Shop Electrical Questions

[crokett]

I am going to start working on the shop electrical next week. I can do it at night after everybody is in bed. I need to trace all the existing wires in the panel, then will add junction boxes as necessary and start adding outlets.

Two questions to start:
1) I have a vague memory of it being a good thing to try to keep the loads balanced as much as possible across both legs of the incoming service. IOW, if I have, say, 8 circuits, don't stack all 8 on one side of the panel.

2) I have an 8/16 100A panel. I plan on 1 existing circuit to light the outside lights, 1 existing to light the inside lights, 1 new for the pool pump/outside outlets, 2 existing 115V circuits for small tools (1 for each side of the shop) and 4 220V(3 new). This would be 1 for the PM66, one for the jointer/planer, one future for a dust collector and one for eventual AC/heat. That gives me 3 single slots left. Should I split the interior lighting and/or 115V outlets off on zones?

[BobSch]

I wouldn't bother splitting the lighting, the load isn't that much.

As far as the 115v outlets are concerned, do you think you'll be using both at once? In other words, will you have something plugged in and turned on at the same time on both sides of the shop? If not, or if not often, then splitting them won't make any difference because only one will be loaded at a time so the split wouldn't accomplish anything.

Did that make any sense?

[pelligrini]

I'd keep the outlets off of the lighting circuit. Are you doing just one lighting circuit or going with bi-switched (50/50)? That could still be on the same breaker depending on the load. I don't like putting tools on the lighting in case the tool trips the breaker leaving you in the dark, and it can make the lights flicker.

You probably don't need two separate 220v for the TS and the jointer. Unless you see yourself running both at the same time. I'd run two 115v circuits for the outlets, just in case you want to run a couple machines at once; like a router & a shop vac.

I like having pretty much a full 15a or 20a 115v to my outlets. With my three 115v outlet circuits I can pretty much have each tool that I'm using at the moment on it's own breaker; sanders, vacs, saws, tasklights etc.. It's usually just two circuits, but I like having the 3rd just in case one. I tried to set them up so constant loads would be fairly equal on both legs. DC on one, TS on the other. Lights on one, AC or heater on another. The 4plex box on the front of my shop where most of my high amp cutting tools get power from is on two separate breakers, one on each leg. DC &/or vac on one, tools on the other.

I used to run my shop off of a single extension cord from the porch, and then I added another extension cord from the nearest bedroom. When I finally ran my sub-panel I spread the power out well. I really hated not having enough power.

[Hellrazor]

1. Do not put outlets on a lighting circuit. Make 2 lighting circuits in case a ballast takes a dump and trips the breaker. This is extremely annoying when it happens at work and we have to check tons of light fixtures to find the problem.

2. Make dedicated outlets for your power hogs. 20A dedicated circuits for TS, dust collector,etc.

3. I install outlets every 6' around the whole shop and make them 6-8" higher then a workbench/etc top would be. Make sure you split the circuits.

4. Try to keep the circuits balanced in the panel. It isn't a huge deal but it helps and looks purdy when the box is loaded evenly

5. Remember that junction boxes must be accessable and can not be hidden in the wall without having an access panel.

[billwmeyer]

I would split the lighting. I agree that the load isn't that much, but if you ever had a circuit go bad where all the lights were on it, you would agree. I never put all lights or outlets for one room on 1 circuit. I think of it as a safety issue, as I would want some lights if there was a problem I also would put the second circuit on the other leg.


Bill

[chopnhack]

If you look at the panels, most are self balancing, i.e. if you go down one side, the tabs that engage the breaker actually alternate between phases.

[cgallery]

And also remember that in residential there is no limit to the # of receptacles per circuit (but inspectors start raising eyebrows above about twelve, I've noticed). For commercial, I think there is a limit, but I'm not sure how it works.

I don't know how your building would get classified, but I think I'd run two circuits for receptacles, and two for lighting.

[LCHIEN]

chopnhack is right - the normal breaker boxes alternate legs R&L so if you fill the box from top to bottom on the right or left or both right and left then the loads will be balanced at least as far as number of branches on each side.

its sort of up to you to try and distribute loads evenly amongst the breakers.

[Uncle Cracker]

All good info above. One other thing to do is think about isolating those loads that might come on suddenly, such as a window air conditioner or big compressor, from those circuits that might have other considerable loads. You don't want to be using a tool pulling a big load, and have the A/C come on and starve the circuit right in the middle of everything. Means more breakers and more wiring, probably, but you'll be glad you did it someday.

[crokett]

The lights and outlets will not be on the same circuit.

Bill, good point on the lights and having to fix things. So I think what I will do is the exterior lights and some interiors on one, then the rest of the interiors on the other. I am also thinking that I can knock out one 220V circuit and the TS, jointer and planer can all share. I won't run any two of those tools at the same time. By code the pool is supposed to be on its own circuit so I might put the exterior outlet on one of the inside circuits. It doesn't matter with the pump I have now but will if I get a bigger above ground.

Another two questions I thought of - air cleaners, are those typically 115 or 220V? I want a circuit for eventually getting one. Also, assuming I do some 2 gang boxes for 115V stuff, is it ok to have 2 outlets in the box on one circuit and 2 on another? I am thinking the shop vac would be dust collection for the smaller tools and it would be convenient to be able to plug them in at the same spot.

[pelligrini]

Grizzly's 1400CFM cleaner G9956 is 110v 3A. You could probably put an outlet on one of the lighting breakers. That would save you from running additional dedicated circuit to it. Not sure how you want to switch it though. Some guys like putting it on a switch with a timer.

I've got a 10" fan from a rackmount server cabinet blowing up through a turbine vent I put in the shop. I used to have it directly on the switched light circuit, along with the stereo. It's still on that breaker but before the light switch now on a rheostat switch. There are times where I like to leave it on to keep the air moving. Mostly when getting finishing fumes out of the space.

I don't know of any code saying you can't wire each duplex outlet in a 2 gang box on separate circuits, but I'm not well versed with the NEC. It is really handy for me.

[LCHIEN]

the big 20, 30 and 40-A loads are the Heating/AC and cooking appliances - they tend to be 220V so the biggest loads are already spread equally between the two legs. Then don't forget that you and the other 20 or so neighbors on the same center tapped transformer are evening out the load on the two legs. So you don't have to be too perfect, the law of averages does this.

[pelligrini]

I was just sitting out front having a smoke and thinking about your shop David. Probably because I was thinking about how something like yours would work in my backyard.

Anyways, you might consider putting in a J-box for your future covered porch, ceiling fans, lights etc. while you're pulling wire. Probably want some outlets out there too. You might have already planned for them, but I was making sure they got done in the version in my head.

[crokett]

I've already planned on a motion detector light at the corner but no lights on the porch. A ceiling fan is a good idea though. Of course I could just do a fan/light. Thanks for the idea.