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Rinnai rl75 hot turns cold after about 10 minutes

My tankless heater turns cold after 10 minutes in all showers. It is less than three years old. I am in Florida and it is mounted outside with no additional venting.

Comments

  • SWEI
    SWEI Member Posts: 7,356
    Did you just buy the house, or is this a new problem?
  • Jack
    Jack Member Posts: 1,045
    What is the flow rate when the shower is running? You can read it off the touch pad. Turn the water temp down on the Rinnai. With a tank, to get more hot folks turn up the t-stat. With a tankless you may want to turn it down.
  • hippchip
    hippchip Member Posts: 3
    I talked with the guy who installed it. I had recently turned it up to 140. I turned it down to 120 yesterday and its working so far. I have a well and the pressure seems a little low. I checked and the bladder tank is at 60psi and the pressure switch on at 55 off at 68. If I turned the temp down even more would I get more flow? How do I check the flow from the touchpad
  • hippchip
    hippchip Member Posts: 3
    SWEI said:

    Did you just buy the house, or is this a new problem?

    Well I had this house built 13 years ago. I had a similar Rinnai unit and never did maintenance to it. Then 2.5 years ago I had a new unit installed with a flush kit. I talked to the guy who installed it and he told me to buy a submersible pump and run 5 gallons of white vinegar through for 50 minutes. He said I should turn down the temp to around 102-104 while doing this to allow more vinegar to cycle through. Of course turn off the hot and cold valves so the vinegar does not go into the house plumbing.
  • Jack
    Jack Member Posts: 1,045
    I suspect that your 140 temp is the problem. Consider that use temps are less than 110*. I run mine at 115*. Go to Rinnai.us, water heaters, model, documents, installation/operation manual and read it.