Best way to set up new outlets in workshop

Question

Context: I have a workshop used for woodworking. On one wall, I have a two-pole (240v) 30a outlet and a regular 120v 20a outlet. I'm building some cabinetry and I plan to convert the outlets in the wall into a junction box and mount the outlets onto the cabinets in a more accessible location.

I'm curious how I should set up the new boxes because I was wanting to do the following:

• One single 20a 240v receptacle (from the 30a circuit - uses only black wires - reserved for future table saw)
• One duplex 20a 120v receptacle (from the 30a circuit - fin removed, using black & white wires from 30a circuit)
• One duplex 20a 120v receptacle (from the 20a circuit)

I don't think I can put them all in a 3-gang box since I won't find an outlet cover with two duplex / one single. So I guess I need 2 separate boxes.

I could do a 2-gang box with four receptacles (the four 120v ones), and a single gang box with the 240v. This would look cleaner in a way, but the wiring is probably messier since there would need to be wires going between the two boxes.

Or, I could do a single gang box with 120v duplex, and a two-gang box with a combo 120/240 receptacles, using a cover like this.

I guess I'm leaning towards the latter but it would be nice if I could have put this all together in one box.

(If it matters, one of the 120v circuits will power a shopvac and the rest of the plugs will power a tool (router/miter saw/table saw etc). Only one tool will run at once but vac/tool will be on separate circuits so they can run together).

edit: The 30a circuit is wired for a dryer but is unused. The electrician put that in when I asked him for a 240v circuit in case I wanted to re-wire the table saw.

edit: Upon further inspection, my 30a circuit is only wired with 10/2 romex, so my proposal isn't going to work without running new cable anyway.

Answer 1

Can't put 20A receptacles on a 30A circuit.

If your 30A circuit is 4-wire, you can convert it to a feeder to a sub panel. Then, you can fit the requisite 20 amp 120V and 240V circuits as you wish, without any real restriction.

However a 30A feeder cannot have any receptacles at all, so if you jury rigged this off the dryer circuit as many do, that whole thing will need to be re-done (with separate neutral and ground if not already so). Once the subpanel is in, you can run a 30A circuit back to the dryer. That will use 100% of the feeder's capacity when you're drying, so don't use other tools then.

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Since your 240V loads are 15A or 20A, you can use normal 240V sockets - you don't need to pay a fortune for the wackadoodle twist-locks LOL. If your community prefers those, pay them no mind. It's your shop.

You might also think about multi-wire branch circuits (MWBC) to the cabinets. These use 4 wires and connect both 120V and 240V outlets to the 20A circuits. They even make "combo" receptacles that accommodate both 120V and 240V outlets on one yoke. You get dual 120V "half circuits" so you can run two 16A loads, one one each half-circuit. Any 240V loads add amps to both 120V half-circuits.

If the cabinets will be screwed to the wall, they can be cabled in with normal Romex as long as the Romex is physically protected.

If the cabinets will be free moving, I would use cord-and-plug connections and EMT or FMC metal conduit with metal boxes for the wiring internal to the cabinets. Have proper cordage (SO, SW, SJOOW and any of those "S" cables) for the cord/plug connections, and proper strain reliefs where they enter the metal box knockout. Design the cabinets to protect the cord from injury. No inspector will argue with that!

However if you cord-and-plug run an MWBC, you'll need a 4-wire 20A socket. Straight blade 14-20 sockets are rare, probably forcing you into the far more common but expensive L14-20 twist-locks. However you could just hard-wire it with FMC or a AC/MC wire whip.