Multiple 240V outlets on one circuit OK?

[Brian Glendenning]

Hi -

I hired an electrician to put in some additional 240V and 120V circuits in my shop, i.e. garage. Since I will only be running one machine at a time, he has one 20A 240V circuit with multiple outlets (and a separate 30A circuit with one outlet for future expandability). I assumed that this was OK given that he's an electrician and should know his business, but I think I might have read in the extensive 240V plug thread that in fact this might in fact not meet code.

What's the scoop?

Cheers,
Brian

[Chris Padilla]

Daisy-chaining 240V circuits, I believe, is an AHJ (authority having jurisdiction) decision. Personally, I don't have a problem daisy-chaining such circuits but I ran single receptacles for all my 240V/30A circuits (which, of course, I can plug in something only needing 240V/20A) because I had the room and just wanted to do it that way.

[Don Jarvie]

No issue as long as it's one tool at a time.

[Ben Rivel]

Sure as long as you dont over draw the circuit. Just make sure to only use one tool at a time and its fine.

[David L Morse]

No issue as long as it's one tool at a time.


Sure as long as you dont over draw the circuit. Just make sure to only use one tool at a time and its fine.

You can use as many tools as you like as long as you don't draw more current than the breaker will allow.

[Jesse Busenitz]

No issue as long as it's one tool at a time.

Until you sell the house and someone else doesn't know that fact. But in all reality the odds of someone using multiple outlets simultaneously in a home shop is slim. Right?

"I had a couple friends over to help on my project and we were cruising along until we fired up the table saw and planer at the same time, and then the lights went dim and wires started sparking and it was like new years eve in September."

[David L Morse]

Until you sell the house and someone else doesn't know that fact. But in all reality the odds of someone using multiple outlets simultaneously in a home shop is slim. Right?

"I had a couple friends over to help on my project and we were cruising along until we fired up the table saw and planer at the same time, and then the lights went dim and wires started sparking and it was like new years eve in September."


So please explain how that's different from having multiple 120V receptacles on one breaker.

[Mike Henderson]

Until you sell the house and someone else doesn't know that fact. But in all reality the odds of someone using multiple outlets simultaneously in a home shop is slim. Right?

"I had a couple friends over to help on my project and we were cruising along until we fired up the table saw and planer at the same time, and then the lights went dim and wires started sparking and it was like new years eve in September."

If that happened, something is wrong with your wiring. The breaker should be sized to the wire so as soon as you pulled more current than the breaker allowed, the breaker should have tripped.

If the lights in the house dimmed when you drew the breaker amount of current, you have problems other than in this 240V circuit.

And if the wires started sparking, you have some other problems. Maybe the breaker is too big for the wire or your wiring installation is defective.

A proper installation would have been that the breaker tripped and your tools wouldn't work - nothing else.

Mike

[As David said, it's exactly the same as a multi-drop 120V circuit. If you draw more than the breaker amount of current in a 120V circuit, the breaker trips, nothing dramatic.]

[Robert Engel]

The electrician who wired my shop wired all my 240 machines (4) on the same circuit. No problem. I think one time I left the jointer and planer both
running and when I cranked up the big bandsaw the breaker popped. That's what its supposed to do ;-)


.....and then the lights went dim and wires started sparking and it was like new years eve in September."
Like Mike said....or something doesn't pass the smell test.

[John Lankers]

You could take it even a step further and have him install a bigger breaker (40 Amp?) and heavier wire so that you can run 2 machines simultaneously, it should be very cheap to upgrade.

[Wade Lippman]

So please explain how that's different from having multiple 120V receptacles on one breaker.

It is exactly the same. But when you when you ask an electrical question here you will get "well, I'm no expert, but I heard that....".
For some reason they have to weight in, even though they are aware they don't know.

I wired my 240v just like 120v; a single circuit with outlets every 10 feet. Using two machines will trip the breaker, but it has never happened, and if it does will not matter. (I also have a single outlet 30a circuit for my cyclone, but that is an exception)

[Wade Lippman]

You could take it even a step further and have him install a bigger breaker (40 Amp?) and heavier wire so that you can run 2 machines simultaneously, it should be very cheap to upgrade.

