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Capacitor on 1 1/2 hp motor of table saw

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  • Capacitor on 1 1/2 hp motor of table saw

    I have a very good 10 year old cast iron table saw. A few months ago I started having a problem with the motor. When I try to start it in my cold garage in the morning, it immediately trips the breaker and continues to do so until the air in the garage warms up significantly. I have replaced the switch, the power cord, the heavy duty extension cord, had the bearings packed, etc. Still does the same thing. I have discovered through trial and error that if I use a hair dryer blower on the motor to warm it up in the morning it works fine. I was wondering if it was possibly the capacitor that is causing the problem. You can probably tell that I am not an electrician, I'm a woodworker. The specs. on the motor are as follows: Brand-Rexon; Mod.-RM-323; Volt. 115/230; Amp.-12/6A; RPM-3450; Class A; 60 hz. The specs on the capacitor are: Motor Starting Capacitor; Cap 400 MFD; WV 125 VAC; Type 129. Would appreciate any help that you can provide me. Thanks in advance.

    arthurgimplowitz1@msn.com

  • #2
    Re: Capacitor on 1 1/2 hp motor of table saw

    It could be the capacitor and they aren't that much $ so it might be wise to just replace it. About how cold is your shop in the morning? I have in mind that the grease in the bearings my be so think that the motor just can't start and come up to speed in a reasonable time. With the power plug pulled, how much effort does it take to rotate the motor or blade some by hand? Try it cold and then also warmed up some. If your shop is below 35 or 40 F in the morning, I think you would do well to put some heat in it so that's it's not really cold when you want to work that day.

    If you want to replace the capacitor, I can help you find one. I will need the diameter and length of it. Does it have two standard quick (slide on) connectors?

    When you blow warm air at your motor are you heating mainly the capacitor or more the bearings and such?

    Try turning the motor by hand when cold and see if it takes much effort on your part. Another idea would be to remove the belt(s) and see if the motor will then start up like normal when cold. My first thought is to just replace the capacitor, but that won't fix it if the grease it getting too stiff-thick.
    Last edited by Woussko; 02-09-2007, 10:32 PM.

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    • #3
      Re: Capacitor on 1 1/2 hp motor of table saw

      check the bearings of the motor and the saw arbor, they may need some oil or replacment,
      Push sticks/blocks Save Fingers
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      • #4
        Re: Capacitor on 1 1/2 hp motor of table saw

        Does your capacitor look like this one? Click on it for a larger picture.
        Attached Files

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        • #5
          Re: Capacitor on 1 1/2 hp motor of table saw

          Thanks for your quick response to my question on the capacitor. I went out this morning and followed your advice. The temperature in my garage is about 50 degrees. (I live in Phoenix, Az). I turned the motor by rotating the saw blade and also by turning the drive belt. They both turned relatively easily as if there was no resistance due to hardening of grease. (Bearings were recently packed). The capacitor that I have looks like the one in your photo and has the clip-on terminals. The capacitor measures approx. 4" in length and the circumference is approx. 6". Would appreciate any information on where I can obtain a replacement capacitor. Thanks again for your help. I'll keep you informed of my progress.

          arthurgimplowitz1@msn.com

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          • #6
            Re: Capacitor on 1 1/2 hp motor of table saw

            The best place to find and get a motor starting capacitor would be WW Grainger, but they only sell to commercial customers. If you can give them a business PO that should work and pay cash for it. If you are just yourself, then look in your yellow pages for an electric motor repair shop. They should have one in stock that's close enough so it will work for you. You may need some electrical tape too. If the new one is smaller, wrap it with tape so it fits into the cover nice and snug. Be sure to put several layers of electrical tape over the connection end. Good luck and at 50F my bet is that the capacitor is bad. When the motor tries to start does it make a GRRRR sound until the circuit breaker trips?

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            • #7
              Re: Capacitor on 1 1/2 hp motor of table saw

              No, it trips the circuit breaker immediately. Also, in answer to you inquiry about whether I apply the blower heat to the motor or the capacitor, it seems to start more quickly when I concentrate the heat on the capacitor. I will check out Grainger for a replacement capacitor. Thanks again.

