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  1. #1
    Join Date
    Sep 2010
    Location
    miami,fl.
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    674

    706 motor controller

    omnitemp condensing unit m#wa1-ac-h-2-0-3 s# 5023-j05 it has 2 compressors one for walk in cooler one for walk in freezer. seperate circuits but share the same condenser coil. the condenser fan motor failed mechanically bad bearings. it has a motor controller in series m# hc 706 so i called local motor supply. after the run around they didnt have it. its a dayton so i called grainger motor is discontinued so they cross referenced it to a new model i installed it and hosed down the condenser coil. started it up. new motor wouldn't operate with this speed controller. for low ambient conditions. it also has 2 head masters for low ambient. so i eliminated it once i started it up the fan runs full speed. but my liquid line for both cooler and freezer was 115 degrees. the aluminum fins are seperating form the copper tubing alot of corrosion buld up inside the coil. but my cooler evap has a 7 degree split and my freezer has a 5 degree split they are both pulling down. my first time at this school maintenance guy and kitchen staff said it hasnt drok in atleast a year. motor is running full speed and i made sure the tip of the blade is above the fan shroud so the air doesnt get recirculated into the condenser. a few questions
    i usually see a 4 degree split for evaps on freezers is good. Whats the temp difference yall look for?
    Also would this speed controller be considered a potentiometer i googled it but couldnt really find info. from my understanding the only way to slaow down a motor is to slow the frequency down (vfd) or potentiometer im guessing is a variable resistor that increases the resistance in turn slows the fan down not allowing voltage to flow through freely.???

  2. #2
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    19,495
    Another approach to motor speed control is to duty-cycle the triac (a power transistor for alternating current) so that it it only conducts for a portion of the sine wave.

    If your new Grainger motor has ball bearings, you should be able to install a new speed control, such as a P66.
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  3. #3
    Join Date
    Sep 2010
    Location
    miami,fl.
    Posts
    674
    Quote Originally Posted by timebuilder View Post
    Another approach to motor speed control is to duty-cycle the triac (a power transistor for alternating current) so that it it only conducts for a portion of the sine wave.

    If your new Grainger motor has ball bearings, you should be able to install a new speed control, such as a P66.
    i eliminated the fan control since each circuit has its own head master. plus after feeling that liquid line i dont think theyhave to worry about low ambient conditions we live in miami it doesnt get to cold here.

  4. #4
    Join Date
    Aug 2002
    Location
    Southold.calm
    Posts
    6,319
    Headmaster or fan cycle not both

  5. #5
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    19,495
    The fact that it had a fan speed control along with the headmasters suggests that they were trying to fix a problem....

  6. #6
    Join Date
    Aug 2002
    Location
    Southold.calm
    Posts
    6,319
    Quote Originally Posted by timebuilder View Post
    The fact that it had a fan speed control along with the headmasters suggests that they were trying to fix a problem....
    If thats the case then there covering up the problem not fixing it

  7. #7
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    19,495
    Quote Originally Posted by pecmsg View Post
    If thats the case then there covering up the problem not fixing it
    ...and this could be just such an opportunity to find and correct an old problem.

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