But of course you would have to use 40a outlets and plugs. It would also leave the inferior wiring on the machine exposed. I realize the breaker is not intended to protect the machines, but it is nice when it does.

[Mike Cutler]

Hi -

I hired an electrician to put in some additional 240V and 120V circuits in my shop, i.e. garage. Since I will only be running one machine at a time, he has one 20A 240V circuit with multiple outlets (and a separate 30A circuit with one outlet for future expandability). I assumed that this was OK given that he's an electrician and should know his business, but I think I might have read in the extensive 240V plug thread that in fact this might in fact not meet code.

What's the scoop?

Cheers,
Brian

Not unless it's not allowed by your local code.
Yes, you can have multiple 240vac outlets on the same breaker, just as you can have multiple 120 receptacles on a breaker. The breaker will be sized for the code required application versus location. There is nothing wrong with what you have. If it was not acceptable, the electrician more than likely wouldn't have installed it.
Don't get confused by the motor section of the code.The NEC stops at the receptacle.
Put your DC, dust collector, on the 30 amp breaker circuit and run your machines off the 20 amp circuit. Don't put the DC and a machine on the same circuit, and you should be fine.

[Brian Glendenning]

OK, sounds like I'm good. Thanks everyone for the reassurance. (It would have been pretty annoying if after paying an electrician rather than DIYing it there was a problem!).

[david scheidt]

Hi -

I hired an electrician to put in some additional 240V and 120V circuits in my shop, i.e. garage. Since I will only be running one machine at a time, he has one 20A 240V circuit with multiple outlets (and a separate 30A circuit with one outlet for future expandability). I assumed that this was OK given that he's an electrician and should know his business, but I think I might have read in the extensive 240V plug thread that in fact this might in fact not meet code.

What's the scoop?

Cheers,
Brian


Don't assume a residential electrician knows anything about how to wire commercial space. In a lot of ways, a work shop with large power tools is a commercial space, and should be wired that way. (With the possible exception of still using NM cable, if your local codes allow it.)

If you put in a subpanel, I'd pull seperate circuits for each machine.

[Mike Henderson]

If you put in a subpanel, I'd pull separate circuits for each machine.

That's good advice but the situation in most shops is that you wind up rearranging the tools over time. And when you do, if you haven't put in enough of the right kind of outlets, you have to do some re-wiring. A good reason to multi-drop outlets (both 120 and 240) is not that you'll use all of the outlets at one time, but that you'll have power (of the right kind) in many places in your shop. If you think through some of the possible rearrangements, you can move tools around and not have more than perhaps two on a 240V circuit.

But if you're sure that you're never going to rearrange your tools, I'd do the same and run a separate circuit to each tool. That's what I did in my shop - and when I changed things around, I hooked into the existing circuits and extended them to the new location (and left the old outlet).

Mike

[Mike Heidrick]

I am sure I have posted this before but here is what I did since I was building from scratch. I put in several outlets 240v per circuit (30amp 10ga for all 240v and I use L6-30 plugs and receptacles) but no two 240V outlets next to each other are on the same circuit. Same for 120V outlets times 2 - no 4 120V outlets next to each other are on the same 20amp 12ga circuit. Also the East half and the West half of the buildings have their own pairs (240V) or quad circuits (120V) of circuits. So if you are on the South East end of the shop doing something its different circuits than on the South West end. Also the North walls and South walls have different panels So North is different than South. So North West end is different than North East end. Also Dust collection and air compressors have their own dedicated circuits. Also the ceiling outlets for drops down to tools away from walls all have their own circuits - dedicated 240V circuits in ceiling and the 120Vs are again east and west are separated but NW and SE are the same 120V and NE and SW are the same 120V circuits. All my outlets are labeled as well as labeled in the panels. Chances of using multiple tools for me is highly likely - Using a CNC machine with dust collection while using a table saw with a different dust collector or a drum sander with a dust collector while CNC is running is fairly common. Or wood CNC running while using a mill. I wanted the new shop amp usage layout to be well thought out and thorough.

[Roy Turbett]

You can use as many tools as you like as long as you don't draw more current than the breaker will allow.

+1 I ran 10 gauge wire wire in my shop and had three 1 hp wood lathes running at the same time on a 30 amp 240v breaker.