duped" someone into their higher price. That drives me nuts and I tell them refuse the work and don't even give a quote if you don't want to do the work. In Canada the code allows you to run 80% of your capacity. So if you were looking at putting a compressor in which is a continuous load then I would look at running it off a sub panel (I take it the compressor is in the garage) just for the garage. Depending on the draw of the compressor I typically run a 60Amp out to the garage and run all my circuits from there. If you are looking at putting in a new panel and not upgrading yet - look for a panel that is rated for 200Amp. The service can be updated at a later date. When I first got into side jobs I charged $35-45 an hour + material costs for my work. I claimed all the income I made . I now charge more as my experiences have built and I've always warranted the work done and insurance costs. People tell me my prices are low but then again I'm keeping busy and they aren't. I've also quoted entire jobs so no matter how long it takes it's the same price which CAN be very beneficial to someone if the time estimate goes over they aren't getting per hour charge.
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3onthetree
last year
Also GarageJournal (.com), but there would be a lot to weed through similar to your situation and if you post the pro comments are fewer in between the fluff.
mtvhike
Original Author
last year
So, an update here. I spoke to my electrician and he pointed out a problem: if I want to have a 100A service in my garage, I have to reduce the capacity of my house, since they both come from the same 400A meter. How do I reduce the capacity? I have two 200A panels, so would I replace the main breakers with 150A ones? Replace one with a 100A one? My second panel has a 125A breaker for the boiler for my heating system, and 4 20A ones. The first panel (which originally was the main panel) has 39 miscellaneous breakers, most of which are 20A but there are four bigger ones for my DHW heater, well, electric oven, and clothes dryer. He didn't seem concerned until I mentioned that I also have a solar panel system. Any comments?
mtvhike
Original Author
last year
New problem: the electrician who gave me the above advice and was going to do the job is now "too busy", and I haven't found any others. The foundation was poured yesterday, the slab will be poured next week and the framers are coming on August 1, so I decided to do it myself (I was aready planning to do the interior wiring). I was told by my local building code enforcer and he said that I can do it myself; the wires have to be 18" or more deep, and run through sch 80 PVC pipe where they are exposed. So my question is, what kind of wire should I get for 100A service. As far as I can tell, for copper wire I would need 3 GA and for aluminum I would need 1 GA. My run length is about 120 feet. A few questions:

1. Aluminum or Copper? AL is cheaper and CU is more flexible (because it's smaller).

2.Do I need 3 conductor or 4 conductor?

3. Do I need an external ground rod?

One practical problem is that some of the cables only come in 1000 foot rolls (for upwards of $900).
dennisgli
last year
last modified: last year
[Where have all the "PRO"s here gone?]

My take is that aluminum is fine if you have experience using it - I don't.

If you are installing conduit why are you buying cable?

I would assume that you need at least one ground rod - why not ask your "local building code enforcer"?
mtvhike
Original Author
last year
I need conduit where the cable runs under the driveway.
mtvhike
Original Author
last year
last modified: last year
My excavator pressured to move on with this, so I bought 150' of 2-2-2-4 direct bury cable. As stated above, I then found out that the part of the run which goes under the driveway must be in sch 80 PVC, so I bought 120' of 2". The excavator dug the trench and helped me pull the wire through the PVC, glue the sections together (along with two 90° bends and two conduit bodies), and run the wires into the top of the sill plate of the garage and into my house near the existing panels. That's all I'm going to do until the garage is completed and I can wire the interior, and then connect to one of my panels. That will probably be in about one month.

Do I have to run the cable inside conduit in my basement and/or garage? I probably could run it inside 1" EMT if necessary. All the heavy wiring in my basement is in EMT already.

Also, how do I properly connect the aluminum wiring? Are there special connectors made for that?

Electric service for stand-alone garage

3onthetree

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