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  • Time for new Air Compressor?

    I have a home use 20 year old Craftsman 3 hp air compressor. Oil level ok. It is now tripping my 20 amp circuit breaker. Anything I can do or is it time for a new one?

  • #2
    Re: Time for new Air Compressor?

    i would start with taking the belt off the pulleys and plug it in and see if it still trips the breaker. also then you can turn the compressor pulley by hand and see if its stuck.
    another thing that can cause problems is if the compressor is in an unheated garage and the wiring isn't heavy enough, the cold oil makes it harder for the compressor to spin and will blow the breaker too.

    Comment


    • #3
      Re: Time for new Air Compressor?

      DamageInc,

      I agree with MAS, you really need to identify what is causing the compressor to overload the circuit.

      Key to determining your need of a replacement compressor would surely depend on how well the unit is performing and of course, how well you've maintained it. So when it runs, is it supplying the air you need, no leaks anywhere, tank in good condition (can we presume that you've diligently kept the condensate drained from the tank so no significant corrosion exists), etc.?

      Obviously, there's something that is causing too much load on start-up. In addition MAS's instructions on the belt and the oil viscosity. Cold oil is too "thick" and causes too much load on the motor as it tries to turn the compressor).

      Likewise, you need to check the relief valve to ensure that it is properly functioning. (This is NOT the safety valve, but the valve that relieves the pressure between the compressor and receiver tank. It is usually mounted on or near the pressure switch) When the compressor is shut down, this valve releases the air pressure between the cylinder and the tank... if it fails to clear the line, then the compressor is trying to start with pressure already in the cylinder, which is sure to cause and overload. As mentioned, the pressure relief valve is usually in the line that runs between the pressure switch and the tank... it can get dirty and thus fail to function properly.

      I hope this helps,

      CWS

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      • #4
        Re: Time for new Air Compressor?

        OK. without the belt the motor runs great. Hand pulling the compressor wheel seems fine, I can feel the tug and release as the piston (i guess) goes up and down. I found the relief valve (its has a small needle type relief) and cleaned it. Reconnected everything and it seems the on/off switch and the sensor to the relief valve are not working correctly. I will look into that and see whats inside.
        Thanks

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        • #5
          Re: Time for new Air Compressor?

          sounds like to me that either the motor is worn out (20 year old)

          or

          you have to replace the breaker. they wear out too.

          if you have an amp meter (the kind with the loop/jaws) see how many amps it's pulling at start-up.

          if the motor is pulling more amps than the breaker can provide, it might be the motor.

          if the motor is pulling less than the breaker is rated for, it might be the breaker.

          Vince

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          • #6
            Re: Time for new Air Compressor?

            I'm with Vince, check that breaker because they go bad!

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            • #7
              Re: Time for new Air Compressor?

              OK
              In the ON/AUTO mode the switch hates 55-60 psi which is the setting for turning back on. If the switch is activated at 55-60 psi it goes straight to throwing my breaker switch, it wont even attempt to turn the motor. If the psi is below 55 turns on fine and runs great and will go all the way to 100 psi, which is the cutoff. If I turn it off and bleed it down to 40 it activates fine and goes to 100 again. If I bleed it to 55psi and switch it back on, no-way, the breaker overloads. If I bleed it down quickly in the ON position to 55psi its 50-50 that the breaker will blow. If I bleed it down slowly (normal operation) in the On position to 55 psi, the breaker blows.
              I took the cover off the switch and everything looks clean and corrosion free, heck it looks brand new inside.

              Thanks for any advise or where to find a replacement switch.

              Comment


              • #8
                Re: Time for new Air Compressor?

                I dont think its my breaker because I went back to using the 15 amp that is in the garage for the above testing (about 30 times on/off). The 20 amp is the plug in the house for the washing machine, so using that is not my long term solution.
                thanks

                Comment


                • #9
                  Re: Time for new Air Compressor?

                  Capacitor start motor? My guess is bad cap on the motor. Knowing Sears, it is probably sealed in and not serviceable.

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                  • #10
                    Re: Time for new Air Compressor?

                    Originally posted by JTROANOKE View Post
                    Capacitor start motor? My guess is bad cap on the motor. Knowing Sears, it is probably sealed in and not serviceable.
                    Dang! thats what I was gonna say!

                    can you just adjust the startup pressure down and live with it?
                    This is my reminder to myself that no good will ever come from discussing politics or religion with anyone, ever.

                    Comment


                    • #11
                      Re: Time for new Air Compressor?

                      Capacitor start motor. Now where would I find that? And if I did, how would I tell if it was bad? I found a replacement for the pressure switch for $55, but if thats not the problem then Im still stuck with a 20 yo compressor that blows. I might try resetting the startup pressure as ACE advises, but I will need to find my manual online.
                      thanks

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                      • #12
                        Re: Time for new Air Compressor?

                        i was discussing this an electrician that works for the same company i work for. he suggested checking the capacitor.

                        i'll ask him how one goes about doing such a test. it's probably got something to do with resistance. i'm not that familiar with electrical type stuff yet.

                        Vince

                        get/buy a used/new motor. 20 years service. that's pretty good. original cost divided by 20yrs = one darn good compressor.

                        Comment


                        • #13
                          Re: Time for new Air Compressor?

                          You need to check if the compressor is not stuck. somethings is surely overloading the compressor. Call an expert if you cannot do it on your own.
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