As a follow-up to this previous post, once you have electricity supplying your workspace, it’s time to consider the placement of receptacles. There are a few considerations here. First, receptacles should be spaced close enough together to avoid using extension cords where possible. Secondly, consider the height above the floor for locating them. In your home, the standard height above the finished floor (AFF) for receptacles in the U.S. is 12″ (30cm). However, in your shop, figure that the average height of workbenches, table saws, and other worksurfaces averages out around 36″ (92cm). Most of the benchtop or portable hand tools that would be used in your shop will be on a workbench. Plus, floor space can quickly get crowded, often blocking lower receptacles.
For my MiniMax Workshop, I chose to install a two-gang receptacle box on every other stud in the walls. Since the stud spacing is 16″ (40cm) on-center, that makes a total of four receptacles located roughly every 32″ (81cm). For my way of thinking, it’s better to plan for more receptacles than you think you’ll need because you’ll, at some point, wish there was one closer to where you need it. Yes, I tend to go overboard on the number of receptacles, but I’ve never been sorry.
As for the height, I mounted all of the boxes 48″ (123cm) above the floor. This way, they would be easily accessible above worksurfaces and stationary power tools.
Here is my usual disclaimer. With anything involving electrical work, please consult with or hire a licensed electrician. If you’re running the cables yourself, they can advise on how the wire should be installed and fastened, what size wire to use, and how to make the connections. Also, cooperate with your local code officials and obtain the proper permits and inspections. It’s for your safety.
I used inexpensive 2-gang electrical boxes that have a nailing flange on the front. I regret this decision. I found that the boxes can distort, making it difficult to fasten the receptacles and install the cover plate after the wall board is installed. And there’s always the possiblity that the plastic threads will strip. In the future, I’ll spend a little extra to buy metal boxes.
When it comes to running the wiring, I made another decision I sort of regret. Remember from this previous post that I ran two 20-amp circuits to the shop. My original thinking, and the way I wired it, was to dedicate one circuit to the recepactles on the north and west walls, and the other circuit to the east and south walls. The better solution would have been to run both circuits to each receptacle box. This way, each duplex receptacle in the two-gang box would be on a different circuit. This just helps even out the electrical load and prevent overloading in case you have power-hungry tools all along one wall. Again, this where your electrician can help you with how to do this per electrical code.
Another consideration, especially if your MiniMax Workshop is in a separate building, is whether to install outdoor receptacles. I took advantage of the open walls while I was running wires and poked through to the outside to install an outdoor-rated electrical receptacle box. I simply branched off the nearest receptacle box on the inside with the wiring. This outdoor receptacle has come in handy multiple times.
One of the things your electrician may mention to you is the use of Ground Fault Circuit Interrupters (GFCI) or residual-current device (RCD in th U.K.) for the receptacles. In the U.S., they are required for circuits used outdoors, laundry rooms, bathrooms, basements, kitchens–anywhere there’s a potential for exposure to liquids. I could have used GFCI breakers at the main panel in the house. This would have protected both circuits going out to the MiniMax Workshop. But these can be pricey. Instead, I opted to install a GFCI receptacle at the start of each circuit then branched off to the other receptacles. This way, all of the receptacles downstream are protected.
After installing all of the boxes and wiring and making the final connections, it was time to flip on the breakers. This is always a sweat-inducing moment for me. But the worst that has ever happened to me is that I had a wire crossed somewhere and the breaker tripped immediately. If the breaker stays on, it’s a good sign your wiring is correct! To be sure, I checked each receptacle with a tester.
At this point, I called for my an electrical inspection as required by the local code officials. They looked at the breaker panel, the underground cable, and made sure I was using GFCI receptacles correctly. I passed the inspection which meant that I could insulate the walls and add the wall covering.