Wiring a workshop

[manfre]

I've reached the stage of my workshop where I need to wire it from scratch. I figured I'd think out loud to make sure I'm not missing something.

It's a 12'x20' building that is close to my house and I should only need about 45' of the expensive wire from the main to the lug. The plan is to run 4' from the main to the floor, 11' conduit to get past the concrete patio to dirt, 14' of buried line 2-3' down and then ~9' up to the load center. I'll need to contact the inspector about minimum depth for the buried cable and also about grounding requirements. I really wish there was a national standard for both of those.

How many amps are actually needed for a workshop? I've been planning towards a 60 amp connection from the main to the workshop, but was wondering if it should run a thicker line in case I would need more in the future. How many amps do you guys/gals run to your shops?

I plan on wheeling my DC around as I shift from tool to tool and was thinking about dropping a 230v in each corner to half the amps needed. These will probably be a dedicated series of outlets on a single breaker to cut costs. I'm also thinking about rewiring all possible machines to 230v. It'll also cut down on the amp requirements and help prevent the motors from bogging down (at least that is what the internet tells me). Would the workbench benefit from a 230v outlet, or would that just be an unnecessary expense and sit idle? I can't think of any tools that would go on the bench that would use 230v.

I've read elsewhere that putting outlets at 52" allows resting plywood against the wall without blocking the outlet. I don't plan on laying plywood everywhere , but I can see its value. Outlets that high would inhibit my ability to move tools away from the wall because I'd lose ~3' of cord length with the drop. Less if the tool is on a stand. To address this problem, I was thinking of chaining another outlet down at ~12" for the more common situation where there is no plywood. Should I run the high and low outlets on separate breakers?

I also intend on putting an outlet in the rafters for the air filtration. Should I put more outlets up there for lights, drop cables or some other reason? I do have 4'x12' lofts at each end of the shop. I wonder if I should put the little air compressor up there instead of under the work bench.

I'm not really sure which approach to take for wiring the lights. Is it worth the cost to run another one to two 12/2 or 14/2 lines from the main panel for the workshop lights? That will guarantee that I'm never in the dark if the subpanel circuit goes. It does mean that I could be in the dark with the machines running, but very unlikely. Is it better to connect lights to an outlet or direct wire?

There is an external 115v 15 amp outlet on the house that is only 15' from the side of the workshop, but it is on the same breaker as this computer. Should I wire any external outlets on the workshop? Or would it make more sense to just put a few outlets closer to the doors?

The post is a bit long, but any feedback would be greatly appreciated.

 

[JackLeg]

Start with a MINIMUM of a 100A service panel. I've got a 200A and don't regret it a bit. Be sure you have PLENTY of circuits. Space your receptacles no more than 5' apart and closer if you can afford it. Run 12 ga to all 110v outlets, 10 ga for your 220 circuits, and separate circuits for lighting. Don't tie lighting and outlets together.

Having the DC and the Air Cleaner on their own circuits is a good idea. Think about where you'll need light most. White ceilings and walls will help a LOT with light reflection.

You'll need GF receptacles as the first outlet in each run. Buy the good ones or you'll be aggravated by them!

Good luck. :wsmile:

 

[junquecol]

Instead of direct burial cable, I would run PVC with THHN wire in it. Run larger PVC than needed if possible, so if later you find that you need to up size, you already have a hole from main to sub into which pull new wires. I have a 60 amp sub in my shop, and I have never tripped the main, or feeder breaker in house panel. I have the ususal suspect tools, along with both a stick and wire welder.

 

[cptully]

Right now my shop is less than ideal, but slated to be a beauty...

