Safe amperage for my garage shop

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Forum topic by jprado posted 01-10-2014 09:01 AM 893 views 0 times favorited 3 replies Add to Favorites Watch
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2 posts in 1629 days

01-10-2014 09:01 AM

I’m about to purchase a cabinet saw that runs on 220.
I’ll be adding a breaker to my sub panel in the garage, where I have my shop.
The saw I will purchase is rated at 3 hp and operates at 60 Hz. It can be used with single phase 208-240V
power. The motor draws 13 amps at 208-240V power.

I will use my home-shop dust collector when I run the saw and in the evening have the florescent lights on in the shop.

What amperage should I install for the breaker?


3 replies so far

View Fred Hargis's profile

Fred Hargis

4999 posts in 2516 days

#1 posted 01-10-2014 12:16 PM

20 amps will be plenty, with #12 wire. You’ll probably notice the plug (if it has one) will be a 15 amp plug. The 20 amp outlets (120V and 240V) are configured to accept both the 15 amp and the 20 amp plugs.

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View brtech's profile


1029 posts in 2946 days

#2 posted 01-10-2014 03:07 PM

20 A would be my answer too. The DC and lights are on separate breakers in the sub panel, right?
Then your only concern is what the rating on the sub panel breaker in the main panel is. You don’t normally start the DC and the saw at the same time unless you have some iVac like device. The start currents on the motors are much higher than the run current. Of course it would be best if the sum of the breakers in the sub was less then main panel breaker for the sub, but it’s often a bit more because you don’t run max power on all branch circuits at the same time. If you have at least 40 A on the main panel breaker, it’s gonna work fine. The lights are pretty negligible (even if you had 15×50 watt tubes, which would be a whole lot of light, that would be only 750 watts, a little more than 7 amps).

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5723 posts in 3255 days

#3 posted 01-10-2014 03:20 PM

For your question, I am assuming you are asking about the breaker just for the Table saw circuit. Not sure about where you are, but here in Texas, code says 12 ga wire and a 20 amp breaker… YMMV depending on your local building code.

If you are talking about the feeder breaker from your main, to a sub panel however, you leave out a lot of vital information. However…

I have a 100 amp sub panel in my garage / workshop that is fed by a 60 amp feeder breaker off the main panel. The major circuits on the sub panel are…

#1. A single 20 amp circuit that runs the dust collector. #2. A single 20 amp circuit that runs the table saw, or other tools. #3. A single 20 amp circuit that runs the HVAC. Right now with the weather warmer than it was earlier than this week, that means a simple box fan.

My lighting and ambient air filter share a single 20 amp circuit that is original to the house…

Everything is 110V. However both the DC / compressor circuit, and the main tool / table saw circuit have 220 available. My plan when I had the sub panel wired was to eventually go with a SawStop 3HP PCS, and a 3-5HP cyclone dust collector, although my 29 gallon 110V compressor I believe can be wired 220, I don’t think I am going to bother…

I have run lights, ambient filter, dust collector, table saw, and a 13.5K BTU air conditioner all at the same time with no issues what so ever.

I had worked with my electrician to come up with this plan, and it was signed off by the city inspector knowing full well and good what I was going to do with the power I was having pulled in.

Before the sub panel job, I had a prior arrangement that literally relied on turning the AC on, cool the shop down, turn it off, plug the table saw and DC into separate circuit outlets inside the house via extension cords, and working fast… This is MUCH better.

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