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Thread: fan motor replacement

  1. #1
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    fan motor replacement

    Hi,

    I was wondering what happens when we replace the OEM fan motor (on condenser or evaporator) with another fan motor which has a bigger power input (more current draw), but has the same RPM as the OEM motor, and the blades stay the same?

    So, to summarize it, the only difference between the OEM motor and the replacement motor is the power input (RPM and the blades are the same).

    Thanks.

  2. #2
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    Since the blower will be doing the same amount of work, wheel size and rpm, the bigger motor will be using less amps than it’s rating but probably more than the previous motor due to the size or hp of the motor.

    In effect, I don’t see a problem except wasted energy.

    Anyone else see an issue?

  3. #3
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    You got it covered. When there is an option for condenser fan motors I always go for TEC vs ODP.

    If it has a vfd there may be issues.

  4. #4
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    If you go too big and use less Amps ... I've "Heard" the motor runs hotter

    It makes no sense ,but thats what the word is

    They like to run near RLA

  5. #5
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    Quote Originally Posted by Snapperhead View Post
    If you go too big and use less Amps ... I've "Heard" the motor runs hotter

    It makes no sense ,but thats what the word is

    They like to run near RLA
    It believe it does run hotter, if that energy is not used to move air then it becomes heat

  6. #6
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    You need the exact replacement. 1 size up MAY cause it to overheat

  7. #7
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    Thread Starter
    Guys, thanks for your answers, I really appreciate this.

    I forgot to explain on the type of motors I was thinking about.
    Here is a link:

    https://www.amazon.com/EBM-PAPST-M4Q...6292439&sr=8-2

    Motors like these are very common in Europe, and they are used mostly for small condensers.


    This overheating makes sense.
    I've tried to run a small motor without blades for around 5 minutes (not the same manufacturer like on a link above, but other), it turned out to be so hot I couldn't put my hand on it.

    When a motor like this burns out, the technicians change it with a new motor where they attach old blades on a new motor.
    Often during replacements like these, they like to put "1 size up" (stronger motor than the old one).
    I often wondered what are they trying to accomplish it the blades and rpm are the same.

  8. #8
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    if you get another motor , make sure while running it pulls the correct amps listed on its label , you're good to go

    Its easy to make a fan blade pull a little more air if you know how to tweak the blades a little

    You just have to keep checking how many Amps shes pullin , because it takes more amps to pull more air

  9. #9
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    Quote Originally Posted by BobFrost View Post


    This overheating makes sense.
    I've tried to run a small motor without blades for around 5 minutes (not the same manufacturer like on a link above, but other), it turned out to be so hot I couldn't put my hand on it.

    .


    Any of them will overheat without the blades if rated for air over cooling.
    Some equip mfgs will also utilize the service factor to meet performance specs. Carrier has used 1.5 service factors to get by with smaller frame sizes and you cannot use a same hp motor with a lower service factor without overloading.

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  11. #10
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    Thread Starter
    Quote Originally Posted by Snapperhead View Post
    if you get another motor , make sure while running it pulls the correct amps listed on its label , you're good to go

    Its easy to make a fan blade pull a little more air if you know how to tweak the blades a little


    You just have to keep checking how many Amps shes pullin , because it takes more amps to pull more air
    I measured the amps draw, they were little lower than on a nameplate. I am referring to a situation without blades.

  12. #11
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    Quote Originally Posted by ehsx View Post
    Any of them will overheat without the blades if rated for air over cooling.
    Some equip mfgs will also utilize the service factor to meet performance specs. Carrier has used 1.5 service factors to get by with smaller frame sizes and you cannot use a same hp motor with a lower service factor without overloading.
    Thanks!

  13. #12
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    Quote Originally Posted by Snapperhead View Post
    If you go too big and use less Amps ... I've "Heard" the motor runs hotter

    It makes no sense ,but thats what the word is

    They like to run near RLA
    I've heard the word is "electrical inverse proportionality" is what causes the oversized motor to overheat.

    My one Boss wanted me to adapt a 7.5 HP blower motor to a 5HP blower motor load. I mentioned "inverse proportionality" to him. He mentioned that I was a BIG PITA. He also mentioned that he was the BOSS. I mentioned to him,after I changed the out the 7.5 hp for the 5hp AND the larger motor overheated and shut down, I mentioned to him "what do you want me to do now BOSS". He mentioned that I give him an upset tummy.

  14. #13
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    Quote Originally Posted by TechmanTerry View Post
    I've heard the word is "electrical inverse proportionality" is what causes the oversized motor to overheat.

    My one Boss wanted me to adapt a 7.5 HP blower motor to a 5HP blower motor load. I mentioned "inverse proportionality" to him. He mentioned that I was a BIG PITA. He also mentioned that he was the BOSS. I mentioned to him,after I changed the out the 7.5 hp for the 5hp AND the larger motor overheated and shut down, I mentioned to him "what do you want me to do now BOSS". He mentioned that I give him an upset tummy.
    well, duh the increased load from pushing that much cfm, its the same as putting a 400hp 350 torque v8 ford motor into a 850hp 2,000 torque semi because its cheaper...its not about the HP the torque (amps) makes all the difference

  15. #14
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    i always get the ball bearing motors....i see much less failures with them...

  16. #15
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    Fasco's Fast Facts brochure is a good resource to have for motor information. See p.19-20 where it talks about oversized motors:

    https://www.marsdelivers.com/wps/wcm...20ventilation.

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