I have a nominally 20 x 40 1.5 story garage (double roll up doors on the front 20' wall) built by the last owners of the house. It is currently unfinished inside (no insulation, heating/cooling, etc.) and powered by a 60 amp tap off of the house's 100 amp service. Additionally, I have a so called "trailer panel" as my garage circuit breaker.:BangHead: The only outlets in the main body of the building are the ceiling outlets for the plugged in lights... This means that I brown out the lights every time I fire up my table saw...:saw:

My electrical plan (as discussed with and amended by two electricians) is as follows:

1. Upgrade the house to 200 amp (the only way the current configuration works is that ALL of my major appliances are gas).
2. Take 100 amps out to the garage. Fortunately the guy who built the garage put in 2 1/2 in conduit for his 60 amp tap, which is over sized, so I can just finish the conduit (he neglected to connect it all the way to the house's panel) and pull a new heavier gauge (6 instead of 8 I believe) wire out to the garage.
3. Replace the "trailer panel" with a proper 100 amp panel.
4. Hard wire 8 foot fluorescent lamps in the ceiling.
5. Install outlets above bench height in an AB or ABC pattern every 4 feet through out the shop half of the garage and every 6-8 feet in the parking area (expansion room, once I back the cars out :gar-Bi). I will likely have one or two designated areas for plywood and just not put outlets there.
6. Like you I will switch every machine that I can to 220 V operation. I haven't decided yet if I can get away with hard wiring my big machines and keeping them in one place or if I will want them mobile - that will have a major impact on how many 220v outlets I put in and where I put them.
7. I haven't called the power company yet but there are industrial shops less than 1/2 mile from my house that I am 99% confident use 3 phase, so I am hoping that when I am ready to do this I can get true 3 phase 220 V, it will depend on cost and whether I can run that into the house and use the existing tap to the garage, or if I would have to get separate service to the garage...
8. The garage currently has a piece of Galvanized roof hinged to the back wall. Three sides open. I'm planning to make that into a Shed for garden tools, and to hose my compressor and DC outside the main shop area.

Grand plans, now I just have to scrape together the money.....:gar-Bi

PS. After reading other posts that came in while writing the above:

1. Skip the GFCI outlets and get GFCI breakers (or better yet modern AFCI breakers see: http://www.thecircuitdetective.com/afci_circuit_breakers.htm, specifically you want to look for AFCI breakers with the same GF protection as GFCI breakers; and talk to your local inspector to make sure this is OK).
2. Definitely have the lights on their own dedicated circuit, or maybe even two circuits.

 

[Bas]

Obviously, there is a limit on how many machines you can place in what's a modest-sized shop (12x20), so 60A sounds reasonable. However, if you ever want to add some HVAC and run a beefy dust collector/ compressor/ jointer, it wouldn't hurt to have a little extra capacity. 100A would certainly be plenty for whatever you could want. So look at the difference in cost and think how you'd feel if you had to re-dig the trench. When in doubt, go slightly larger. You'll be kicking yourself otherwise. But in a 240sq.ft. you're not likely to go over 60A, unless you decide to get a welder or something. I have a 100A pane/ feeder, but it's actually limited to 80A in the main panel. I don't think I'll ever need more.

If you had a 110V circuit that was 200ft. away from the panel, then the voltage drop would be a factor and you'd definitely see a degradation in motor performance. That won't matter in your situation, since you're going to have very short runs from your subpanel to your outlets. But going to 220V _will_ cut down on the amps, which is usually a good thing. I don't see the value of a 220V outlet on your workbench either.

I have a block of four receptacles every 4', using two separate circuits. That means you can plug in the router on the left and shop vac on the right without worrying it will trip. I also have several 220V outlets in strategic locations. Overall, there are 42 outlets in my 400sq.ft shop. Having outlets high (52") means you never have to bend down to unplug something, or crawl behind a tool. I like to unplug things, for example when changing the saw blade, cleaning the jointer knives, swapping out the drum sander paper etc. Much easier this way. If you're worried about the length of the cord on the tool, replace the cord.

An outlet on the ceiling is nice. I have one for the air filtration unit. They're really handy when you have large open spaces and you're working more than 4-6 feet from the wall. In a small shop, that's unlikely to happen, so you may not find it all that useful. I would not put a compressor there, since you do need to service it occasionally.

I would definitely separate the light circuit from your outlets, but running an extra wire from the main panel just to be totally separate may be overkill. I actually have that configuration in my shop, but I'm in a basement that was already set up this way. You could always get a battery-powered emergency light just in case you're working at night and you trip the breaker to your subpanel. There's no real advantage or disadvantage on whether you hardwire the lights or use outlets. If you hardwire, you obviously need to add a switch, with is preferable anyway. No reason you can't switch the outlets of course. In my shop, I have both - hardwired lights on a switch, and a couple of cheap leftover auxiliary shop lights that I can turn on via a pull switch.

