240-Volt Wiring For Woodshop

[Josh Williams]

When it comes to wiring, one can never be too safe. I've spent a lot of time looking through posts and think I know how to safely complete the 240-volt wiring in my basement woodshop but thought I'd post my plans just to ensure I'm not making any mistakes. I currently have four woodworking machines requiring 240-volts that I'd like to wire up:

1) 1.5 HP Dust Collector: 5.5-amp (manual specifies minimum 15-amp circuit)
2) 1.5 HP Jointer: 7.5-amp (manual specifies minimum 15-amp circuit)
3) 3 HP Planer: 15-amp (manual specifies minimum 20-amp circuit)
4) 2 HP Shopsmith Mark 7: Hasn't arrived yet and no access to manual. Advertising states it works on 15-amps @ 120-volt so @ 240-volt 15-amps should be sufficient for the DVR motor (Digital Variable Reluctance).

I plan to hang these on two 240-volt 20-amp circuits. The center of the woodshop is about 40' from the main electric panel for the home so there's no need to run a subpanel. Both circuits will use a Siemens Q220 20-amp 2-pole 240-volt circuit breaker. Wiring will be 12-gauge. The first circuit will have a single 20-amp receptacle. I plan on using this circuit exclusively for the dust collector since it'll be running at the same time any of the other tools are running. The second circuit will have two 20-amp duplex receptacles in the same junction box providing four outlets. This allows me to plug in the jointer, planer, and Shopsmith all at the same time and provides one extra outlet for a future tool. In general, there would never be a reason to have two of these tools running at the same time.

Does this all sound like a good safe plan? Note that I have two additional 120-volt 20-amp circuits for general 120-volt tool use.

My primary concern was finding out if all three tools could be on the same circuit without issue and if by chance two did get switched on at the same time there wouldn't be any danger to the circuit or the motors running on it. From what I think I've read in the forums, 240-volt circuits at 20-amps or less have the same rules as 120-volt circuits. You can put multiple outlets on them, they can be used at the same time, and if a circuit overloads, the breaker trips. It's only 240-volt circuits at 30-amps and greater that have to be dedicated to a single tool? Am I understanding things correctly? The requirements for the Shopsmith and jointer seem small enough that they could potentially run at the same time on the same 240-volt circuit and I'm wondering if that's safe.

Thanks for any info!

[Rich Riddle]

You can run your electric this way and proves very similar to 120 VAC. Code there calls for a maximum number of receptacles but if one places too many loads at once, a circuit breaker trips. Doesn't matter if it's 220 VAC or 120 VAC. Your breaker will trip once you exceed the maximum. If it was me, I would run ten gauge wire in case I ever acquired a tool requiring 30 amp service. It's saved more than one person to run the 10 gauge and not have to update later. You might not know this, but they do manufacture a dual 120/240 voltage receptacle where you can have both voltages available on the same receptacle. Here is a 15 amp example of one:

http://www.amazon.com/Leviton-5031-W...voltage+outlet

[Ole Anderson]

But 10 ga is such a pain to run and wire boxes. Heck 12 ga is bad enough after running 14 ga. Personally I wouldn't do it unless I really plan on some 5 hp motors (my 3 hp ones are plenty) or I was going to cover everything up.

[Rich Riddle]

I thought the twelve gauge was a pain to run it when I ran it....then came along the first of two tools with 5 hp motors and I had to run the 10 gauge. It added insult to injury. Work properly once, pay once, cry once.

[Marty Tippin]

Definitely wishing I had run 10 ga for my 240V circuit so I could upgrade from 20A to 30A. Also wishing I had run a second 240V circuit, as I'm considering adding a cyclone dust collector that will need a dedicated circuit. Hiindsight is always 20/20...

You might consider whether regular 240V receptacles are what you want. I used NEMA L6-20 locking plugs and receptacles in my shop, as I wanted to ensure a solid connection. May not have been necessary, but sure looks "professional"... Only downside is you're limited to one receptacle per box - there are no duplex receptacles for that style of connector.

As for the number of machines on one circuit, if you're a one-man shop, you'll be hard pressed to ever run more than one machine at a time. And if you *do* run two machines, one of them is going to be idling along pulling very little current while you're actively using the other one. If, on the other hand, you anticipate having multiple people in your shop using tools at the same time, you'll want more capacity.

