I’m planing on converting my attached single car garage to a workshop and I need some advice. I am planing on putting in a 40 amp sub-panel then installing:
One 120 VAC 20 amp circuit for a planer and mitre saw and 4 spare receptacles.
Two 220 VAC 15 amp circuits, one for a bandsaw, table saw and jointer plus 3 spare receptacles, and one circuit dedicated to a dust collection system.
Three 120 VAC 15 amp circuits, one for lighting (10 4 ft. fluorescent fixtures), and one circuit for 8 receptacles, and the third circuit dedicated to a small compressor.
Is this overkill? Am I trying to put too many receptacles on each circuit?
Thanks in advance for your advice.
Replies
For that many breakers you should have at least 100 amp service.
All of the 120 volt circuits should be 20 amp, the cost savings from using smaller 14 ga wire instead of 12 ga is minor.
I'd put each major tool on its own circuit breaker if practical, you might want to run the tablesaw and the jointer at the same time for instance, and both on a single breaker would possibly be too much of a load.
There is nothing wrong with a lot of receptacles on a circuit, it just means you will have an outlet convenient to wherever you are working. You might want to put the outlets on two circuits with separate breakers, a shop vac and a router running at the same time would be a large load for a single breaker.
John W.
Thanks for the advice John. I was thinking that 20 amps would make more sense than 15 amps, and would cover a wider range of tools.In order to have a 100 amp subpanel, would my main panel not have to be upgraded from 100 amps to 200 amps?
I just wired my shop last year, and critical to my success was getting my plans checked by the city inspector prior to doing any of the work, and getting an inspection once the work was done.
I mention this because you may or may not, depending on your local jurisdiction, be able to get away with having multiple 220v receptacles on a single circuit. As many have correctly pointed out, there's nothing inherently unsafe about this practice, but in my city at least, that would not pass inspection.
I personally also wonder if you're going to be underpowered with 40A. If your lights are on, the compressor cycles, and your DC and saw are all going, you may well exceed the panel's capacity. And what if you have to add heat in the winter? The heater I use in my (attached) garage draws over 20A by itself.
My own setup, all tying into the main house panel, includes two general-purpose 110 circuits with 1 GFCI and 4 normal outlets each, five 220v/30A circuits for big tools and the heater, two separate lighting circuits, and another utility 110 circuit that was already there.
Thanks for the comments.Yes, I do plan on having my plans checked by an inspector prior to doing any work. Right now I am trying to gather ideas to develop the plans.I do believe that I will need to up the amps on the panel, and take your scenario into consideration.In my area, (Ontario, Canada), the only information I have been able to find so far on the number of receptacles on a circuit is a max of 12 on a 120 V circuit. I haven't been able to find information on 220 V circuits. From what I've read, this seems to be up to the inspector.I forgot to take heating into consideration. Thanks for that.
I was able to talk with my inspector prior to having complete plans. This saved me a lot of wasted time, actually, as he functioned as an electrical consultant free. I had two fifteen-minute conversations with him, and he did an onsite pre-inspection as well; the final inspection was under fifteen minutes because everything was clean and professional and exactly to plan.
From his point of view, spending a bit of time helping me get my plans right was a good investment because 1) his inspection would go easy and not require a revisit, and 2) good practices means I probably won't burn my house down.
Glad my experience helped a little. I did what JohnWW suggested as well, laid in two separate 110v/20a circuits; each workstation has a duplex box, the left pair of outlets is circuit A and the right pair of outlets is circuit B. That means, anywhere in the shop, I can plug in a shop vac and a tool that draws a lot of 110, and be in no danger of overloading a circuit. (I was worried that this would be illegal, because throwing the breaker on circuit A would leave the circuit B juice still active in every j-box and outlet box, but he said it was fine.)
It's great once you have it done. My next big project (after I get my jointer and bandsaw set up) will be getting good lighting installed. Right now it sucks...
Good luck and have fun!My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
Thanks for the input John. I will try again tomorrow to get more information from the inspection office. My call today got me guided to the FAQs on their web site which would tell me everything I needed to know. The only thing that was clear was the fees that would be charged. The rest of the FAQs were next to useless. Yours seems to be very organized.
The city website only had fees. But, there's a phone number that allows me to call the inspector (I got this number once I paid for my building permit). I did some initial reading (not on the city site, on electricians' sites and in books), and made my initial plan. Then I called the inspector and explained my plan, and he disabused me of some of my misconceptions.
