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Rinnai Tankless Water Heater air intake issue

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  • Rinnai Tankless Water Heater air intake issue

    I have an 11 year old Rinnai R75-LsiN
    We are a family of five. A few months ago, I was getting an error code 10 (air intake or a blocked flue) when multiple sources were using hot water. The hot water would turn off. I checked the blower/fan thinking maybe it was clogged with bugs/dirt/debris. It was in pretty good shape. One dead bug and a little dusty. I blew it out with compressed air and reinstalled it. The water heater worked great and was quieter for a while. Now it's happening again (2 months after cleaning fan). It was due to be descaled, so I flushed it out and descaled it. I'm still having the issue. It is getting very loud and will cut out if multiple showers/washing machine or dishwasher are running. It will recover when we turn one of the hot water sources off. So, it seems to be getting overloaded, but we're not doing anything different than we've been the last 11 years. I went on the roof to see if I could check the vent, but I wasn't sure how to remove the cap and didn't want to force it and damage it.

    Any help would be appreciated.

    Thanks in advance.

  • #2
    What sort of loud noise? Maybe the bearing is going on the blower motor or wheel assembly and the blower cannot deliver enough combustion air. Maybe try spinning the blower by hand and see if it spins freely. If not that's probably the cause.
    Last edited by blue_can; 02-25-2021, 12:50 PM.


    • #3
      When I cleaned the blower two months ago, it spun very freely and appeared to be in good shape. I doubt it would go bad that quick. It's hard to describe the noise, almost like an engine rev noise.


      • #4
        Yes that sort of noise can come from a worn bearing. Other possibilities include a damaged motor. Do you know what sort of cfm airflow is required. You could buy a cheap rotating vane anemometer on Amazon and check to see what sort of airflow is present on the intake and compare that to what is required. Some of those anemometers are not very accurate but should be good enough to help diagnose issues like this. Are you able to take the cover off and confirm that the noise is in fact coming from the motor? Sometimes the issue may only present at higher speeds and that may explain why spinning it by hand does not show any issues.


        • #5
          I removed the cover to listen. It's definitely the motor. When one hot water source was running, it was quiet, when I turned a second source on, it got loud. It seems to be vibration noise. Depending on how I touched/pressed the motor housing, it either got loud or quiet. I'm wondering if something is loose. The two screws fastening the motor to the unit are tight. Do you think it may be something loose on the motor itself, or do you think the motor is just going bad?


          • #6
            It could be something loose but if you cannot see anything obvious it could be the bearing and likely will require a new motor. Pressing the housing may be aiding the wobble pattern to decrease the noise. Does the motor shaft have excessive side to side play?

            It would be worth checking if the motor shaft has a retaining nut which may have come loose and is causing a wobble or similar issue.


            • #7
              Yeah, I think you're right. I think the bearings are bad. I'll order a new one. It's an older model. So far, I'm having a little difficulty finding the replacement. I'll call some places tomorrow and try to find it.

              We live in a ranch and the water heater is right by all of the bedrooms, so it will be so nice when it works quietly. Looking forward to getting it replaced!

              blue_can, I really appreciate all your help with this! Thank you!


              • #8
                Good luck and hope the repair works out. Yes it can be hard to source parts for older tankless. I have an 18 year old tankless - Boch Aquastar 240FX which is the same as a Takagi TK1 and there is almost nothing available for it. So far it has not had any issues but if something goes wrong I will have to install a new one unless what fails is one of the very few things still available.


                • #9
                  Good luck to you as well. Hopefully it gives you another 18 years.


                  • #10
                    Ha Ha - thanks.