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Capacitor on 1 1/2 hp motor of table saw

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  • #16
    Re: Capacitor on 1 1/2 hp motor of table saw

    WW

    I agree to a point.

    It might be a very marginal problem and that the breaker just happens to trip unless the motor gets up to speed fast. 1/4 second can make a difference.

    If he has a receptacle on a 20 Amp circuit, maybe he can try cold starting the motor on that circuit. Another idea would be to install a 20 Amp breaker for the saw receptacle, and just give it a try, and then put back the 15 Amp breaker unless all wiring is #12 gauge on that circuit. In that case the 20 Amp breaker is fine. Sometimes breakers after time get to tripping too soon and simply replacing it with the same helps. I've had to do that a few times.

    Most likely the motor needs to be removed and taken to a motor rebuilding shop. They need to know that the problem is when it's cold in the shop. Without the motor here, I'm really just taking wild stabs in the dark.

    Art
    I would like to know about what happens when the extension cord isn't used. If it was here, I would put that motor in my freezer overngiht, then try to find out if it's real hard to rotate the shaft when real cold and also try starting it on my bench with it clamped down. Got to be careful of jumping motors....
    Last edited by Woussko; 02-13-2007, 06:39 PM.

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    • #17
      Re: Capacitor on 1 1/2 hp motor of table saw

      You may consider getting a current and voltage reading at the motor terminals via amp/voltage meter with this data and a motor curve you should be able to determine whether your motor is drawing too much current. You need to get the amp/voltage curve for your specific motor from the manufactures website. Take the readings you collect from the motor and plot them on the theoretical curve. If your dots are not on the curve then you have a motor issue if you are on the curve then your electricals whether it be your thermal overloads, breaker or wire gauge are likely to be the issue. I suspect your thermal overloads because a 20A circuit should be sufficient to drive a 1.5 HP motor. Keep in mind these small motors run on the flat part of the operating line so you should be drawing about 90-95% of faceplate with no load on it. If you find you have an motor issue as stated in my previous thread give the folks at arz armature a call. They used to be very helpful.

      I piece I forgot; when you use and extension cord you will experience a voltage drop; so to make up for the voltage drop you will notice an amp increase. I used to know all the voltage drops/foot/wire gauge but I have long since forgotten

      good luck

      tgomez
      Last edited by billie_bob; 02-14-2007, 12:36 AM. Reason: missing piece

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      • #18
        Re: Capacitor on 1 1/2 hp motor of table saw

        Good Morning Gentlemen,

        Here is the latest report in the saga of my non-starting cold motor. This morning, before trying anything else, I rerouted my extension cord from the outlet that I had been using (which was on a 15 amp breaker) to an outlet with a 20 amp breaker. With the drivebelt disconnected, the motor started immediately with no tripping of the breaker. I started it numerous times and it worked every time. I then reconnected the drive belt and repeated the same process. Same result, it worked like a charm. So, I now know that I either have to replace the 15 amp breaker to the outlet that I normally use to a 20 amp, or use another outlet that already has a 20 amp breaker. I can't thank you guys enough for the constant feedback that you have given me over the past few days. I probably would never have found the solution to the problem without your help. My only regret is that I did not find this forum sooner (before replacing the cord, extension cord, capacitor etc. Oh well, at least my saw has now been partially upgraded. If I ever have another electrical problem, I surely now know where to go to try and troubleshoot it. Let me know if I can ever help with a woodworking question. (which by the way, I have a lot more answers than I do about electrical). Till the next time. Thanks Again.

        art12576

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        • #19
          Re: Capacitor on 1 1/2 hp motor of table saw

          Art

          That is great news. Look at the wiring that runs from your breaker box over to the receptacle that you were using. You should see some numbers like 14-2 or 12-2 or 12-3 on it. Forget any letters. It will be one of the above. If you see 12-2 or 12-3 on it, then just install a 20 Amp breaker and you're set. If it's the steel jacket BX cable then you need a wire size gage. In that case try another 15 Amp breaker and take along the old one to be sure of proper matching. Over time I've found that motors (especially the 3450 RPM ones on saws and such) take a good bit of starting current. Anyway I'm glad that on the other circuit things did work for you. Please keep us posted, welcome to the forum and I'm sure in time you'll be helping us out.

