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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The Rinnai relys on good water flow to fire it up. In saying that it runs out of water; thats actually not possible. The Rinnai just heats up water as it goes. Usually fault for installs on bore or well water is a problem with water flow. Causes are blockeed filters or you water pump from the bore starting to fail. I would expect you to have a large filter somewhere on the water line from the well. Try and find it and clean it our. The Rinnai also has a filter. It,s like a plastic round shaped nut just under the heater on the miidle connection. Turn the water off first, it should almost unscrew by hand, take it out and clean it (make sure you don't drop the O ring on it. Also some tapware has water filter right in the end of the spout, check these too. After you tried all this focus on the pump. Make sure no ther water id flowing, try the hot tap and see if it works. Do the same but slowly turn on a cold tap, slowly increasing the flow. Have someone out by the heater and see if the heater shuts down at any point. If it does it could be the water pump at fault. From what you have told me and am certain water flow is the culprit here. Really focus on anything that might lessen the flow before you start messing with the heater. Best of luck.
If you can get to the gas valve make sure it is in the on position and not in pilot or off. Does it sound like
a spark ignition system? Even though you say the gas valve is on, by code thered should be a gas shutoff valve located within site of the unit. Follow the
gas pipe until you find such a valve and make sure its on
sounds like the water line is frozen before it gets to heater. You can take a blow dryer and try to thaw the line.You should be able to hook up a hose on the hot side of water heater. turn valve off so it wont flow into house.You can turn on hot water valve on in kitchen but you will have to thaw cold and hot line. Make sure you know where water shut off is to the house just in case a line breaks.
The only way that I have found to work is to place a small electric water heater close to the point of use. Yes this does defeat some of the efficiency of having a tankless water heater but if you figure electric rates are now cheaper than gas rates in some areas, it may save you money.
Another alternative is to put a domestic circulator in-line and recirc the domestic water either all the time or install a timer.
None of these options are "low-buck" options.
15' of 1/2" copper holds less than 1 gallon of water so something is wrong with the heater if it takes 3 gallons to get hot water to the faucet.
It sounds like the Rinnai units are working correctly but you've got some plumbing problems. Any tankless heater has a minimum water flow required to keep the burners going. If the burners were going with very little water flowing through them to carry the heat away, the heat exchanger could overheat and fail. The solution is generally to the electronic controls to set the desired temperature and then just use hot water. Once you start mixing cold water in, you actually reduce the flow of hot water and the burners turn off. If you are right near the cut off point, the burners will cycle on and off resulting in those very annoying hot-cold-hot-cold showers.
The fact that you've got those very loud noises indicates some other sort of plumbing problem. Hooking up two tankless units in series is much more complicated. In heavy draw situations, the second unit is asked to finish heating the water up to temperature when the first unit couldn't quite get it there. Now you're putting hot water into a heater and heating it more. You have a lot more issues with fluctuating temperatures and pressures within the pipes which could conceivable cause these horrible noises. Everything's got to be set up right to for things to function properly and it's easy to get something wrong.
From your description, it sounds like a better solution would have been to mount the two heaters in different places. e.g. One in the basement to serve basement and first floor faucets. The other on the second or third floor to serve those two floors. Since these units are direct vent (don't use inside air), they can even be mounted in a closed closet as long as the vent can get to the outside. With this setup you avoid the complexities of a series installation and you also have a much shorter wait time (and therefore less waste) for the fixtures on the upper floors.
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.
Question, is there any other equipment that uses propane? You indicate that the problem started after a delivery of propane after running out. If so, I suspect a blockage in either the gas train or the rinnai itself. If tou have the temperature control that regulates the water temperature, you can recall error codes to pinpoint the issue. They are optional equipment so if you can wire one in or ask your propane gas supplier if their service department has one, it will aide in the diagnosis.