Page 1 of 2 12 LastLast
Results 1 to 20 of 27

Thread: Heat Pump Operations Question...How low can you go?

  1. #1
    Join Date
    Jan 2021
    Posts
    103
    Post Likes

    Heat Pump Operations Question...How low can you go?

    I've been wondering...how much 410a can leak out of a heat pump system before a homeowner would notice that it is not heating or cooling correctly? Can heat pumps work with a certain level of reduced charge? (I'm asking because I suspect I've had a slow leak from one of the Schrader valves because I was finding oil on the plastic cap, and have since replaced it with a nice brass cap)

    Thanks!

  2. #2
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    32,937
    Post Likes
    How much air can you loose out of a tire before it wears differently?

  3. #3
    Join Date
    Jan 2021
    Posts
    103
    Post Likes
    Thread Starter
    You can run a tire 1-2 psi above or below the recommended setting and not notice much difference. You can run a car 1/2 qt low on oil and it will run fine. So what about a heat pump? At what level of loss of 410a will the system stop working or will a homeowner notice a significant loss of heating/cooling?

  4. #4
    Join Date
    Jan 2010
    Posts
    22,862
    Post Likes
    Well once you have no sub-cooling it's down hill fast from there.

  5. Likes R600a, jacob-k liked this post.
  6. #5
    Join Date
    Jun 2014
    Location
    Dover, DE
    Posts
    12,473
    Post Likes
    Your asking a generic question about your unit that has no generic answer.
    It would be determined by your specific system and setup.
    I havent failed. Ive just found 10,000 ways that wont work. - Thomas Edison

    Its not whether you get knocked down, its whether you get up. - Vince Lombardi

    "In this house we obey the laws of thermodynamics" - Homer Simpson

    Local 486 Instructor & Service Technician

  7. #6
    Join Date
    Jan 2014
    Location
    New England
    Posts
    8,885
    Post Likes
    Great to hear..thanks. I'll check it with soap and just keep an eye on it.

    https://hvac-talk.com/vbb/threads/22...ighlight=Scguy

    Above is from your last post, from earlier this year, when they replaced the indoor coil. Did you find it leaking then? Did you replace the cap then or recently?

  8. #7
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    32,937
    Post Likes
    Quote Originally Posted by SCguy View Post
    You can run a tire 1-2 psi above or below the recommended setting and not notice much difference. You can run a car 1/2 qt low on oil and it will run fine. So what about a heat pump? At what level of loss of 410a will the system stop working or will a homeowner notice a significant loss of heating/cooling?
    NOT notice much deference!

    1/2 qt low really, why do they say X amount of oil and not Just Under this much?

  9. #8
    Join Date
    Jan 2021
    Posts
    103
    Post Likes
    Thread Starter
    Bazooka Joe:

    Never saw bubbles but what I noticed was after running the AC (infrequently since not too hot yet) there would be a small amount of oil on the outside of the plastic cap. Just enough to feel between your fingers. So just yesterday I replaced the plastic caps with a brass ones thinking if the valve has a small leak that a brass cap would stop it.

  10. #9
    Join Date
    Jan 2010
    Posts
    22,862
    Post Likes
    If the core in your Schrader valve is leaking it should be replaced.

  11. Likes dan sw fl liked this post.
  12. #10
    Join Date
    Jan 2021
    Posts
    103
    Post Likes
    Thread Starter
    Yes, that's my next step... call a pro out to replace it.

  13. #11
    Join Date
    Jan 2014
    Location
    New England
    Posts
    8,885
    Post Likes
    I suppose check with soap ( system off ) here and there, later in warmer weather and run in cool, your looking for 18-20 give or take degree temperatures difference using a accurate thermometer ( not IR Gun ) and let system run 15 minutes to stabilize before checking. Put the thermometer in a register closest to the Air Handler, same with the return. Having a good load on the inside of the residence also, say 75+ degree.

    They make two types of brass caps, circular with a neoprene O ring, which is finger tightened firmly or the Hexagon type ( no neoprene O ring ) that needs to be tightened with a adjustable wrench.