A few external outlets is an EXCELLENT idea. Outside is great for breaking down plywood, rough cutting lumber, dusty sanding jobs etc. Outside outlets mean shorter extension cords, being able to close the door etc.

 

[Phil S]

Just a few additional thoughts. 60 amps should be adequate for a 12 x 20 shop. I would feed it with three #4 copper conductors for the two hots and neutral and a # 6 for ground run in a 2" pvc conduit. You only have to bury the conduit 18", if you use a direct burial cable then you will need to go to 24" deep. I would install a 60 amp breaker in your house panel. You will not need a main breaker in the shop but many people add them as a way to quickly disconnect all power. The panel in the shop is a sub-panel and you will need to make sure the neutral strip is not bonded to the enclosure - the ground bar should remain bonded but the neutral must be floating. As for internal wiring, outlet location will depend on equipment location but remember you will be reorganizing at some point. All circuits can be wired with #12 as your runs will be short, that includes the 220v circuits.
Good luck

 

[JimmyC]

I agree with the others about a 60amp panel be adequate ( i put one in a previous shop), and working for almost anything other than indusrial size equipment. That being said, it's only a little more to run the 100 amp panel so why not do it. BTW, I have a 200amp service (put in by previous owner) in a 32'x40' shop and I love my options.

Good Luck,

 

[manfre]

Thanks for the feedback so far. 60 amp will be plenty for me. I just found out that my dad's huge garage/shop (~36'x40') only has a 60amp feed and he welds without flipping the breaker.

 

[eyekode]

Phil knows tons more than me but if I were doing it again I would run 10 AWG instead of 12 for the 220v runs. That leaves flexibility to go to a 30A breaker without running new wires if your needs change or if you find some awesome deal on a 5HP cyclone instead of a 3HP .
Salem

 

[Phil S]

Salem, You are correct, I had not thought about 5hp equipment that is going to draw 18+ amps. All of my 220 equipment is 3hp or less drawing less than 15 amps. Thanks

Phil knows tons more than me but if I were doing it again I would run 10 AWG instead of 12 for the 220v runs. That leaves flexibility to go to a 30A breaker without running new wires if your needs change or if you find some awesome deal on a 5HP cyclone instead of a 3HP .
Salem

 

[MarkE]

When you are looking at breaker panels be sure to consider how many circuits the panel will support. 60 amps may be enough power, but the 60 amp panels usually have room for fewer breakers. Count up the number of circuits you intend to install and make sure the panel you select has enough spaces.

You may be better off getting a 100 or 125 amp panel to allow for a larger number of circuits, even if you don't need the extra power. The price difference won't add up to much.

 

[cpowell]

When you are looking at breaker panels be sure to consider how many circuits the panel will support. 60 amps may be enough power, but the 60 amp panels usually have room for fewer breakers. Count up the number of circuits you intend to install and make sure the panel you select has enough spaces.

You may be better off getting a 100 or 125 amp panel to allow for a larger number of circuits, even if you don't need the extra power. The price difference won't add up to much.

+1

Install a larger panel (100 or 125A) to give you plenty of breaker capacity.

60A feed from the house panel is plenty.

Chuck

 

[manfre]

I have been noticing the lack of space in subpanels. Most of the ones I've seen are 12/24, which would be very tight. I want four separate 230v runs and would need to fill the remaining 4 spots with piggy back breakers.

 

[Bill Clemmons]

Others have already provided excellent technical advice, so I won't try to add anything there. But I do have some other advice. Building inspectors can sometimes remind us of a hemorrhoid, but they can also be a valuable resource. When I built my shop, if I didn't know the right way to do something, I went to them for advice. They were actually very helpful from both a practical sense, as well as knowing exactly what the code specified. Additionally, asking their advice get's them on board w/ your project, and they are less likely to give you grief when they come to inspect.

Bill

 

[jlayell]

My shop is aproximately 25 years old, and I have a 30amp panel that has given no prolems. I do not have 220v. I am planing on redoing the wiring next summer, from everyones advice I think I am going with a 100amp service. All of my tools are 110v., when redoing will there be any advantages of rewireing any of the motors to 220v. and installing the circuits while I have everything opened up?

