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  • 110v vs 240 v

    Hi
    I have the rigid 3650 table saw and love it but I am going to be doing some rewiring of my garage and would like to know if there are any benefits to running my saw in 240v as opposed to the stock 110 it is now. Is it worth the effort to put a 240 outlet just for the saw? I know the outlet could then be used for a welder or DC but I currently dont have either and I dont believe my panel would be able to handle 2 240 outlets anyways without upgrading to a 150 or 200 amp service.

    Thanks for any and all help and advice

  • #2

    Re: 110v vs 240 v

    Re: 110v vs 240 v

    What an electrical device needs to run is watts. Watts are volts multiplied by amps. If you double the voltage you halve the amperage to get the same amount of watts (same amount of power). This means less current has to flow, so the wiring can be skinnier and still do the job. If the saw is currently wired with a gage of wire sufficient for its needs, then there is no benefit to switching to 240V. If it was barely getting by with the wire it's currently using then it could be a minor benefit.
    Last edited by Mike in Orangeville; 11-15-2008, 05:00 PM.
    Mike in Orangeville, ON
    http://ifonlyyouwood.blogspot.com/

    SPCHT

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    • #3

      Re: 110v vs 240 v

      Re: 110v vs 240 v

      Any large motor will benefit from a 240 connection, so I you can I suggest you add it. When I did my shop the only 240 volt thingy I had was a table saw. I put a plug in the ceiling in the centre of the garage with a 240 and two 120 plugs on the same two breakers. All the tools in the centre of the shop run on the same breaker, but I can't use (say) two table saws, band saw, planer and jointer all at the same time, so it is OK.

      I have used the big saw on 120 and it works much better on 240.

      I also put a total of six plugs around the walls about waist high for all the other stuff. Now I wish I had put one on the big door too.
      In an age when scientists are creating artificial intelligence, too many of our educational institutions seem to be creating artificial stupidity. - Thomas Sowell

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      • #4

        Re: 110v vs 240 v

        Re: 110v vs 240 v

        I just converted my ridgid tablesaw to 240V. I can't say that I've noticed a difference yet but I have not used it much.

        I've read on other forums people saying that the motor runs smoother and has more power but I can't say for sure if that's true.

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        • #5

          Re: 110v vs 240 v

          Re: 110v vs 240 v

          This question comes up every two to three months it seems. Doesn't anybody ever try using the search or tag feature?

          Or how about looking in the sub-forum dedicated to electrical issues, where this thread probabbly belongs in itself.
          Kevin

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          • #6

            Re: 110v vs 240 v

            Re: 110v vs 240 v

            It's not worth putting a 240v line in unless your current 120v line is struggling....lights dimming, saw is slow to come up to speed. etc. If you've got 240v already available, then there's no harm, and might be some benefit....240v tends to have less voltage loss at peak current draw, like startups and recovering from heavy load.

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            • #7

              Re: 110v vs 240 v

              Re: 110v vs 240 v

              Originally posted by scott in rochester View Post
              It's not worth putting a 240v line in unless your current 120v line is struggling....lights dimming, saw is slow to come up to speed. etc. If you've got 240v already available, then there's no harm, and might be some benefit....240v tends to have less voltage loss at peak current draw, like startups and recovering from heavy load.
              Right. At times of heaviest draw the increased resistance of a smaller wire causes a voltage drop. If the wire is heavy enough for 120V in the first place then this isn't an issue, but if the saw was improperly wired in the first place, or if it's a cheap Chinese motor with windings too thin to reasonably run on 120V, anyway, then you will see a difference. A decent quality dual-voltage motor, wired properly, will run the same on 120V or 240V.
              Mike in Orangeville, ON
              http://ifonlyyouwood.blogspot.com/

              SPCHT

              Comment


              • #8

                Re: 110v vs 240 v

                Re: 110v vs 240 v

                Originally posted by Mike Graham View Post
                ... or if it's a cheap Chinese motor with windings too thin to reasonably run on 120V, anyway, then you will see a difference ...
                If "thin" refers to the gauge of the wire it makes no difference since the current in each winding is exactly the same whether it is running off 120 or 240V. In the 120V case the 2 windings are in parallel and in the 240V case the 2 windings are in series. Each of the 2 windings has 120V across it regardless of the configuration.

                billh

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                • #9

                  Re: 110v vs 240 v

                  Re: 110v vs 240 v

                  Originally posted by billh View Post
                  If "thin" refers to the gauge of the wire it makes no difference since the current in each winding is exactly the same whether it is running off 120 or 240V. In the 120V case the 2 windings are in parallel and in the 240V case the 2 windings are in series. Each of the 2 windings has 120V across it regardless of the configuration.

                  billh
                  So tell me, if the windings are in series at 240 volts, how come my motor is 12 amps at 120 volts and 6 amps at 240 volts? As somebody said earlier, you get the same watts.

                  In series the same current must flow through both does it not?

                  I don't know how the motor is wired inside, I only know how to switch it from 120 to 240, or I did when I switched it. The picture and instructions are inside.
                  In an age when scientists are creating artificial intelligence, too many of our educational institutions seem to be creating artificial stupidity. - Thomas Sowell

                  Comment


                  • #10

                    Re: 110v vs 240 v

                    Re: 110v vs 240 v

                    Originally posted by Gene45 View Post
                    So tell me, if the windings are in series at 240 volts, how come my motor is 12 amps at 120 volts and 6 amps at 240 volts? As somebody said earlier, you get the same watts.

