Running two motors on one 230V Duplex circuit, woodworking shop
I had a house built and asked the electrician to wire the garage with a 230V receptacle for a Delta tablesaw. He ran a 30A circuit with 10ga wire, more than I needed as distance from breaker was only 20 feet. The 230V tablesaw draws only 12.4 amps. I'd like to add a 230V dust collector to the shop that would run at the same time as the tablesaw. The JET cyclone vac only pulls 8 amps. I'm wondering if I can replace the single receptacle with a duplex 230V receptacle and have both plugged in and running at the same time. The duplex receptacle is a 20amp and says it can handle #10 wire. Can I run both at the same time? The other option is to run a dedicated 110V line out there, but it seems like there is plenty of capacity to for the tablesaw and dust collector to share that breaker. Any help would be appreciated. The 110V circuit in the garage is already loaded and I'd like the benefits of the 230V vac if possible.

Many thanks. Here's a link to the receptacle:

http://www.amazon.com/Leviton-5822-W...pr_product_top (http://www.amazon.com/Leviton-5822-W-Receptacle-Commercial-Grounding/dp/B000U3I1S0/ref=cm_cr_pr_product_top)

Please clarify, is the branch circuit (from the panelboard to the receptacle outlet) a 30 amp circuit (a double pole 30 amp breaker) or a 20 amp circuit (20 amp double pole breaker).

I believe that since you have a dual receptacle outlet, you cannot have fixed in place equipment that is more that 50% of the circuit. I'll have to look that up to make sure. But that means that your answer would be no.

Correct, it is a double-pole 30 amp breaker. The dual receptacle is different than other 20 amp receptacles in that it can handle #10 wires, leading me to believe that it can handle the load. So if my breaker is large enough, the wire is large enough, and the motors together are less than the total capacity of the breaker and wires, then it appears that the only factor is whether the receptacle can handle both running at the same time?

Motors require a 125% load factor so taking 20.4 X 25% we get over 25 Amps. Startup will run the Amperage up so you will overload the receptacle but not the breaker. However, why not use 2 NEMA 20 Amp / 240 VAC single receptacles? Change the single box to a double and use an old work box if necessary.

Wouldn't that be kind of the same thing? For example, if I broke the tab off the duplex receptacle and pigtailed each outlet to the feed, then that would be the same effect? Alternately I could run two pigtails to separate receptacles as you suggest in a large box. It's just a matter if the tab con thie receptacle is better than the pigtail wire.

I see your point with running separate receptacles, this one just looked like it was made for exactly this situation.

No. The load on each receptacle would not exceed 15 Amps while with a single you will exceed 20 Amps.

I am going to disagree with Don and Brian and agree with you. First since you are using a receptacle and not hard wire, this is not a fixed in place load. The saw may be stationary but that is because it is big and heavy, but it is not electrically fixed in place.
I would also interpret the 20 amp limit of the duplex receptacle as being 20 amps each outlet half. The contact points of each half would certainly be rated 20 amps.

I see no advantage of breaking the tabs and then pig tailing to each half. The tabs between the terminals certainly rated for 20 amps in order to have 20 amps pass through.

Replace the outlet and plug things in.

210.21(B)(1) or 210.21(B)(3) or any way you would like to consider this..
A 30 ampere circuit breaker does not protect a 20 ampere receptacle and the
Total load of the saw and vacuum is 20.4 amperes which exceeds the rating of the receptacle.

So clearly this idea does not comply with the letter of the code although I agree it will likely work for a while... this choice is always yours.

Harold, I agree, the load is not a fixed in place load in order to be that it would have to be hard wired to the branch circuit. Thanks for the catch!

However, that still opens the door to the 80% load for multiple receptacles on a branch circuit, correct? If that rule applies and he has a 30 amp circuit than the max load he can place on that circuit would be 24 amps. Again, that is if I am getting the code correct.

With respect to the receptacle, I know we can use a higher listed receptacle on a lower rated branch circuit (as in a 50 amp receptacle on a 40 amp clothes dryer circuit), bur I can't find any support for a 20 amp receptacle on a 30 amp circuit.

I do find support for a 15 amp receptacle on a 20 amp circuit, so I ask, what am I missing?

You know life can be a little feisty from time to time. I've got the 2005 through 2014 editions of the NEC in the living room. So near yet so far!

I had knee surgery on Monday and I'm still flat on my back and the dumb books just refuse my telepathic command to march in here. I guess I'll actually read the NEC on line! I still think the books are IR impaired for refusing my command! :)

I did not consider fixed vs corded. However, not sure how a 20 Amp outlet be considered OK for 40 Amp-"20 amps each outlet half". Would that infer a 15 amp outlet could be used with a 30 Amp load? I would still consider 2 single 20 Amp/240 outlets as the safest long lasting approach.

Ma, I agree...

Don, Godspeed on your recovery!

I have to recover soon, otherwise my wife is going to kill me for being such a "PIA" :)

Yes, stay off you feet and get well soon Don. I make no argument that the 20 duplex receptacle meets code. Clearly it does not. I would however, argue that it is safe. Nothing can be connected to either half that exceeds the 20 amp capability of each half of the receptacle.

I would also question the 12.4 and 8 amp loads unless those are the max loads ratings. 12.4 amps is to large for a 3 hp motor unless it is max draw. Too small for a 5 hp. If you have a 5 hp table saw it must be industrial size. Likewise a 1 hp motor is the largest I have ever seen on a shop vac. So 8 amps must be max draw.

If loads are max loads, you can probably change breaker to 20 amps and be with in code. A time delay breaker to avoid nuisance trips.