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Tankless Water Heater NOISY, shuts off

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  • Tankless Water Heater NOISY, shuts off

    I have twin Rinnai R75LS tankless water heaters installed side-by-side. (Prev Owner's middle name was "Overkill").

    Big snowstorm earlier this year covered one of the exterior vents with a big drift. Turned on the hot water, loud vibration and that unit shut off.
    Went outside with a shovel, drift gone, everything returned to normal.

    New snowstorm (Wisconsin), same/louder noise when Rinnai kicked in. Outside with shovel...but vents were clear. One unit is working fine, the other groans and shuts down. There is maybe a tablespoon of water in the cabinet. The noise is definitely from the exhaust fan but there is no evidence of the vent being clogged.
    Could snow have blown in the exterior vent and is not clogging the fan?

    If yes, how to deal with it, if no...I am interested in your online diagnosis.

  • #2
    Re: Tankless Water Heater NOISY, shuts off


    Inexplicably, second unit is now running just fine.

    My guess:
    Snow blew in the exhaust vent, fan didn't like it. Water was melting snow in the fan...once melted, fan operates fine.



    • #3
      Re: Tankless Water Heater NOISY, shuts off

      Works for me.


      • #4
        Re: Tankless Water Heater NOISY, shuts off

        Sounds like the installer might of not used the cold weather through the wall kit. Also if its to close to the ground it could be an issue.

        With out seeing the install I can not really tell you why it is happening.

        Having two R75Ls units is not an overkill for your area. If your incoming water temperature is around 50º F your heater will have to give you a 70º F temperature rise. So the flow rate will be 4 GPM with a single unit. So the max you could do is run a single shower (2.5 GPM) and a single sink (2 GPM) Now if you tried to run more than that or do laundry while taking a shower the heater will only flow the 4 GPM total So one fixture will flow more water than the other. But since he was wise enough to install two units and I hope he was wise enough to use the EZ connect cable now the units will work with each other. When the demand gets greater than the 4 GPM the single unit can delver the second unit will kick on which will give you a total of 8 GPM flow capability.
        Ron Hasil Lic #058-160417
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        A-Archer Sewer & Plumbing specializing in:
        Tankless Water Heaters | Drain and Sewer Cleaning
        Sump and Ejector Pumps | Backflow RPZ Testing