We scheduled the pre-work inspection, and he came out and pointed out a few more things I needed to do (like adding two grounding rods). During that visit, we had another conversation about my plan.
Finally, I had one more short phone call with him once I had my work under way.
Then he came out for the inspection. He spent well under 15 minutes, said it was a good, safe installation, and left.
The key for me was being prepared so he didn't feel like he was giving a course to someone not willing to work on his own. Also, a lot of inspectors take a lot of crap from homeowners who resent the inspectors' function, so when a homeowner is cooperative and recognizes the value the inspector provides, I think they're pretty willing to help. Besides, the whole point of the building codes is to prevent people from making mistakes that cause fires and cost lives, and they do want you to do it right.
Again, good luck!My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
I guess that having the permit is the key. I understood that I required a wiring plan prior to applying for a permit. I will see what I can find out today.
On the permit, I had to specify what I was doing. But it was pretty darn general, like "five 220v outlets, two 20A 110v circuits with several sockets each, and possible main panel replacement." So I had a LOT of wiggle room to do the right thing as I went from general ideas to pulling wire.My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
Hi John,I'll keep that in mind. I think I'm starting to get a handle on what I need to do. I have done a fair bit of research, and I'm getting a copy of the code just to be on the safe side. I've looked at quite a few sites, and I'm about to start drawing up my plan.Thanks for all the input.
If you go to HDepot they sell an electrical booklet for about ten bucks that has alot of good information related to the canadain building code.
I just bought the book at Home Depot a couple of days ago, but to be honest I didn't find it to be a lot of help so far, when it comes to wiring a workshop. I've also ordered a copy of the full code. I hope that it has more detail.Any reference to 240 V I've found so far in the "Simplified" book has to do with wiring a stove. What I have found on the number of branches on a circuit is pretty general. It states the maximum number is 12. However, people I've talked to, and advice on this site indicate that when it comes to 20 amp circuits, you may have a maximum of two branches as in split receptacles in a kitchen, and only one on a 240 V circuit. I find that very confusing. The basic units appear to be watts, and that doesn't change for a given tool whether it's wired for 120 or 240 volts. So why is it if I run two tools (combined amps being approx. 14) at the same time on a 120 V 15 amp circuit without tripping the breaker, but if I rewire them for 220 V, (the combined amperage would be 7) I need to install 2 separate circuits? As I said. I find it very confusing, and I can only hope that the full copy of the code has more information.
Just something to consider: If your ceiling height isn't too great (i.e., you can reach it comfortably), put outlets on the ceiling over your workspaces. It's nice to be able to plug in overhead, keeping tool cords off worksurfaces and out from under your feet.
Mike Hennessy
Pittsburgh, PA
Thanks Mike. That's a good point, but unfortunately, I can't reach my ceiling. It is fairly low, but then, I'm fairly short.
First: how big is your shop? How will you heat it? Are you the only person who will be working in it or will there be someone else with you? When I built my shop five years ago I put in a 60a 120/240v sup- panel from the house. The panel has 24 spaces for lots of future expansion. Have never had a problem. I also put a max of four receptacles on one circuit to help reduce nuisance tripping. The largest space between receptacles is about 4'. I used three conductor #6(good for 65A). My house panel is only 100A. As for your 20A receptacle you're right it is up to " the inspection authority" as stated in the CEC. I would check your tools, as was said earlier and put each tool on its own breaker. It will also make the inspector in your area happier. If you need advice talk your local electrician, or if you don't know any send me an message and I'll help you out as best I can(17yrs as an electrician).
Edited 3/31/2006 4:09 pm ET by DanAlberta
Hi Dan.The shop is 10 x 24 (single car garage), and I will be the only one working in it. Currently I'm heating it with a radiant heater, but I will probably install electric baseboard heaters. I'm in the process of gathering the electrical requirements for all of my tools, heaters and lighting. Looks like it will be a separate 220 V circuit for each of the big tools and for heating, a couple of 120 V 20 amp circuits, and two 120 V 15 amp circuits, one for lighting and one for small tools (I was thinking six receptacles) in addition to the existing circuit. I haven't done the calculations yet, but I think that 60 amps should be sufficient.Perhaps you could tell what the maximum number of branches allowed on a 220 V circuit?Thanks for the input.
Only your inspector can give you a definitive answer on the number of allowed receptacles on a 220v circuit. There's no logical reason to make it only one, and the code doesn't really cover our situation (home shop) directly. But in my city for residential installs, it's one outlet per 220v breaker, that's it.
