Rinnai hot water temperature fluctuates

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    • #279823
      Todd A Crowel


      We have a Rinnai Continuum tankless water heater and here is the problem.

      1) we JUST had it serviced (cleaned and flushed with vinegar). The day after service the hot water barely came so i went down and checked the silt filter/trap and it was FULL (dirtier then i’d ever seen it) with silt and dirt.

      I cleaned the trap out, and things were better for a day. Now everytime we shower, after about 5 minutes the temperature starts to fluctuate. I cleaned the trap out 2 more times but this did nothing for the problem. I also tested the water in the sink right next to the rinnai and the temperture fluctuates there as well.

      I called my technician and they want to charge to come our and service the unit again?

      One other thing to mention that around the same time as the service call, we noticed some city work possibly on a water main? down the street.

      My question is, could all that dirt be a result of work on the water line? and if so, why would it have gotten past the trap and into the system.

      if it did get into the system, would it cause this behaviour?

      is there anything else that I can do to either clean or flush the system myself (I am fairly handy and follow directions well) instead of having them out again


    • #301768

      There are a number of questions I would have to ask a client of mine with the symptoms you have described before proceeding with anything else such as servicing the heater such as : did this water heater have this problem before the service people called, did they check and reset the gas operating pressures for both high and low settings, from what you have said they have flushed out the heat exchanger with “vinegar” probably in an endeavour to clear any lime or calcium buildup that may have been in it. Didi they clean out the water flow valve as well – if they did not some of the “muck” may have lodged in the rotor valve and in turn tells the heater’s computer what the inlet flow rate is so the computer can adjust the gas and water rates to provide correct temperatures. If the rotor “sticks” then the computer would try unsucesefully to adjust the flow of water and gas to attain the set temperatures. It is more likely that the fault lies with a fluctuating water flow into the heater from the town supply system but in EVERY case when servicing these units the gas pressure settings MUST be checked and if required adjusted, after all too little gas equates to a lower than set temperature and too much gas could cause the heater to turn itself off and on when a low flow such as a shower is being used otherwise it would self destruct when trying to get rid of all the surplus heat.

      My initial thoughts are check the gas pressure settings and the water flow settings to ensure things are what they are suppost to be first.

    • #301779

      Hi Selgas,

      thanks a lot for your reply. Turns out one of our check valves failed so it needs to be replaced.

      Our water and heating systems are not isolated (the system was here when we bought the house and we know they didn’t install it correctly) which also exacerbated the problem i am sure.

      gas pressure was good and the water flow setting (if you meant the flow rate) is in the 25-30 range

      just wanted to provide an update and thank you for your reply.

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