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  1. #1
    Join Date
    Jul 2004
    Posts
    20

    Confused

    I need some help with medium temp controls and operation. The system I need help on is a walk in cooler. It has a remote bulb t-stat, liquid line solenoid, dual pressure control at condensing unit, and a time clock. It is wired so that the thermostat directly cycles the condensing unit off and on. Am I correct in thinking that the thermostat should control the liquid line solenoid, which in turn should pump the system down to the pressure setting of the low pressure control? I think that this unit is wired incorrectly!


  2. #2
    Join Date
    Feb 2004
    Location
    Western New York
    Posts
    1,027
    You are right, it's wired wrong. Defrost timer should also pump-down system.
    Experience is what you have an hour after you need it.

  3. #3
    Join Date
    Jul 2004
    Posts
    20
    Thanks for the confirmation. I thought I was right but am not as familiar with refrigeration as comfort A/C. Keep up the good work!!

  4. #4
    Join Date
    Jun 2004
    Posts
    182
    kool kat, OEM's will wire a system up either way. It's hard to say one is right or wrong, but I prefer that the solenoid would close and pump the unit down then go out on low pressure control. This gives better control of the refrigerant during the off cycle.

    One word of caution, watch your defrost cycle. If the unit was set to defrost with liquid in the coil, after you convert it to pumpdown, the heat transfer will change during defrost. Be certain that the coil is free of ice after defrost, the termination switch may need changed.

  5. #5
    Join Date
    Jul 2001
    Location
    Gold Coast of Connecticut
    Posts
    4,543
    I prefer that the t-stat does just what your does. Of you add all the hours the damn thing runs pumping down with no cooling pluss the short cycling the pumpdown causes I think i would just let it be...........thats how i wire them!

  6. #6
    Join Date
    Feb 2003
    Location
    NH & Cebu
    Posts
    1,608
    I always pump them down with a t-stat and defrost timer. Being in a cold climate, I don't want liquid sitting in a cold suction line outside, just waiting to slam into some valves after a defrost.

  7. #7
    Join Date
    Mar 2004
    Location
    Windsor, ON Canada
    Posts
    168
    I agree with baub. May I ask just one question...what is the point of having a LLS the way the system is currently wired?

  8. #8
    Join Date
    Jan 2004
    Location
    Earth
    Posts
    4,879
    I would use the LL sol for temp control, and kill both the solenoid and comp with the clock for defrost. Personally I think the coil defrost better with some vapor in it.
    A Diamond is just a piece of coal, that made good under pressure!

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