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  1. #1
    Join Date
    Aug 2002
    Posts
    490

    OK here it goes
    this one really had me going still
    1995 condenser unit 3 ton 11.5 S.E.E.R.
    plugged in my gauges looked like over charge did recovery on the refrigerant r-22.
    Then pulled it in a vacuum then shot it with nitrogen figured clean out any contaminants then pulled it back in a vacuum.
    Now put the charge back weighed it in 115 oz this is what the factory charge was on the label when it was made.

    72 degrees outside
    high side 250 psig

    low side 61 psig

    highside line temp. 115

    lowside line temp 55


    OK so now I now the charge is perfect so I clean the condenser coil real good.
    now after it dries I plug in gauges again
    now it is still 72 degrees out
    now I get

    high side 220psig yes 220
    low side 60 psig

    high side line temp 95
    low side line temp 55
    = superheat 21
    = subcooling 13

    thing is now its freezing up outside by the compressor the suction line.

    now its not undercharged
    air filters clean

    This homeowner has a small apartment in the basement now the blower is down there and they added vents.
    Also there is a 12 inch by 12 inch return down there the blower is just 18 inches behind the wall of the return also 3 feet above the return is a 8 inch supply vent.
    Now would that air not go down and back in without even cooling that hallway, the homeowner did this maybe this is part of the problem its screwy or am I missing something.
    spent hours there don't like not fixing them not a good feeling every now and then I get stuck on one, this was that one.



    [Edited by TheDuke on 07-07-2005 at 10:21 PM]

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,880
    Restricted distributor tube, or a kink in the vapor line.

    Would be what I would check for first.

    What was the delta at the indoor coil.
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  3. #3

    Question Evap Freezup

    Hiya Duke,
    Quick question about your post, you said that you pulled vacuum after shooting in the Nitrogen and then weighed your refrigerant back into the system with the factory settings of 115 oz. My question is did you remember to add in your line refrigerant? The unit itself has 115, but you also have to add more to accomodate for your lineage. You might have done this, but you might want to check on it. I have had this throw me for a loop also and was told to remember that when you do the weigh in to add so many ounces for every foot of line to your indoor coil. Hope this helped you.

  4. #4
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,880
    Good point h-pickle.

    But, if you think about it, isn't a 250 head pressure high for a 72° outdoor ambient.
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  5. #5
    Join Date
    Apr 2004
    Posts
    7,680
    its not freeezing at the suction line if you are reading 55 degrees. You must mean ift freezes up after you leave. It could be low load. When they added a return in the basement it may have lowered the return air temp at the unit to below 70 degrees which will likely freeze a unit running at nominal airflow. They also may have the stat set to 65 degrees.

  6. #6
    Join Date
    Aug 2002
    Posts
    490
    im reading 55 degrees at the suction line comming out of the evap at the furnace.
    yes the line set is only 25 feet I added one oz
    ducholiday yes im reading 55 degrees at the evap above the furnace line comming out, also yes the return air is 69 degrees and the air in is 55
    that will cause the freeze up then thats it really.
    69 degrees return

  7. #7
    Join Date
    Aug 2002
    Posts
    490
    sorry I did not put this after i cleaned the condenser the high side pressure was 220 psig

  8. #8
    Join Date
    Sep 2004
    Posts
    172
    Low airflow across evap in almost every instance where you see the symptons you describe. Go into the house, remove the pesky decorative diffusers with the tiny slots, yeah just pull them up and throw them in a pile and also remove the 6x6 squares of solid cardboard air freshener thingys sticking on the face of the return air filters and everything will probably work just fine.

  9. #9
    Join Date
    Apr 2005
    Posts
    53
    Hope I dont insult anyone's intelligence here, but how long did you wait to read the pressures after you cleaned the coil?

    [Edited by splitbolt on 07-07-2005 at 10:54 PM]

  10. #10
    Join Date
    Aug 2002
    Posts
    391
    Is the evaporator coil clean?
    The obvious is obvious

  11. #11
    Originally posted by beenthere
    Good point h-pickle.

    But, if you think about it, isn't a 250 head pressure high for a 72° outdoor ambient.
    That's what jumped out at me...it seems high especially for an 11.5 SEER unit.

  12. #12
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,880
    Originally posted by TheDuke
    sorry I did not put this after i cleaned the condenser the high side pressure was 220 psig
    11.5 seer, 72 outdoor temp 220 head, still sounds high, look for a restriction.
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  13. #13
    Join Date
    Mar 2005
    Location
    Suppy NC
    Posts
    4,513
    could be an air flo problem
    i think you have a restriction in the system
    one question even though it is a 11 seer condenser is was the coil matched to it or is it an old coil with cap tubes because they run higher presures the newer coils do

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