Do you have a problem with your Rinnai tankless water heater? Use the error codes found on the unit or remote control to troubleshoot Rinnai problem. See also what causes the unit malfunction and what you can do to avoid it or fix it.
Rinnai as other manufacturers requires professional installation, regular cleaning and maintenance for the proper water heating, great performance and long unit life. This article will show you the most common error codes and problems found in almost all Rinnai water heaters, non-condensing and condensing.
One of the frequent problems many home-owners are dealing with, in on demand water heating, is the presence of hard water. The high concentration of mineral deposits in water is the main cause of the sediment build-up, especially in the heat exchanger. Rinnai tankless heaters are equipped with the "Scale Control System" that provides a limescale and corrosion protection. You will notice the error codes LC0-LC9 for scale build-up inside the heat exchanger.
Another problem associated with every tankless unit is the temperature fluctuation, associated with the unstable or low water flow. The unit must have a minimum flow reached, otherwise, even with the slightly higher flow, you might have the problem. Increase the flow rate and the problem might be solved.
Troubleshooting Rinnai water heaters is much easier if they come with the diagnostic system. Units equipped with the remote controller MC-91-2 will provide the most recent diagnostic information and allow you to react immediately by recognizing the error code.
Bath Fill function is disturbed after the power outage. You should turn the hot water taps OFF and press the power button twice to resume the Bath Fill.
Check the venting system (both intake and exhaust) for blockage.
When there is no gas ignition the heater is OFF. Test the igniter and see is it still working. This includes checking the loose connections, damaged wiring harness and removing the deposits from the electrodes. Check the burner and clean it if necessary from dirt and debris (also condensation). Are all electric elements properly grounded and does the gas valve have short circuits?
If there is no flame, use some of this tips for troubleshooting: check the loose connections and proper voltage on the power supply, PC board and igniter. Ensure that the burner is not clogged and igniter does not contain carbon build-up.
Thermal fuse has been activated due to the high temperature in the combustion chamber and venting. Ensure that there is no blockage in the vent system (lack of the combustion air). Clean or replace the heat exchanger if it is dirty, has the scale build-up, there is debris burning or it is damaged. Increase the water flow if it is too low.
Over temperature sensor reacts if the unit is too hot so it shuts the unit down. Make sure that problems such as those found when dealing with the error code 14 are resolved.
Make sure that the electrical grounding is properly done and there are no shorts.
If there is a problem with the outgoing water temperature sensor or sensor on heat exchanger check the elements resistance, ensure that the wiring is not loose, clean the elements from deposits or replace if damaged.
Problem in venting or air supply. Ensure that your water heater gets enough combustion air and that the vent system is not blocked. Make sure that fan is operating properly, that sensor is not damaged or wire connection loose. Check the resistance on the sensor.
This code is found on the outdoor models only. Use the same approach as with other sensors above.
Make sure that the valve coil resistance is OK and that the wiring harness is not damaged and connections loose.
Ensure that burner is not clogged and that the flame is stable with light blue color.
Check the resistance of the fan motor, that it is turning freely and there is no damaged wiring or loose connections.
Replace the water flow sensor if it is broken.
Make sure that it gets the electrical power without obstructions. If it is damaged replace the board. Also replace the board if you get the error 71, which indicates the problem with the solenoid valve circuit.
Make sure that the flame sensor is touching the flame. If there is a limescale build-up use fine sand paper and clean it. All the wiring should be without damages and connections must be tight. Replace the element if it is needed.
Check the internal elements and plumbing for leakage.
The error codes from the above were taken from the manufacturer instructions so troubleshooting Rinnai becomes easier and convenient for readers of this website. Keep in mind that the warranty does not cover the unit if the problems were related to freezing, water quality, flooding, fires, improper installation or handling.
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Pictures - courtesy of Rinnai WH company