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  1. #14
    Join Date
    Jun 2003
    Location
    Tampa Bay, FL.
    Posts
    120
    I think you may be on to something Hurtin. The cap may only be necessary for 115v application.

  2. #15
    Join Date
    Jul 2011
    Location
    Lehigh Valley, PA
    Posts
    471
    I' m thinking along the same lines too. May not be necessary. Guess i could run a cord and manually test the motor wired at 115 to see if it'd start or not without a cap.

    Even though a fryer hood, no fryer grease in/on the motor. It's very clean and sealed off from the grease.

  3. #16
    Join Date
    Oct 2008
    Posts
    837
    I've only seen a few fan motors that DON'T have an external start cap. I assumed that those had an internal cap. I may be wrong on that, since a phase shift can also be created by other means. However, in refrigeration & HVAC applications, a capacitor is nearly always present.

    For any single-phase motors, a phase shift creates an electrically rotating magnetic field. Three-phase motors already have that, so no additional components are necessary to trick it into rotation.

    The start components get a single-phase motor rotating... AND rotating in the right direction. A centrifugal switch (or a start relay on heavier loads like a compressor) removes the capacitor and the motor's start winding from the circuit once operating RPM is achieved.

    Are certain you're installing a properly rated capacitor for that motor? Otherwise, like others have said, the centrifugal switch in the motor may be faulty.

  4. #17
    Join Date
    Mar 2013
    Location
    swan valley idaho
    Posts
    732
    agree- if you have relay or centrifugal switch its not releasing start winding after start up. also sounds like run cap from rating

  5. #18
    Join Date
    Aug 2009
    Location
    Maine
    Posts
    3,712
    20 seems a bit low for a start and a bit high for a run. Probably by the time you get all done it will be cheaper to just replace the motor.

    Quote Originally Posted by Capz View Post
    I wasn't sure where to post this but since it is used in a commercial kitchen, figured I hit the refrig gurus. I have a problem I have never seen. I have a small Dayton blower motor used in a Giles vent less hood which will melt the start cap.

    Details, small approx 1/4 hp Dayton blower motor, 115/230v wired for 230, data plate 3.7 amps @ 230v, uses a 20uf, 250vac start cap. Last week it melted the original, today I installed a generic Dayton 21-25uf 250vac replacement. (Original oem part made by other than Dayton no longer available at Grainger nor Giles). The generic replacement popped & melted in 5 mins. BUT the motor runs perfectly, no bearing noises, pulls 2.1amps, will start WITHOUT the start cap installed and the unit is working.

    The actual line input volts is 249vac. Little high but I can't see this being the issue. I didn't think to check at the actual volts at the cap terminals at the time. But if this motor is running cool & quiet, what can cause this issue? I'm gone to check the volts at the terminals with the motor running, maybe install a 330vac, 20mf start cap.

    Is this motor defective? Any ideas?

  6. #19
    Join Date
    Jul 2011
    Location
    Lehigh Valley, PA
    Posts
    471
    Quote Originally Posted by ECtofix View Post
    I've only seen a few fan motors that DON'T have an external start cap. I assumed that those had an internal cap. I may be wrong on that, since a phase shift can also be created by other means. However, in refrigeration & HVAC applications, a capacitor is nearly always present.

    For any single-phase motors, a phase shift creates an electrically rotating magnetic field. Three-phase motors already have that, so no additional components are necessary to trick it into rotation.

    The start components get a single-phase motor rotating... AND rotating in the right direction. A centrifugal switch (or a start relay on heavier loads like a compressor) removes the capacitor and the motor's start winding from the circuit once operating RPM is achieved.

    Are certain you're installing a properly rated capacitor for that motor? Otherwise, like others have said, the centrifugal switch in the motor may be faulty.
    I removed the original 20uF +/-, 250v, installed a 21uF-25uF, 250v. The exact replacement is not available as already stated. Thanks for you response.

  7. #20
    Join Date
    Jul 2011
    Location
    Lehigh Valley, PA
    Posts
    471
    Quote Originally Posted by lytning View Post
    20 seems a bit low for a start and a bit high for a run. Probably by the time you get all done it will be cheaper to just replace the motor.
    I called Grainger/Dayton motor tech service the other day. While the original oem cap was no longer available, he suggested a 20uF, 370vac Grainger part to go with the Dayton motor. Claimed the faulty original was a run cap and not a start cap.

    I installed it today and it runs perfectly. No need for new motor. BTW, I checked the voltage on the cap leads prior to installing. I saw 200vac continuous. Voltage never dropped out.

    I had it running this week without any capacitor but motor would hesitate on start up and with each start it would change direction CW--CCW. With new cap it starts and runs correct direction with each start.

  8. #21
    Join Date
    Aug 2009
    Location
    Maine
    Posts
    3,712
    I remember trying to free stuck compressors by running them backwards with capacitors.

    Quote Originally Posted by Capz View Post
    I called Grainger/Dayton motor tech service the other day. While the original oem cap was no longer available, he suggested a 20uF, 370vac Grainger part to go with the Dayton motor. Claimed the faulty original was a run cap and not a start cap.

    I installed it today and it runs perfectly. No need for new motor. BTW, I checked the voltage on the cap leads prior to installing. I saw 200vac continuous. Voltage never dropped out.

    I had it running this week without any capacitor but motor would hesitate on start up and with each start it would change direction CW--CCW. With new cap it starts and runs correct direction with each start.

  9. #22
    Join Date
    May 2000
    Location
    Salem, WI US
    Posts
    63
    Could I ask what the part/model number is on the motor?

    Beta
    Betabass



    Success is to be measured not so much by the position that one has reached in life as by the obstacles which he has overcome.

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