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  1. #1
    Join Date
    Jul 2014
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    Superheat and sightglass

    Super heat between 6-13 degrees, low pressure 65-69 with associated temperatures, sight glass at evaporator half full, some bubbling top half, TXV adjusted for super heat, TXV has a bleed compensation. System pulled to vacuum 400-500 microns after triple flush N. Pressure tested to 275 psi, 24 hours, no leaks.

    Question: If the amount of R-22 increased, pressure should drop, and this would fill sight glass which currently indicates evaporator is receiving some flashed R-22 as well as liquid. However, saturated temp would below 40 degrees at compressor. I am assuming high pressure not relevant in this situation.

    R-22 $/30 pounds here. Sound about average?

    Thoughts.


    Dennis
    Last edited by beenthere; Yesterday at 04:44 PM. Reason: Price

  2. #2
    Join Date
    Apr 2003
    Location
    St. Louis
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    63
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    Charge by subcooling 10* is average. You have to have a load on the system and run the head up if it's cool outside.

  3. Likes dloefffler liked this post
  4. #3
    Join Date
    Dec 2014
    Location
    midwest
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    WB, DB, ambiant, line length/size, equipment data, HP, SC, temp across dryer, airflow, comp pumping o.k.? Etc. Why would HP not be relevant?

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  6. #4
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    10,210
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    Pricing not allowed

    Charge by what icy783 said, not a sight glass.

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  8. #5
    Join Date
    Jul 2012
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    2,284
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    If it does not have a liquid receiver on it, it should not have a sightglass. Never ever charge an ac system to "clear the sightglass" unless it has a liquid receiver on the liquid line which most do not. Stick to 10 subcool, make sure the outdoor temp is up enough or block the fan to simulate higher ambients. 7-10 superheat at the suction service valve with a txv is good.

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  10. #6
    Join Date
    Jul 2014
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    7
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    Yesterday, finish install, etc., numbers as noted in first post.

    Today:
    ambient 81 degrees F, no wet bulb outside as it doesn't matter, interior at 72, humidity wnl. Lazy, the sock and thermosister are for the Fluke outdoors.
    HP 170 measured temperature of HP line 79.2 vs saturation temp approx 90, so bit of excess subcool
    LP 120 plus, measure temp 51.9. Yesterday, LP was wnl, measured temp was approximately 11 degrees, within error measurement.

    Yesterday, could observe TXV working, pressure varied from approx 63 to 69.

    Length of lines approx 40-50 feet, 30,000 btu, line size 3/8 and 3/4 per manufacture instructions for this unit.

    This is an attic unit, lines are insulated, commercial foiled flex outside and in, plenums insulated to R-10 with appropriate vapor barrier, unit itself isolated from attic in purpose build enclosure with R-10. No air flow issues, matched unit, maximum blower speed, adequate duct sizing.

    Very difficult to access, need to remove ducting to get there, no alternative. Drain pan, code, etc., work area provided, lighted, access once there adequate, but getting there is very difficult. Prefer not to return. Unit was installed to allow future service as the first two units had failed - without building floors for access, the first guys did a great job working like monkeys with their toes curled around the rafters, only cracked the dry wall ceiling in one place.

    As noted, high vacuum pulled, 24 hour pull, pressure test done, dry N purgex3.

    What happened to the low pressure?

    Dennis

  11. #7
    Join Date
    Dec 2014
    Location
    midwest
    Posts
    151
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    81f ambient, 170HP 120LP Amps actual? Amps RLA? Bad pump? What is wnl? New install is r-22? Should it have 410a in it?

  12. #8
    Join Date
    Jul 2014
    Posts
    7
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    RLA13.5
    Measured 6.6 per leg.
    Unit designed for R-22, initial replacement only, entire system replaced including line set. Repair expanded to a rebuild.

    wnl - with in normal limits.

  13. #9
    Join Date
    Mar 2015
    Location
    Medford, N.Y.
    Posts
    1,983
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    Yea , I agree,what is "wnl" in AC language!?? In AC language WTHELL does "high pressure not relevant" mean? HarHar,not funny! What was suction line measured temp at the comp w/ 120+ suction press?

  14. #10
    Join Date
    Jul 2014
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    Measured temp 79.2 as noted.
    Assume if super heat wnl, 10 degrees previously, sub cooling wnl, 10 degrees previously HP not relevant for discussion, my mistake.
    Thanks for taking time to reply.

    Baffled why with no change n TXV settings, no change in charge LP changed.

    Measured air temp from evaporator coil was 49-51 degrees if I remember correctly. This was an open system as the final supply duct was open to the attic due to previously noted access issues.

    I am the third guy on this project, it apparently has never been an easy project.

    Lines are wnl of manufactures guide lines for lift - no more than 14 feet, sized appropriately for length, lift, pressure per manufacture.

    There is no "sump" on the vacuum line at the bottom of the run.

    Thanks,

    Dennis

  15. #11
    Join Date
    Jul 2014
    Posts
    7
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    About to leave job, covered condenser with cardboard, ran pressure to 220, no problems, measured HP temp held approx 79 degrees as noted previously, raining, end of day, I am out of here.

    It does cool the house with no issues. With the LP gauge at near the end of its travel, possible faulty gauge?

    Thanks,

    Dennis

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