Making room for another 220V machine

[Brent Bell]

My shop is wired with two 220V circuits. One is 20A for the dust collector (dedicated). The other is a 15A for the TS (the TS manual says it requires a 15A circuit). Both circuts have 12G wire. The TS circuit has a outlet for a 15A plug. Now comes a new machine - a jointer that requires a 220V 20A circuit. The question is can I just change the 15A circuit to a 20A circuit by replacing the breaker in the subpanel and changing the outlet to a 20A type and then use this same outlet for both the TS and the jointer? I would never run both the TS and jointer at the same time. I know I would have to change the plug for the TS to a 20A plug. Is it a safe to have the TS on a 20A circuit if the manual says 15A? My subpanel is full.

[Jason Beam]

I'd have to say yep

[Von Bickley]

Yes you can since you have 12 gauge wire. I would also install another outlet for the jointer so you wouldn't have to unplug one tool and plug in another. Just wire up two outlets together........

[Chip Lindley]

Big Jointer! 3HP?? Just wondering...whats the HP. and Amp draw on the motor plate at 230v?

Sometimes manufacturers *take the path of least resistance* (LOL) by upping the electrical requirements to minimize any consumer complaints or warranty work.

#12 wiring can handle a 20A circuit at 230v. #10 wiring for a 30A circuit. #8 for 40A. #6 for 50A.

[Dan Friedrichs]

The question is can I just change the 15A circuit to a 20A circuit by replacing the breaker in the subpanel and changing the outlet to a 20A type and then use this same outlet for both the TS and the jointer?

Yep. Assuming the run of #12 wire isn't too long, you're fine. I see a lot of very general comments here like "#12 is good for 20A at 230V...", which is not universally true. If it's a long run, you want thicker wire.

I know I would have to change the plug for the TS to a 20A plug.

Not necessarily. If you're using a NEMA 6-15 plug on the TS, that will fit into a 6-20 outlet (the 20A outlets, for both 120V and 240V, have a "T"-shaped slot so they can accept either 15 or 20A plugs).

[Rod Sheridan]

My shop is wired with two 220V circuits. One is 20A for the dust collector (dedicated). The other is a 15A for the TS (the TS manual says it requires a 15A circuit). Both circuts have 12G wire. The TS circuit has a outlet for a 15A plug. Now comes a new machine - a jointer that requires a 220V 20A circuit. The question is can I just change the 15A circuit to a 20A circuit by replacing the breaker in the subpanel and changing the outlet to a 20A type and then use this same outlet for both the TS and the jointer? I would never run both the TS and jointer at the same time. I know I would have to change the plug for the TS to a 20A plug. Is it a safe to have the TS on a 20A circuit if the manual says 15A? My subpanel is full.

Brent, what machine did you purchase?

Before I start ripping out the wiring, I'd try it out on your existing circuit.

All of my machinery runs on a 15A circuit, including a 3 HP saw, 3 HP shaper and a Hammer A3-31 12 inch jointer planer.

Regards, Rod.

[Rick Christopherson]

Yep. Assuming the run of #12 wire isn't too long, you're fine. I see a lot of very general comments here like "#12 is good for 20A at 230V...", which is not universally true. If it's a long run, you want thicker wire.

And people wonder why these discussions get so convoluted. Was there any reason to add this complexity into a discussion without first giving it any thought, other than for attention?

Utility power will vary by up to 5% throughout a day as neighbors and businesses increase and shed loads. That's 10 volts at 240 volts.

A 3 hp motor will draw 12-14 amps FLA, however, as a woodworking tool, these motors will spend 95% of their entire lives below 75%. Nevertheless, at an FLA of 14 amps at 240 volts, you would need 475 feet of #12 copper to get a 5% voltage drop, so this circuit could be 240 feet away from the load center without a problem. So unless you are going to wrap the circuit all the way around your house, it is not a concern the typical homeowner needs to worry about.

These statements get made far too often without ever giving them much thought or doing the math. It is something that you may need to worry about with a feeder, but not a branch circuit.

[Dan Friedrichs]

And people wonder why these discussions get so convoluted. Was there any reason to add this complexity into a discussion without first giving it any thought, other than for attention?

Sorry my statement rubbed you the wrong way, Rick. I agree that voltage drop on a 240V line is rarely a problem for a home workshop, and your math and analysis is absolutely correct. However, I know a lot of users reference old SMC threads, so I think it is prudent to provide very accurate information, in case someone in the future applies the advice here to a different situation.

In any case, I don't think adding the qualifier "for short runs of wire" makes the explanation unacceptably more convoluted.

[Rick Christopherson]

I am sorry Dan, but it is just something that gets repeated too often, and the people that read it end up repeating it themselves, even if they don't understand it.

It may be applicable when someone is running a set of feeders out to a separate building, but the need for applying it to a branch circuit for a residential dwelling is extremely rare.

I have seen the topic brought up even though it was known that the load center was in the same garage as the outlet. People repeat it because they hear someone else state it, and mistakenly think that it is something of great importance, when it is not.

In any case, I don't think adding the qualifier "for short runs of wire" makes the explanation unacceptably more convoluted.

Actually it does add to the confusion. You've got the background, you should know that it is not necessarily the length of the run that poses a problem. You could have a mile-long circuit with a 20 amp breaker, but if the load is only a couple of light bulbs, there won't be an appreciable voltage drop.

Voltage drop is not calculated by the ampacity of the circuit, but by the actual load present on the circuit. It is of such a minor issue with most circuits that the NEC does not require voltage drop calculations nor compensation. Bringing it up on branch circuit discussions does not serve the best interest of the readers.

[Chip Lindley]

#12 wiring can handle a 20A circuit at 230v. #10 wiring for a 30A circuit. #8 for 40A. #6 for 50A.

I bear my share of the responsibity for *generalizing* in this thread. In my advanced years I failed to remember we live in an age of legalese and blind political correctness, countered by nit-picking, nay-saying, and devils-advocating! All parts of the spectrum collide Here!

I was relating to the basic question posed by the OP, concerning his existing *shop*! With only two 230v circuits, I safely surmise his *shop* does not sprawl over industrial acres! Even without the aid of hard data at the tip of my fingers or an EE degree, I can safely bet that within....say, a 30'x30' area, the #12ga./20A norm would work well without incident.

Of course I try to use *common sense* which may or may not be in generous supply during this Century. If a machine's FLA rating is too close to the 20A max, I would bump it up to a 10ga./30A circuit. I may not be up to strict NEMA or OSHA standards, but my small one-man shop has never had a motor fried, or a 230v breaker tripped, from excessive resistance. (....there WAS that ice pick incident back in '94....) Nevermind.

In my youthful *ignorance*, I ran a 230v, 225A *buzz box* welder on a 25' length of 12ga. Romex as an extension to get the smoke and sparks out of the shop and onto the driveway. I never had a breaker trip, but I DO have several nice mobile machine stands made of 1/4" angle iron, to show for my *ignorance.* When I look at the welder now, I see a 50A plug, for which even my 8ga. extension cord would theoretically be too small.

[Brad Sperr]

I would also just try to run the new jointer on the 15amp circuit and only upgrade if you get a lot of nuisance trips.