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  • blodgett convection gas oven DFG-200.

     ectofix updated 1 year, 11 months ago 1 Member · 12 Posts
  • guest

    Member
    August 24, 2018 at 12:00 am

    I have a blodgett convection gas oven DFG-200. The capacitor is only 10 uf which seems small for a start capacitor. I’m assuming it is a start capacitor because when it fails the fan motor will not start. I put a 15uf in and it burns out after 6 months or so. What’s the issue?

  • fixbear

    Member
    August 24, 2018 at 9:28 pm

    That is not a start capacitor!  You have a PSC motor and it needs the correct run capacitor.  Especially the 370 voltage. Make sure to measure the operating current after install.  If high, it will take out the cap.  Means that the motor is in overload from something.  Like a bearing or dirty fan wheel or even a shorted winding.

  • ectofix

    Member
    August 24, 2018 at 9:29 pm

    The issue is the 15µf you installed isn’t what the engineers prescribed for that motor.  According to YOU, the original was a 10µf capacitor.  So, 15µf is 150% of the capacitance the engineers designed it for.

     

    I’m not an engineer.  Engineers get paid FAR more than I do.  Nonetheless, I’m REALLY good with electricity and could probably, with enough research, come up with an answer about WHY a 15µf will eventually fail.  However, NOBODY is paying me for my response to your question here.  I’m sure that the motor’s impedance and horse power factors in there somewhere.

     

    I suggest that you simply put the proper capacitor in there. Here’s the part you need:

    https://www.partstown.com/blodgett/bl23077?pt-manual=BL-DFG-100_pm.pdf 

  • ectofix

    Member
    August 24, 2018 at 9:35 pm

    fixbear wrote:

    That is not a start capacitor!  You have a PSC motor and it needs the correct run capacitor. 

    I overlooked that…

     

    YES!  That motor is so misunderstood.  The centrifugal switch in it CLOSES to enable the HEAT circuit.  People always think it’s for the START capacitor, which it’s NOT.

  • bruni92

    Member
    August 25, 2018 at 5:45 am

    Thank you all for the replies. I will get the correct capacitor. Franklin Machine Products, http://www.fmponline.com, has it for $54, Parts Town wants $84. I have a feeling there is an issue with the centrifugal switch, because the heat cycle works when the motor is not running. How do I test it?

  • bruni92

    Member
    August 25, 2018 at 5:46 am

    Thank you all for the replies. I will get the correct capacitor. Franklin Machine Products, http://www.fmponline.com, has it for $54, Parts Town wants $84. I have a feeling there is an issue with the centrifugal switch, because the heat cycle works when the motor is not running. How do I test it?

  • ectofix

    Member
    August 25, 2018 at 7:36 am

    bruni92 wrote:

     

    I have a feeling there is an issue with the centrifugal switch, because the heat cycle works when the motor is not running. How do I test it?

    What makes you think the heat cycle is on when the motor is not running?  Can you actually see burner flames when that happens?

  • guest

    Member
    August 25, 2018 at 4:12 pm

    yes, you can see the flame

  • fixbear

    Member
    August 25, 2018 at 9:10 pm

    Well then, since that’s supposed to happen.

    I think you mean NOT supposed to happen.

  • ectofix

    Member
    August 26, 2018 at 5:18 am

    Well then, since that’s NOT supposed to happen…and Blodgett probably designed it that way for safety reasons, I strongly suggest that you remove the oven from service until that’s fixed.

     

    The switch wiring can be accessed with the control panel pulled out from the quick-disconnect plug. 

     

    So, remove power from the unit and connect an ohmmeter across pins 2 and 4.  Those pins lead to the centrifugal switch.  It obviously should read open when the motor is static. 

    If it reads CLOSED, then the motor will need to be replaced.  A cheaper alternative would be to take the motor to a motor shop for them to fix it.

    If it read OPEN, then something is wired wrong behind the control panel.

  • ectofix

    Member
    August 26, 2018 at 5:21 am

    Darrnit!  Right.  Thanks, I fixed it.

  • fixbear

    Member
    August 26, 2018 at 7:33 am

    ectofix wrote:

     

     

    YES!  That motor is so misunderstood.  The centrifugal switch in it CLOSES to enable the HEAT circuit.  People always think it’s for the START capacitor, which it’s NOT.

    That is so true.  A capacitor start motor the switch goes open at speed to disconnect the extra start winding.  Before the PSC motors came out we only had shunt wound for fans and low starting  torque motors. Then the energy shortage period started and some electrical engineer figured out why not save all that wasted Gauss. Added a set of winding’s at a certain degree to a capacitor to make power and return it to the motor slightly behind the main winding’s. Half the power to do the same work.  Problem is the capacitor has to be just the right size or one of the winding’s will overheat.  And it will develop a vibration.   I have had to bump the capacitor size up or down to smooth out a motor in the past,  but usually from a load change in the design of the equipment.  Like a wrong fan blade or bearing problem.  But I have also come across motors that were wound wrong.  Local scrap yard had a truck full of Dayton grinders that were junked just for that vibration I mentioned. Hate to think of all the labor that was wasted to scrape off the labels and apply a judicious sledge hammer blow to the stator.

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