Check with your inspector.
I'd also suggest forgoing the 15A small tools circuit. Running 20A isn't much more $$ and then everything's the same. I don't know about the lighting. Also don't forget you'll probably have to GFCI your outlets. Easiest, cheapest way is to use one GFCI outlet on each of your 110v circuits (except lights, don't think you need 'em there), then attach the rest of your tool/misc. outlets to the load side of each of those three GFCI outlets. That way all three of your 110v circuits will have full GFCI protection. I didn't have to GFCI the 220v.
Look forward to hearing you've gotten it all done and are happily sending electrons to their deaths. :)My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
You're right the unit of measurement is watts. A quick rule that sparkys use is take the watts and divide by the voltage the tool has run to it(either120 or 240) to get your amps. Another equation thatt comes in handy is to know that 746 watts equals 1HP.This will give you what you need for wire size. An example would be a 3HP table saw. You would run 240v it. 3hpx746=2238. Take 2238 divide by 240v= 9.3A. According to the tables in the back of the CEC you would 3 conductor/#14 wire as a minimum. It would also be put on a 15A breaker. For this example I would run a larger size wire in case I ever wanted to put in a larger table saw. I would run either a #12(good for 20A circuits) or #10( good for 30a). I Believe the code says that only one device is allowed on each 240v breaker. You said you have a copy of the code coming, read Section 12( Wiring Methods) very closely as well as Section 10 (Grounding and Bonding). Other Sections that may come in handy are Sections 26 (Installation of Electrical Equipment) , Section 8 (Circuit Loading and Demand Factors)and the tables that are near the back of the book. Be careful because the Appendices have tables in them too, but they wil be labeled a bit differently.
The formula I gave you for finding the wire and breaker size for the table saw works with almost anything you may use in your shop. To find out what you need for your heaters do the same as I did. Some base board heaters can be wired for 240V. Same output but lower input current(read smaller wire size)
you also asked about split receptacles. These are a whole other animal than 240v ccts. In a kitchen there are split receptacles. These are just a regular receptacle that has had the small tab between the two hot screws removed to allow two ccts on one receptacle. They are great for work benches. But you will need to run 3 conductor to them. And you can put more than one split recept. on each breaker. Usually in a kitchen they are alternated using 4 ccts. The receptacles in the shop are not required to be ground fault protected, bit JohnD is right, it would be a good idea. And the cheapest way to go is to use GFI receptacles.
As for your lighting needs check the light fixtures. They probably have electronic ballasts, which means they wil probably draw about .75A each(educated guess). The code says you can put up to 12 outlets on each breaker unless you know the exact draw on that cct., in which case you are allowed to put more on. For your ten lights, you could put all of them on one cct and still be way under what you are allowed for breaker loading.If you want you could still put them on two ccts and two switches so you don't have to have all of your lights on all at once.
A few more tips. The Code says a maximum of 80% load is allowed per breaker. So for a 15A breaker the max is 12A, for 20A breaker the max is 16A, etc. When you get your Code book make sure it is the right one. A new book comes out every four years and the newest one is about to come out again. You don't want follow a rule that will be outdated in the next year. Check each of your tool motors or paperwork. There should be a number stated FLA. This is the Full Load Amps for that motor. The hardest that motor can work and still turn. This will also help when you wire your shop.
Edited 4/1/2006 11:20 am ET by DanAlberta
Wow! Thanks Dan. I just learned more in 5 minutes of reading than I have in the two days I've been going through the simplified code book. I really appreciate the advice form yourself and all the other folk. I'm sure I would eventually find the information in my reading, but a few hints and advice from those in the know sure makes it easier and is a great help.Thanks to all of you, and I will let you know how it all turns out.
If you do 3-conductor wiring for your 110, there are two things to keep in mind. 1) The two hots must be from different legs. Why? If you have two 20A circuits from the same leg, your neutral will be carrying back 40A. Doubleplus ungood. 2) You cannot GFCI a 3-wire circuit.
I have NO knowledge about CEC, so Dan may be right that GFCI is not required. For me, in the US in my city, I HAD to GFCI the 110 circuits, specifically because they're in a garage. No options.
Glad you're getting such good answers from these guys. I got a lot of help getting up to speed, too, and my installation went off without a hitch.