                    In series the same current must flow through both does it not?

                    I don't know how the motor is wired inside, I only know how to switch it from 120 to 240, or I did when I switched it. The picture and instructions are inside.
                    Because it's alternating current. In 110 V the power line (L1) goes to one end of each winding, The neutral line (L2) goes to the other end of each winding. There is 110V at each winding and each draws 6 amps for a total of 12 amps at L1.
                    In 220 you have a line (L1) at one end of one winding and one line (L2) at one end of the other winding and the other two winding ends are joined together. The windings draw 6 amps each and you have 6 amps at L1 and 6 amps at L2. You are still drawing a total of 12 amps.
                    Because it's AC, the current alternates at L1 from power to neutral at 60 times per second. L2 is out of phase with L1 and alternates opposite. When L1 is power, L2 is neutral and vise versa.
                    HTH
                    J.P. Rap Mount Hope Ont.
                    Carpe Ductum (Seize The Tape)


                    "In this world, you must be oh so smart, or oh so pleasant." Well, for years I was smart. I recommend pleasant. Elwood P. Dowd

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                    • #11

                      Re: 110v vs 240 v

                      Re: 110v vs 240 v

                      Originally posted by billh View Post
                      If "thin" refers to the gauge of the wire it makes no difference since the current in each winding is exactly the same whether it is running off 120 or 240V.
                      True. I didn't have my brain engaged when I typed that.
                      Mike in Orangeville, ON
                      http://ifonlyyouwood.blogspot.com/

                      SPCHT

                      Comment


                      • #12

                        Re: 110v vs 240 v

                        Re: 110v vs 240 v

                        Originally posted by Gene45 View Post
                        So tell me, if the windings are in series at 240 volts, how come my motor is 12 amps at 120 volts and 6 amps at 240 volts? As somebody said earlier, you get the same watts.

                        In series the same current must flow through both does it not?

                        I don't know how the motor is wired inside,...
                        Dual-voltage motors typically have 2 coils plus the start winding coil which doesn't matter for this discussion. EDIT: This may not be totally true since in the 240V case the extra start winding current does flow through one of the run windings since the voltage has to be dropped to 120V (the start winding is always 120V so it can be used in the 120V connection as well. The start winding is a lower inductance, higher resistance coil so it does not provide the same magnetic field as a run winding.

                        For 120V operation the 2 coils are connected in parallel. The hot wire goes to one end of each winding and the neutral goes to the other end of each winding. Since each coil draws 6A there is a total current of 6A+6A=12A. The "power" is 12Ax120V=1440W. This is good enough for a simple discussion but being AC with a power factor it isn't quite correct.

                        For 240V operation the 2 coils are connected in series. There is twice the voltage but also, since they are in series, twice the impedance so the current remains the same at 6A. The coils have equal impedance so the voltage divides equally across each at 120V per coil (120V+120V=240V). A neutral is not required in this type of connection. The "power" as calculated above is 6Ax240V=1440W, exactly the same.

                        The heating losses in the motor from the resistance of the winding wire, the so-called "I-squaredR" losses are if we assume that each winding has a resistance of R ohms:
                        For 120V, 6Ax6AxR=36R watts. Since there are 2 coils in parallel the total loss is 2x36R=72R watts.

                        For 240V, the 2 coils in series make the total resistance inside the motor 2xR so the loss is: 6Ax6Ax2xR=72R watts, exactly the same.

                        This shows you do not decrease the resistive heating losses inside the motor by connecting it to 240V - which is often in the back of one's mind when first contemplating changing the voltage.

                        As pointed out the main benefit of using 240V is reducing the voltage drop on the supply wire from the panel by a factor of 2 and if the supply wire is sufficiently large/short then the voltage drop is too small to be a concern.

                        billh
                        Last edited by billh; 11-16-2008, 10:28 AM. Reason: Added startwinding coil edit.

                        Comment


                        • #13

                          Re: 110v vs 240 v

                          Re: 110v vs 240 v

                          If you are interested in motor internal wiring and the colour codes used for the leads (be careful, your motor may or may not conform) here is a handy document with schematics of motor internal configurations.

                          Save the PDF document to your hard-drive since who knows how long the link will be available.

                          http://www.akmcables.com/MotorWiring.pdf

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                          • #14

                            Re: 110v vs 240 v

                            Re: 110v vs 240 v

                            Thanks billh, that makes sense. I guess I should have read yur first post more closely.
                            In an age when scientists are creating artificial intelligence, too many of our educational institutions seem to be creating artificial stupidity. - Thomas Sowell

                            Comment


                            • #15

                              Re: 110v vs 240 v

                              Another 240 v Advantage

                              The other reason to go 220V is that for the same guage of wiring you can draw twice the number of watts.

                              I.E. Standard house wring is normally rated for 15A @ 110V. If you use the same wire in a 220V circuit you can still use 15A. 15A @ 110V ~ 1650W, 15A @220V ~ 3300W.

                              That means you can run a bigger motor without running special wiring.

                              As far as the same motor running at 110V or 220V I don't think there is much difference, the windings can only handle so many watts, whether they come in as 110V or 220V doesn't make much difference.

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