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Yo, Jake...

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  • Yo, Jake...

    (and Dave, et al, I'd like to ask about 240 service for four of my tools. Because of a cramped panel, I need to limit this to one outlet. I don't want the expense of a sub-panel, and I really don't need more 120 outlets.

    But the four tools vary widely in current draw. One is the new TS 2424; one is an air compressor (with an Emerson motor) that draws about 6.5 amps; one is a Jet jointer w/ a 1 hp motor; and a bandsaw whose data plate says 15.1 amps (all at 240v).

    I understand the efficency issues of restricting myself to the single outlet. Right now I'm focussed on the concern of using all those different tools on a 25 amp 240 circuit. Any electrical problems there?

    Thanks for your time and assistance.


  • #2
    First thing that comes to my mind, Joe, is Holey Cow! That's a big bandsaw! I'm making that at 3.5 to 4 horsepower? I usually recommend people wire their 3 horsepower cabinet saws (off the top of my head, I think they are 12 amp FLA) with 30 amp circuits, so I might suggest going higher than 25a. Otherwise, you may get some nuisance trips on startup, a bandsaw has a pretty big starting surge due to its design.

    Here's the way I would do it. I'm nothing like an Electrician, though. I would wire for the largest load and go wild. I see a lot of very precise sizing of 220v circuits, and it confuses me some. With only a couple exceptions, every 110v circuit in my house is 20 amps. Doesn't matter if I only plug a clock into it, it's still 20 amps.

    I don't see a difference for 220v. I know there is a NEC rule for direct attached circuits, but that obviously isn't yours.



    • #3
      Joe, I are an electrician and I still can't spell it! (Sorry, old joke). The National Electrical Code is indeed national but believe me it is enforced on a very local level. What will satisfy an inspector varies not only from state to state, city to city, but even from inspector to inspector. Anyway, I think you will be very unhappy with only one 240 volt circuit. Either you will have to loop all four of the machine's individual receptacles to the same source, (Not acceptable in these parts) or you will have cords laying all over the shop floor. The cost difference in my mind would not justify the later hassels. Find an electrician that needs a piece of furniture and go with the subpanel. Good Luck!


      • #4
        Joe, I think the guys have some good ideas. I would go back and check the plate on that bandsaw, most likely its 13 amps at 120V. I'm no electrician but if I were limited in the number of circuits I could run, I would place the air compressor on a dedicated circuit and then put the other tools on the other circuit. The air compressor tends to run when it wants, while the other tools get used one at a time. As with all things obey local codes!!!


        • #5
          My two cents worth:

          If you're going to the trouble of wiring a 220 (or 240) outlet back to your existing panel (which I gather has at least two adjacent breaker spaces open, but not much more), it isn't much more work to install a sub-panel in the shop. I'd run 30A 220, from which you can branch a couple of 20A outlets for your tools, and something bigger, if needed, for the compressor. (I'm assuming the compressor is single-phase.)

          If your question was, is there anything wrong with plugging a device into an outlet that is rated for far more current than your device draws, the answer is no. Circuit protection (i.e., fuses or breakers) is sized to protect the wire that is "south" of the protection.

          When figuring loads, remember to take into account "starting" load, which is typically 2 to 5 times running load. Smaller tools (using universal motors) generally have only a single rating, but larger motors have a significant starting current draw.

          Last: if you do install a sub-panel, remember that the neutral and ground buses are NOT bonded in the sub-panel.