Have fun!My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
I am contemplating using the 3 conductor for some of the 110s simply because of the number of circuits it appears I'm going to require. According to what I've read so far, I need to use GFCI protected receptacles wherever they are easily accessible for outdoor use. It seems to make sense just to protect the entire circuit with GFIC initially. If I have trouble with tripping I could easily change in the future and just protect the ones that are required to be protected. I did think that GFCI on 3 wire was possible but I will need to look at it closer to make sure.
you're right about two different legs for the three-wire ccts John but you can protect them with a GFI . But the cost of the breaker is nuts, and can usually only be found at an electrical wholesaler. Most home centers don't sell them because they aren't used all that often, and of course the cost.
Dan, the way it was explained to me is that a GFI works by monitoring the hot and the neutral, ensuring that all the return current is coming back on the neutral. If you use one neutral for two hots, the GFI cannot "see" the return from either leg (eg, if you're drawing 10A on one leg and 10A on the other, there's actually no return at all, so both GFI's will think there's a ground fault and trip).
Basically, what both the electrician I hired to help me do the panel change, and the city inspector, told me it's not possible to protect a 3-wire 2-circuit 110 install with GFI. If you do it this way, any time you use both circuits at the same time you can expect a lot of nuisance tripping.
The only way to do it is to put a GFI receptacle at every required location. If you connect anything to the LOAD side, you cannot re-merge the neutrals and still get GFI protection downstream. So you can only run 3-wire from the box to the first GFI receptacle, everything else downstream has to be independent circuits.
I sure wanted to do it that way. Running one set of 12/3 (+ground) is a lot easier than two sets of 12/2 (+ground), but as Einstein said, "Make everything as simple as possible, but no simpler." :)My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
Many good ideas have been given. So I'll just cover a couple of safety issues. First if you are using one circuit branch with multiple outlets, put the GFI in the oulet closest to the panel. This way all outlets downstream from the GFI will still be protected and this avoids the cost of a GFI breaker. As stated however if you take two hots and a neutral to each outlet so that you can have circuit A and B as mentioned earlier, THIS WILL NOT WORK as the neutral will still be carrying current from either the A or B sides. And you need a ground wire in addition to two hots and a neutral.
This leads directly to my second comment learned the hard way at great risk. Years ago, at my parents, the electrician said the pool motor would run better on 220 which was correct. What I didn't know was that to do this he borrowed one 110 leg from the pool light circuit and the other leg was the old neutral. Somehow he either used the conduit or the green for his 110 neutral. (Not code, not good and deadly).
Needing to service the pool light, I carefully turned of fthe breaker. Then I opened the deck box. Just to be sure, I had a tester in hand and verified the black was dead. Then I started to undo the wire nuts. To my surprise and SHOCK (yes!) there was still 110 in the box. This was the neutral which should not have been carrying any current. Good thing I was on dry concrete and not touching the water.
So when I had my shop wired up, I specified only one type of voltage could be in a box. Yes it means another run of cable, but if you are doing it yourself, you save more on the labor and it makes better sense and safety. While some codes permit it, in my opinion you should never have more than one circuit in a box. If you open the breaker the box should be safe regardless if the circuit is 220 or 110.
A good book is almost any that bills itself as the NEC illustrated. (I know it may not be the bible in Canada, but the wiring diagrams cover 220 for something other than dryers and ranges as well as providing other useful information about the number of wires in a box, conduit, etc.
Hope this all helps.
I'm also in the process of wiring up my shop. I am planning on using a 100 A subpanel off of my 200 A main service which is about 30 feet away. The shop is a separate building with no water or gas lines. Reading what I can I find two different grounded wire configurations. In each case there are ground rods at the subpanel location. But then I find one runs a #6 or #8 wire from the ground in the main panel to the ground in the sub. The other leaves out this ground wire. Which is recommended.I also find recommendations for running #4, #3, or #2 wire from main to sub. Again, what is recommended.Any enlightenment will be greatly appreciated!
Your question sounds simple but really isn't. The reason you are finding suggestions for different wire size for the same size of sub-panel is becuase there are different ratings for insulation on wires. My recommendation(as an electrician in Canada)would be a #3 as minimum with R90 insulation. The R90 is just a temperature rating. This may be a little different in the US.
As for grounding; I would leave out the ground rod at the sub-panel and run a #6 back to ground at the main panel. But because I am unfamiliar with the codes where you live, you should double check with the inspector in your area.
