Page 1 of 4 1234 LastLast
Results 1 to 13 of 52

Thread: TXV issue?

  1. #1

    TXV issue?

    Went on a call today where the high pressure switch was short cycling the outdoor unit. Coil was iced up and capillaries iced cleat to TXV. Suction line iced line clear out to outdoor unit. I looked at the txv sensing bulb and it was mounted vertical with the capillary coming out of the bottom. I checked the coil paperwork and it said bulb must have capillary coming out of the top of it. Has anyone else experienced such a thing, and did flipping it over solve the issue? After I thawed the coil and switched the bulb around I fired it up and had sub cool reading of 11 deg. This was in range with manufacturers chart- within 2 deg. I would appreciate any feedback.

  2. #2
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    16,000
    Quote Originally Posted by bjonesplumb View Post
    After I thawed the coil and switched the bulb around I fired it up and had sub cool reading of 11 deg. This was in range with manufacturers chart- within 2 deg. I would appreciate any feedback.
    To see if a valve is properly working, you really need a SH reading also.
    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

    "Never let success go to your head, and never let failure go to your heart". - Unknown

  3. #3
    Superheat was 11

  4. #4
    I mean superheat was 16 sorry I put wrong value on last post

  5. #5
    Join Date
    Feb 2009
    Location
    Tallahassee, FL
    Posts
    6,048
    Was the sat temp above freezing?

  6. #6
    Yes

  7. #7
    Join Date
    Jan 2006
    Location
    McQueeney, Texas
    Posts
    3,858
    Quote Originally Posted by bjonesplumb View Post
    Went on a call today where the high pressure switch was short cycling the outdoor unit. Coil was iced up and capillaries iced cleat to TXV. Suction line iced line clear out to outdoor unit. I looked at the txv sensing bulb and it was mounted vertical with the capillary coming out of the bottom. I checked the coil paperwork and it said bulb must have capillary coming out of the top of it. Has anyone else experienced such a thing, and did flipping it over solve the issue? After I thawed the coil and switched the bulb around I fired it up and had sub cool reading of 11 deg. This was in range with manufacturers chart- within 2 deg. I would appreciate any feedback.

    I have always been taught the tube from the bulb should always be higher than the bulb to keep the liquid in the bulb and to always keep the liquid away from the tube. I always make a rise in the tube when the bulb is mounted horizontally.

    There are always conflicting opinions, but I have never had problems doing this.

    If after you changed the bulbs position and you checked the airflow across the evaporator, and other conditions as a blower motor quitting, dirty filters and such (sticking contactor) and so on and your pressures and SC and SH are normal, I would say you found the problem- and good show on doing that. Many would have missed it.

  8. #8
    If the liquid migrated would that cause the txv to meter the flow improperly?

  9. #9
    Join Date
    Jan 2006
    Location
    McQueeney, Texas
    Posts
    3,858
    There is a varied degree of liquid in the bulb and you want as much of the liquid in contact with the suct pipe area per the position of the bulb- 4-8 o'clock or 10-2 o'clock as the manufacturer requires.

    I had a Ruud system icing up and found the bulb at 4 o'clock when it was required to be at 10 o'clock. Moving it cured the problem.

    In a vertical position, allowing the liquid to fill the tube takes away from the bulb that is in contact with the suct pipe and you will also have the top of the bulb trapped with gas instead of liquid- these two can affect it's performance so I have been advised.
    In your case this could have caused the valve not to open enough.

    Like I said- this is what I have been taught- perhaps someone has a better description.

  10. #10
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,058
    Quote Originally Posted by bjonesplumb View Post
    Went on a call today where the high pressure switch was short cycling the outdoor unit. Coil was iced up and capillaries iced cleat to TXV. Suction line iced line clear out to outdoor unit. I looked at the txv sensing bulb and it was mounted vertical with the capillary coming out of the bottom. I checked the coil paperwork and it said bulb must have capillary coming out of the top of it. Has anyone else experienced such a thing, and did flipping it over solve the issue? After I thawed the coil and switched the bulb around I fired it up and had sub cool reading of 11 deg. This was in range with manufacturers chart- within 2 deg. I would appreciate any feedback.
    Bulb location won't cause the system to cycle off the high pressure switch. Unless its over charged.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  11. #11
    It only has the factory charge plus 3 oz for lineset , the factory charge should have been accurate right?

  12. #12
    I am thinking it cycled off on head pressure because the inside coil iced over because the txv malfunctioned because the bulb was upside down. Just a theory .

  13. #13
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,058
    When the inside coil is iced over. A large amount of the liquid refrigerant stays in the coil. Refrigerant return to the compressor is decreased, lowering head pressure.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

Page 1 of 4 1234 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
  •  
Comfortech Show Promo Image

Related Forums

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