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Rinnai Tankless Water Heater only putting out warm water

I have a Rinnai tankless water heater (R94LSi) that has been working perfectly for 10 years. Each year I flush the system with white vinegar as instructed in the manual. After doing some unrelated plumbing, I turned the water back on and now the Rinnai is only putting out warm water. I suspected sediment might be blocking something so I flushed out the system for several hours with vinegar. It is still only putting out warm water. The water flow through the heater is very strong. It sounds like it is running normally but then slows down as if running at a slower speed. I'd be surprised if it decided to break at the exact time that I was doing my plumbing work. Could sediment fool the flow sensor? Would that cause this problem or could it be something else? There aren't any error codes being displayed.
Thank you for your help,


  • delta Tdelta T Member Posts: 807
    check your air inlet to make sure it isn't clogged with a wasp nest or something similar, pull the fan and check the fan blades for obstructions, and check the air inlet outside. I was tracing a similar issue recently on a c51 and it turned out the fan was full of dead wasps. Did you pull the water filter out and check it for an obstruction?
  • michaelnadelmichaelnadel Member Posts: 4
    The air intake both inside and outside are clear. The fan is clean as well as the water filter at the intake.
    Thanks for your response
  • michaelnadelmichaelnadel Member Posts: 4
    I have also removed and inspected the flow turbine as per technical bulletin #105. No help.
  • michaelnadelmichaelnadel Member Posts: 4
    I did find 2 small chips on the bottom of the flow turbine. Is it possible that this could be the cause?
  • SuperTechSuperTech Member Posts: 1,208
    > @michaelnadel said:
    > I did find 2 small chips on the bottom of the flow turbine. Is it possible that this could be the cause?

    It's possible, seeing that the flow of water is what turns the burner on.
    delta T
  • SlimpickinsSlimpickins Member Posts: 322
    Sounds like you have a crossover connection in your plumbing. If you shut off the supply ball valve on the cold feed to unit and open the relief valve and have pressure and flow, that's your problem.
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