 

[Bas]

when redoing will there be any advantages of rewireing any of the motors to 220v. and installing the circuits while I have everything opened up?

The short answer is no. By going with 220V you're halving the amperage, but that doesn't mean anything in your case. You'll want to wire everything with 12 gauge wire, which can carry whatever load your tools generate today. If you had a tool that used 30A, that would require you go with 10 gauge wire, which is slightly more expensive. Assuming you don't have any voltage drop issues today due to an excessively long connections between the outlet and subpanel, you're not going to get any additional power by going to 220V.

But tools certainly "feel" more powerful when wired for 220

 

[DaveD]

When sizing the main panel and feeder to it think about future needs 5 or 10 years out. It becomes more important if you have multiple hobbies like woodworking, cars, welding/metal working, machining, etc. As you sink money in to tools it typically becomes buying bigger, more power hogging tools.

If you get a bigger air compressor and a decent sized dust collector you almost have to consider that they both will run a the same time as you are also powering up your biggest stationary power tool.

If you get in to any serious welding you can figure a dedicated 40A circuit as a minimum. Even bigger if you have old/big transformer mig/tig welders. I have a plasma cutter (a small one at that) that sucks 30A at the same time as the air compressor to support it is running. If you plan to ever have any 3 phase power tools that usually entails a rotary phase converter. My 10HP converter runs on a 40A breaker, idles at a few amps, but pulls 80A instantaneously at startup. You may not think you will ever have a need for 3 phase power but you will find you can get some fantastic deals on bigger 3 phase equipment. Sometimes for scrap price.

So after all that I'd opt for a minimum of a 100A sub panel with feeders that will support the full 100A. If I was building a 1000-2000+ sq ft shop I'd even go 200A.

If you look in to the cost of having 3 phase power run to a bigger shop be sure you have had a recent physical that included a heart stress test. Rich relatives would help too.:wsmile::gar-La;

 

[manfre]

My current shop on has about ~200 sq. ft. of usable floor space for tools, unless I want to climb over/under tools. The workshop is also located is a spot that makes moving tools a challenge and the steep driveway doesn't help. All of this guarantees that I will not own any of the larger, non-hobbyist equipment. At least not in this shop. If this hobby grows in to the commercial realm requiring commercial sized tools, then I will probably look at renting industrial space. There are many hurdles to operating an industrial business in a home.

 

[MrAudio815]

Manfre,


One thing that was not mentioned and is very important knowledge in my book is you can get 250 feet of 12/ wire for $63+/- and 50 feet for $50. So for an extra $13 you get 200 feet more.

I bought this 12/2 wire and have everything in the shop wired with it. Along with an already packaged 50 foot 6/3 wire(black cable) which was also cheaper than having it cut. I have a 100 amp panel with a 50 amp circuit breaker on the main, I used all 50 feet of wire to the sub panel.

I have 2, 220V machines one 2hp, one 3hp and will be adding one more.
I have 15 total lights above me all but two sets are hard wired.
I have 2 DC's one 1.5, one 2hp.
I have run both DC's, two 110 jointers all 15 lights and a radio with no flickering (both jointers being used).

I added 6 110V 20amp outlets to my shop 3 on one wall. 2 on the other with one more outlet from the main panel for the garage door opener (with another outlet on the ceiling for the garage door, leaving me one plug to use) And the last one on another wall with a strip outlet.

When I walk in my shop I turn on the breakers I am going to use for the day. I usually don't use my Bandsaw and tablesaw at the same time (both 220) if I need another tool, I just flip the breaker and I am in business. I have a 19.5' X 20' garage.

Hope this helps you save some MONEY~!

And can't wait to see your pictures~! WE LOVE 'EM :gar-Bi

 

[ehpoole]

As someone who has done quite a lot of electrical over the years (my grandfather was the electrician and I spent many years helping him growing up) these would be my thoughts.