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              • #8
                Re: Capacitor on 1 1/2 hp motor of table saw

                At Grainger look at catalog number 4CU45. That one should work. More than likely it's smaller in size, but the specs check out. Today they are making them in smaller cans than the older ones. If necessary (out of stock on 4CU45), you can try a 4CU44 or 4CU32 which are close enough that they should work OK.

                Because you claim that heating up the capacitor helps, I would just replace it and I bet it works. Catalog cost on the 4CU45 is $6.44.

                http://www.grainger.com/Grainger/wwg...?ItemKey=4CU45

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                • #9
                  Re: Capacitor on 1 1/2 hp motor of table saw

                  We had a member have a similiar issue in early dec of 2006. Below you will find my post on how to test a capacitor.

                  Here try this, it is relatively easy; first, make sure the motor is unplugged in fact it is usually best if you pull the start cap to perform this test.

                  First discharge capacitor paper clip or screwdriver accross the probes. To check capacitor, set volt-ohm meter to RX 100 scale and touch its probes to capacitor terminals. If capacitor is OK, needle will jump to zero ohms, and drift back to high. Steady zero ohms indicates a short circuit; steady high ohms indicates an open circuit.

                  This method will help you determine whether the cap is dead; however, it is usually not very useful at determining whether it is weak or not. An alternate method is used to determine the latter. Good luck let me know if this helps.

                  A few years ago when I lived in Phoenix there used to be a place called Arizona Armature (south phoenix near sky harbour) which did fantastic work. I don't know if the are still in business that was over 10 years ago.

                  tgomez

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                  • #10
                    Re: Capacitor on 1 1/2 hp motor of table saw

                    Well, here I am back again at square one. Purchased a new capacitor at Grainger yesterday. Installed it in the afternoon. The saw started perfectly time after time. Thought that solved my problem. Went out this morning feeling sure that the motor would have no trouble starting in the 50 degree plus temperature in my garage, but to my dismay I still have the same problem. I now have a new power cord, new switch, new heavy duty extension cord, newly packed bearings in the motor, and still the same problem that I started with. I'm sure that if I physically warm the motor or wait until this afternoon when the temperature rises, it will once again work perfectly. Thanks to all for your suggestions. I am open to any other advice that may be out there short of replacing the motor since I know that the motor in itself is fine. Otherwise, I guess I'll just have to depend on my trusty hair blower to get my saw started. Funny, I never thought that a hair dryer would become the most important tool that I have in my shop. Thanks again.

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                    • #11
                      Re: Capacitor on 1 1/2 hp motor of table saw

                      art

                      Please try this and report:

                      Remove the belt(s) and then try starting up just the motor when it's cold. In addition, because the motor does run fine once warmed, it may well be something like the starting switch inside it. I doubt that's the case, but strange things do happen. If with the belt(s) off it still has starting problems, before replacing the motor, I would take it to an electric motor rebuilder. Most good size cities have such places.

                      For what this is worth, please tell about all the electricals in detail.

                      Breaker Ampere rating
                      Are you running your saw on 120 or 240 Volts?
                      What wire gauge and what length is your extension cord used with the saw?
                      What wire gauge and length is the power cord?
                      Is the receptacle (outlet) very far from your breaker panel?
                      It may be that there is a Voltage drop problem. Electric motors take loads of starting current for a few seconds. This can trip a breaker if the motor fails to get up to speed within a few seconds.
                      Does the motor grunt at all when it won't start, or does the breaker trip right as you flip the power switch?

                      Please tell all that you can and good luck with this. Just in case it comes down to motor replacement, with good info from the nameplate, I'm pretty sure one of us can find a good deal on a replacement that will be cheaper than trying to buy the exact replacement. A proper spec generic should work fine and for what it's worth a totally enclosed motor is a good idea on dust making machines.

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                      • #12
                        Re: Capacitor on 1 1/2 hp motor of table saw

                        Woussko,

                        Followed instructions in your latest EMail this morning when motor cool. Removed the belt and tried to start. Same results. Waited a few hours until the garage warmed up a bit (did not use hair dryer on motor) and tried to start again. Worked fine multiple times with belt still removed. Then I reattached the belt and tried again. Also started multiple times without any problem at all. Am enclosing as much of the information that you asked for that I could find.

