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  1. #1
    Join Date
    Jul 2013
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    Strange new noise after heat pump installation

    New heat pump installed last week for our 2nd floor. The unit seems to be performing just fine. We are not upstairs very often and since the installation we’ve heard a noise a few times which I would describe as if someone were pounding on a wall upstairs to hang a picture or something. The pounding is constant for about 30 seconds and then stops. This morning we heard it again and my wife opened the window to look at the outside unit while I went upstairs to check the air handler. By the time I got upstairs the noise had stopped. She said the unit was not running when she looked outside.
    I can’t imagine how this noise is somehow connected to the new heat pump but it seems coincidental that the noise started soon after the installation. Anyone have an opinion as to whether it could be something going on with the new unit?

  2. #2
    Join Date
    Mar 2008
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    Fuquay Varina, N.C.
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    One of the installers got trapped in a wall of your house and the pounding you hear is him/her trying to get out, could the noise be coming from where the ran the line set up the wall to upstairs unit, do you hear it only at certain times or after the unit has run? Further investigation is necessary to determine cause!!!!


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  3. #3
    Join Date
    Aug 2009
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    Beatrice, NE
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    It is possible that a check valve is hammering under certain conditions. I had a unit 25 years ago do this, it sounded like someone was siding the house. The noise is actually carried on the refrigeration lines and amplified by whatever house framing it is against.

  4. #4
    Join Date
    Jul 2013
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    Thread Starter
    Quote Originally Posted by BNME8EZ View Post
    It is possible that a check valve is hammering under certain conditions. I had a unit 25 years ago do this, it sounded like someone was siding the house. The noise is actually carried on the refrigeration lines and amplified by whatever house framing it is against.
    Is the check valve located in the air handler or the outside unit?

  5. #5
    Join Date
    Aug 2009
    Location
    Beatrice, NE
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    Can't tell you, it may not even have a check valve, some new units use bi-flow TXV's, or it may be that both units have one. If it is a check valve my guess would be it happens when the unit shuts off and the pressure start to equalize. Have the company come check it out but be warned they may not find anything the first time or 2. The closer you can nail down when it happens the better chance they have in finding it. The worst part is it happens for such a short time being in the right place when it happens is difficult.

    In the case I relayed inside the house it sounded like someone hammering on the house, outside where this check valve was it was s small metallic click.

  6. #6
    Join Date
    Jan 2014
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    New England
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    Raise the thermostat and let it run for 10+ miniutes, then have someone satisfy the thermostat while your near the Air Handler, could be once it satisfies the internal refrigerant pressures are equalizing, and the noise is coming from the check valve, if you have a TXV metering device. Piston metering device do not use a check valve, the piston slides, possibly its rattling a tad during the equalization period.

    I would start at the Indoor Air Handler first. Certainly there are check valves at the OD unit, or an internal check valve at the TXV, you can also have a piston metering device at the OD unit. Or a combo of a piston and a TXV metering device on your system.

    Make sure lineset is secured in the attic also.

  7. #7
    Join Date
    Jul 2013
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    Thread Starter
    Still making the new, strange noise, but very infrequently. Only last about 20 seconds and has happened only 3 times in 10 days so hard to get upstairs and closer to the air handler that quickly to see if it's coming from there. I'm here all day most days so I would hear it if it happened more often. I believe it's something to do with the new installation but apparently the contractor doesnt think so. I informed him but he had no ideas as to what it might be. My wife thinks it sounds like it's coming from the attic above the 2nd floor. The ducts run across the joists in the attic but they've been there for 28 years so I dont know why they would suddenly start making a noise.

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