Results 1 to 9 of 9
  1. #1
    Join Date
    Dec 2009
    Posts
    35

    bubbles in sight glass.

    why do bubbles in the sight mean low on refrigerant charge I don't understand how that works. I was also told that on start up you'll get bubbles in the sight glass why is that.

  2. #2
    Join Date
    Jan 2009
    Location
    Indiana
    Posts
    3,228
    Quote Originally Posted by bojolad77 View Post
    why do bubbles in the sight mean low on refrigerant charge .
    another rule of thumb that is not necessarily true

  3. #3
    Join Date
    Dec 2008
    Location
    "Bay Area", Cali
    Posts
    167
    its basicly acting like a "metering device"
    refer is flashing off into the sight glass becuase of the increase of the space in the sight glass compared to the liquid line
    SMW 104

  4. #4
    In my opinion, a sight glass is useless on R-22 A/C units, unless it has a moisture indicator, they are good for that I suppose.
    Hey cockroach, don't bug me! ©

    www.AskTheDiceman.com

    www.TheColdConspiracy.com

    www.Pennwood-HVAC.Com

    Bring Em Home....

  5. #5
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,946
    In order to properly function, a TXV requires a solid column of liquid refrigerant entering it.

    A sight glass provides a quick glance into the system and, on some equipment, can allow a quick verification of charge.

    It shouldn't always be wholly relied on, though. There are other ways of verifying charge that are more accurate.

  6. #6
    Join Date
    Mar 2007
    Location
    South Texas
    Posts
    220
    On some systems under the right conditions the presence of bubles in the sight glass can be considered normal. Was on a job once where someone had put a sight glass on a package unit, found out they had grossly overcharged the system.

  7. #7
    Join Date
    May 2000
    Location
    Rochester, NY, USA
    Posts
    14,509
    Quote Originally Posted by Diceman View Post
    In my opinion, a sight glass is useless on R-22 A/C units, unless it has a moisture indicator, they are good for that I suppose.
    Quote Originally Posted by jpsmith1cm View Post
    In order to properly function, a TXV requires a solid column of liquid refrigerant entering it.

    A sight glass provides a quick glance into the system and, on some equipment, can allow a quick verification of charge.

    It shouldn't always be wholly relied on, though. There are other ways of verifying charge that are more accurate.
    Quote Originally Posted by SouthTex View Post
    On some systems under the right conditions the presence of bubles in the sight glass can be considered normal. Was on a job once where someone had put a sight glass on a package unit, found out they had grossly overcharged the system.
    as these guys said:

    you should never put a sight glass on a residential a/c system.

    why? Glad you asked. Because many "newbies"(and even some old timers) believe if they see bubbles in a sight glass the system is under charged. If you charge a system properly, there is a good chance your going to see bubbles in the sight glass on a 72°-78° day. If you come back on a 90° day the bubbles will be gone.

    Use proper techniques for checking the charge of a system, DO NOT rely on a sight glass.

    everytime I come across a system with a sight glass, the damn thing is over charged, every single time. People get lazy and don't check using superheat and subcool, then you have problems
    I only drink a little, but when I do
    I turn into another person and THAT person drinks a lot

  8. #8
    Join Date
    Oct 2003
    Location
    South Carolina
    Posts
    1,242
    I put a sight glass in my system when I installed it in my home because I wanted a method of checking the condition of the refrigerant through visual inspection and to monitor for the presence of moisture.
    Bubbles don't mean a loss of charge, proper technique is the only thing that can provide that diagnosis but, sight glasses have their uses.
    “Two things are infinite: the universe and human stupidity; and I’m not sure about the universe.” —Albert Einstein

  9. #9
    Join Date
    May 2000
    Location
    Rochester, NY, USA
    Posts
    14,509
    Quote Originally Posted by william antley View Post
    I put a sight glass in my system when I installed it in my home because I wanted a method of checking the condition of the refrigerant through visual inspection and to monitor for the presence of moisture.
    Bubbles don't mean a loss of charge, proper technique is the only thing that can provide that diagnosis but, sight glasses have their uses.




    only if you know what your looking at.

    Joe HomeOwner doesn't have a clue and when HE see bubbles, he's going to think the system is under charged or that something is wrong.

    For you! ya maybe a sight glass has some value, but generally speaking, in a residential system a sight glass is not a good idea
    I only drink a little, but when I do
    I turn into another person and THAT person drinks a lot

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event