                        Breaker Amperage rating-15A
                        120 Volts
                        Extension cord is 12G/25'
                        Power cord is heavy duty, polarized and 8' long
                        The receptacle is about 15' from the breaker panel
                        Motor does not grunt, the breaker trips immediately upon flipping the switch.

                        I'm sure that the motor will run fine for the rest of today. Tomorrow morning, when the motor is again cold, I will attempt to move the saw close to the wall receptacle and plug it directly into the receptacle without the use of the extension cord. I'll let you know what happens. Thanks. Art

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                        • #13
                          Re: Capacitor on 1 1/2 hp motor of table saw

                          art

                          Here's your problem. The starting current on a 1-1/2 HP motor running on 120 Volts will trip most breakers even when the motor is fine. You really need to upgrade everything. A 20 Amp. breaker, and a 20A 125V rated receptacle and be sure everything is connected with #12 or #10 wire. That should fix it. Be sure the only thing on that circuit is the table saw. By the way the extension cord being a 12-3 and only 25 feet should be OK and the same for the power cord. While the running current is OK the motor normally will take several times the rated running current to get it started. The best thing would be to run it on 240 Volt power but then you may not have that anywhere near the location you have the table saw in. Over time, it's a good idea to have an electricial install a sub-pannel (little breaker box) in your shop area. I've had this same problem myself. The upgrading of the electric system wasn't cheap but to me it was well worth every penny in the long run.

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                          • #14
                            Re: Capacitor on 1 1/2 hp motor of table saw

                            I forgot this. From the breaker panel to that receptacle be sure to use 12-2 with ground Romex or BX. If it has a 15 Amp. breaker it might be 14-2 and would need to be changed. Another idea would be to install a private receptacle beside your breaker panel just for the table saw if your 25 foot HD extension cord would make it. If not you might just get 50 feet (measure with tape measure and get an extra foot or two) of 10-3 type SOW cord and make up a super power cord for your table saw. Or get a 10-3 Heavy Duty extension cord and use that. You have several choices. Take a little time and think which will work out best for you. The main idea is to have #12 or better yet #10 wire all the way (from saw to breaker) and a 20 Amp breaker. You also really should use 20 Amp plugs, connectors and receptacles on this circuit. NEMA 5-20 or if you want, go with twist lock type NEMA L5-20 but that's really not needed and is extra $$$. For right now check the wiring from the breaker box to the receptacle. See if it has 12-2 or 14-2 on it. If 12-2 or maybe 12-3, then all you need for now is to change the breaker for the same brand & type but 20 Amp. and change the receptacle to a 20A 120V rated one. The circuit breaker is to protect the installed wiring and receptacle(s).

                            By the way in a garage or basement (especially if it's damp) be sure to use GFCI receptacles or circuit breakers. They can and do save people from getting zapped. Yes, you can get a 20A 125V rated GFCI receptacle. You may need a larger 4 x 4 box and special cover for it. It's your choice what you upgrade, but the 15 Amp breaker is just not gonna do for a 1-1/2 HP motor. When you do any heavy ripping of wood and make that motor work hard, it will trip.
                            Last edited by Woussko; 02-13-2007, 04:16 PM.

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                            • #15
                              Re: Capacitor on 1 1/2 hp motor of table saw

                              Originally posted by Woussko View Post
                              art

                              Here's your problem. The starting current on a 1-1/2 HP motor running on 120 Volts will trip most breakers even when the motor is fine. You really need to upgrade everything. A 20 Amp. breaker, and a 20A 125V rated receptacle and be sure everything is connected with #12 or #10 wire. That should fix it.
                              I rather doubt that is the problem here. That really wouldn't make any sense with the hot/cold symptoms he is experiencing. I ran my saw on a 15A for about a year with no problem and had my shop vac on the same circuit also running with no problems. I agree that running on a 20A would be better (and what I have now), but I don't agree that is his problem. I would continue to investigate the capacitor and any other motor suggestions that were provided here.

                              JMTCW....
                              Still enjoying all 10 fingers!

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