  14. #12
    Join Date
    Jan 2010
    Posts
    22,862
    Post Likes
    Quote Originally Posted by SCguy View Post
    Yes, that's my next step... call a pro out to replace it.
    It's a very simple procedure and I'd be surprised if a service provider would charge more than a service call.
    Well, maybe a small fee for the core.

  15. Likes R600a liked this post.
  16. #13
    Join Date
    Jul 2019
    Location
    Oklahoma home its in the name
    Posts
    7,719
    Post Likes
    One thing about heat pumps is they are often configured for comfort over efficiency and the backup heat kicks in so quickly that no one notices when it has totally run out of refrigerant. That said I am sure you would notice if your heat pump was not running anymore.

    Sent from the Okie state usin Tapatalk

  17. #14
    Join Date
    Jan 2010
    Posts
    22,862
    Post Likes
    That is true until they get their next electric bill 😳

  18. Likes R600a, BALloyd, BBeerme liked this post.
  19. #15
    Join Date
    Jan 2021
    Posts
    103
    Post Likes
    Thread Starter
    Yes, once our usual hot and humid SC summer kicks in, I'll take those measurements. The brass cap I have is circular with a neoprene O ring but as suggested above will likely have the valve replaced too. Thanks!

  20. #16
    Join Date
    Jan 2021
    Posts
    103
    Post Likes
    Thread Starter
    UPDATE:

    So the heat is on here in S.C! The difference between the intake and output at the register was only 13-14 degrees, and it took much longer than expected to cool the house at night (1 hr to lower temp one degree). So called for service.

    Told them the story of the oil around the Schrader valve. His electronic sniffer could not confirm a leak at the valve but he stated the valve "was loose" so he carefully tightened them. He said the sub-cooling was off and that I was down 2 lbs of 410a, so he added it. Now temp difference between intake and output registers is 18.

    Hope it's NOT the coil in the air handler that was replaced this past winter that's leaking! Fingers crossed.

  21. #17
    Join Date
    Jan 2014
    Location
    New England
    Posts
    8,885
    Post Likes
    Sounds like you got shoe maker service company, or a inexperienced service Tech. last time, was the valve cover cap loose or the valve stem loose. To me it’s on them for not tightening the caps when they left last time..

    What does the invoice say, ...please tell me they gave you a legible somewhat detailed invoice....

    Weren’t you talking about replacing this system sooner than later in your other threads?

    If so IMO, get a uncomplicated less bells and whistles system.....

  22. #18
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    32,937
    Post Likes
    B S
    !!!

  23. Likes Bazooka Joe liked this post.
  24. #19
    Join Date
    Jan 2021
    Posts
    103
    Post Likes
    Thread Starter
    No, after the coil was replaced, I notice recurrent oil around on one the plastic caps that was on tight. I since replaced it with a brass cap and no more oil was seen.

    But, could tell the AC was not cooling as well as it should which made me call for the service call.

    He could not confirm a leak from the Schrader but he "tightened" the Schrader valve based on what I had seen with the recurrent oil (not the cap but "tightened" the inside piece which I guess is the valve stem?), and add the 410a.

    No plans to replace system but if we do would not get a bells and whistle system.

    They Email invoices 10 days after service, so don't have it yet.

    So the question is, can the inside of a Schrader valve (the stem) be "loose" as the tech suggested and cause 410a loss?

  25. #20
    Join Date
    May 2014
    Location
    Bay Area California
    Posts
    30,729
    Post Likes
    For what it is worth, my electronic leak detector is so sensitive, I can remove the shrader cap and pick up a leak on every shrader. What's fun is to show a rookie how much refrigerant vapor is still in the cap after you remove it.

    If your tech could not pick up a leak, he has a very inexpensive leak detector. If he did not replace the shrader valve, it's likely he doesn't even know there is a tool out there so you do not lose any refrigerant. Or, if he knows about it, he is not professional enough to go out and buy it. Or, he isn't getting paid enough to buy the proper tools. Or . . . It could go on and on . . . Maybe a judge took all he owns and had it sold at the Flea Market to pay back child support . . . LOL . . . Or . . . Or . . .
    I do a triple evac with nitro to remove non condensables.

  26. Likes R600a liked this post.
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
  •