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  1. #1
    Join Date
    Dec 2019
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    Gurgling noise in VRF

    Hello - we have installed some VRF heat pump systems and ever since heating season starts, there have been complaints of gurgling noises that can be very loud and disturbing while in heating mode, when the evap is off. This of course only happens when the condensing unit is on (so at least another evap is on in the same network) and the noise starts during defrost and continues for about 20-30 minutes afterwards, happening pretty frequently. This is happening on all 6 condensing units that were installed there, same problem everywhere.

    We emptied one of the units of refrigerant completely and there is no leak, so we refilled and added an extra 20% surplus of refrigerant but the noise remained. We are not sure what to do.

  2. #2
    Join Date
    Jul 2009
    Location
    Columbia, MD
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    Depends on the manufacturer.

    There are settings that can quiet the noise. Might be a dipswitch, could be some buttons you have to push or might be a programming change.




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  3. #3
    Join Date
    May 2014
    Location
    Bay Area California
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    When talking heat pumps, it's better to call the coils indoor and outdoor. And saying there are two evaps when in heat mode is also not proper terminology. Gets confusing when you use the wrong words and terms.


    Quote Originally Posted by INSPECTO View Post
    Hello - we have installed some VRF heat pump systems and ever since heating season starts, there have been complaints of gurgling noises that can be very loud and disturbing while in heating mode, when the evap is off. This of course only happens when the condensing unit is on (so at least another evap is on in the same network) and the noise starts during defrost and continues for about 20-30 minutes afterwards, happening pretty frequently. This is happening on all 6 condensing units that were installed there, same problem everywhere.

    We emptied one of the units of refrigerant completely and there is no leak, so we refilled and added an extra 20% surplus of refrigerant but the noise remained. We are not sure what to do.
    I do a triple evac with nitro to remove non condensables.

  4. #4
    Join Date
    Dec 2004
    Location
    Chicago area
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    Is the gurgling like pipe movement? Or something coming from the coil thats off?


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  5. #5
    Join Date
    Nov 2011
    Location
    East Side
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    make sure the EXV's shut off 100%when the unit is off. like was said, prolly a setting.

    bigger question is why did you add "20% more refrigerant"?

  6. #6
    Join Date
    Jul 2009
    Location
    Columbia, MD
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    Quote Originally Posted by 71CHOPS View Post
    make sure the EXV's shut off 100%when the unit is off. like was said, prolly a setting.

    bigger question is why did you add "20% more refrigerant"?
    To stop the gurgling


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  7. #7
    Join Date
    Dec 2019
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    Thread Starter
    With VRF systems, the expansion valve of the indoor units always stays open in heating mode, so even though the unit is off, during and after defrost cycle, there is always a noise. Manufacturer says that valve does not close 100% in the indoor units so that refrigerant is not get "trapped" inside and this is the same everywhere.

    Mitsubishi is stating that they don't have this issue anywhere else, however we are getting the same issue on all 6 condensing units.

    We added refrigerant as we figured perhaps we were missing some, but it has not helped the noise issue.

  8. #8
    Join Date
    Jun 2014
    Location
    Dover, DE
    Posts
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    Refrigerant charge is NOT added as a guesstimate repair.
    Blind charging should expect to cause problems and abnormal operation. Charging should only be done via the calculated charge amount from the manufacturer, while noting important readings of operation like discharge temperature and delta, among others.
    It should be noted that certain parts of certain manufacturers VRF systems have disclaimers that the equipment should not be placed in certain noise sensitive places due to concerns over equipment making sounds that would affect the surrounding environment.
    EEV operation is based on oil return to the outdoor units.
    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

  9. #9
    Join Date
    Dec 2019
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    Thread Starter
    Absolutely - the manufacturer is guiding us here when we add or take away, since we did follow their formulas with regards to condensing unit, piping length etc. We are adding and taking away small quantities.
    Also, these units are approved for installation in noise-sensitive areas. Manufacturer claims they have no issues elsewhere, and really this is a quite loud and abnormal noise. It is the sound of water running but extremely loud

  10. #10
    Join Date
    Nov 2006
    Location
    Southeastern Pa
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    Is Mitsubishi willing to help you with some onsite tech support, since this is 'not happening anywhere else?'
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist
    Member, IAEI

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  11. #11
    Join Date
    Dec 2019
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    Thread Starter
    Yes, they have been helping us on-site but they too are stumped and are not sure what to do. They have asked Japan for their advice, and waiting to hear back.

    What is strange is that the same issue is happening on many indoor units here (all wall-mounted) on all 6 condensers. It is not specific to one of the 6 VRF systems..

  12. #12
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
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    Well..that makes is a Tokyo-level mystery...one where some department might suffer some dishonor, and even as a Gaijin, I can see this as a problem they will be willing to work on until it is solved.

    Please keep us up to date on their progress.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist
    Member, IAEI

    AOP Forum Rules:







  13. #13
    Join Date
    Dec 2019
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    10
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    Thread Starter
    By the way, here is a link to see a 5-second clip of the noise. This is happening in heating mode but with thermostat on OFF.

    https://drive.google.com/drive/folde...0e?usp=sharing

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