Getting ready to install sub panel in attached garage

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Forum topic by Paul Ciura posted 02-23-2012 04:49 PM 27497 views 0 times favorited 21 replies Add to Favorites Watch
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Paul Ciura

19 posts in 3802 days

02-23-2012 04:49 PM

Topic tags/keywords: question electrical sub panel installation

Hello all,

I am slowly getting ready to pull a trigger on a 220v table saw, which most likely be the Grizzly G1023RL. Before I do that I am going to install a sub panel in my attached 2 car garage. I’d like to verify that what I got planned so far looks like a good plan.

Current needs in the sub panel:

I don’t have a need for any lighting circuits on the sub panel as that is already taken care of. I don’t see myself using any more than 2 to 3 items running at the same time (table saw/dust collector/air cleaner, etc, etc.).

Distance from main panel to where the sub panel will be installed is about 40’. Looking to use 60 amp double pole breaker at the main.

For the installation part:

  • Install sub panel box (100 amp main lug only panel with 8 spaces/16 breakers max).
  • Pull feeder cable between main and sub panel (#6/3 with ground).
  • Attach feeder cable to sub panel (black wire to main lug #1, red wire to main lug #2, white wire to neutral bus bar, bare/green wire to grounding bar).
  • Turn off main panel.
  • Attach feeder cable to main panel (black wire to 60 amp breaker slot #1, red wire to 60 amp breaker slot #2, white wire to neutral bus bar, bare/green wire to grounding bus bar).
  • Snap in the 60 amp double pole breaker in place with off position.
  • Turn on main panel, turn on 60 amp double pole breaker.
  • Test at the sub panel for juice.
  • Turn off the 60 amp at the main.
  • In the garage run my required circuits to their locations from the sub panel.
  • Turn on the 60 amp at the main panel.
  • Test circuits.
  • Give yourself a pat on the back.

I think that about sums it up at the moment. Any feedback would be much appreciated.


21 replies so far

View HorizontalMike's profile


7874 posts in 3724 days

#1 posted 02-23-2012 04:57 PM

I used a 125amp box (w/100amp breaker at house box) for all of my shop needs, including lights. I have three 240v breakers and six 120v. If I had it to do over again, I would go with a larger box with more breakers. I am well wired, but think the extra breakers would be a convenience in the long run.

-- HorizontalMike -- "Woodpeckers understand..."

View crank49's profile


4032 posts in 3781 days

#2 posted 02-23-2012 06:11 PM

You mentioned 220volt for the table saw. You need to be aware the breaker for a 220volt circuit takes two, adjacent slots in the panel.

I would not use 15 amp breakers for outlets.
Run 12 ga wire and 20 amp breakers.

Only place I use 14ga wire and 15amp breakers is lighting circuits; and you said you have those covered.

View Grandpa's profile


3263 posts in 3485 days

#3 posted 02-23-2012 07:13 PM

In my shop I also used 20 amp receptacles. Homes in my area use 15 amp receptacles. I just feel more comfortable with these. Might save a tool one day. Use a larger panel than you think you will need. Mike is correct. Might be convenient in the future.

View Paul Ciura's profile

Paul Ciura

19 posts in 3802 days

#4 posted 02-24-2012 01:24 AM

Thanks for the input so far. I managed to make my way to local store and picked up a few things for this project already. Should be a fun weekend!

View brtech's profile


1068 posts in 3732 days

#5 posted 02-24-2012 01:53 AM

Crank49 is spot on. Do you have one of those 3 lights on a plug electrical testers? If not, get one. Test each of your outlets with it to make sure all of the wiring is right. Wouldn’t help much with any direct wired outlets, 220V outlet for the TS, etc, but it’s a mighty handy tester. Don’t forget when you are looking at your 220 connection, you measure between hots, there is no neutral, and you would measure 110 between one hot and ground.

As with a prior thread on sub panels, there is some regional difference on code for grounding. In your area, you may be required to run just the hots, and have a separate ground rod, with the neutral to ground tie in the sub. In most areas, what you are doing (#6/3 with ground, no ground rod, no neutral to ground tie in the sub panel) is what code says. With your wiring, make sure there is no neutral to ground tie in the sub panel – it should only be in the main.

