Results 1 to 4 of 4

Thread: sight glasses

  1. #1
    Join Date
    Jul 2002
    Location
    Stamford, CT USA
    Age
    46
    Posts
    74
    Rep Power
    22

    Question sight glasses



    could some body clear up my confusion about charging to a full sight glass? Do some refrigerants need a full sight glass while others do not?



  2. #2
    Join Date
    Jun 2001
    Location
    N.Ireland
    Age
    50
    Posts
    1,632
    Rep Power
    24
    Hi Angry,
    where is the sightglass fitted? Is one quetion springs to mind. If it is at the unit generaly charge to a full glass, but this is dependant on other things, head contol, prevailing ambient and system aplication. Realy you have to use your own experience, there is no good in chargeing a unit to a full glass on a freezer aplication and putting it out on head during pulldown, charge until the a point where the head is managable and wait for temperature pull-down.
    Hope this helps.
    Regards. Andy.
    If you can't fix it leave it that no one else will:rolleyes:

  3. #3
    Join Date
    Mar 2001
    Location
    St. Louis, MO
    Posts
    510
    Rep Power
    24
    A full sight glass is your visual indication that you have subcooling. On any system employing a TEV, you should have at least a small amount of subcooling ahead of the TEV.

    On systems employing a capillary tube or short tube restrictors, this is, of course, not the case. One should charge to a desired superheat with the systems, and not be too concerned with the quality of the refrigerant ahead of the expansion device.

    As Andy points out, there are other issues to consider, particularly if you are replacing the refrigerant with one of the newer service replacement blends. For example, you may not have enough condenser to obtain the subcooling you want without running excessive head pressures. So you compromise. But having flash gas in the sight glass is not a "normal" condition, and the Prof has problems with blanket recommendations stating not to charge a system with a TEV to a full sight glass.
    Prof Sporlan

  4. #4
    Join Date
    Jul 2002
    Location
    Stamford, CT USA
    Age
    46
    Posts
    74
    Rep Power
    22
    thanks for the information and fast responses guys. it is greatly appreciated!
    John K.

Similar Threads

  1. liquid line sight glass mystery
    By austech in forum Technical Discussions
    Replies: 19
    Last Post: 18-07-2006, 08:16 PM
  2. sight glass
    By daleworne in forum Trouble Shooting
    Replies: 10
    Last Post: 17-06-2006, 11:43 PM
  3. Sight glass , Flashing ?
    By kfjoe in forum Fundamentals
    Replies: 15
    Last Post: 14-02-2004, 05:41 AM
  4. Sight Glass Located
    By Abe in forum Trouble Shooting
    Replies: 3
    Last Post: 22-01-2002, 02:22 AM

Posting Permissions

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