When I built my shop about five years ago I put in something called Teck cable. It has a black outer jacket with a flexible armor underneath. It is suitable for direct burial and comes with the right size ground so there is no guessing. Most electrical whoesalers will know what you're talking about. It is more expensive than going to your local home center for cable but it takes all the guess work out of wiring your sub-panel.
Edited 4/4/2006 4:41 pm ET by DanAlberta
Run the ground wire. You will need it if you should ever have a phone, cable connection, water pipe, etc. installed to your shop.
Agree on the GFI being closest to the panel. As I said above, it will protect all outlets on the LOAD side of the GFI outlet.
Agree too that you cannot GFI a 3-wire circuit, that is, a circuit with two hots sharing a single neutral; this is what both my inspector and my electrician told me. Of course you're right about still needing a ground, which is why I mentioned 12/3 (+ground) for 3-wire.
It's unfortunately you had such an idiotic electrician, wiring your pool that way. I'm glad you survived his error. You make it obvious why we should stick to code -- even if we know what we've done, the next guy to own the house may not.
I was of two minds on the multiple circuits in a box issue. Actually the NEC specifically disallows it, but my inspector said it was OK and I gave in to convenience. I think, though, I could bring it to code by adding a tie between the two breakers, but what I actually wanted to avoid was one circuit blowing because the other did. I've compromised by adding a sticker on EVERY OUTLET stating that the two outlets are on different circuits, in consideration of the next homeowner.
Your main point is well taken, that getting educated is a good start. I'll add that having a competent electrician and/or inspector is worth it, both to get it right, and for peace of mind.My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
All good points to which I will add, type up what you have done and paste on the inside of the panel cover to remind yourself and the next guy (me) what you have done. And it wouldn't hurt to detail which circuit where.
For my shop I spec'd at least two different circuits on each wall for much the same reasons you set up that way. One other thought, for convenience, I installed one overhead circuit for an electric reel. Its setup puts power an arm reach overhead, just set it up for your height. This has become real convenient for plugging in sanders, etc.
I am too old and too new to woodworking to survive the mistakes of my youth again. So I practice safety all the time to teach my self good habits. One that is a pain in the b_tt is to ALWAYS unplug power tools like the saw and router before changing blades and bits. Another habit, lower the saw blade whenever you are done with it and keep distractions out of the shop when using anything sharp (which is most everything). Music is not a distraction unless you need to conduct.
Preaching to the choir I'll bet, but professionally I have seen too many electrical injuries, and hand injuries from a moments inattention with terrible consequences.
For split receptacles the Canadian Electrical Code says that the handles of the two circuits feeding a split recepatacle must be tied together. This is for two reasons; one is to prevent what happened to you at the pool from ever happening and to turn off the other half of a receptacle in case of a short circuit. The NEC is probably very similar in how this is stated since the CEC is based on the NEC.
It also says that the conduit CANNOT be used a neutral conductor. If two sources of voltage are present in a junction box there must be a sign on the cover of the box stating this.
We agree that the electrician at my parents was a fool. Your comments and the Code make good sense for safety. I was too lazy to look in my copy of the NEC as I was writing. But I made the comments simply because I think we should never take the short cut simply to save a little time/material cost. All the regrets in the world won't undue an elctrocution or replace a lost finger etc.
The incident with the pool also reflects what has been happening since the 60's -- a lack of professionalism in many trades by a few, I hope, lazy tradespeople.
Another example: guy came to install new refrig for parents with ice maker. He went into crawl space to tap into cold water line. Visiting parents, keep smelling natural gas near sliding door to kitchen. After a couple of visits, I decided to check out the smell and went into the crawl space. The guy installing the ice maker had drilled into the gas line by mistake and rather than tell anyone, he had simply wrapped the pipe (1/4 inch hole) with duct tape. Of course I pulled the pipe and installed a new piece. But I think of all the times my parents were at risk.
Now I apologize to all for going so far off topic except to say safety is mostly common sense and doing things in a way unlikely to hurt others. I am just amazed at the thoughtfulness and ingenuity displayed by the many who respond to forum topics.
I don't know about you but there seems to ba a lot of talk about electricity in this page, maybe it would be a good idea to start a new page dedicated solely to wiring. That way ant readers can go to that page and find exactly what they are looking for. I know that I am not the only electrician who is on here, but I try to help if I know. I'm sure other electricians could help out with questions that come from US andus Canadian electricians could help out with the Canadian side of things. Just an idea though.
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