Shop Wiring Advice

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Old 04-18-17, 08:07 PM
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Shop Wiring Advice

Good evening all,

I am in the process of turning my garage into a shop. I will have a table saw that comes 120 but can be configured to 240. I'll also have a bunch of standard woodworking tools (band saw, drill press, sanders, etc). I also want to get a welder at some point.

The house has a newer (year and a half ago I think) 100 amp panel with quite a few open spots (6 I think). My house is 1200 sf and I live alone so usually not a lot of equipment running at any given time. I've never tripped a breaker or had any flickering lights.



I want to add some 120 20 amp outlets on the ceiling and two of the walls. My plan is 6 outlets on one wall, 4 on the ceiling, and 8 on the opposite wall.

To summarize, 18 total 120 outlets and 2 240 outlets.

My questions are:

1) Given what I want to do, is my panel okay?

2) Should I do the 120 outlets on multiple circuits?

3) For the 240 outlets, how many amps should they be? I've heard 50 is common for a welder.

4) Is it common for electricians to come into a home, see what the owner wants to do, and say "you need to do a, b, and c and x, y, and z"?

Thank you for your replies.
 
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Old 04-18-17, 08:25 PM
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Attached or detached garage? Electric, oil, or gas heat? Electric or gas water heater? Clothes dryer electric or gas.
 
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Old 04-18-17, 08:29 PM
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The garage is attached.

Gas heat.

Gas water heater.

Electric dryer.

Thanks
 
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Old 04-18-17, 08:49 PM
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Then your hundred amp panel should be okay.
 
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Old 04-19-17, 10:14 AM
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2) Should I do the 120 outlets on multiple circuits?
I wouldn't install more than two 20A 120v circuits in your workshop. It's doubtful that you'd be using multiple high-amperage tools at the same time. Even one would probably be sufficient. Note that they most likely need to be GFI protected.

3) For the 240 outlets, how many amps should they be? I've heard 50 is common for a welder.
It depends on the requirements of the device you're connecting. You'll want to size the breaker/wiring/receptacle to the specific table saw and/or welder. I'd personally hate to spend the money to install an oversized 50A circuit for a 30A welder. That money is likely spent elsewhere!

4) Is it common for electricians to come into a home, see what the owner wants to do, and say "you need to do a, b, and c and x, y, and z"?
Yes... but an electrician may have the same issue that we have here. There are lots of options, depending on what you want to do. It all should be pretty straight forward though if you know where you want your tools and what tools they will be.


One last question for you. Where is the panel in relation to your new workshop? If it's close, you can start small and upgrade as time goes on. If it's a longer distance, you may want to consider a subpanel for future upgrades.
 
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Old 04-19-17, 07:44 PM
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Thanks for the info. The panel is in the basement but only about 6 feet from being able to reach the garage. You can see the location in the image below. It's directly below the laundry room.

 
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Old 04-19-17, 09:23 PM
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Don't bother putting the table saw on 240. You won't gain anything, it'll just cost you a breaker space (and a more expensive breaker). If it were 3 phase that's a different animal, because those motors run more efficiently, but 120 vs 240, there's no difference.
 
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Old 04-20-17, 06:19 AM
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All 120V outlets in the garage need to be GFCI protected, even the ones on the ceiling. You are not to use a GFCI outlet as one of the ceiling outlets to protect the others because being on the ceiling is not considered as readily accessible.
 
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Old 04-20-17, 09:23 PM
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If you are serious about it being a shop...

My 2 cents. Install a subpanel. Your feed to the subpanel is short so you won't be spending a lot on the big cable.

This will give you flexibility for more circuits if needed in the future. It will also make it easy to convert a circuit from 120 to 240, for example if you get a saw that really should run on 240.

Like appliances, any fixed base shop machine should have it's own circuit.

Will you be wanting to run a dust collector? If so, that should be on it's own circuit.

Then, you'll want two circuits for portable hand tools and benchtop tools.

Yes you could squeeze your minimal needs into your currently available breaker spaces, but, you'll limit your future flexibility. Perhaps you'll later want more circuits in the rest of the house.

There are several advantages to running 120/240V machines on 240V. Resistance power losses for one, and drawing so much current that you trip a breaker for another.
 
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Old 04-21-17, 03:36 AM
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Taz, although watts are watts, and nothing electrically is gained by converting from 120 to 240, there is an immediate torque advantage and spoolup increase with 240. I have all my fixed equipment running off 240 and don't have the lagging that I did with 120 volts.
 
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Old 04-21-17, 01:02 PM
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Agreed, but that isn't going to give you any advantage on a table saw either. That is something that a compressor for example could take advantage of (it would certainly help with the startup surge current as well), but shaving a half-second off the table saw's spinup time doesn't scream "worth it" to me.
 
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Old 04-22-17, 05:41 AM
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When I changed my table saw (Delta contractor) from 120v to 240v I saw a great improvement in performance. Start up was faster and it wouldn't bog down (or stop) cutting tough or thick wood such as 2x material.

I also would recommend a small sub panel in the shop space. After you get it set up it will only get bigger.
 
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Old 04-22-17, 01:00 PM
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Thanks for the replies, everyone. Really great info there.

I have considered the sub panel route. I assume that even with a subpanel the 100 amp on the main panel needs to be taken into consideration, is that correct? Or does a subpanel draw the power before it gets to the main panel? How big would I make the subpanel? Could I do another 100 amp panel? My electrical knowledge is pretty limited and I dont really understand how the subpanel works.

Thanks
 
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Old 04-22-17, 02:52 PM
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A sub panel does not draw any power, only the loads (anything that is using electricity) does. You can install a 100 amp sub panel that is fed with 100 amp feeder/breaker with no issues.

That said, I doubt you need a 100 amp feeder to the sub panel. I would recommend a 40 or 60 amp feeder to the sub panel. A 40 amp feeder will needs 8/3 cable while a 60 amp will need 6/3 cable (copper). That can change if conduit is the wiring method used.

The sub panel can be any size you choose. Since it is an attached garage it is not required to have a main breaker and can be a Main Lug Only. (MLO) Some times you can get a better deal on a pre-packaged panel with breakers, sometimes called a value pack.

Example with main Breaker: Square D Homeline 100 Amp 20-Space 40-Circuit Indoor Main Plug-On Neutral Breaker Load Center with Cover - Value Pack-HOM2040M100PCVP - The Home Depot

Example MLO: Square D Homeline 125 Amp 12-Space 24-Circuit Indoor Main Plug-On Neutral Lug Load Center with Cover - Value Pack-HOM1224L125PGCVP - The Home Depot
 
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Old 04-22-17, 07:58 PM
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Roger. Thanks for the info!
 
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