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  1. #14
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,945
    Quote Originally Posted by furiac View Post
    Really good stuff, thank you guys. I would think that with a heated and insulated receiver you could omit the time delay in series with the LP or perhaps both would compliment each other.
    One last thing......
    Now when "Summer" rolls around and ambient temps reach a scorching 78* for a month or two, do you need to make adjustments to the LP? Do they make self adjusting or regulating LP controls?
    Thanks again.
    Why would you need to?

    In this case, the low pressure control is more of a safety control than an operating control.

    It acts as a loss of charge switch and to prevent the compressor from running in a vacuum.

    It isn't a temperature control device.

  2. #15
    Join Date
    Jul 2007
    Location
    colorado
    Posts
    33
    Understood, thank you.

  3. #16
    Join Date
    Jan 2004
    Posts
    69
    This is what the time delays look like on the heatcrafts I have worked on here

    http://www.ssac.com/catalog/HRDM1A01.pdf


    I still have a few seafood coolers where the pressure switch is the primary control with no time clock antique tech at its best
    Last edited by aprophet; 04-25-2013 at 07:06 PM. Reason: forgot link

  4. #17
    Join Date
    Jul 2011
    Location
    Nanaimo,BC, Canada!
    Posts
    346
    I live in Canada where we are no strangers to low ambient conditions , and outdoor condensing units.
    Typically an outdoor condensing unit has a heated recieved to keep refrigerant pressure up during pump down on cold days, it also utilizes a flooded head pressure control to maintain high side pressure.. Occasionally you will see a time delay relay in
    Parallel with the lp switch, but not always. In any event I like to set the cut in on the lp control at approx equal to 44f, and cut out a approx 5f below typical sst when box is at temp.. That way if the t-stat fails, The cooler will continue to operate close to normal with out freezing up, and run slightly colder which will alert the shop owner of an issue with out product loss.

    For freezers i never like to see lp controls set too close to 0 psi as if the control looses calibration and allows the system to pump into a vacuum, if there's a leak I. The low side then you're pulling air into the system ..

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