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Mitsubishi Mini-Split Outdoor Condenser Hissing when in heating mode

One of my outdoor units is making hissing sound which is heard near the compressor and the valves when the unit is in heating mode. The unit is Mitsubishi 30k BTU MXZ unit.
I've attached a short video depicting the sound:

Is this the reversing valve hissing when energized or something else? My other 2 outdoor 20k BTU units do not make this kind of hissing sound when in heating mode. The unit heats & cools just fine and makes no hissing sound when in cooling mode.

Comments

  • RomanGK_26986764589
    RomanGK_26986764589 Member Posts: 229
    Bump. Anyone?
  • GW
    GW Member Posts: 4,323
    edited June 2
    When “don’t” you hear the noise? 
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • RomanGK_26986764589
    RomanGK_26986764589 Member Posts: 229
    @GW When it's in cooling mode. No hissing sounds of any kind.
  • GW
    GW Member Posts: 4,323
    Ok so no matter what the output is? No matter if it’s one zone or both zones? Can you kinda tell where it’s coming from? Did you take the panels off at all? I’d have the rep come at look 
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • pecmsg
    pecmsg Member Posts: 2,346
    What's the outdoor temperature while your trying Heating mode?
  • RomanGK_26986764589
    RomanGK_26986764589 Member Posts: 229
    @GW No matter how many zones are running. I even posted a video above to depict that sound. It's where the compressor and the valves are. Only in heating mode. I am guessing it's the reversing valve hissing when energized? Do you know if the reversing valve is energized in heating or in cooling in Mitsubishi?
  • RomanGK_26986764589
    RomanGK_26986764589 Member Posts: 229
    @pecmsg When we use heating the temp outside is usually 45-55ish degree range.
  • pecmsg
    pecmsg Member Posts: 2,346
    If that charge isn’t perfect 55* may be too high. 
  • mattmia2
    mattmia2 Member Posts: 3,995
    really hard to tell from that video what it sounds like, but sounds like refrigerant being throttled through the expansion valve.
    RomanGK_26986764589
  • GW
    GW Member Posts: 4,323
    I don’t know if it’s powered in heat or cool,. I changed a reversing valve on a 3c30Hyper last year- not a fun time. Quite the process, flowed nitrogen on every joint. almost a full day job to get it done and recharged 

    get the rep there 



    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
    RomanGK_26986764589
  • RomanGK_26986764589
    RomanGK_26986764589 Member Posts: 229
    @pecmsg You mean if it could be overcharged or undercharged?
  • pecmsg
    pecmsg Member Posts: 2,346
    @pecmsg You mean if it could be overcharged or undercharged?
    Only way to tell tell is to pull it and weight it!