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  1. #1
    Join Date
    Nov 2006
    Location
    Athens, Ohio
    Posts
    1,697

    Difference between a condenser fan motor and a blower motor?

    I was called out for a no-heat on an electric furnace today. A different company was there yesterday but according to the customer the system did not run last night. The customer tried to contact the other company but evidently they don't answer the phone on the weekend so the customer called our company.
    The first problem was a failed transformer which I replaced. Before operating the furnace I checked for any other problems. The other company had replace the blower motor with a sealed case condensing fan motor. That surprised me. The specs on the motor were correct for the furnace but I have never seen a condenser fan motor used for a blower. In the interests of doing the job properly, I replaced it with a blower motor.
    Would the use of a condenser fan motor be okay? The only objection that I can think of is that a blower wheel is heavier than fan blades.
    What do you guys say?

  2. #2
    Join Date
    Dec 2008
    Location
    Ontario Canada
    Posts
    538
    Sometimes the condenser fan motors have a different RPM, I'm not sure they have quite as much torque either, but if the HP matched, it should be close

    The open style indoor fan motors dissipate the heat better than the enclosed condenser style, for obvious reasons, but I would think that there would still be enough air flow to cool the motor, unless it was installed opposite the return air opening, then it may be an issue

    Other than that, not sure how bad it would be, I would do it in an emergency to get the heat going, but probably still go back and swap

  3. #3
    Join Date
    Jul 2009
    Location
    South Carolina
    Posts
    3,096
    I've put in plenty of condenser motors for blower motors & have never had a problem. I think they might even last longer than blower motors being totally enclosed & running in a lot cooler environment than they were designed for. Come to think of it I can't ever remember ever having one go bad in all the years I've been doing it which is more than I can say for blower motors.
    Gary
    -----------
    http://www.oceanhvac.com
    An engineer designs what he would never work on.
    A technician works on what he would never design.

  4. #4
    Join Date
    Dec 2008
    Location
    Ontario Canada
    Posts
    538
    Quote Originally Posted by garyed View Post
    I've put in plenty of condenser motors for blower motors & have never had a problem. I think they might even last longer than blower motors being totally enclosed & running in a lot cooler environment than they were designed for. Come to think of it I can't ever remember ever having one go bad in all the years I've been doing it which is more than I can say for blower motors.
    Good to know, thanks

  5. #5
    Join Date
    Jan 2013
    Location
    California
    Posts
    87
    Yes you can do it. You should not, however, install a IFM as an OFM. Needless to say, I have not personally tried either - I always install what should be in there to begin with.
    Last edited by Strkout499; 01-12-2013 at 11:00 PM. Reason: Post incomplete

  6. #6
    Join Date
    Feb 2009
    Location
    Winnipeg MB
    Posts
    13
    As long as the spec's match up, enclosed or open motor does not matter.

  7. #7
    Join Date
    Jul 2005
    Posts
    5,380
    Quote Originally Posted by thepresence View Post
    As long as the spec's match up, enclosed or open motor does not matter.
    And there's the rub. Most blower motors are multi-speed, and the lower speeds are often required for proper airflow.

  8. #8
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,158
    Quote Originally Posted by hvacrmedic View Post
    And there's the rub. Most blower motors are multi-speed, and the lower speeds are often required for proper airflow.
    With electric heat there isn't an issue with too much air unless the customer complains the air isn't warm enough coming from the registers.

  9. #9
    Join Date
    Dec 2010
    Location
    Somewhere in Cali
    Posts
    172
    As long as it is not multi-speed.

  10. #10
    Join Date
    Jul 2005
    Posts
    5,380
    Quote Originally Posted by 54regcab View Post
    With electric heat there isn't an issue with too much air unless the customer complains the air isn't warm enough coming from the registers.
    That's true. But the cooling cycle might require use of a lower speed. Suppose the blower on high puts out 2020 cfm but the condensing unit is only 3.5 ton. Sure, there are a lot of instances when a condenser fan motor would work fine as a replacement for the blower motor in an air handler, but there are also a lot of instances where it won't. Even if the specs on the two motors match it won't necessarily be ok to make the switch. That's all I was pointing out. Like I said "the lower speeds are often required for proper airflow."

  11. #11
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,158
    Quote Originally Posted by hvacrmedic View Post
    That's true. But the cooling cycle might require use of a lower speed. Suppose the blower on high puts out 2020 cfm but the condensing unit is only 3.5 ton. Sure, there are a lot of instances when a condenser fan motor would work fine as a replacement for the blower motor in an air handler, but there are also a lot of instances where it won't. Even if the specs on the two motors match it won't necessarily be ok to make the switch. That's all I was pointing out. Like I said "the lower speeds are often required for proper airflow."
    Of course it's always best to use the correct motor for an application but if a condenser motor is all he had on the truck, it might do the job well enough. Yes, too much cooling airflow in cooling mode may cause poor humidity removal. I've never seen too much airflow on a system 3+ tons, but I suppose it could happen. In many instances ductwork is so bad it needs all the help it can get from the higher blower speed. Add a dirty blower wheel and/or A-coil and enough airflow ain't gonna happen, much less too much. The fact that the system is using electric resistance as a primary source of heat in Ohio makes me wonder about the budget for the entire install.

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