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  1. #1
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    Lennox compressor unusual noise

    Lennox XC 14 -032 installed June 2008. Slab mounted.
    Has worked without problem since installation and is still working, cooling well. On a very hot day when it has been going almost non-stop, temp drop = 17F, measured at supply and return ducts.

    The compressor has always made a "RUM-rum-RUM-rum" noise, heard inside the house nearest the outside unit.
    This summer that noise can be heard at more distant locations inside the house, and it is _much_ faster, almost twice as fast. There is also a fairly loud "Clack" outside when the compressor turns off.

    Am wondering if this is a sign of potential failure, of if the refrigerant might be low.
    Professionally maintained every year, but not yet this year. Suspected leak of refrigerant a few years back; dye added, no leak found. Previously was told it needed topping up almost every year.
    Is it now standard practice to charge extra, above the annual maintenance fee, for any topping up of the refrigerant? I was quoted $ (Cdn) per pound this year, and have never heard of that before.

    Thanks in advance for any comments.
    Last edited by beenthere; Yesterday at 04:38 AM.

  2. #2
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    Lennox units are pretty darned quiet in my opinion, but that is such a subjective thing... noise / loudness.

    You know what it used to sound like or didn’t sound like, so I’d say it probably needs to be looked at.

    As far as “topping” off goes, I know there are times when that is the only way to get a unit back on, but consider that your system is supposed to be a closed system. No different from your fridge, really. When’s the last time you had your fridge topped off?

    If at all possible, it would be really good if you could get a tech to isolate and repair the leak(s) and seal that sucker up for you.

    The excessive noise in the outdoor unit is likely because something is amiss. I would get it checked asap if it were me. Compressors are expensive to replace, so it’s a good idea to keep the compressor happy. It sounds like yours may be groaning and that could be for any number of reasons but ultimately it’s probably too hot or overloaded for some reason.

  3. #3
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    Thanks for your helpful reply.
    The system was checked with dye in 2014 and no leaks found. In 2015 the same tech did the yearly maintenance and found the refrigerant level correct.
    The techs for the following two years did not gauge it, as the delta T was good. Right now I am getting an 18 degree drop, with outside temp (inside the compressor box) of 83, about the same as in 2016. Perhaps the losses of refrigerant were the result of refrigerant escaping while gauging the system.
    I remain puzzled by the apparent increase in speed of the compressor and wonder if it could be a difference in the supply voltage, which is currently 122, but has been as low as 116 some summers when there has been heavy demand on the provincial system up here in Ontario.

    I will follow your suggestion and have a tech look at it - my regular guy seems to be on vacation.

    Thanks again!




    Quote Originally Posted by KeyResults View Post
    Lennox units are pretty darned quiet in my opinion, but that is such a subjective thing... noise / loudness.

    You know what it used to sound like or didn’t sound like, so I’d say it probably needs to be looked at.

    As far as “topping” off goes, I know there are times when that is the only way to get a unit back on, but consider that your system is supposed to be a closed system. No different from your fridge, really. When’s the last time you had your fridge topped off?

    If at all possible, it would be really good if you could get a tech to isolate and repair the leak(s) and seal that sucker up for you.

    The excessive noise in the outdoor unit is likely because something is amiss. I would get it checked asap if it were me. Compressors are expensive to replace, so it’s a good idea to keep the compressor happy. It sounds like yours may be groaning and that could be for any number of reasons but ultimately it’s probably too hot or overloaded for some reason.

  4. #4
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    Quote Originally Posted by Pianoplayer View Post
    Thanks for your helpful reply.
    The system was checked with dye in 2014 and no leaks found. In 2015 the same tech did the yearly maintenance and found the refrigerant level correct.
    The techs for the following two years did not gauge it, as the delta T was good. Right now I am getting an 18 degree drop, with outside temp (inside the compressor box) of 83, about the same as in 2016. Perhaps the losses of refrigerant were the result of refrigerant escaping while gauging the system.
    I remain puzzled by the apparent increase in speed of the compressor and wonder if it could be a difference in the supply voltage, which is currently 122, but has been as low as 116 some summers when there has been heavy demand on the provincial system up here in Ontario.

