u2slow said:
I'd go the other way. #12 wire, and cheap 15A plugs. Easy to change the plug. Harder to change the wire later...
I've never quite understood running wire in the walls in garages. Everything in my garage is fluid, I rearrange it constantly to support new projects. Everything in my garage is in conduit, and even a few places in the house (all my comm/telephone circuits save one drop to the boxes via conduit, makes it easy to rewire or add additional CAT-5e for more ethernet connections).
None of the 1/2 mile of new wire I've installed in the house (we replaced about 85% of the original wiring) is smaller than 12ga with 20A breakers, and the main trunk to the far end of the house is 1/4 mile of 8AWG stranded in a 2.5" conduit. Each of the four bedrooms has 7200W available, though only 2400W of that is dedicated, and the remaining 4800W in each room is shared with the adjacent room. We're computer and electronics geeks. I intend to never trip a breaker again.
This is the current setup in my smaller attached garage. The wiring in the garage isn't complete, I've only wired the side I'm currently working in -- but this garage is used primarily for fab, woodworking, and bikes, so almost all my work is still near an outlet for now. Photos linked to save my buddy a little bandwidth:
Photo 1 is my central/welding circuit. This was originally positioned to let me run my small 135A mig in a convenient central location. It's a 20A multiwired 120 duplex on the bottom (4800W total available, 2400 per side) with a single 220A plug in the higher box. The 240 outlet was originally intended to power a larger MIG or a small SMAW box. The 220A GFI breaker that powers this circuit was the most expensive single item in the electrical renovation excluding the panel boxes themselves. I'm a firm believer in GFI on any circuit I'm likely to be using near water or damp concrete.
Photo 2 is of my primary work area. These were taken back in May during a rearrangment, so things look quite a bit different now. My "light duty tasks" workbench is now just below that single 20A 120V circuit. The bench is used primarily for carb rebuilding, electrical/electronics projects, and another tool station for light fab work and bike work. There's also now a shallow shelf for aerosols and 64 ft^2 of of pegboard on that wall.
Photo 3 is why I'll probably never use the 240V outlet on the central pole. No more need for a larger MIG box or a small SMAW.
She runs on a 100A breaker, which is still slightly underrated at max output duty cycle ... but I really don't know when I'll need 300A at 50%+ or 200A at 100%, so I'm not concerned. The baseboards were salvaged from the house, 1500W apiece and work like a charm.
Photo 4 is the power distribution area. The 200A subpanel on the right is original to the house, formerly the primary panel, and still runs about 15% of the house circuits, plus the washer, drier, and 100A pass through to the larger detached garage (which has significantly less in the way of power requirements). The large 200A/40 panel on the left is the main distribution center for the garage and the main trunk to the house. The large conduit top and center supplies the four bedrooms, among other things. Smaller conduits to the right supply outside lights (all run off a light sensor on the roof), garage lights, the circuit in Photo 1, and the space heaters in the bathrooms. The 200A trailer panel in the center is the main panel for the building, which I wanted just so I'd have a convenient single switch to isolate me completely from the grid for when I'm rearranging things.
I think Jim (Kart) has the right idea with the quad/12ga extension boxes, though I'd use 10ga flex if I could find it. Having cords snake over your workbench is a pain in the ass. I run most anything not physically on the bench off of the center outlet, particularly now that my baby welder is now sitting on the Shopmaster and plugged into the single 20A outlet just below the center trailer panel.