Any advantage to switching tools to 220V?

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  • seahawk
    Forum Newbie
    • Oct 2012
    • 54
    • Maryland
    • BT 3000 x 2!

    Any advantage to switching tools to 220V?

    Several of my stationary tools, the dust collector, RAS, Bandsaw and Shopsmith, can be wired for 110V or 220V. My shop (Garage) already has a sub panel with 220 available. In several places, I have seen some dual voltage tools deliver more HP when operated with 220V. Same motor, just using the existing, motor specified, alternate wiring arrangement (and plugs outlets of course). Have any of you rewired a tool from 110V to 220V, and seen a useful benefit?
  • LCHIEN
    Internet Fact Checker
    • Dec 2002
    • 20920
    • Katy, TX, USA.
    • BT3000 vintage 1999

    #2
    My first comment is that all US power is going to be 120 V and 240 V now as the target from the power company, with a +/-5% target which means you'll generally see 114 to 126 V. and 228 to 252 V

    I usually have 122 to 123 volts.

    The Chief advantage of the higher voltage is that you can only get to 1800 W with 120 V 15 A circuit or 2400 W with 20 A circuit, but you can get 3600 W with a 15 A 240 circuit which is about 4.8 HP max

    Generally dual voltage devices (motors and transformers) parallel or series two windings. So the power should be should be the same either configuration provided the circuit can supply enough amperage. I don't know why one would not get the same power with either winding config and adequate current. The only thing I can fathom is that of the unit is rated to 2400 W which is 10A at 240 then you'll be limited by your 15 A circuit breaker to 1800 W if you use 120 V. Its not a motor limitation.

    other than that the only reason 240 V is better is more power being available.
    There is a small benefit on the order of a percent or two or three running 240 V where the line loss due to lower current counts for anything.if you are trying to eke out every last bit. Frankly without precise instruments I doubt you can tell the effect of 0-3% power difference.

    If you are happy with the performance of your tools at 120 V, changing to 240 V will make them work pretty much exactly the same. There is no magical 2x improvement, or even 1.5x or even 1.25x improvement. Not even 1.1x or 1.05x.
    Last edited by LCHIEN; 11-13-2020, 01:06 PM.
    Loring in Katy, TX USA
    If your only tool is a hammer, you tend to treat all problems as if they were nails.
    BT3 FAQ - https://www.sawdustzone.org/forum/di...sked-questions

    Comment

    • mpc
      Senior Member
      • Feb 2005
      • 979
      • Cypress, CA, USA.
      • BT3000 orig 13amp model

      #3
      For a given power level (Watts or Horsepower) using a higher voltage reduces the current draw (amperage) needed. Lowering the current reduces voltage losses at poor connections or along wires. All wiring has a little resistance; the thicker the wire the smaller the resistance typically (assuming same type of conductor - e.g. copper). A power tool that is wired for 120 volts and requires 15 amps will draw half that = 7.5 amps when wired for 240 volts. If the wiring, outlet, and plug have 0.1 ohms total resistance (which represents clean/good connections... old/oxidized power outlets and plugs would be higher) the voltage "lost" before the power tool = 15 amps * 0.1 ohms = 1.5 volts. Not huge... but on a 240 volt circuit only 7.5 amps * 0.1 = 0.75 amps would be lost: half as much. If that resistance were higher - say 0.5 ohms - the voltage losses would be 7.5 volts on the 120 volt & 15 amps circuit and 3.75 volts on the 240 volt circuit. 7.5 volts out of 120 to start with is a loss of 6%. 3.75 volts out of 240 is 1.6% loss so dirty connections have far less effect on the 240 volt version.

      Also, power (in Watts) = current in amps ^2 * resistance in ohms
      Thus, 15 amps across 0.1 ohms = 15*15*0.1 = 22.5 watts being dissipated across that 0.1 ohm connection.
      At 7.5 amps, the power loss is a quarter as much: 5.6 watts. Much less heat.
      Those power losses would be 5 times higher if the outlet + plug have 0.5 ohms of resistance; i.e. almost 100 watts would be converted to heat on a 120 volt circuit!

