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Tankless shutting down intermittently

Rinnai RU 98i
about 5 years old never a problem until now. While showering water temp goes from where you set to super hot then cold then correct. Screen is showing no codes. cleaned the inlet filter / blew air into turbine, spinning / took cover off and found mouse nest and chewed wires / cleaned nest / removed 2 harnesses and repaired (not sure if I can get new ones yet, its the weekend). Ive observed the unit while running the shower. The burner and "in use" light go off after about 2 minutes and 45 seconds then 5 to 10 seconds later the burner and "in use" light kick on and it goes for another 2 minutes and 45 seconds and so on....
I understand this could be completely related to the wiring i found and repaired or could be damaged wiring I havent found or could be related to urine or other "fluids" from the mice or maybe completely unrelated to the mice. Before taking apart I combed this site for a few hours, it seems there are some very helpful and knowledgeable people here. Any help would be appreciated!

Comments

  • SuperTech
    SuperTech Member Posts: 1,854
    Do you have a mixing valve? You should. When was the last time you had the water heater serviced and the coil flushed? It sounds like either a bad mixing valve or possibly a scaled up coil.
  • olpalbud
    olpalbud Member Posts: 3
    Its never been flushed. Doing it now.
    SuperTech
  • Slimpickins
    Slimpickins Member Posts: 327
    De-scaling it first is what I would have recommended. Hope that did it.
  • Intplm.
    Intplm. Member Posts: 1,417
    If all checks out with the Rinnai look to the mixing. The symptoms you a describing sound like a mixing valve failure,
    .
  • If this only occurs when showering, it could be debris in your shower head which will reduce flow which can prevent the heater from turning on.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour
  • Intplm.
    Intplm. Member Posts: 1,417
    And if it is -----only----- the shower then the temp stop needs adjustment or shower spindle needs to be replaced.
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 3,504
    edited February 2019
    Intplm. said:

    And if it is -----only----- the shower then the temp stop needs adjustment or shower spindle needs to be replaced.

    Temperature limit stop? OK, I know what that is, but what is a shower spindle? Is it like a muffler bearing?
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour
  • Intplm.
    Intplm. Member Posts: 1,417
    @Alan (California Radiant) Forbes LOL No. It's a term that Symmons valve uses Part( TA-10 ) It automatically adjusts for water temp. in that valve.(The original inventors of temperature balancing ) When it fails it behaves like the above description.
    Was using that term as an example. Probably should not have used the brand specific term. Some in my area use it as a general term to describe the above issue. Your description is also right on track.
    .

    Intplm. said:

    And if it is -----only----- the shower then the temp stop needs adjustment or shower spindle needs to be replaced.

    Temperature limit stop? OK, I know what that is, but what is a shower spindle? Is it like a muffler bearing?