Page 1 of 2 12 LastLast
Results 1 to 13 of 22
  1. #1
    Join Date
    Sep 2011
    Posts
    6

    Confused a/c unit failures

    I have a Lennox 12ACB42(3 1/2 ton) split central a/c unit that from time to time quits cooling. This has happened 4 times this summer in Plano, TX where it's been real hot. Anyway, With each cooling shutdown I have done the following:
    Turn the compressor off at the thermostat leaving fan running
    I have hosed down the unit
    I waited about 30 min's and turned it back on
    In each case it started cooling again - sometimes 6 weeks between failures?
    I have had the unit checked on 2 seperate occasions and everything checks out? Freon full - Compressor running OK
    However the last time I had it checked the technician noticed that the compressor had some high head pressure readings and he thought it was slowly dieing.
    Does this sound right???????
    Thanks

  2. #2
    Join Date
    Jun 2011
    Location
    Wake Forest, NC
    Posts
    352
    The compressor is locking out in thermal overload. Could be one of a few problems. Could be a bad compressor thermal overload switch, if nothing else is truely wrong. That would be sad as it would require replacing the compressor. Possibly a restriction in the refrigerant line, clogged filter dryer or a kink in the line. Dirty condenser coil would probably be the easiest possibility to find and repair. A measurement of superheat and subcooling would be helpful in determining if there is a restriction in refrigerant flow, and narrow down where it might be.
    It's not rocket-science...

    It's electromechanical thermodynamic engineering

  3. #3
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,060
    Look at your service ticket and see if he entered pressures and temperatures. To say you have high head pressure without telling you why is like the doctor telling you that you are running a fever and slowly dieng.

  4. #4
    Join Date
    Sep 2011
    Posts
    6
    Thanks - I will see if I can locate the pressure readings

  5. #5
    could be txv

  6. #6
    Join Date
    Sep 2004
    Location
    Lancaster, Tx
    Posts
    183
    My first thought was dirty filter just because I see that so much... But have to agree with the rest of the posts above as well...
    If we didn't do this what would we do for fun?

  7. #7
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    18,316
    It sounds like a maintenance issue.

    Have the tech clean the indoor and outdoor units. This uses professional chemicals and should not be attempted by a homeowner.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

    AOP Forum Rules:







  8. #8
    Join Date
    Sep 2011
    Posts
    6
    Thanks for all responses. Two questions:
    1) What about the Capacitor?
    2) Are there still 12SEER Units with the old Freon available?
    Thanks,
    Jack

  9. #9
    Join Date
    Sep 2011
    Posts
    6
    If I install a 13 Seer system that requires the R415A freon, can I use the existing coils???? I have read where this practice is not recommended by all technicians?
    Thanks

  10. #10
    Join Date
    Feb 2011
    Location
    North East Ohio
    Posts
    772
    Quote Originally Posted by jackhipp View Post
    Thanks for all responses. Two questions:
    1) What about the Capacitor?
    2) Are there still 12SEER Units with the old Freon available?
    Thanks,
    Jack
    sounds as if this has nothing to do with the capacitor and I would not recommend using existing evap. coil with a switch to R-410a. There are dry ship units that can use R-22 in a replacement situation (which this is) and you could use your existing coil for that. The draw back to using your existing coil is that a dry ship unit is marked 13 SEER but with your existing coil you will not get that level of efficiency. 12 SEER units are not manufactured anymore. 13 is the minimum allowed by law. Good Luck
    Last edited by NCHeat; 09-15-2011 at 10:38 AM. Reason: added content

  11. #11
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,060
    The capacitor would not cause the problem that you stated.

    Yes R22 condensers are still available.

    No you should not install just install the outdoor unit.
    Did you find your invoice with the diagnostic information on it, and can you post it?

  12. #12
    Join Date
    Sep 2004
    Location
    Lancaster, Tx
    Posts
    183
    There are Nitrogen Charged R22 units available (Minimum SEER rating manufactured is 13 SEER) for use when replacing just the condenser.

    You would need to have a qualified tech check the condition of the capacitor, condenser fan motor

    I believe that you are a bit confused... A SYSTEM would include all components inside and out... I believe that you are talking about just replacing the condenser (the outside portion of the system) - If you go to R410a you will need to change the evaporator coil if it is not currently rated for the pressures that R410a runs at. If the evaporator coil has been replaced in the last few years already then it may be possible to install a TXV, run a flush through the system and be ok, but if the coil is more than 5 or 6 years old the is a very good chance that you will need to replace the evaporator coil as well...

    Hope this helps...

    I would strongly advise you to find a qualified company in your area from the contractors map on this site...
    If we didn't do this what would we do for fun?

  13. #13
    Join Date
    Sep 2011
    Posts
    6
    Lonestarheir - Are you referring to the Air Filter? We replace that on a monthly basis with a good quality filter.

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
  •  
Comfortech Show Promo Image

Related Forums

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