Page 1 of 2 12 LastLast
Results 1 to 13 of 18
  1. #1
    Join Date
    Jul 2010
    Location
    Vegas
    Posts
    63
    Post Likes

    R407C residential AC sight glass intermittent cloudy & clear, hi side fluctuates

    Installed two 3.5 ton dry charged York straight cool condensers on existing old 12 seer R22 system, with 4 ton furnaces and coils, and existing orifices (no txv).

    Unit cools great, charged until sight glass clear, pressures in spec, return line was cold, but then noticed that sight glass would cycle from cloudy to clear every 30 seconds or so.

    Ambient was around 90, and I noticed when sight glass was clear, high side pressure was around 225. Then, pressure would begin to climb, while at the same time sight glass would get gradually cloudy, until it was solid white when reaching a peak of 250 psi. This would take about 30 seconds, then pressure would slowly drop, while at the same time the sight glass would begin to clear, until it was completely clear at the bottom pressure of 225 psi. This would also take about 30 seconds, then it would begin to rise again. Repeat. etc. The low side would also go up and down in sync with the high, from 65 to 70 psi.

    I have good airflow at the furnace and temp split is around 24-25 degrees. Return was around 82 and supply at plenum after coil was around 58.


    This was my first 407c changeout. Is this normal?

    The sight glass is an Emerson, and it is installed immediately after the condenser, but right before the drier, on a 3/8 line. The suction line is 3/4, and the furnace is upstairs, I'm guessing around 50 possibly 60 feet away, and perhaps 25-30 feet above ground level.

    I also notice when this unit starts, there's a brief grunting/vibration for less than one second, which makes me wonder if the compressor is loaded with liquid or excess oil draining back into it when shut down? Also when I remove my gauges, there's a lot of oil blow off from the high side, and even some from the low side.

    The system was flushed and evacuated prior to charging., and a 163 liquid line drier installed after the sight glass

  2. #2
    Join Date
    Aug 2009
    Location
    Beatrice, NE
    Posts
    4,418
    Post Likes
    Superheat, subcooling, wet bulb? Sounds like your undercharged a little or maybe the system just hadn't had time to settle in yet. That's where the extra readings come in.

  3. #3
    Join Date
    Jun 2003
    Location
    Chicago, IL
    Posts
    5,738
    Post Likes
    A lot of times a sight glass is cloudy it's from oil flowing by. Are you sure the compressor is not getting floodback? Make sure you measure superheat using the dew point table. Also you can feel the compressor and make sure it's warm

  4. #4
    Join Date
    Feb 2014
    Location
    Santa Rosa, CA
    Posts
    463
    Post Likes
    more info would help, but it sounds like oil to me. I know you said you flushed the system, (with r-11 I assume) but how confident are you that any oil trapped in the evaporator was removed? did it take an excessive amount of time to evacuate down <500 microns or have a hard time holding? that could be an indication.

  5. Likes Asm Mechanical liked this post
  6. #5
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    10,223
    Post Likes
    Quote Originally Posted by Transformed View Post
    Installed two 3.5 ton dry charged York straight cool condensers on existing old 12 seer R22 system, with 4 ton furnaces and coils, and existing orifices (no txv).

    Unit cools great, charged until sight glass clear, pressures in spec, return line was cold, but then noticed that sight glass would cycle from cloudy to clear every 30 seconds or so.

    Ambient was around 90, and I noticed when sight glass was clear, high side pressure was around 225. Then, pressure would begin to climb, while at the same time sight glass would get gradually cloudy, until it was solid white when reaching a peak of 250 psi. This would take about 30 seconds, then pressure would slowly drop, while at the same time the sight glass would begin to clear, until it was completely clear at the bottom pressure of 225 psi. This would also take about 30 seconds, then it would begin to rise again. Repeat. etc. The low side would also go up and down in sync with the high, from 65 to 70 psi.

    I have good airflow at the furnace and temp split is around 24-25 degrees. Return was around 82 and supply at plenum after coil was around 58.


    This was my first 407c changeout. Is this normal?

    The sight glass is an Emerson, and it is installed immediately after the condenser, but right before the drier, on a 3/8 line. The suction line is 3/4, and the furnace is upstairs, I'm guessing around 50 possibly 60 feet away, and perhaps 25-30 feet above ground level.

    I also notice when this unit starts, there's a brief grunting/vibration for less than one second, which makes me wonder if the compressor is loaded with liquid or excess oil draining back into it when shut down? Also when I remove my gauges, there's a lot of oil blow off from the high side, and even some from the low side.

    The system was flushed and evacuated prior to charging., and a 163 liquid line drier installed after the sight glass
    Please show me where in the York Manual it says to clear the Sight Glass!

  7. #6
    Join Date
    Apr 2003
    Location
    Maple Grove, MN
    Posts
    2,080
    Post Likes
    In case you missed this day in HVAC school, you can NOT charge up a fixed metering device system by subcooling or by looking at a sightglass. The only thing you should be using that sight glass for is to see if the little dot in the middle is green.

    The only proper way to charge up a orifice type system is to use superheat, wet bulb, and a charging chart.

  8. #7
    Join Date
    Jan 2010
    Posts
    10,302
    Post Likes
    .....and for those times a sight glass is required, please install it after the filter/ drier.

  9. Likes syndicated liked this post
  10. #8
    Join Date
    Jul 2010
    Location
    Vegas
    Posts
    63
    Post Likes
    Quote Originally Posted by ammoniadog View Post
    In case you missed this day in HVAC school, you can NOT charge up a fixed metering device system by subcooling or by looking at a sightglass. The only thing you should be using that sight glass for is to see if the little dot in the middle is green.

    The only proper way to charge up a orifice type system is to use superheat, wet bulb, and a charging chart.
    I never used a sight glass before... guess I forgot this... and was just curious and trying to do an even better job by being able to observe what's going on in the liquid line since 407c is new to me but I've installed hundreds of r22 systems with no problems failures or comebacks at all.

    I guess it's no big deal then?

  11. #9
    Join Date
    Jul 2010
    Location
    Vegas
    Posts
    63
    Post Likes
    Quote Originally Posted by pecmsg View Post
    Please show me where in the York Manual it says to clear the Sight Glass!
    Ok, let's throw the sight glass out then. Why is the high pressure side fluctuating up and down from 225 to 250, in 30 to 60 second cycles? is that normal?

  12. #10
    Join Date
    Aug 2009
    Location
    Beatrice, NE
    Posts
    4,418
    Post Likes
    Are you sure it doesn't have a TXV, that sounds like a TXV hunting.

  13. #11
    Join Date
    May 2016
    Location
    Tulsa
    Posts
    24
    Post Likes

    R407C residential AC sight glass intermittent cloudy &amp; clear, hi side fluctuates

    Sounds like oil or noncondensables. Oil being sucked back and pumped thru the system from the evaps.


    Sent from my iPhone using Tapatalk

  14. #12
    Join Date
    May 2014
    Location
    Bay Area California
    Posts
    8,647
    Post Likes
    Sounds under charged. I'll bet when you get that cloudy sight glass, your subcooling will have dropped to something close to 0-1*F. Add more freezey juice and see what happens.

  15. #13
    Join Date
    Feb 2014
    Location
    Santa Rosa, CA
    Posts
    463
    Post Likes

    Freezey juice?

  16. Likes BBeerme liked this post
Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

Related Forums

Plumbing Talks | Contractor MagazineThe place where Electrical professionals meet.
Comfortech 365