220V Circuit with multiple receptacles?

[Sean Kinn]

I've searched a bit, and I can't seem to find a clear answer. I'm in the process of wiring my unfinished basement and I'm trying to figure out how many 30A 220v runs I'll need. I'm also a one-man shop, so I will only ever have two 220v machines running at once (dust collector + BS or TS or planer or jointer). I've researched the amperage requirements of all the machines, and the highest combination of any two machines will be 28amps. Here are my questions:

1. Can I run two 220v machines on the same circuit as long as I don't exceed the amperage rating of the circuit? All of the information I've found seems to refer to one machine per circuit.

2. If yes to #1 above, is there a reason I can't have multiple 220v receptacles on the same circuit (one at each machine) so that I don't have to constatntly plug/unplug machines?

Again, I would only ever use a combination of two 220v machines at one time.

[Christopher Dopp]

Yes, you can run two 220v machines off of one circuit as long as you don't exceed the amperage rating of the breaker. All this assumes you are using the proper breaker size and gauge wire for the circuits.

You can have multiple outlets on the same circuit. I have three 220 circuits in my garage. Two of the circuits have two outlets each (on separate sides of the garage) while the third has a single outlet for the dust collector.

Works fine for me.

[Sean Kinn]

Thanks. I forgot to mention that I'm planning to us 10ga wire, and the overall run will only bea about 30ft. I was thinking of this in the same manner as a 110v circuit with multiple outlets (you could have 4 outlets on a 15a 110v circuit, but it's up to you to ensure that you aren't drawing more than 15a at once. I just haven't found too mant references to multiple outlets (or machines on a 220v circuit) and thought there may be some other aspect to it....perhaps a code issue?

[mreza Salav]

I'd suggest to have a dedicated circuit for the DC and one other circuit for the rest if you use one of them at each given time.
Note that although the full draw of the two machines might be smaller than 28amp the start-up draw on some machines (like DC, bandsaw, etc) are MUCH higher than the full load.
Chances are you'll trip the breaker if have one of them running and turn the other one.

[Ron Natalie]

It's NOT a code issue. I don't know where you get 4 15A 110V outlet limits from either. That's not a number that appears anywhere. There's no code limit for residential use, and for commercial it's still way more than 4.

For a 15 or 20A circuit (be it 110 or 240) you can have multiple receptacles. Once you get to 30A you need to make it dedicated. 10G is *WAY* overkill for a short run of 15 or 20A. Voltage doesn't enter into the wire sizing issue (actually 220 makes it easier as the drop is a smaller percentage of the voltage).

[Will Rowland]

It's NOT a code issue. I don't know where you get 4 15A 110V outlet limits from either. That's not a number that appears anywhere. There's no code limit for residential use, and for commercial it's still way more than 4.

It is true the NEC doesn't explicitly state a maximum for the number of receptacles on a single circuit in a dwelling, but most inspectors I've come across believe 13 receptacles on a 20A circuit or 10 receptacles on a 15A circuit is "code".

And, as I've learned the hard way more than once, the inspector is right, regardless if the NEC says he is wrong.

[Van Huskey]

As Mreza mentions you want a second 220v circuit for the DC. If you don't have a 220V DC at the moment go ahead and wire for one. When you run your wiring one thing I will mention is make sure your boxes are LARGE. Since you will have 2 stiff 10ga wires in each box (except the last one on the run) you want the room to fit the extra wire which is a pain or impossible if you get wimpy little boxes.

[Greg R Bradley]

"Wimply little boxes" will cause more problems than that.

You are only allowed 5 10ga wires in a 4x2 handy box. Less two wires if there is also a switch or outlet in the box. That means 3 wires. How are you going to wire it?

BTW, if the box is less than 1 7/8" deep, you are only allowed 4 10 ga wires.

This explains why you see many 4x4 2" deep handy boxes in commercial installs since that changes the number of 10ga wires allowed to 12.

[Ole Anderson]

In general, the FLA (full load amperage) of the motor should be no more than 80% of the breaker, so a 30 amp breaker would limit you to a 24 amp motor, or a combination of simultaneous loads totalling 24 amps. Likewise a 20 amp breaker to 16 amps of load. The breakers have some ability to handle starting loads higher than the breaker rating, similar to a time delay fuse. But spinning up a heavy dust collector fan can sometimes exceed the time delay factor, so you may want to use a number less than 80% when sizing your breaker, provided you have a mag starter with built in motor overload protection.

And I agree with others that your DC should be a dedicated circuit.

[Sean Kinn]

Thanks again everyone, especially those of you that mentioned the issues with the size of the boxes. When I mentioned "4 receptacles" above I just pulled the number out of the air....I could have said "X receptacles." I took a closer look when I got home today and two separate runs (one for the dc, and one for the "others") makes the most sense when factoring in the location of the machines in relation to the panel. Also thanks for reminding me about the startup load. For some reason I was having a real mental block on this one since I had found several references to folks running separate 220v lines to each machine.

[Kerry Kling]

I have three 220 boxes off of one 20amp breaker. I used stranded 12 wire in EMT pipe. I run my Powermatic PM2000 and the Grizzly GO548Z dust collector at the same time with no issues. The band saw is plugged into the third outlet. I haven't tried running all three at once. Figured that would be pushing my luck. :-)

[Tad Capar]

Another good reason to run one circuit for dust collector and one for everything else is an ability to wire DC at the panel (or near it) to an "automator" that will turn the DC on as soon as one of the machines ( on other circuit) is turn on.