Ask Me Help Desk

Ask Me Help Desk (https://www.askmehelpdesk.com/forum.php)
-   Heating & Air Conditioning (https://www.askmehelpdesk.com/forumdisplay.php?f=150)
-   -   A/c condenser fan motor stalls (https://www.askmehelpdesk.com/showthread.php?t=377144)

  • Jul 18, 2009, 04:58 PM
    cesar44
    a/c condenser fan motor stalls
    I do maintenance and repairs on some residential properties. Couple of weeks ago I installed a condenser fan motor and blade with a new Emerson 1860 48Y, 1/4HP,
    208-230V, 1075RPM. The a/c unit is a Day & Night, split, 3 ton, and the previous motor went bad after 10 years).
    The new motor was working fine but now stalls after 1/2 hour operation. I wait until the motor cools off and it will restart again for another 1/2 hour and it will stop again.
    I also replaced the capacitor with a 40+5MFD/370V dual run capacitor.
    No doubt that the motor is overheating, but I can't find the reason why.
    When the motor runs the unit cools the house fine.
    I'm not sure if the capacitor is the right one, or the blade pitch has something to do with it.(the angle of the pitch is a few degrees grater than the blade removed)

    Can somebody help me with this? It will be greatly appreciated.
  • Jul 18, 2009, 08:02 PM
    wmproop
    on the side of the new motor is written what capicitor that is needed,, that size only for the motor only,, leave the original installed for the compressor==2 seporate capicitors
  • Jul 18, 2009, 09:05 PM
    hvac1000
    If you make sure the capacitor is correct and GOOD then it is possible the higher pitch fan blade can cause a problem. When you go out of the design parameters on fan blades any additional pitch can and will cause problems.
  • Jul 19, 2009, 06:46 AM
    cesar44
    Thank you all for the prompt response!! I have additional information on this motor that may be important. The label calls for a PERM SPLIT CAP, 5mfd/370V. The one I got from the supplier is a DUAL RUN CAPACITOR 40+5MFD/370V.
    Do you think that using a dual run cap instead of a perm split cap as the label indicates will cause the motor to overheat?
    Thanks again for all your help!!
  • Jul 19, 2009, 10:53 AM
    hvac1000
    The 5 MFD is used for the motor so since 5 MFD = 5 MFD I do not believe that is the problem as long as you have it wired correctly to used the 5 MFD side of the capacitor for the fan motor.
  • Jul 19, 2009, 11:47 AM
    cesar44
    Quote:
    Originally Posted by hvac1000 View Post
    The 5 MFD is used for the motor so since 5 MFD = 5 MFD I do not believe that is the problem as long as you have it wired correctly to used the 5 MFD side of the capacitor for the fan motor.
    Thanks again for your answer. I checked the connections to the CAP as follows: White wire to C, Brown wire to Fan, Black wire to Black wire side of starter, an existing yellow small wire that goes from the White wire side of starter to C at the CAP. (the brown/white wire from the new motor not used).
    I'm also thinking about something that I failed to check. The property in question is 60 miles away so I'm trying to get as much information as possible before I go back Monday.

    Will the motor still run with only 110V if one of the fuses at the service panel blew out?
    I thought that a 208V cannot run on 110V, but I heard that it can still run on 110V but it will overheat and immediately stall. Is it possible?
  • Jul 19, 2009, 09:51 PM
    hvac1000
    Will the motor still run with only 110V if one of the fuses at the service panel blew out?

    Not if it is a 208/220/240 motor. It needs both legs of power
  • Jul 20, 2009, 12:52 AM
    cesar44
    Quote:
    Originally Posted by hvac1000 View Post
    Will the motor still run with only 110V if one of the fuses at the service panel blew out?

    Not if it is a 208/220/240 motor. It needs both legs of power
    I'm trying to check all possibilities. If the condenser fan motor works well when cooled, the cap is good, the starter works fine, and once the unit starts the house gets cooled fine, until the fan motor overheats and stalls. Is it possible that the compressor may be getting bad and increase the amps at the starter? When the fan motor stalls, I can hear a humming sound until I shut the unit off.
    The other thing remaining is the thermal start kit. Can this part also be the cause for the overheating when going bad?
  • Jul 20, 2009, 04:05 AM
    hvac1000
    The new motor was working fine but now stalls after 1/2 hour operation

    The motor will have the exact type and value of the required capacitor listed on it along with the exact wiring diagram.

