Shop electrical wiring

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Forum topic by Bobmedic posted 03-05-2013 11:34 AM 2280 views 0 times favorited 20 replies Add to Favorites Watch
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381 posts in 3007 days

03-05-2013 11:34 AM

I am in the process of wiring my shop/garage and I am looking for some ideas that I may have overlooked. To start out, I will explain the situation I started with. My shop is in a 17.5’ x 20’ attached garage. The existing wiring had 4 outlets and a single incandescent light bulb all on a 15 amp circuit. You can already imagine the problems I had here. I couldn’t turn on my dust collector and any of my tools at the same time or it would blow the breaker. Also lighting was a huge issue. I installed a sub panel in the garage fed from the main panel in the basement. I have the sub panel wired for 60 amps. The walls were all finished so I did all the runs in metal emt conduit. I wired 3 circuits, 2 with 4 outlets each and a third that drops down from the ceiling to power my table saw, jointer and router that will be mounted in an extension wing of my table saw. I added 5- 4 foot fluorescent lights to the ceiling that are on the original garage wiring. One question I have is several of my tools can be converted to run on 220 volts. Will there be any advantage to doing this other than a decreased amp draw? Or if there are any other concerns or ideas I would appreciate the feedback.

20 replies so far

View sprucegum's profile


324 posts in 2202 days

#1 posted 03-05-2013 11:45 AM

I have switched some motors over to 220 volts over the years. My experience is that they just plain run better on 220. They seem to make less noise, come up to speed quicker, and just plain run stronger.

-- A tube of calk and a gallon of paint will make a carpenter what he ain't

View Fred Hargis's profile

Fred Hargis

5177 posts in 2698 days

#2 posted 03-05-2013 12:01 PM

While I have all my tools switched to 240V that can be, there is really no electrical usage advantage to doing so. They do seem to run better, but the total amperage is split between 2 hots….so you draw 1/2 the amps on each leg, total stays the same. Even so, there are some other advantages. The lower amps per leg will lose less in the power cords due to any very small heat loss, and if you see lights dim while on 120V, the 240V conversion may help with that. I would recommend it if you have the space in your panel.

-- Our village hasn't lost it's idiot, he was elected to congress.

View Charlie's profile


1100 posts in 2491 days

#3 posted 03-05-2013 01:11 PM

My shop is roughly the same size and I also have a 60amp subpanel. I have 1 20amp circuit dedicated to the dust collector as that pretty much runs when anything else is running. 1 lighting circuit for the flourescent overheads. And then 3 more circuits to wall plugs Those 3 circuits kind of hopscotch around the shop so they alternate as you go around the shop.

I haven’t switched anything over to 220v yet. I might at some point but I have so many other things to do right now I don’t see it as an emergency.

View SantaClaus's profile


8 posts in 2659 days

#4 posted 03-05-2013 01:25 PM

220 runs cooler, which means cheaper (less ele is wasted being converted to heat) and your motors will therefore last longer. You can also run lighter gauge wire since the amps are halved. Since you are doing new wiring anyhow, I’d say go 220.

-- I'm a professional Santa Claus and a hobbyist woodworker.

View HorizontalMike's profile


7770 posts in 3119 days

#5 posted 03-05-2013 01:43 PM

Sounds like a plan. The only other thing I might add, would be to double or triple the number of 4-gang outlets. You will not believe just how much more convenient you will find the added outlets. The cost in doing so is minimal at this point. Additional outlets does NOT mean you have to put in any larger breakers, since you will still only be using a limited number of tools at any one time.

FWIW, in my 24’x30’ shop/garage I had started with seven 4-gang 120v boxes and ended up adding two more, all because of the location of equipment within the space. I also added four 240v outlets for my saws and jointer, but I still needed those 120v outlets in selected/specific places.

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

View Bill White's profile

Bill White

5132 posts in 4165 days

#6 posted 03-05-2013 03:45 PM

I have 120 and 240 v outlets, plenty of breakers, and I put all the outlets 4’ above the floor.
8 4’ t-8 2 bulb fixtures on the ceiling, and plenty of “task” lighting with incandescents.
1 trick I stumbled upon…...use 40 watt OVEN bulbs in the task lights (or some LEDs). They sure do last longer.


View toolie's profile


2148 posts in 2833 days

#7 posted 03-05-2013 04:48 PM

Will there be any advantage to doing this other than a decreased amp draw?

this is the primary reason for doing it, assuming none of the motors in question develop higher HP ratings in 220v configuration (and very few of the motors on the tools hobbyists use have such higher hp 220v motors) . what you will find is that you get more “mileage” out of your available sub panel amperage with 220v motors. my subpanel is 30A. my now sold unisaw, with it’s dual voltage 3 hp baldor motor, needed 32A in 110v configuartion, so in theory, it wouldn’t operate under full load in my shop. as it was wired for 220v, it’s draw against my 30A was reduced to 16A. not 16A per leg, as some think, but 16A total draw on my 30A service. so i was able to run the unisaw, a 1.5 hp dust collector (also wired for 220v and drawing 6A), a shop vac and lights, all on a 30A service without incident. had i known the benefits of 220v operation earlier in my WW experience, i’d have focused a little more on dual voltage tools, as i do now. hope this helps.

-- there's a solution to every just have to be willing to find it.

View Bobmedic's profile


381 posts in 3007 days

#8 posted 03-05-2013 04:48 PM

These are all great suggestions, just what I was looking for. Charlie, I did a similar thing with the hopscotch thing. Except, I just ran another conductor to each box and split the hot side on the duplex. I used a shared neutral but each outlet’s top and bottom are on different circuits. That way no too tools in any one location will be drawing off of the same circuit. Bill, the oven bulbs are a great idea if I add any incandescent task lighting. I mounted my boxes 50 inches off the floor so I could lean sheet good against the wall and not obstruct the plugs. In the future I will probably convert the tools I can to 220 v. The nice thing about wiring in conduit is it is easy to change things as I need to.

