I have an issue that is stumping my installer and level 2/3 tech. I also contacted Rinnai.
I have this unit for about 7 years and have had 5.5 great years with it. The last 1.5 years though I have had a decrease in my water temp to 103-5 degrees at best (i measured with a thermoter). sometimes it pulses to colder than that. I have very sporatic moments of normal 120 degrees - once every couple of weeks perhaps.
I have hard water and iron riich. I have a softener and Acid nuetralizer on the well supply to my home. I do get some rust (iron) sediment build up on occasion. I've flushed the system, cleaned the barrel screen on the water inlet and had two service techs in to take a look at it. #1 the installer and #2 the level 2/3 tech. The second of the two recent suggested it may be my flow sensors. I managed to find the one on the top right and that looks normal.
Anyone have any suggestions? My level 2/3 guy is very busy and not anywhere near my location so it is hard for him to get to us.