Rinnai rl75 hot turns cold after about 10 minutes

hippchip

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.

SWEI

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

Jack

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

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

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

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.