Extending the life of a central AC unit

Ian S
Ian S Solar Expert Posts: 35 ✭✭
One month ago, our 16 y.o. Trane AC system (roof mounted 5 ton gas pack) had a coil freeze up due to low refrigerant. The HVAC tech said it was almost certainly a leak in the coil and if so would not be worth repairing on such an old system. I declined to pay to have the leak traced and figured I'd just see how things went with the addition of refrigerant while I considered replacing the system. A month later the AC system appears to be working fine so the leak can't be a huge one. In fact it's probably pretty small (AC hadn't been checked for several years.) I'm not going to spend thousands on finding and fixing a coil leak and instead am wondering if a product like this might be a way to stretch the life of this system for another year or two.

Most web comments from the HVAC pros seem to poo-poo the product and claim it could damage the system. Others seem to think it a reasonable thing to try on an old system, especially if the alternative is to simply replace the unit. Has anyone here had any experience with such a product and if so, how did it work out? I would have a pro do this instead of doing it myself. Obviously, the system will have to be replaced at some point but I'd like a little more time to plan for the $7000 to $8000 expense.


  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    Re: Extending the life of a central AC unit

    Sounds like a reasonable thing to do on an old unit. Just be prepared to fork out for a new one.

    I generally have my units checked every other year, occasionally the do take a shot of freeon. I really trust my AC guy.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Extending the life of a central AC unit

    In for a dime, in for a dollar. If you are prepared to scrap the system anyway if it fails, I don't think thte is any harm. Many pooh-pooh these sealers (especially in the auto A\C field, as t hey claim they eventually clog compressor and expansion valves. If you knew it it going to crater, what the hack?

  • CDN_VT
    CDN_VT Solar Expert Posts: 492 ✭✭✭
    Re: Extending the life of a central AC unit


    AUTO is not the same as Central HVAC . they suffer different things.
    Auto has a shaft seals , rubber hose's that weep / blead etc.
    Central has tubing & sealed , no rubber .

    I first would add Dye tracing , Just to see where the weep is , now that takes good eyes , and every line & heat exchanger to be checked. I use green florescent that is black light hot showing green.. Make sure that all heat exchangers are clean , if they are dirty blocked they over-temp & sometimes blow off on over pressure on the high side.

    Work smart , keep power off , the fins are needed to be straight & bend lightly.
  • Ken Marsh
    Ken Marsh Solar Expert Posts: 114 ✭✭✭✭
    Re: Extending the life of a central AC unit

    You did the right thing by topping off the charge, particularly if it is first time.
    Most small leaks plug themselves due to the trash circulating in the oil.

    As for the stop leak, I have had good and bad experience with it.
    The loosers seem to be small units like refrigerators.
    The stop leak can cause the compressor to cease.
    You don't want to put too much in and this is hard to control.

    If you can find the leak, fix it-even if it is in the coil.
    It is not that hard.
    But most HVAC techs would rather sell you a new unit.
    And there are a lot of other things that can cause an evaporator coil to freeze.
  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    Re: Extending the life of a central AC unit

    I dealt with a small leak with one of our systems for a few years. I knew where the leak was, my father-in-law had a sniffer and found it in the furnace but I wasn't going to spend the bucks on a system that was already 10 years old (at the time). First refill lasted 2 years. Next refill lasted a year, the next another year and then I gave up on it and turned it off for good. I'll replace it and the other system in a few years, for now a window A/C takes care of us downstairs. If your experience is good maybe I'll give it another chance.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • Ian S
    Ian S Solar Expert Posts: 35 ✭✭
    Re: Extending the life of a central AC unit

    I think I'll give it a try come September. R22 refrigerant has become gold plated at $80 per lb. Replacing the 5 ton gas pack will be close to $8K and if I do it now, I'll have to take it out of an IRA. If I can get another two years out of it, then I'll be happy to replace it with a more efficient unit.
  • RCinFLA
    RCinFLA Solar Expert Posts: 1,484 ✭✭✭✭
    Re: Extending the life of a central AC unit

    Make sure your evaporator coil grid is cleaned. Dust clogging the evaporator can also cause freeze up of evaporator coil by blocking air flow across coils.

    Home Depot sells coil cleaner for about $10 for pint bottle. Smells like Formula 409 cleaner. Spray it on and use a wet vac to suck up water from a garden hose sprayer to clean it out.
  • Shadowcatcher
    Shadowcatcher Solar Expert Posts: 228 ✭✭✭
    Re: Extending the life of a central AC unit

    Having done leak testing as part of my job I would be doing a leak test.