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  1. #1
    Join Date
    Jun 2010
    Location
    Danbury Ct 1/2 hour from NYC
    Posts
    204

    Ever had this problem?

    I did a big house on CT shoreline roughly 9000 sq ft. I used 6 first co hbxb variable sp ah's with Ruud 14AJM outdoors. There was a group of four units that did the main portion of the home. Two of the units were for the room over garage and pool house. The other four were located 40 ft off the house in a dedicated area. Each of the four linesets ran through individual 4in PVC ran by excavator. I had 300lbs of nitro hold for a wk. Went back evacuated the nitro vac down and opened. Power was all set with sub panel at condensers so was able to start up. 3 units were running great but had a short in the low voltage on 1 unit so I opened the valves and left off until electrician fixed the short. Two weeks later I go back to start and when put gauges on It wouldn't equalize. I can't remember what the readings were but they scared the crap out of me. Somehow the oil migrated to the evaporator and plugged up the TXV. Thank god the first co is compression fitting and not brazed in. I disconnected the expansion valve and blasted nitrogen through and blew oil all over the knee wall of the attic. It was one of the worst problems I had on a new install and was worried about how much oil was lost from compressor. a year later system is running fine but what a day!!

  2. #2
    Join Date
    Feb 2009
    Location
    Tallahassee, FL
    Posts
    6,048
    Ummm txvs aren't supposed to let the pressures equalize. That's part of the benefit of having them.

    Hard shutoff is the term.

  3. #3
    Join Date
    Jun 2010
    Location
    Danbury Ct 1/2 hour from NYC
    Posts
    204
    I was talking about before the system was started. I can't remember what the pressures were exactly but they were bad enough to scare the crap out of me. I knew there was a restriction and wasn't thrilled because the linesets were 200 ft long and 70 ft were underground. I was worried somebody did something when they were back filling the ditch were the pipes ran or even somewhere else. I don't always sit there and watch the sheetrockers or insulaters but I've had things damaged many times. A couple months ago I had the rest of the lineset roll hanging at the furnace not tied in to evap yet and someone bent the roll down right at my hanger(copper 2 hole strap) and kinked it. Well they straightened it back out and without pulling the armaflex off you would never know. I sure as hell found out when sent nitrogen in. I heard it outside coming out of the split in the lineset. I asked the carpenter if he saw anybody messing with my lines and he told me he just had to pull it out of the way for a second but he put it right back in same spot hanger and all. I said thanks for putting it back so nice and neat but you split it. He was apologetic and actually cared which was rare for people around here.

  4. #4
    Join Date
    Jan 2006
    Location
    McQueeney, Texas
    Posts
    3,867
    Certainly hasn't happened to me lately.

    If it did happen, it would be so long ago, I'd forgotten by now.

    200 feet?

  5. #5
    Join Date
    Feb 2009
    Location
    Tallahassee, FL
    Posts
    6,048
    I don't think there was anything wrong air movers. I'm not sure how you put the freon in there but don't be alarmed just because a unit with hard shut off txv isn't equalized.

  6. #6
    Join Date
    Jul 2012
    Location
    Stratford
    Posts
    27
    Aren't you slugging the compressors being that far away? I turned a job down like that because the manufacturer said it was too far. They said the line set couldn't change temperature more than 3 feet before it hit the coil.

  7. #7
    Join Date
    Feb 2010
    Location
    Calgary, Alberta
    Posts
    1,111
    Quote Originally Posted by SBKold View Post
    Ummm txvs aren't supposed to let the pressures equalize. That's part of the benefit of having them.

    Hard shutoff is the term.
    An externally equalized TXV will balance in the off cycle

  8. #8
    Join Date
    Feb 2009
    Location
    Tallahassee, FL
    Posts
    6,048
    Quote Originally Posted by syndicated View Post
    An externally equalized TXV will balance in the off cycle
    Wrong brother.....an externally equalized TxV has nothing to do with off cycle equalization.

  9. #9
    Join Date
    Jul 2007
    Location
    Virginia
    Posts
    5,591
    Quote Originally Posted by syndicated View Post
    An externally equalized TXV will balance in the off cycle
    Agree with SBKold.

    The subject of pressure equalization during system off cycle should not be confused with the external equalizer of the TXV.

    System pressure equalization is accomplished by allowing a certain amount of refrigerant to leak through a machined notch or hole in the valve seat during system off cycle.

    The external equalizer of the TXV, simply allows the valve to sense evaporator pressure. The external equalizer does not provide pressure equalization during system off-cycle.
    Instead of learning the tricks of the trade, learn the trade.

  10. #10
    Join Date
    Aug 2001
    Location
    Mechanicsville, Virginia
    Posts
    1,314
    A hard shut-off type TXV does prevent flow during the off cycle but the pressures do equalize to the ambient temp of each coil. When the outdoor temp is close to the indoor temp, the system will certainly look equalized.

    An externally equalized TXV incorporates the leaving evaporator coil pressure to compensate for the pressure drop thru the coil.

    So you're both right ....or I'm wrong

    "If perfection is your goal, you may end up with good enough, what might you end up with when good enough is your goal?"
    Wayne Pendergast, efficientcomfort.net

  11. #11
    Join Date
    Feb 2009
    Location
    Tallahassee, FL
    Posts
    6,048
    Quote Originally Posted by penderway View Post
    A hard shut-off type TXV does prevent flow during the off cycle but the pressures do equalize to the ambient temp of each coil. When the outdoor temp is close to the indoor temp, the system will certainly look equalized.

    An externally equalized TXV incorporates the leaving evaporator coil pressure to compensate for the pressure drop thru the coil.

    So you're both right ....or I'm wrong
    But we had another factor that made the systems look unequalized ....long underground linesets.

    And when the condenser is at 90deg sat and indoor/ground is 70deg that looks pretty unequalized

    Last edited by SBKold; 06-04-2013 at 01:47 PM.

  12. #12
    Join Date
    Jun 2010
    Location
    Danbury Ct 1/2 hour from NYC
    Posts
    204
    The Ruud tech support told me that I had a problem with that unit only because it sat undercharged for over two weeks since electrician had short couldn't start the one unit as I said in original post. He said that the prob was with the length of the lineset and it not being fully charged allowed the oil from compressor to migrate and flood evaporator coil. he also said The builder running the heat at night up as high as 80 to dry out the house before sheetrock and flooring didn;t help. The same air handler was running on heat cycle for over a month just not ac. I appreciate all the opinions of you guys thx

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