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I hate my tankless water heater

2 months ago

We have the Rinnai RL94i propane tankless water heater. It was the worst thing we put in our house. We have been dealing with this POS for 7 years. Great when it works. Every year at least 3 to 4 times a year showers go cold. Sometimes it was due to a bug getting in the fan. What a stupid design that allows bugs to get into the fan. Other times the fan is clear but shower goes cold. We cleaned the flame rods with 000 steel wool the kast time it qwent cold as there was corrosion on them. Was good for a bit. Then shower went cold again and fan was clear. We deicded to replace the flame rods with new ones. thinking maybe that was the issue. Went a few days without issue until tonight. Shower went cold. We turn shower off and wait a bit and turn back on and have hot water again. So sick of this thing. Next we will replace the fan the thinking being maybe the fan is no longer balanced correctly from cleaning it out over the years. Any other ideas?

Comments (7)

  • PRO
    2 months ago

    You probably aren’t using it correctly. With tankless, you set the flow rate and temoerature output to use almost all hot water, and only temper it back a small bit with cold. You have to keep the flow rate high enough to properly trigger the burners. And it has to be sized correctly for your incoming winter water temperature. Which is why in summer, it can cut out, because the incoming water is warmer, and the flow is not high enough to trigger the burners when you try to use it like a tanked water heater with a 50/50 mix of hot and cold. You have to high flow the hot in summer.

  • 2 months ago

    Clyde, based on your comments: remove and replace.

  • 2 months ago
    last modified: 2 months ago

    The temperature is set at 120. I have no idea what you mean by temper it back. I have a single handled faucet in the shower. What am I tempering back? I am on well water. The water that comes out in the summer when just turning on cold is pretty darn cold.


    Sorry. Houzz is really annoying. For some reason when I get email notifications and reply through the notification it comes out under my old user name. I am Clyde kalvin.

  • 2 months ago

    There's a required minimum flow rate to activate a tankless water heater, and to keep it activated during use. Specifications for Rinnai RL94i says minimum rate is 0.26 GPM (gallons per minute), although a slightly higher rate may be needed to initially activate it.

    Tempering the flow is via turning the single-handle faucet toward the cold side to reduce the volume of hot water flow so as to attain a comfortable showering temp below 120°F .... which in turns cuts back on how much water is flowing through the tankless heater, which could in some instances put the flow rate below what's required to keep the burner activated.

    The flow rate may be dropping below the trigger point, regards to your statement that turning the shower off briefly and back on restores the heated water. However, it seems unlikely that you'd be reducing the hot flow rate below 0.26 GPM in consideration of your description of the cold supply temperature ... but that depends on what is your comfortable shower temperature.

    Some shower/tub faucets have a temperature limiter feature to avoid scalding, which involves inherent tempering. Perhaps there's a problem with that feature if your shower faucet has it.

    My (electric) tankless is in a broom closet in my laundry room adjacent to the kitchen and spare bedroom wing of the house, which makes it easily accessible for setpoint adjustment, 50°F to 140°F in 1°F increments. I frequently adjust it so that the setpoint is AT the desired temperature I want for a given hot water task, and run only the hot tap ... showering, washing clothes, hand-washing dishes (dishwasher has onboard heating to target temperatures for all cycles so no need to set it high for that). I've never had a performance problem or lack of heated water in 20+ years.

    Perhaps you can determine what is your comfortable shower temperature and do a test of setting your tankless at that temp or a smidgen higher so you can run nearly full-hot flow and see if that has an effect on the problem.

  • 2 months ago

    @dadoes thanks for the information but I do not think that is the issue. The first few years of use it was fine except for when a bug got in the fan. I do not take very hot showers. It is certainly lower than 120. Today and yesterdays showers were an issue but the day before it was fine. We do not have a temperature limiter on any of our shower faucets. Today is threw a code 10. When we looked it up it said something about the exhaust. But it threw code 10 other times when a bug was in the fan. Tomorrow we are going to look at the exhaust pipe to make sure nothing got in there and is blocking it and we will also check the fan for bugs again. It can go a month or 2 with no issue and then we get a cold shower. What a PITA.

  • last month

    I'm sorry that's happening. I've not had that experience with them. I have used Rheem natural gas units and have been very happy. I don't know if you have just a bad unit, a bad installation or a particular model that was prone to problems (or perhaps some combination).


    Is this an indoor unit or an outdoor unit?

  • last month

    @Jake The Wonderdog It is an inside unit. It has an exhaust/intake that goes to the outside. The thing is so sensitive that a small bug getting into the fan through the exhaust causes it to code and we get cold water in the middle of a warm shower. Several times a year we would have to open it up and clean out the fan.


    Recently it is coding and we thought it was a bug again. Opened it up and no bug in the fan. It would be okay for a bit and then again have problems. We cleaned the flame rods as they had corrosion on them. Was good for a bit and then again started having issues. We decided to replace the flame rods as they looked like they had rust on them. It was okay for a few days but started having issues again.


    We are going to check the fan again and replace it. I do not know if the fans can get off balance. There appeared to be little weights on the fan or something that looked like it may be weights. Not sure if all the times we had to clean it something fell off or a fan blade got bent. Worth a shot. We already have the part.


    So here is what it says to check for code 10. Some I am unsure about what they mean. Any help would be appreciated.


    Check that nothing is blocking exhaust-Will do this today


    Check condensation collar-Will check this today


    Check that dip switches set properly-I have no idea what or where these dip switches are or how they are suppose to be set. Any idea?


    Check fan for blockage-will check this today


    Check fins in heat exchanger-Again no idea about this. I will have to figure out where exactly the heat exchanger is.


    If we still have issues guess we will pay to have someone come look at it.