    I will follow your suggestion and have a tech look at it - my regular guy seems to be on vacation.

    Thanks again!
    What does this mean?

    Does Canada run a different voltage to their outside equipment?
    The Food Stamp Program, administered by the U.S. Department of Agriculture, is proud to be distributing the greatest amount of free meals and stamps EVER.
    Meanwhile, the National Park Service, administered by the U.S. Department of the Interior, asks us to "Please Do Not Feed the Animals". Their stated reason for this policy "... the animals become dependent on handouts and will not learn to take care of themselves."
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  5. #5
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    No we do not unless it is 575V 3 phase, which is only commercial/industrial equipment.

    His unit would be 240 VAC on the outdoor unit. Now if he has a gas furnace inside, which would be common in Ontario, then that would be 120 VAC.
    Quote Originally Posted by pacnw View Post
    What does this mean?

    Does Canada run a different voltage to their outside equipment?
    Sent from my SM-N910W8 using Tapatalk

  6. #6
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    As mentioned previously, your unit is considered a closed system and should never need topping up of refrigerant unless there is a leak. Now someone who incorrectly removed their gauges from a system could have removed a noticeable amount of refrigerant. If the caps are left off the access ports they could have leaked a small amount over time.

    It is also illegal in Canada to add any refrigerant to a system suspected of having a leak. Unit is supposed to be leak tested and proven to be leak free before recharging. While part of the onus is on company and technician, the equipment owner is also responsible. I cannot say I have ever heard of an inspection at a residential site though.


    Quote Originally Posted by Pianoplayer View Post

    Suspected leak of refrigerant a few years back; dye added, no leak found. Previously was told it needed topping up almost every year.

    Thanks in advance for any comments.


    Sent from my SM-N910W8 using Tapatalk

  7. #7
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    Thread Starter
    I am only able to measure voltage at the household wall receptacles. I assumed that the voltage sag there would be proportional in the AC, electric stove and dryer circuits.

    The outside temperature sensor for the Bryant Evolution thermostat was installed inside the compressor housing.

    Quote Originally Posted by BALloyd View Post
    No we do not unless it is 575V 3 phase, which is only commercial/industrial equipment.

    His unit would be 240 VAC on the outdoor unit. Now if he has a gas furnace inside, which would be common in Ontario, then that would be 120 VAC.

    Sent from my SM-N910W8 using Tapatalk

  8. #8
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    I would consider having it checked by a third party, outside of the company you normally use to check and do PMs. Ask friends and family who they use and check them out, have them give it a look.

  9. #9
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    Clacking noise at shut off is the scroll reversing a second from the pressure on the high side relieving through the compressor to the low side and is not too uncommon to hear.

    The modulating "thrumming" is probably a standing wave (harmonic) generated by two motors running at a slightly different RPM and you are hearing the "difference" Do you have two condensing units next to each other?

  10. #10
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    Quote Originally Posted by Juan Madera View Post
    Clacking noise at shut off is the scroll reversing a second from the pressure on the high side relieving through the compressor to the low side and is not too uncommon to hear.

    The modulating "thrumming" is probably a standing wave (harmonic) generated by two motors running at a slightly different RPM and you are hearing the "difference" Do you have two condensing units next to each other?
    Thank you! That makes great sense, esp. to a musician. The neighbors had a new AC installed this summer, which might account for the change in the difference tone.

  11. #11
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    Quote Originally Posted by bhenry1013 View Post
    I would consider having it checked by a third party, outside of the company you normally use to check and do PMs. Ask friends and family who they use and check them out, have them give it a look.
    Your point is well taken -- there are not many Lennox dealers in the area, and they seem to change often, but I imagine a large Carrier dealer would also be able to carry out the various checks.

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