Page 1 of 2 12 LastLast
Results 1 to 13 of 19
  1. #1

    Outside unit turns on/off repeatedly

    Hello, I'm new to this forum and am hoping to learn a lot of useful information!

    I got my HVAC system for my house replaced a 2 years ago, a Lennox 16-seer system (I don't remember the model numbers off the top of my head). Last night I was sleeping and I hear some odd tone coming from my outside unit and wondered what it could be. The tone can be described as: a high pitch sound gradually getting lower and lower over a 3-second span, make sense? This tone sounds like the fan is slowing down and eventually stopping. A few minutes later I hear it again somehow thought it couldn't be the outside unit of my heat pump, because hot air was still blowing out in the house. A few minutes later, again and again all night. Occasionally, it would "sound" like it was normal because it would not shut on/off repeatedly.

    Maybe I haven't noticed it until now, but is this normal? I don't want to call a tech over if this is normal behavior of a typical system.

    The system (or at least my heater) still works great though.

    Thank you.

  2. #2
    Join Date
    Aug 2002
    Location
    Southern NJ
    Posts
    962
    There is nothing wrong with calling a service company out to check the system if you are concerned about it's operation. Better to do it now if there is an issue before it becomes a costly disaster.......
    I love to Cook...HVAC is a hobby that pays the bills!

  3. #3
    in heat mode, see if there is cold air blowing out of your unit outside. also, feel the copper lines connected. the small line should be slightly warmer than your hand; the larger line should be hot. the exception would be if it is in defrost. defrost occurs when ice is detected on the outside coil. in defrost, the fan should not be running outside and the larger freon line will be cool. if it is in defrost, once the ice is melted off, it should soon return to normal heat operation (first description).

    this is a non-technical way to determine if your heat pump is working. whether it is performing properly is something that should definitely be checked by a professional. if your house is warm, it is possible the heat pump is not working and your aux heat is heating your house. if you think something is wrong outside, you should be able to place your thermostat in the 'emergency heat mode' with a switch, which disables your heat pump to prevent possible damage while awaiting service.

    some heat pump sounds are normal that do not occur with a regular condensing unit (outside). if you are hearing a new sound, it's worth checking out. my first impression of the sound you described is that you may have a compressor stalling. the other clue there could be a problem is that you notice it isn't cycling on and off at a regular frequency.

    good luck.
    Last edited by nomadpeo; 01-26-2011 at 10:22 AM. Reason: added info / spelling / phrasing

  4. #4
    Thanks, I will take both advice when I get home. I will also take more advice if anyone else has any.

  5. #5
    Join Date
    May 2007
    Location
    DC Metro Area (MD)
    Posts
    3,369
    Is it defrosting? Part of what you wrote (high to low pitch noise, fan slowing down) makes it seem like it could be. If it is, it's normal operation for heat pumps.

  6. #6
    Good to hear that news Ryan. I'll keep that in mind.

  7. #7
    Join Date
    May 2007
    Location
    DC Metro Area (MD)
    Posts
    3,369
    Sorry, after rereading your post -- if this is happening every few minutes, does not sound like it is defrosting (at least the way it should be). Something happening this often should be checked out.

  8. #8
    Oh really? How long should it be occurring then?

  9. #9
    Join Date
    Feb 2004
    Location
    St Louis, MO
    Posts
    54
    Pretty sure Lennox uses a 30 second compressor shutdown going into, and coming out of defrost, so it would be normal to hear some noises. Does the unit seem to be clear of ice, that is defrosting properly?

    Your OD fan is shut off during defrost, so that would be normal. Your electric heat is turned on during defrost, so you should be feeling hot air inside while all of this is happening...normally hotter than when it's just running as a pump.

    Just average numbers, your defrost cycle might last 2 - 10 minutes depending on how frosted it is. So you'll hear the reversing valve shift, the compressor shutdown, the fan turned off, the compressor come back on for the duration of the defrost, the the compressor turned off again, the reversing valve shifted again, and then the compressor restarted again....there is alot going on and it's all normal stuff.

  10. #10
    Join Date
    Jul 2010
    Location
    nebraska
    Posts
    1,629
    Normal to hear that defrost cycle every few hours. Not normal to hear that noise every few minutes over and over again.

  11. #11
    So the service guy just left, he said it was normal and the sound I was hearing was the unit defrosting.

    However, he went out to check the unit while he was here, and he heard another noise that he thinks MAY be in the compressor. He said the part can range about $1,000 for labor to repair? Totally unexpected, I was expecting about $100. This is a 2 year old unit!!! The service guy said all the pressures and everything look right, just he heard something fishy that may be inside the compressor.

    Has anyone had to repair/replace their compressor?

  12. #12
    Join Date
    May 2007
    Location
    DC Metro Area (MD)
    Posts
    3,369
    Is the unit defrosting every few minutes or every 30-45 minutes? If it's defrosting every few minutes, certainly not normal.

  13. #13
    Quote Originally Posted by RyanHughes View Post
    Is the unit defrosting every few minutes or every 30-45 minutes? If it's defrosting every few minutes, certainly not normal.
    Well, it only happened that one night, but after that, it hasn't been doing it every few minutes anymore.

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