          If the wiring has 14-2 on it, you need to stay with a 15 Amp breaker. Also remember to think safety. If you have a good battery powered work light, shut off the main breaker before removing the cover on your breaker panel. I kind of like your changing receptacles. The one you were using the saw on can be used for other things with lower starting current requirements. Maybe the shop vac or such.

          Above all else think and practice safety.
          Last edited by Woussko; 02-14-2007, 04:10 PM.

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          • #20
            Re: Capacitor on 1 1/2 hp motor of table saw

            Hi one thing to consider is mositure forming in the motor over night.
            Possible causing a earth or ground fault, which is why your circut breaker is tripping.
            50 dregee f is quite cool from my way of thinking.
            Hope this is of some help best regards Vic

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            • #21
              Re: Capacitor on 1 1/2 hp motor of table saw

              Many of the small motors can be very simply rewired to 240v. If you converted to 240v you could add a 2 pole 15a breaker in the panel and use the #14 wire if there are no other 120v devices on that circuit. You would also need a to convert the extension cord and receptacle to 240v for safety purposes. When you double the voltage to 240v you will drop the amperage by 1/2 and this will effectively cure any excessive voltage drop. The voltage drop will increase amperage draw and is not good for the motor. When it is 50 deg you also may have a lower voltage due to all the neighbours running their electric heaters. (is that what is used for heat in your area?) If you can run the motor on 240v it is the way to go.

              Use this to calculate voltage drop. Half the distance is the distance you are from the panel.
              http://www.csgnetwork.com/voltagedropcalc.html

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              • #22
                Re: Capacitor on 1 1/2 hp motor of table saw

                One thing is note: If you do convert to 240 Volts and have to use the white neutral as L2 (the other hot) be sure to put red tape on both ends. You don't need a neutral as long as you have a good grounding conductor. For any motor 1 HP and over it is a good idea to run it on the highest Voltage it is made to run on. Less Voltage drop and lower overall current draw. There are special estension cords made up for 240 Volt use, but they are costly and a bit hard to find. Changing the plug and connector and receptacle would work, or maybe just install a nice long power cord on the table saw.

                Moisture sure is something to think about. It might be a good idea if you stay with 120 Volts, to install a GFCI receptacle or use an in-line GFCI.

                GFCI = ground fault circuit interupter. They can and do save us from getting zapped.

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                • #23
                  Re: Capacitor on 1 1/2 hp motor of table saw

                  Another thing to remember for the next time: Your motor may have a centrifugal switch on it which switches the capacitor in and out of the circuit for starting. I just had the same problem on my 40-year-old Craftsman table saw (they just don't make 'em like they used to), and simply replacing the capacitor solved the problem. However, if your centrifugal switch is hanging up in the "running" position, your motor won't start. Also, if it's hanging up because of thickening lubricant, heating it might free it up. You've got to disassemble the motor to check it, but it should be pretty obvious how it works. Spritz it with degreaser, compressed air, and WD-40 and make sure it moves freely, and you should be good to go.
                  Last edited by AnotherMikey; 03-07-2007, 05:04 PM.

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                  • #24
                    Re: Capacitor on 1 1/2 hp motor of table saw

                    Since your motor is drawing 12 amps and slightly more when the motor is cold, you may be maxing out your circuit breakers capacity. If its a 15 amp circuit breaker and you have other loads on that same circuit , such as lighting, especially cold ballasts in your work area will draw slightly more when their first turned on in a cold work area. If you have fluorescent lights on the same circuit this could be adding to the load . Try plugging the table saw into a known 20 amp circuit without any other loads on it and see what happens. Also the length of your extension cord and the wire gauge will affect the performance of the motor. A minimum of 50' with a 14 gauge extension cord or 12 gauge wire with any length exceeding 50' will help keep voltage drop to a minimum which in turn will keep amperage from increasing. Let us know what happens, Thanks Gary

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