    The motor HP is designed for the SAME size and PITCH blade that was originally installed on the unit. When you go to a higher pitch blade you usually have to go with a larger or HIGHER HP motor.

    So if the motor is calling for a 5 MFD capacitor and you have a 5 MFD capacitor installed and wired correctly as per the instructions on the motor then the problem is with the fan blade that is not the same pitch as was originally installed.

    If you have a Amprobe to measure the current draw you will see that the fan blade you now have is OVERLOADING the motor.

    WHY ARE YOU FIGHTING A Losing SITUATION. You keep posting when the answer has already been given to you. CHANGE THE FAN BLADE to the correct one OR Change the motor to a higher HP one. It is your choice. I gave you the solution in my first post to you. IT is the fan blade.

    The reason the motor runs for about a 1/2 hour is the fact that the overload condition brought on by the WRONG fan blade is of a small amount. This small amount of higher current draw takes a short while (1/2 hour or there abouts) to cause the internal overload on the motor to trip. If it was not for this internal overload built into the motor you would have burnt up the new motor by now. Quit playing around causing the motor to trip because of the WRONG fan blade because after so many trips on the overload it might not reset and you will be buying another new motor. Motor warrentys do not cover abuse and you are abusing the motor.

    FIX the problem,change the fan blade to the correct size,rotation, and pitch or get a bigger motor.

    Now all this is taking into account that you wired the motor and capacitor correctly as stated on the motor wiring diagram on the side of the motor. I am not there to see or test the problem but I have been doing this for way to many years to know there is NO magic cure because you are going to have to change something to get it to work correctly.
  • Jul 20, 2009, 06:54 AM
    cesar44
    Quote:
    Originally Posted by hvac1000 View Post
    The new motor was working fine but now stalls after 1/2 hour operation

    The motor will have the exact type and value of the required capacitor listed on it along with the exact wiring diagram.

    The motor HP is designed for the SAME size and PITCH blade that was originally installed on the unit. When you go to a higher pitch blade you usually have to go with a larger or HIGHER HP motor.

    So if the motor is calling for a 5 MFD capacitor and you have a 5 MFD capacitor installed and wired correctly as per the instructions on the motor then the problem is with the fan blade that is not the same EXACT pitch as was originally installed.

    If you have a Amprobe to measure the current draw you will see that the fan blade you now have is OVERLOADING the motor.

    WHY ARE YOU FIGHTING A LOOSING SITUATION. You keep posting when the answer has already been given to you. CHANGE THE FAN BLADE to the correct one OR Change the motor to a higher HP one. It is your choice. I gave you the solution in my first post to you. IT is the fan blade.

    The reason the motor runs for about a 1/2 hour is the fact that the overload condition brought on by the WRONG fan blade is of a small amount. This small amount of higher current draw takes a short while (1/2 hour or there abouts) to cause the internal overload on the motor to trip. If it was not for this internal overload built into the motor you would have burnt up the new motor by now. Quit playing around causing the motor to trip because of the WRONG fan blade because after so many trips on the overload it might not reset and you will be buying another new motor. Motor warrentys do not cover abuse and you are abusing the motor.

    FIX the problem,change the fan blade to the correct size,rotation, and pitch or get a bigger motor.

    Now all this is taking into account that you wired the motor and capacitor correctly as stated on the motor wiring diagram on the side of the motor. I am not there to see or test the problem but I have been doing this for way to many years to know there is NO magic cure because you are going to have to change something to get it to work correctly.
    Before going back to repair the unit I wanted to have all the other possible things checked. What created my doubt was that on another condenser unit(Coleman), with the same 1/4HP motor and 1075RPM, the blade has the same pitch as the new one I replaced on the Day & NIght unit and it works fine. But I will follow your advise and I will replace the blade.
    Thanks again for all your answers!! I will let you know how it worked out.
  • Jul 20, 2009, 07:24 AM
    hvac1000
    The condensers could have a different draw pressure through the coils which would explain the difference or the position of the blade in the fan shroud can make a difference also.
  • Jul 29, 2009, 04:35 PM
    cesar44
    Hello Hvac1000, and thank you for your help! You were absolutely right, I replaced the condenser fan blade and the unit works fine. I never had to replace a fan blade before so now I learned how important it is to have the right blade pitch for the motor. Before I thought that installing a fan blade with a higher pitch would be better for cooling, but I did not realize that it was overheating the 1/4HP fan motor.
  • Jul 29, 2009, 05:15 PM
    hvac1000
    Glad you got it going

    • All times are GMT -7. The time now is 03:01 PM.