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  1. #1
    Join Date
    Dec 2010
    Location
    Virginia
    Posts
    355

    Confused Cant get bubbles out of sight glass

    Went on this call at a church, back for leak check today, but pressures where I left them. Turned the unit on and it was 76 inside and turned down to 72. Pressures were 200/75. Coil split was 18, and sweating all the way through on all u bends. Super heat was 2 to 3 and subcool was 1 to 2, with bubbles in sight glass, but very minimal, almost milky looking. T-stat satisfied in a half an hour. Went over evap coil with leak detector and nothing. Went to outdoor unit and found a leak on top of suction service valve with cap off( not shrader portion) tightened cap up and not leaking. Found a leak on true suction service port. Seemed like someone had over tightened the shrader b/c could not get core tool on shrader, so leak locked cap. My boss says to keep throwing refer to it but that goes against the grain. Indoor piston(#83) low super heat(measured at service valve), but has low subcool, and bubbles in sight glass. Added a total of 7lbs counting both visits. I knoiw it has to be overcharged, but delta t good and RH 50% db 70 wb 60. Outdoor unit Trane M# 2TWA0048A3000AB S# 3471N213F, indoor unit is 4 ton dont have numbers though. I wonder if the comp valves are bad? Should have tried to pump down. At a loss with this one, any help would be appreciated.

  2. #2
    Join Date
    Dec 2010
    Location
    Virginia
    Posts
    355

    Confused Bubbles in sight glass

    Posted this problem in cant get bubbles out of sight glass but didnt go through, so try again. What would cause low super heat, low subcool, sight glass bubbles. Indoor temps are RH 50%, db 70, wb 60. Set stat from 76 to 72 and satisfied within 45 minutes. Pressures are 79/205, sh 2 to 3, sc 1 to 2. No temp drop across sight glass, valves all the way opened. Boss said to keep charging it so I did, about 7 lbs worth, still bubbles. Trane hp M# 2TWA0048A3000AB S# 3471N213F. This thing has to be overcharged, but temp split is good, supply 73 and return 53. I probably should have tried to pump down b/c I think the compressor valves may be bad. Indoor unit is also 4 ton but dont have numbers. I am at a loss with the bubbles in the sight glass, any help is appreciated.

  3. #3
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    16,110
    Quote Originally Posted by millertime77 View Post
    cant get bubbles out of sight glass .
    Best way to fix this is, put a piece of duct tape over the glass, and break out your temp. meter and check SC and SH, that will be a good start.
    __________________________________________________ _______________________
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  4. #4
    Join Date
    Jun 2011
    Location
    Seattle WA
    Posts
    1,245
    Quote Originally Posted by Mr Bill View Post
    Best way to fix this is, put a piece of duct tape over the glass, and break out your temp. meter and check SC and SH, that will be a good start.
    Sorry to go off topic but that is the most awesome HVAC-Talk avatar
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    then we make laws to take it away.

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  5. #5
    Join Date
    Dec 2002
    Location
    SouthEast NC ICW & Piedmont Foothills
    Posts
    7,635
    4 ton hp; no reason for a site glass; especially if it's at the hp

    what Mr.B said!
    It`s better to be silent and thought the fool; than speak and remove all doubt.

  6. #6
    Join Date
    Nov 2011
    Location
    USA
    Posts
    400
    Quote Originally Posted by millertime77 View Post
    Pressures are 79/205, sh 2 to 3, sc 1 to 2.
    The few times I've seen similar numbers, it was an over-feeding TXV or fixed orifice piston installed backwards.

  7. #7
    Join Date
    Sep 2012
    Location
    New York
    Posts
    175
    Most systems are charged by superheat so if your pressures, temp. split etc are alright dont worry about a few bubbles there has been plenty of times ive left systems with some bubbles in the sight glass. Is there a lot of bubbles? what is the size of them where in the glass are they flashing more towards the outlet? Is there a leak on the system or a history of adding gas?

  8. #8
    Join Date
    Feb 2012
    Posts
    1,268
    Pumping down and starting fresh with new refrigerant and filter drier would be my guess...adding refrigerant to a system with non condensables would not help anything.

    Checking compressor amps and system pressures would give you an indication of id the compressor is bad or not.

    What refrigerant are you running?

  9. #9
    Join Date
    Jul 2010
    Location
    From AZ to N.E. OHIO
    Posts
    10
    Sounds like its overcharged, does the system need a fan cycle control installed? Cooler outside than inside. what were the pressures before adding refrigerant? R-22?????

  10. #10
    Join Date
    Apr 2011
    Location
    michigan
    Posts
    172
    Suction pressure doesnt look like the valves are bad, what was the temp outside? You said the glass was "milky", could there be moisture in the system, has anyone had the system open? Think I would try removing the charge, replace the dryer, pull a good vacuum and recharge with new refrigerant.

  11. #11
    Join Date
    Mar 2009
    Location
    Mid-Mo
    Posts
    3,596
    How is your airflow? Belt drive? Sheaves/belts/etc in good shape?

  12. #12
    Join Date
    Jan 2009
    Location
    Etters PA.
    Posts
    500
    What was the pressure and superheat subcooling after you added all the refrigerator

    Sent from my PC36100 using Tapatalk 2

  13. #13
    Join Date
    Aug 2012
    Posts
    39
    Based on the those measurements and your observations I would suspect contamination of the refrigerant (R22/R410a mix).

    Recover the refrigerant and try a clean charge in it.

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