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  1. #1
    Join Date
    Nov 2008
    Location
    Northern California, foothills.
    Posts
    212

    Heat Pump Pumpdown AND Recovery.

    Yes, I mean "AND."

    Maybe I've never pumped down a heat pump unit before.
    I would have thought I have, but if I did, I didn't have
    problems and didn't think much about it. Likewise for
    recovery.

    But yesterday, I was involved with an air-handler removal so
    I ended up attempting both a pumpdown and a recovery
    on a split heat pump. (Goodman. No, I didn't bother
    with the model number.) Ambient was about 60 F. Inside
    dry bulb was maybe 65.

    First, the low-side pressure would not fall below about
    30 psi for at least 10 minutes so I decided something was
    up. I called up two seasoned techs and they thought the
    low ambient, 60 F, should not matter. And yes, I had
    the system running via the tstat in cooling mode with
    the high-side service valve tightly closed--at least the
    allen bolt was tight. So after not having any clues, I
    decided maybe the service valve was leaking and decided
    to do a recovery. (The installers were anxious to remove
    the old air-handler so I had to do something resembling
    progress.)

    My Appion G5 is usually really fast, but yesterday the system
    finally got down to about 25 psi and sat there for maybe a half
    hour. There was some icing on the suction line
    and a bit of frosting on the reversing valve. Shuttting it off
    for 20 minutes and then starting it back up seemed to
    stir up some progress, so the pressure dropped to about 15 psi
    then went back to 25 and then slowly worked back down.
    What am I ignoring? I figured that with the liquid line
    service valve closed, the heat pump orifice played no
    part in anything, so the whole thing should be just
    like an A/C-only system. Obviously I'm doing some
    wrong thinking.

    Thank you for any enlightenment.

  2. #2
    Join Date
    Aug 2009
    Location
    Beatrice, NE
    Posts
    2,180
    Sounds to me like the compressor may have bad valves, and/or it was grossly overcharged. How much refrig did you take out?

  3. #3
    Join Date
    Feb 2009
    Location
    Tallahassee, FL
    Posts
    6,051
    Sounds like you had a lot of freezon in there. Also possibly a bad compressor.

    That is actually a good test for you to use if you think you could have bad valves.

    In cool ambients it also takes a long time it seems to get from say 30 down to close to 0.

    In your case I would have done the following.

    Pumped it down as much as I could and recover the rest. Should have been quick that way.

    Then the installers can get to it whiles you recover the condenser if necessary.

    HTH

  4. #4
    Join Date
    Nov 2012
    Location
    Tahlequah OK
    Posts
    131
    Sounds to me that maybe the internal pressure relief valve was opening or you just have bad valves. As far as the recovery is concerned you could have a lot of refrigerant trapped in the oil which can take longer to recover. Sometimes I will apply heat to the compressor shell on cold days to speed up the recovery.

  5. #5
    Join Date
    Nov 2008
    Location
    Northern California, foothills.
    Posts
    212
    The things-going-badly theme carried to my charging scale.
    I did weigh the recovery tank before I started, and I was
    weighing it as it slowly recovered, but then the 9V battery
    in my scale controller (Fieldpiece wireless scale) died.
    But the unit label said it held just shy of 14 lbs, not counting
    the rather long--two-story house--lineset, 223 ounces.
    Uh, no, I don't carry spare 9 V batteries. But I have not
    recovered any other unit to the recovery tank, so I just
    need to weight the tank. I know it initially weighed 25 pounds.
    I had taken out at least 6 pounds before the battery died.

    The outside unit looked fairly new. The previous owner
    had replaced just it, not the air-handler. The new owner
    didn't even run the unit, I think. The house is vacant.
    He simply wants to go with gas heating, plans to keep
    the condenser. (I guess we'll wire the reversing valve
    to the contactor coil?)

    I go back tomorrow to braze the lineset at the evap coil.
    And I think I will be charging it, so we shall see. I really
    hope it DOESN'T have bad valves.

    Thank you.

  6. #6
    Join Date
    Feb 2009
    Location
    Tallahassee, FL
    Posts
    6,051
    I should mention scrolls don't have valves.

  7. #7
    Join Date
    Aug 2009
    Location
    Beatrice, NE
    Posts
    2,180
    For future reference, if you have a system like this that won't pump down, close both valves, then you only have to pump down the coil and line set, which goes for vacuum pumping also as most of the refrig is still in the cond.

  8. #8
    Join Date
    Nov 2008
    Location
    Northern California, foothills.
    Posts
    212
    As a follow-up, I went back to this unit today to finish up.
    I brazed up the new evap coil and pressure tested with
    nitrogen. Even the nitrogen seemed to empty slowly,
    so I opened both lines at the condenser, sealed them
    up, and ran nitrogen in both directions. It seemed normal
    enough. I then put it all back together, evacuated,
    charged with the prescribed 14+ pounds, and passed the
    HERS test. Perhaps the large capacity and the accumulator
    just makes things seem a lot different than most systems.

    Thanks for the efforts to help.

  9. #9
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,171
    Were you only recovering from the vapor port?
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  10. #10
    Join Date
    Nov 2008
    Location
    Northern California, foothills.
    Posts
    212
    Quote Originally Posted by beenthere View Post
    Were you only recovering from the vapor port?
    No. I think the problem was a combination of sheer volume and icing
    at the suction service valve. But I was recovering from the liquid line
    service valve as well as the suction one.

  11. #11
    Join Date
    Jul 2010
    Location
    Eastern Kentucky
    Posts
    55
    Next time you are pumping down refrigerant open the high and low side gauges both. This will allow refrigerant to flow through your gauges if there is a restriction in your indoor metering device. Also speeds up the pump down process

    Also next time you are recovering refrigerant, take a heat gun to that accumulator and heat that refrigerant out of the system. Makes it faster.

  12. #12
    Join Date
    Nov 2007
    Location
    Mississippi
    Posts
    1,356
    Quote Originally Posted by georgelass View Post
    As a follow-up, I went back to this unit today to finish up.
    I brazed up the new evap coil and pressure tested with
    nitrogen. Even the nitrogen seemed to empty slowly,
    so I opened both lines at the condenser, sealed them
    up, and ran nitrogen in both directions. It seemed normal
    enough. I then put it all back together, evacuated,
    charged with the prescribed 14+ pounds, and passed the
    HERS test. Perhaps the large capacity and the accumulator
    just makes things seem a lot different than most systems.

    Thanks for the efforts to help.
    Are you sure your hoses are depressing valve cores adequately?

  13. #13
    Join Date
    Jul 2009
    Location
    South Carolina
    Posts
    3,241
    It's not uncommon for a unit not to pump down all the way & it doesn't mean there is anything wrong with the compressor especially if there is a long line set involved. Either way I've found the fastest thing to do in that situation is just take the recovery can, hook it up to the high side while the unit is running normally & let it pump a few lbs. into the can. After you lighten the freon load a little it usually pumps into a vacuum real quick. You don't even have to bother hooking up the recovery unit. I've done it hundreds of times with rarely a problem.
    Gary
    -----------
    http://www.oceanhvac.com
    An engineer designs what he would never work on.
    A technician works on what he would never design.

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