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Rinnai RUCS65i - have to cycle power to restart

MikeW32 Member Posts: 5
edited January 2020 in Domestic Hot Water
This is an indoor unit but when the temp gets down to the 30's the unit tends not to start. I can unplug and plug back in and it will start most of the time. It might be a coincidence with the temp. I have performed all the flushing and cleaning of filters. No error codes and nothing at all on the small screen.

I am thinking a bad pc board, freeze sensor. Thoughts?


  • SuperTech
    SuperTech Member Posts: 1,691
    Does it draw it's combustion air from outside? It may be running too lean with the cold make up air.
  • MikeW32
    MikeW32 Member Posts: 5
    I am not sure but all the other houses around me have the same heater and installation and do not have this issue.
  • pecmsg
    pecmsg Member Posts: 2,342
    Record the trouble code before resetting. Inform your service provider of the code when making the appointment.
  • MikeW32
    MikeW32 Member Posts: 5
    Is there a capacitor in this heater? Once it is running and turns off, it will seem to work fine until it is not used for alot of hours (overnight).
  • MikeW32
    MikeW32 Member Posts: 5
    no service codes at all. It is like the unit has no power. After unplugging and plug back in 2 dash appear and it works.
  • Charley
    Charley Member Posts: 9
    I do not know, but wonder if the gas to the heater is affected by the cold.
  • MikeW32
    MikeW32 Member Posts: 5
    This has got to be electrical related. Either the flow sensor is not sending enough signal to wake up the heater or the PC board goes to sleep. Either way, you have to remove the power to get it to reset. When it finally powers up it get "--" and then a "1" as it lights.