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  1. #1
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    pump down solenoid

    In refrigeration units with remote condensors we have a liquid line solenoid for pumping all of the refrigerant into the liquid reciever to prevent flooding the compressor with liquid refrigerant during start-up when colder than box temperature ambient conditions exist. My question is why don't we see this with heat pumps? These conditions would exist a lot more often, almost everyday during heating season, yet I have only seen a few liquid line solenoids in residential hvac, and they were for long line set runs to prevent so much pressure being put on the compressor during start-up.

  2. #2
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    maroon lazyboy
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    I would like to hear more on this as well... Most heat pumps have crankcase heaters, but that doesn't take care of the liquid in the coil.

  3. #3
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    Most heat pumps have accumulators (or one built into the compressor like trane)

  4. #4
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    Quote Originally Posted by craig1 View Post
    Most heat pumps have accumulators (or one built into the compressor like trane)

  5. #5
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    Jul 2006
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    Connecticut
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    Suction accumulator prevents liquid from entering the compressor, unless of course there's an overcharge.
    Refrigeration systems I've seen mostly have the solenoid on the outlet of the evaporator, and close from the stat. Then the pressure cntrl turns off the compressor. Ergo-any liquid stays in the evap. and changes to gas when the sol. v. opens, and rising pressure makes the pressure sw., restarting the compressor.
    Tom D. - Long-time Journeyman from CT.

    On account of being a democracy and run by the people, we are the only nation in the world that has to keep a government four years, no matter what it does.

  6. #6
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    Mar 2005
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    burlington county n.j.
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    Quote Originally Posted by tomd7735 View Post
    Refrigeration systems I've seen mostly have the solenoid on the outlet of the evaporator, and close from the stat. Then the pressure cntrl turns off the compressor. Ergo-any liquid stays in the evap. and changes to gas when the sol. v. opens, and rising pressure makes the pressure sw., restarting the compressor.

    in 40 years i have never seen that

    solenoids i have seen where always on liquid line at outdoor unit or just before entering expansion valve. thermostat closes valve and refrigerant pumps down into condensing unit.

  7. #7
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    Quote Originally Posted by t527ed View Post
    in 40 years i have never seen that

    solenoids i have seen where always on liquid line at outdoor unit or just before entering expansion valve. thermostat closes valve and refrigerant pumps down into condensing unit.
    YEP,

  8. #8
    Join Date
    Dec 2007
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    north suburbs of Chicago
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    I hope not to take away from the OP but I run into some Carriers from maybe 15 years ago that have a solenoid in the condenser. If I remember correctly they simply opened and shut with the thermostat as well as the contactor and had nothing to do with pumping down the system.

    I can't say I ever did figure out what use they had.

  9. #9
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    Myrtle Creek. Oregon
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    in 50 + years I have never seen it eather.
    a stupid question is a question you wont to ask, but don't

  10. #10
    Join Date
    Dec 2010
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    Virginia
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    Quote Originally Posted by tomd7735 View Post
    Suction accumulator prevents liquid from entering the compressor, unless of course there's an overcharge.
    Refrigeration systems I've seen mostly have the solenoid on the outlet of the evaporator, and close from the stat. Then the pressure cntrl turns off the compressor. Ergo-any liquid stays in the evap. and changes to gas when the sol. v. opens, and rising pressure makes the pressure sw., restarting the compressor.
    What you have said would work. The trick is to keep liquid from migrating out of the evaporator into the suction line during cold winter days. I have mostly seen them on the liquid line leaving the condensor but have ran into them at the evaporator but can not really remember exact placement, but yours sounds correct to me.

  11. #11
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    Dec 2007
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    north suburbs of Chicago
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    Quote Originally Posted by millertime77 View Post
    What you have said would work. The trick is to keep liquid from migrating out of the evaporator into the suction line during cold winter days. I have mostly seen them on the liquid line leaving the condensor but have ran into them at the evaporator but can not really remember exact placement, but yours sounds correct to me.
    I have too long ago. On the liquid line

  12. #12
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    Quote Originally Posted by Glennhvac View Post
    I have too long ago. On the liquid line
    Yeah you are probably right, I guess they wouldn't want the solenoid valve on the suction line leaving the evaporator because depending on how long it is you would still run the risk of slugging the pump.

  13. #13
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    Jul 2006
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    Quote Originally Posted by t527ed View Post
    in 40 years i have never seen that

    solenoids i have seen where always on liquid line at outdoor unit or just before entering expansion valve. thermostat closes valve and refrigerant pumps down into condensing unit.
    I'm with you

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