1) A 60A panel is more than enough IF you don't intend to install a large 4-5HP air compressor OR electric strip heating or air conditioning. If you intend to do either of these (or even think it may come up in the future), then I would urge you to make it an 80-100A subpanel. HOWEVER: this advice is meant for a more modern residence with a 200A main service. With your limited 100A residential service, anything larger than 60A may not be practical. This means that you will have to give careful thought if you should choose to pursue equipment with large electrical loads (like a large air compressor) or if you wish to heat or A/C the shop electrically.

2) Power tools, especially larger tools, draw tremendous startup currents when their motors are first spinning up to speed. If conductors are sized according to typical NEC codes then you can expect to experience dimming of lights, momentary brownouts, etc. whenever starting these large motor tools. It costs a little more up front, but my advice is to oversize ALL your conductors (EVEN THE SERVICE ENTRANCE RUN) by atleast one standard guage size (e.g. use 10ga instead of 12ga for your 20A receptacles). For your 240V receptacles I would even consider upsizing to 8ga so as to preserve the option for converting a 20A 240V receptacle to a 30A or even a 40A in the future if the need arises without any expensive retrofitting (just swap out the receptacle and circuit breaker and your 20A 240V outlet becomes a 40A 240V outlet with no rewiring or added cable runs). For your 100A subpanel use at least 2ga for a short run, 0ga for longer runs. For a 60A subpanel I would suggest 4ga minimum or 2ga for longer runs.

3) This upsizing of conductors goes a long way towards preventing equipment power robbing voltage sags and ensures that your equipment is always operating at 100% efficiency. This also helps to extend the life of the motor.

4) The general lighting circuit should ALWAYS (IMHO) be a seperate and dedicated circuit. NOTHING but lights should be connected to this circuit. WHY? Because properly installed lights seldom ever trip a circuit breaker... however, plug-in equipment is notorious for tripping breakers when you try to operate that 15A thickness planer on the same circuit as your 12A shop vac. It is very dangerous in a shop environment to lose lighting after dark -- bad things can happen (I'll leave this to your imagination). If you have a very large lighting circuit, then you can split it across two seperate circuits, but for a smaller circuit a single breaker is fine.

5) If you regularly work out in your shop after dark then tripped circuit breakers leaving you stranded in the dark should be the least of your worries -- instead you should give consideration to what happens when your tools are turned on and the power blinks out... maybe for 1/2 second, maybe for 10 hours ... at what point do you decide to risk fumbling in the dark to fund the OFF switch? THINK EMERGENCY LIGHTING. For a typical 2-car garage size shop a minimum of 3-4 emergency lights distributed around the shop perimiter will allow you to guarantee adequate lighting (for 1-1/2hrs+) to safely shut down equipment and move about your shop in the dark SAFELY. Just as importantly, these emergency lights draw power from the same circuit as your general lighting, so if the breaker should trip you still have emergency light to finish your operation. Emergency lights are cheap insurance at around $30ea plus a $10-15 battery that you will need to replace every 3-4 years.

6) GFCI Breakers are nice, but you will pay a premium for them. There is nothing wrong with the traditional GFCI receptacle in a garage setting where it is protected from the elements. You will be required to install GFCI receptacles (or breakers) for all of your 120V 15A or 20A receptacles. You will not need one for your dedicated lighting circuit (nor should you want one, fluourescent ballasts, esp cheap ballasts, are notorious for falsely tripping GFCIs.

With resepect to AFCIs, they are required in all sleeping quarters, and nowadays, for most of the finished living space. However, I would, personally, be hesitant to install them in a garage workshop environment. Maybe in a few more years that would be fine, but I wouldn't do so at the present (not to mention you'll pay out the wazoo for them!).

7) Unless this is to be a finished (as in drywalled or fully panelled) shop, then I would encourage you to use surface mounted EMT (metallic) conduit. It offers flexibility if your needs change in the future. It armors the wiring to protect it from damage and environmental degradation. Additinonally, it provides a redudant ground connection for all your switches and receptacles -- a nice touch for added safety. It is more work to install and costs a bit extra, but it looks much better than bare romex cables stapled here and there and it offers extreme flexibilty with respect to unanticipated future needs.

I hope this rather long-winded response proves helpful. If not, well, then it's your workshop :wink_smil. Most of all GOOD LUCK AND ENJOY YOUR NEW SHOP!!! :icon_thum

... my 2 cents