[Steve Meliza]

My garage in my current home will never see a 5HP tool requiring a 30A circuit, it would be like suggesting that a soccer mom buy the minivan with the V-12 Rolls Royce engine just in case. All of the circuits were ran in conduit so it made the most sense economically to buy three spools of #12 wire (large spools of white and black and a small spool of green) and run everything including lights on #12 wire. It wasn't that difficult and I have girly soft keyboard hands. Should pigs learn to fly I can fairly easily modify my wiring to adapt to needing a 30A circuit. If you find yourself circling the picture of a 5HP tool in the catalog and leaving it laying around where your wife can see it then maybe you want to make one or both circuits #10 wire.

I don't know what code is in MN, but it does seems that having multiple outlets on a single 240V circuit can be an issue in some jurisdictions. A quick call to the inspector could clear that up and save you time and money. If he says one outlet per circuit then that is what you do. What you do after he signs off on the work is up to you.

It would appear to me that only the planer requires 240V. Are these dual voltage tools that you are swapping over to 240V? Unless they are already converted to 240V or your plan to upgrade to larger tools I'd run that dedicated dust collector circuit as 120V, another 120V circuit for the Shopsmith, jointer and that possible new tool, and a 240V circuit for the planer. It uses the same number of slots in your breaker panel, adds one more run of wire/circuit, and you can easily convert between 120V and 240V on any circuit by swapping out the breaker and outlet and wrapping black electrical tape around both ends of the white wire when configured as 240V.

[Duane Meadows]

As for the number of machines on one circuit, if you're a one-man shop, you'll be hard pressed to ever run more than one machine at a time. And if you *do* run two machines, one of them is going to be idling along pulling very little current while you're actively using the other one. If, on the other hand, you anticipate having multiple people in your shop using tools at the same time, you'll want more capacity.

Hmm, I have a dedicated 240V circuit for my air compressor, and my air conditioner. Hard to control when those 2 things run! I also have my DC on a seperate circuit as it always runs with another tool. The rest of my 240 tools are split between 2 others circuits. Could I do with fewer circuits? Perhaps, most of the time, but if I have a friend over, or a helper , I don't worry about tripping breakers.

[Tom M King]

For things that are hard wired, as are most of the big tools in my personal shop, I want each tool on it's own circuit, so the breaker becomes a safety switch in addition to the one on the machine.

[Wade Lippman]

Your plan is fine.

My plan was fine also, until I wanted a new 120v line, and then a second 120v line. Then I put a subpanel in and deeply regretted not doing it right the first time.

My recommendation is to run a subpanel and know you are good for anything that might come up. Running #6 is an experience, but you only have to do it once.

[Rod Sheridan]

Your plan is fine, I might also suggest that you use 12/3 and then you can wire it as a multi wire branch circuit and have 20 ampere 240 receptacles and 20 ampere 120 v0lt receptacles on the same circuit.................Rod.

[Art Mann]

In my opinion, Rod gets the gold star for good advice.

[Chris Padilla]

If you're going to run #10, go with stranded over solid-core. It is TONS easier to work. I ran my whole garage rewire with #10 stranded but I did that back when copper wire was about half the cost it is now. I also put everything in flex conduit so I could pull whatever I wanted later on. As it worked out, I've ended up removing some to use elsewhere in the house!! LOL

[Chris Friesen]

I second the multiwire branch circuit idea...hard to have too many 120V receptacles.

Another vote for running #12. You can always run #10 later if you buy something that needs it.

Personally I think twistlock is overkill for a home shop, I've never had a plug pull out accidentally.

[Jim O'Dell]

Well, I tend to overdue when it comes to the shop, especially the wiring. I have 3 tools that are 220 only (5hp cyclone, 3hp TS and a 2.5hp BS. I have 2 tools that are dual voltage that are wired 220 (1.5hp contractor saw, a 2 hp air compressor, and drill press-hp rating escapes me right now). I have 220 wired for a small welder, a future PTAC HVAC unit, and one for a jointer. All on their own circuits, all 10 guage wiring. I have 6 110 circuits, 2 for lighting in the main shop, 4 for outlets around the walls. Yes, the 10 guage is hard to work with, but you get used to it after the first 2. Use the largest electrical box you can get, Heck, I'd use a double box with a blank plate on one side if I had to. Also, I also used the twist lock outlets for all of the 220 receptacles, and all of the 110 ceiling mounts. They aren't cheap either, but well worth the price. As others have said, do it right the first time. Much easier in the long run. Jim.