I've got a rinnai tankless hot water heater that was installed in July '06 with a wall mounted thermostat. Just recently, I've noticed that sometimes the display on the thermostat is blank as if it is turned off. At other times it is on. Then when you turn on the hot water anywhere in the house, the display will sometimes go off and come back on and stay on which will provide you with hot water. At other times, the display will flash on and off. Of course when it is off, you will not have any hot water. Sometimes it will flash on and off, then go off for about 20 seconds, and then come on and stay on. Pushing the on/off button or the priority button on the thermostat does absolutely nothing. I have checked the plug in the attic and it is okay. Any suggestions?
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Do you have a softener? Water must be 15 GRS/PPM or less in iron and calcium. Hot spots in unit are boiling water and are causing the noises.
Descale and flush unit following Rinnai Specs and check water hardness for compliance with Rinnai standards because too hard an inlet water will VOID the Heat Exchanger Warranty (10 year).
If you have tankless electric, it can simply be insulated... but tankless electric are seldom mounted outdoor. Service bulletin says: "the only way of assuring protection is to completely remove the heater during those times the area may experience freezing temperatures.
There are tankless with built-in heater for exterior installation. Check your manual, or add a comment with specific model number and maybe I can find the information.
Here's why they install tankless outdoors: Because tankless burn more fuel per gallon of hot water. This requires larger gas line and larger vent pipe than typical tank-type gas water heater that is usually installed indoors. They install tankless outdoors, so there is no need for expensive vent pipe, and because there is ample incoming air to support combustion. So if tankless does not have factory-installed internal heater, then the unit can freeze easily when the combustion draws in cold air. Of course you can put heat-tapes on the pipes but the heat exchanger inside will quickly freeze during periods when hot water is not being used, and combustion is not taking place.
You can move the tankless installation inside and use correctly-sized vent and intake pipes directly through the wall. This will generally protect tanklesss from freezing if room is heated adequately.
step one... remove from wall
step two... throw in dumpster
step three... purchase and install a quality tankless water heater.
Rinnai, takagi, Noritz are the only brands I install now. Aquastar (Bosch) always had problems, then purchased by Bosch but never fixed the problems, just put their name on it and sold them at Lowes or home depot.
I have two C85 Rinnai and one is turned off because it leaked... the other one does not heat water... I have it set on 120. Where can I download a repair manual on these? I am in Nicaragua and dealer wants to replace them or something.
Piping of these heaters in tandem is critical. Specified by Rinnai in their design manual, the cold water should be piped to both water heaters with a back-flow presenter installed before the first heater. The hot out piping should be "Tee-d" together and going to your hot water needs. If piped as per the manual, try turning the water off to only one of the units. Turn on a hot water tap and see if the unit stays on without interruption. Then try the same on the second unit. You may find that one unit has a bad flow control, which is shutting off the flow of water. You can get more technical help y contacting Rinnai direct at 1-800-621-9419 ext. 207.