View Bobmedic's profile


381 posts in 3007 days

#9 posted 03-05-2013 04:54 PM

Toolie, I was thinking the same thing about the amperage. According to Ohm’s law if you double the voltage on a circuit you half the amperage. I will most likely switch the voltages on the tools that can be switched, especially on my 2hp dust collector.

View SnowyRiver's profile


51457 posts in 3685 days

#10 posted 03-05-2013 05:09 PM

My shop is about 450 sq ft and I also have a 60 amp subpanel. I have 24 115 v outlets (12 on each side – they are 4 outlet box type) and I also have two 220V outlets (one on each side.) The only machine that is on 220 right now is the table saw. Everything else is on 120. It all seems to run fine including the dust collector and air filter while the other machines are running. I also have 10 2 bulb (48”) fluorescents in the shop for the main light. It is plenty bright with no lights flikering when I turn on stuff. I do have some incandescent task lights on the bandsaw, drill press, and scroll saw. I figured if I started to have problems with current or lights flikering, I could switch some of the machines to 220, but so far (past 10 years) no problems.

-- Wayne - Plymouth MN

View DocSavage45's profile


8725 posts in 3047 days

#11 posted 03-05-2013 06:24 PM

If a motor can be run on 220, it will be more efficient. 3 phase is the most efficient and least stressful on the motor, but as I learned from the electrician that ran the 100 amp ciruit is not available to my home, and would cost a seperate meter.

When I was a lot younger I would install electrical boxes, and ran lines and panels where they connect to the house. The ampere load should also be balaced in the draw from your panel. Harbor frieght sells an inexpensive ampmeter?

Oh yeah, did you install ground fault Interupt circuits for the 110?

Your shop sounds like mine, Just finished a cosmetic makeover for my new”old” 1023sl grizzly. I’m installing a 220 single phase line. Been awhile since I did conduit. The right bend? LOL. Also been told by my inspector that since it is an outbuilding and a shop, I can run romex. And I have “just enough”.

So , quick and tacky, or slow and clean? LOL!

-- Cau Haus Designs, Thomas J. Tieffenbacher

View MrRon's profile


5203 posts in 3448 days

#12 posted 03-05-2013 07:06 PM

Use dedicated circuits for lighting (15A); receptacles (20A); DC (20A). That’s about it; the idea is you don’t run more than one tool at a time, so 20A is fine. The DC can be running along with a tool, so a separate circuit is needed. Use a minimum of #10 wire. It would be good to have 220V if any of your tools can run on that voltage.

View Bobmedic's profile


381 posts in 3007 days

#13 posted 03-05-2013 07:08 PM

DocSavage, I did not install ground faults. I am aware that this is code and if I ever sell my house it will be a 10 minute job to add them at the beginning of the circuits. Aside from that everything is up to code.The electrician that wired my house (before I bought it) connected the plugs from 2 of the bedrooms to the single plug in the guest bathroom that was a GFCI. The GFCI went bad and knocked out power to the 2 bedrooms. The GFCI plug in that bathroom never gets used so it took a while to track down the problem. That is why I chose to omit them, that and I don’t see a need for them for this application. I have no idea why he connected the bedrooms to that circuit except maybe to save money. I was an electrician apprentice for 2 years and wired many houses and we never did that. The electrician that I worked for wired each room separately and the lighting was also on it’s own circuit. It costs a little more to do it this way but there are many benefits to this way of wiring. Bending the conduit is something that I am very familiar with. As an apprentice I bent miles of it. Stub take ups and offsets are permanently ingrained in my mind LOL. Great suggestions though. I appreciate the reminders. These are the little things that I am looking for just in case I missed something.

View Bobmedic's profile


381 posts in 3007 days

#14 posted 03-05-2013 07:21 PM

MrRon, I kept the lighting on the original circuit ran from the house. Nothing else will be on that circuit. None of the tools I have pull more than 15 amps so the # 12 wire that I ran on 20 amp circuits is more than enough to carry that load. # 10 wire is for circuits greater than 20 amps. It’s true that you can run 20 amp circuits on # 10 wire but I think that might be overkill and also #10 wire is difficult to work with attaching it to receptacles. I forgot to mention in my original post that the dust collector is on it’s own dedicated circuit. This is all great information thank you for your reply.

View Charlie's profile


1100 posts in 2491 days

#15 posted 03-05-2013 07:40 PM

ground faults not code here. Not in a detached utility building regardless of use (as long as it’s not a guest house or something you’ll live in). Any receptacle on the OUTSIDE of that building still needs to be GFCI protected.

#12 wire and 20amp breakers is fine for your 110v cicuits. Just remember to use 20amp rated receptacles (not 15amp). You can probably use 15amp receptacles without burning anything down, but if it’s a 20amp circuit, make it a 20amp circuit from one end to the other, right?

The hopscotch layout has served me well in the winter here. My shop isn’t permanently heated. With the DC on its own circuit I have 3 others for tools. I run a propane heater to bring the temp up fast and then switch over to electric to maintain temp. The electric is quieter and I can’t “turn down” the propane heater enough to just let it run. Even on low it would cook me out of there eventually.

SO… I can run the DC, table saw, and an electric heater pretty easily. In summer I can run a couple of fans (not air conditioned either).

Codes can vary. Check them. They really are there to keep you safe.

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