View WOODGLUE's profile


8 posts in 3134 days

#6 posted 02-24-2012 02:20 AM

for what it’s worth.

after having worked for twelve years doing electrical work in a plant (mainly equipment repair) i learned the value for having enough, meaning more.

i am building a 32×40 shop/garage and will install a 200 amp square “D” QO panel (learned from work that is one of the best around). i will be running a 7 1/2 hp 80 gallon air compressor, table saw (i can wire for 230), rather large drill press, miter saw, planer, and everthing else i can get my hands on. will install (plans now, but looks like i’ll change) twelve 8ft light fixtures 110 watts per bulb (two per light) high output, oh forgot a welder pulling 47 amps.

my point is that the panel is just like lighting, more is never too much. you can and will run out of panel room quick and it’s eaiser to put in too much than have to take out and redo it.

just my thoughts.

View Scot's profile


344 posts in 4206 days

#7 posted 02-24-2012 02:40 AM

You do NOT install another ground rod for a sub panel. Sub panels are to be grounded at the originating service ground.
The instructional guide you have written is correct.
A four wire feeder cable is required as you have stated, but you remove the jumper between the nuetral and ground busses. Depending on the manufacturer this jumper could be a heavy gauge solid copper wire or a metal plate, either way they are easily removed. There should be a green bonding screw either already installed (on the ground buss) or loose packed with the panel. The bonding screw bonds the ground buss to the panel can.

The only thing I would consider doing different is going ahead and upsizing the feeder wire and breaker to 100 amp.

I can’t tell you how many of these sub panels at 50 or 60 amps I’ve installed and have the customer tell me later that they wished they had gone with 80 or a hundred amps.

It’s not uncommon for my TS,DC,AC and air comp. to all be running at the same time.

BTW, I should be in my shop most of the weekend with the computer on, any questions just give a shout.

-- If the old masters had power tools, they would have used them. So get off your damn High Horse.

View Vrtigo1's profile


434 posts in 3801 days

#8 posted 02-24-2012 03:05 AM

I went through the exact same project last year. I ended up putting in a slightly larger subpanel than you are looking at. I think mine was a 20 slot panel with main lugs (no main breaker). I ran feeder wire for 100 amps but only put a 70A breaker in the main panel to feed the subpanel as I didn’t envision needing more than that, however with the bigger wire run, upgrading is as simple as replacing that 70a breaker in the main panel with a larger breaker.

My recommendations would be installing a breaker with sufficient expansion capacity. Looks like you have 9 slots spoken for (3 220v circuits and 3 110v circuits), so a 20 spot panel would probably be what I would go with. I found that the larger panels really don’t cost much more, and if you ever want to grow beyond what you install initially, it will be that much easier.

I would agree with installing 20a receptacles instead of 15a. Here in FL all commercial receptacles are 20a, residential are 15a. So, if you were using your tools in a commercial shop, you would be plugging into 20a. If you wanted to run a semi stationary tool such as a planer off one of these receptacles, you might have trouble tripping a 15a circuit.

Also, as someone else pointed out, check the codes in your area regarding the ground in your subpanel. Most panels come with a lug that ties the ground and neutral buses together, and for a subpanel, you usually have to remove this so they are only tied together at the main panel.

I recessed my subpanel in the drywall in my garage next to the main panel so it looks like it belongs there. It was quite a PITA drilling through all the studs in between the two panels to pull the feeder cable through. Had to buy one of those 6’ long flex bits for electricians at Home Depot to the tune of $60 and had to do everything in the dark because I elected to turn off the power at the main disconnect at the service entrance. It was definitely an interesting experience. Once we got the feeder wires pulled through the wall, the install took about 4 hours. I also ran a 2” PVC conduit inside the wall so it comes into the top of the panel and the other end of the conduit pokes up into the attic so I can easily pull new wire if needed. Putting the panel in the wall instead of on the wall made the project a lot harder, but I am happy with how it came out. If you can surface mount everything, it will be a LOT easier.