      The windings of a motor also make heat due to current flowing through them; at 240 volts the current is cut in half so the power/energy converted to heat inside the motor is reduced considerably.

      The energy lost in wiring and bad connections is a function only of the current flow in the wiring and the wiring resistance; it is not due to the actual voltage level being carried. That's why power transmission lines use very high voltages (tens of thousands of volts) so the amperage can be much lower for a given total Wattage. The voltage lost along the long transmission line is kept low by keeping the amperage low. Transformers are used to step the voltage UP at the start of transmission lines, and transformers step the voltages back down near your home. Transformers can be quite efficient - enough so that their losses are less than what would result if transmission lines used 240 volts at high amperages. Those very high voltages, and lower currents, also allow smaller (and thus cheaper) wires to be used for the transmission lines.

      So, a power tool that can be wired for 120 or 240 volts can produce the same net horsepower assuming the amperage isn't limited by circuit breaker capacity... but any resistance in house wiring, tool wiring, outlets, etc. will have more effect on the 120 version. Many countries use 220 to 240 volts as the standard for home outlets; the US uses half that voltage to reduce chances of serious injury from electrocution at the expense of some efficiency and increased heat production (energy lost) from degraded connections. As noted by Loring, you probably won't see a perceptible performance difference if the wiring, outlets, plugs, etc. are in good condition... otherwise you'll see small performance differences and those "not quite good condition" connections will generate higher temps when the tool is wired for 120 volts.

      mpc
      Last edited by mpc; 11-12-2020, 10:57 PM.

      Comment

      • woodturner
        Veteran Member
        • Jun 2008
        • 2047
        • Western Pennsylvania
        • General, Sears 21829, BT3100

        #4
        Great responses for the EE's ;-)

        To help interpret for those whose eyes may have glazed over :-)
        - For higher HP motors, 220 VAC may allow you to use a smaller breaker and wire size
        - For motors that are OK on a 20 A breaker at 120 VAC, for wire runs less than 50' or so, no real benefit to switching to 220 VAC. There will be slightly greater loss in the lines, but it's so small it does not matter
        - If the concern is lights dimming when you turn on the tool, increase the size of the wire, it's the inductance of the wire that causes that issue on startup rather than the motor voltage.
        --------------------------------------------------
        Electrical Engineer by day, Woodworker by night

        Comment

        • leehljp
          Just me
          • Dec 2002
          • 8429
          • Tunica, MS
          • BT3000/3100

          #5
          Originally posted by mpc
          The energy lost in wiring and bad connections is a function only of the current flow in the wiring and the wiring resistance; it is not due to the actual voltage level being carried. That's why power transmission lines use very high voltages (tens of thousands of volts) so the amperage can be much lower for a given total Wattage. The voltage lost along the long transmission line is kept low by keeping the amperage low. Transformers are used to step the voltage UP at the start of transmission lines, and transformers step the voltages back down near your home. Transformers can be quite efficient - enough so that their losses are less than what would result if transmission lines used 240 volts at high amperages. Those very high voltages, and lower currents, also allow smaller (and thus cheaper) wires to be used for the transmission lines.
          mpc
          Thanks for this, particularly the bold above. I think I have read that a hundred times or more over the years, but in more technical terms and just dismissed it as being over my head. Now, voltage, amperage and wattage make pure sense to me. I can use formulas but they make no sense to me until I see the PURPOSE and the interactive relationship between them. I have to be able to mentally visualize it.

          I look at transmission lines all the time and wonder how in the world those small lines can carry so much power, especially when I see larger lines going from a pole to a house or shop. For some reason, I never thought of the power lines locally as being 10's of thousands of voltage. Now it makes sense and I understand the amp/volt/wattage formula. Got it.

          Hank Lee

          Experience is what you get when you don't get what you wanted!

          Comment

          • Carlos
            Veteran Member
            • Jan 2004
            • 1893
            • Phoenix, AZ, USA.

            #6
            I've converted everything I can to 240v except the drill press. With tools that need just a bit more power, like my 1.75HP bandsaw, there was a small but very noticeable difference. Dual-volt things like the plasma cutter can occasionally klll the breaker on 120, but never on 240v.

            Comment

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