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Thread: evap fan motor

  1. #1
    Join Date
    Jun 2013
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    Hemet Ca
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    evap fan motor

    So i was looking at a friends package unit and the evap fan motor ampdraw was a little low i checked the fan cap it was a 12.5 +or- 6% and i read 11.9. -6% would be about 11.75. the data plate says the evap fan motor rla is 2.8 and i read 1.6. is that fan cap slowing down the fan? i don't have any tools to check static or velocity pressures but assuming the duct work is fine could that be the reason why im getting a low amp draw*i didn't have time to get in the aattic to inspect the duct work but as for the unit itself some one cleaned the evap coil the condemning coil and the evap fan blades are clean she moved into the house a year ago some one probably serviced it before she moved in i would have just replaced the cap but didn't have one.....the capacitor is fairly new its a GE after i left i thought tp my self i should have looked at the name plate off the fan motor but ohh well.
    Trane 2.5 ton
    Model# ycc036flmobf
    Serial# m263ydflh
    Evap fan motor rla 2.8
    Actual reading 1.6
    Fan cap ge 12.5 mfd +or-6%
    Actual reading 11.9

  2. #2
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    Jul 2013
    Location
    Harrisburg, PA
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    288
    Fan cap's ok since it's still within its tolerance. Any issues with the unit itself?

  3. #3
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    Sep 2002
    Location
    Virginia
    Posts
    3,148
    id throw a cap on it

  4. #4
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    Dec 2005
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    3,951
    Checking blower motor amperage with the cover off usually leads to a low reading.

  5. #5
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    Jun 2013
    Location
    Hemet Ca
    Posts
    75
    The rest of the unit is in good shape for its age compressor amps are within spec it had had a 20 split it was built in 97 i had the cover back on when i was taking my readings all the controls and fan cap were in separate section not open to fan motor and coil

  6. #6
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    Thanks guys

  7. #7
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    Sep 2008
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    VA
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    Quote Originally Posted by ballane89 View Post
    So i was looking at a friends package unit and the evap fan motor ampdraw was a little low i checked the fan cap it was a 12.5 +or- 6% and i read 11.9. -6% would be about 11.75. the data plate says the evap fan motor rla is 2.8 and i read 1.6. is that fan cap slowing down the fan? i don't have any tools to check static or velocity pressures but assuming the duct work is fine could that be the reason why im getting a low amp draw*i didn't have time to get in the aattic to inspect the duct work but as for the unit itself some one cleaned the evap coil the condemning coil and the evap fan blades are clean she moved into the house a year ago some one probably serviced it before she moved in i would have just replaced the cap but didn't have one.....the capacitor is fairly new its a GE after i left i thought tp my self i should have looked at the name plate off the fan motor but ohh well.
    Trane 2.5 ton
    Model# ycc036flmobf
    Serial# m263ydflh
    Evap fan motor rla 2.8
    Actual reading 1.6
    Fan cap ge 12.5 mfd +or-6%
    Actual reading 11.9
    Seeing as though you have a psc motor, the door off typically loads the motor and main winding current rises, as speed lowers. When door is on speed increases and current falls. This is due to static reducing load.
    I would say the motor may be on low speed tap, or the supply side has high static. This is, of course, if you are taking the reading with the door off.
    "The only true wisdom is in knowing you know nothing" Socrates

  8. #8
    Join Date
    Dec 2012
    Location
    columbus, OH
    Posts
    2,028

    evap fan motor

    Quote Originally Posted by mgenius33 View Post
    Seeing as though you have a psc motor, the door off typically loads the motor and main winding current rises, speed lowers. When door is on speed increases and current falls. This is due to static reducing load.
    I would say the motor may be on low speed tap, or the supply side has high static. This is, of course, if you are taking the reading with the door off.
    Ive seen alot of people on this forum say door off will increase amps. I have found the opposite to be true as newoldtech stated.

  9. #9
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    Sep 2008
    Location
    VA
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    1,762
    That's, why I say typically, and on "RUN winding".
    I have tested this many times. I find a blower motor with 0 static will exceed RLA on run winding, however the start current will reduce slightly. Take a blower out of the unit and test it.

    Just the opposite is true for high static. The RUN current will reduce, yet the START current will increase slightly. With high static the voltage across the capacitor will also increase.
    "The only true wisdom is in knowing you know nothing" Socrates

  10. #10
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    Jul 2009
    Location
    South Carolina
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    Quote Originally Posted by Core_d View Post
    Ive seen alot of people on this forum say door off will increase amps. I have found the opposite to be true as newoldtech stated.
    A PSC blower motor is designed to be under a certain amount of load and static pressure. Take away the static and the current draw goes up and the motor will over amp and over heat. I guess it depends on what doors you're talking about but I can assure you on a standard AH when the door is off and the motor is sucking through the opened door area you will see your amps go up.
    Gary
    -----------
    http://www.oceanhvac.com
    An engineer designs what he would never work on.
    A technician works on what he would never design.

  11. #11
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    Dec 2012
    Location
    columbus, OH
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    Quote Originally Posted by garyed View Post
    A PSC blower motor is designed to be under a certain amount of load and static pressure. Take away the static and the current draw goes up and the motor will over amp and over heat. I guess it depends on what doors you're talking about but I can assure you on a standard AH when the door is off and the motor is sucking through the opened door area you will see your amps go up.
    Yes that is what every one says. I do have limited experience. I have noticed the opposite affect on more than one occasion. Im not an authority on the subject.

  12. #12
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    Jul 2009
    Location
    South Carolina
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    Quote Originally Posted by Core_d View Post
    Yes that is what every one says. I do have limited experience. I have noticed the opposite affect on more than one occasion. Im not an authority on the subject.
    I've been in the field for over 30 years and I've never seen the opposite effect on a running system with a PSC motor. Were you checking the amps both ways or were you reading the amps off the tag and measuring them against your measured amp draw? There might be some other scenarios but that's the only case I can think of where your amps might measure lower with the door off.
    Gary
    -----------
    http://www.oceanhvac.com
    An engineer designs what he would never work on.
    A technician works on what he would never design.

  13. #13
    Join Date
    Sep 2008
    Location
    VA
    Posts
    1,762
    An ECM or X13 motor will have the opposite effect.
    As, Gary said, I've never seen a PSC go up when the door was removed.
    "The only true wisdom is in knowing you know nothing" Socrates

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