Here’s a pic of what my setup looks like (main panel is on the left, subpanel is on the right):

Oh, almost forgot. I am reasonably comfortable working with electricity, but when it came to this I got one of the electricians that does all of the maintenance for the company I work for swing by my house to take a look at everything and give me the warm and fuzzy that it wasn’t going to burn my house down before I energized the subpanel.

Good luck and be safe.

And lastly – I am not an electrician and might not have a clue what I’m talking about, so consult a qualified expert before taking any of my advice!

View SignWave's profile


472 posts in 3845 days

#9 posted 02-24-2012 04:25 AM

I replaced my garage/workshop subpanel a couple of months ago, from an 8/16 like you proposed to one that has 20 slots. They get used up faster than you think, and the cost difference is negligible. I also have 60A and it is fine, even when I use my welder. It wouldn’t hurt to pull larger wires just in case, given that the labor of pulling the wire is the big hassle, relative to the marginal cost of the larger wire. This will probably require a trip to the electrical supply rather than the big box home improvement center, though.

Definitely run 20A circuits for receptacles.

I do want to add that I find patching drywall to be much easier than fishing wires. I know not everyone has confidence in their drywall skills, so YMMV. But fishing wires can be very tedious and time consuming, and may require special tools like flexible drill bits and fish tape, plus crawling around dirty dusty places like crawl spaces and attics.

-- Barry,

View SNB72's profile


13 posts in 3154 days

#10 posted 02-24-2012 05:45 AM

As an electrician by trade your steps are correct, I also agree that you should go with a larger panel like a 12/24 or a 16/20 space, National Electric Code says that since your garrage is “ATTACHED” that you don’t need a ground rod just the wire in the cable. Most new homes , after the 80’s or so, have 20 amp wiring in the garage so thats a safer bet. New code says that all garage outlets should be GFI protected, but if it never gets inspected by the local authority then you can get away with not doing it. I know they, GFI’s, can sometime be a nusiance.

View Paul Ciura's profile

Paul Ciura

19 posts in 3802 days

#11 posted 02-24-2012 02:56 PM

Awesome input by all. Thank you very much. The garage is finished, so I am going to do a surface mount. Right now I am trying to figure out best way to get the feeder cable through to the sub panel.

View Grandpa's profile


3263 posts in 3485 days

#12 posted 02-24-2012 03:40 PM

SNB72, when I wired my shop I used GFI on all my 110v receptacles. I have not had any problems. I just think we need to be as safe as we can make it. It WILL work. I would go for it. My shop is not attached and I built it from scratch. The thing with using the 14 ga and 15A breakers is you run your tools too close to the minimum and that shortens the life of motors. That is like taping your mouth closed and trying to run a race. Just not going to last. Sure we get enough air through our nostrils when we idle.

View SignWave's profile


472 posts in 3845 days

#13 posted 02-24-2012 04:06 PM

I went with GFCI receptacles for the 120V circuits. I prefer the extra safety the provide. Beware of the value packs (contractor packs), though. I had some nuisance tripping with those, but the higher quality replacements have been fine. If you feed several receptacles from a single GFCI, then the cost is manageable. Be mindful of where you put the GFCI, as you don’t want to have to go far away or behind some obstacle to reset it, should the need arise.

-- Barry,

View Grandpa's profile


3263 posts in 3485 days

#14 posted 02-24-2012 06:41 PM

BTW the GFI receptacles can be bought in 20A also.

View Phil20166's profile


2 posts in 29 days

#15 posted 07-15-2020 03:08 PM

I realize this is an old post, but I have a question. Why do you use a 100Amp subpanel but then connect it to a 60-Amp breaker at the Main panel? Wont this make your total available current 60-Amps or less? Or are you planning to change out the 60-Amp breaker to something larger in the future, if needed?

Also, is the 60-amp breaker the only breaker from the main panel to the subpanel? i.e. there is no breaker in the subpanel that the feeder cable first attaches too? I am thinking no, but want to be sure.

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