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  1. #14
    Join Date
    May 2003
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    Dixie
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    Slatts...
    "During defrost the evap shouldn't pump down on a low temp system. The coil should have liquid in it to help transfer the heat from the heaters."


    Huh?...
    It is time for all good men to come to the aid of their country, for we are in deep crap.

  2. #15
    Join Date
    Dec 2007
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    anywhere I want to
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    Freezers in my part of the world, using that type defrost clock, pump down before they go into defrost.

  3. #16
    Join Date
    Mar 2008
    Location
    North Queensland, Australia
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    The LLSV and the compressor should shut down at the same time at the start of the defrost cycle. The liquid in the evaporator helps to circulate the heat from the heaters around the evap.
    Read this page 9
    Mistakes are a part of being human. Appreciate your mistakes for what they are: precious life lessons that can only be learned the hard way. Unless it's a fatal mistake, which, at least, others can learn from. Al Franken, "Oh, the Things I Know", 2002

  4. #17
    Join Date
    Dec 2007
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    anywhere I want to
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    OK I read page nine and I still say freezers in this area of that make and using that defrost clock, pump down, shut off compressor on low pressure, and energize the heating elements. Since most don't pump down to 0 psi or less, then there is still some refrigerant in the evap that may assist in the defrost but , it still pumps down.
    I'm not saying your wrong, just how they work around here.
    I recently installed a unit with 2 solonoids......the one in the evap wired to the thermostat and the one in the condensing unit wired to the defrost clock. First time to see that type system.

  5. #18
    Join Date
    Mar 2008
    Location
    North Queensland, Australia
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    Quote Originally Posted by mdnbiker View Post
    OK I read page nine and I still say freezers in this area of that make and using that defrost clock, pump down, shut off compressor on low pressure, and energize the heating elements. Since most don't pump down to 0 psi or less, then there is still some refrigerant in the evap that may assist in the defrost but , it still pumps down.
    I'm not saying your wrong, just how they work around here.
    I recently installed a unit with 2 solenoids......the one in the evap wired to the thermostat and the one in the condensing unit wired to the defrost clock. First time to see that type system.
    They may well be wired that way md.
    It doesn't mean they should be wired that way. The idea is to have a substantial amount of liquid in the evap to transfer the heat evenly through the coil.
    Get onto your local Heatcraft store or evaporator builders and ask what their engineers recommend. If you do it my way you'll find you have a faster, more efficient defrost.
    Dare to be different mate.
    Mistakes are a part of being human. Appreciate your mistakes for what they are: precious life lessons that can only be learned the hard way. Unless it's a fatal mistake, which, at least, others can learn from. Al Franken, "Oh, the Things I Know", 2002

  6. #19
    Join Date
    Sep 2006
    Location
    Chicago
    Posts
    474
    Just thinking out loud here but wouldn’t a evap full of liquid have refrigerant migrate to the suction line during defrost if it wasn’t pumped out? I mean where I live it can be below zero for many days of the year. I would think certain liquid flood back on start up.

  7. #20
    Join Date
    Dec 2004
    Posts
    508
    appolgies if this has already been mentioned too tired to read all your posts.

    some boxes use 3 stats

    temp

    fans

    termination

    identify them its possible someone turned down the termination stat thinking it controlled temp and now your skipping defrosts because your terminating early.

  8. #21
    Join Date
    Mar 2008
    Location
    North Queensland, Australia
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    Quote Originally Posted by dangpgt97 View Post
    Just thinking out loud here but wouldn’t a evap full of liquid have refrigerant migrate to the suction line during defrost if it wasn’t pumped out? I mean where I live it can be below zero for many days of the year. I would think certain liquid flood back on start up.
    That would be a problem if you left the LLSV open. The Ideas is to shut down the compressor and the LLSV at the same time at the start of the defrost.That limits the amount of liquid in the evap. I have suction lines with old insulation coated with ice which would approximate the conditions you describe and have no problem with flood back unless the LLSV leaks. Also I think all low temp systems should have suction accumulators fitted.
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    Mistakes are a part of being human. Appreciate your mistakes for what they are: precious life lessons that can only be learned the hard way. Unless it's a fatal mistake, which, at least, others can learn from. Al Franken, "Oh, the Things I Know", 2002

  9. #22
    Join Date
    Sep 2003
    Location
    Western PA
    Posts
    1,339
    Turned out to be the defrost termination thermostat. Thanks for all your help.
    Last edited by targetman; 05-31-2008 at 08:09 AM. Reason: sp

  10. #23
    Join Date
    Feb 2008
    Location
    Southern Indiana
    Posts
    83
    Noted you're in PA. Do you work for a pretty large company doing supermarket work? If so; I know who can help knock sense into the service manager. What a bum.

  11. #24
    Join Date
    May 2007
    Location
    Louisianna
    Posts
    88
    are you an in house guy or a contractor if your in house call a company that can fix it if your a contractor get somebody ummmmm your boss that can fix the damnnn thing

  12. #25
    Join Date
    Dec 2007
    Location
    anywhere I want to
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    164
    http://www.hvacrinfo.com/compressor_data.htm

    I must thank Powell for this link. As I tried to explain the defrost solonoid in this post, someone from where the water turns backwards suggested I was wrong and I should dare to be different. I was just on my way out the door to be different and change the defrost sequence in all the freezers in the southeast USA when I saw this link. Now I can go to bed instead and rest easily.
    I won't call Slatts by name but hope the person who said systems should not pump down in defrost cycle will read this..

  13. #26
    Join Date
    Mar 2008
    Location
    North Queensland, Australia
    Posts
    1,050
    Quote Originally Posted by mdnbiker View Post
    http://www.hvacrinfo.com/compressor_data.htm

    I must thank Powell for this link. As I tried to explain the defrost solonoid in this post, someone from where the water turns backwards suggested I was wrong and I should dare to be different. I was just on my way out the door to be different and change the defrost sequence in all the freezers in the southeast USA when I saw this link. Now I can go to bed instead and rest easily.
    I won't call Slatts by name but hope the person who said systems should not pump down in defrost cycle will read this..
    Gedday MD, I did
    Your turn. Page 41. Diagram 4 "Typical wiring diagram for single evaporator / single phase defrost etc"
    edit: through to diagram 11 on page 45.

    If you trace out the diagrams, (all 7 of them) You'll notice that the fans and supply to the T'stat and LLSV de-energise together on defrost. No pump down on electric defrost.
    And the waters turn...
    Last edited by Slatts; 07-16-2008 at 04:42 AM.
    Mistakes are a part of being human. Appreciate your mistakes for what they are: precious life lessons that can only be learned the hard way. Unless it's a fatal mistake, which, at least, others can learn from. Al Franken, "Oh, the Things I Know", 2002

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