If you have a tankless water heater, you’ve made a wise investment that will deliver endless hot water for 20+ years. Tankless water heaters need far less in the way of maintenance and servicing than traditional tank water heaters, but they still do need to be maintained, and when they have problems, it’s important to know what to do. We service all brands, but for this post we’re focusing on Rinnai tankless water heater troubleshooting because the self diagnostics tool provides codes that makes it easier to diagnose and address issues. For questions about other tankless systems (Rheem, Noritz), post questions in the Ask Dave column and we’ll get back to you as soon as possible.
We’re huge fans of Rinnai tankless systems! Your Rinnai tankless water heater is a smart water heater, meaning it is equipped with a self-diagnostic tool that continuously monitors if the unit is functioning properly. When something goes wrong, the unit displays an error code. Using this Rinnai tankless water heater error code guide, you can quickly determine what the problem is and if you need a plumber to service the unit or if you can fix it yourself.
Rinnai Error Codes
Error Code 02: No burner operation during freeze protection mode.
Call a plumber.
Error Code 03: Power interruption during bath fill
Turn off all hot water faucets/taps. Press On/Off button twice. Turn hot water back on and test. You may have to try this a couple times to reset the system.
Error Code 10: Exhaust or air supply blocked
There are several things you can do before calling a plumber. Try the following:
- Check venting material. Is it Rinnai-approved? (See Rinnia-approved venting materials here.) If not, replace venting material or have a plumber replace it.
- Look for blockages in both the flue inlet or exhaust.
- Are the venting components properly connected?
- Check the condensation collar. Is it loose or improperly installed?
- Are the dip switches set correctly?
- Is the fan rotating properly, or is something blocking it?
If the error code still shows, call a plumber.
Error Code 11: Ignition problems
Because this has to do with gas and gas lines, most people will need to call a plumber to handle this. However, these are steps the plumber will take (and you could carefully try some of these yourself):
- Is the gas on? Check at the water heater, gas meter or cylinder.
- Is the gas type and pressure correct?
- Is the gas line, meter and/or regulator sized properly?
- Is the air in the gas line? Have a plumber bleed the air from the lines.
- Are the dip switches set?
- Is the appliance grounded?
- Disconnect EZConnect™ or MSA controls to see if you can isolate the problem.
- Does the igniter work? Is it operational or do you need to replace the igniter? Check the wiring harness and see if it’s the igniter or the harness.
- Examine the gas solenoid valves. Any open or short circuits?
- Remove the burner cover and examine the burners to see if they are one, properly sealed, and two, if the burner surface has condensation or debris on it.
If you are not familiar with these parts and with both wiring and gas, you should hire a plumber to deal with a Rinnai error code 11.
Error Code 12: Flame failure
Because this has to do with gas and gas lines, most people will need to call a plumber to handle this. However, you could carefully try some of the steps a plumber will take. Use the checklist for Rinnai error code 11 (above), and if those steps don’t fix the problem, try the following:
- Check power supply. Any loose connections?
- What is the voltage? Any voltage drops?
- Is the flame rod wire connected? Any problems with carbon build up on the flame rod?
- Check for DC shorts at components.
If you are not familiar with these parts and with both wiring and gas, you should hire a plumber to deal with a Rinnai error code 12.
Error Code 14: Thermal fuse
Something is wrong with the thermal fuse. You may be able to fix it by trying the following:
- Check for air flow restrictions.
- Is water flow in the circulating system low? This can cause problems related to short-cycling.
- Check dip switches.
- Anything gunking up the combustion chamber? What about the exhaust pipe? Obstructions can cause problems with thermal fuse function.
- How does the heat exchanger look? Any cracking or separations? Hot spots? Hot spots indicate scale build up.
- Flush the heat exchanger following the instructions on the owner’s manual.
- Check the resistance of the safety circuit.
Error Code 16: Over temperature warming
This problem usually is caused by a restriction of airflow. Check for clogs or obstructions in the following:
- Combustion chamber
- Exhaust piping
- Heat exchanger
You will also want to check for restrictions in air flow around unit and vent terminal and for low water flow in a circulating system causing short-cycling. Once you clear the obstructions and improve airflow and water flow, the problem should resolve itself. If it does not, call a plumber.
Error Code 32: Outgoing Water Temperature Sensor Fault
This one is simple: carefully examine the sensor. Look for damage and scale build up. You probably have to replace the sensor if cleaning it doesn’t help.
Error Code 33: Heat Exchanger Outgoing Temperature Sensor Fault
Similar to above. Carefully examine the sensor. Look for damage and scale build up and make sure the fan blade is tight on motor shaft and is undamaged. You probably have to replace the sensor if cleaning it doesn’t help.
Error Code 34: Combustion Air Temperature Sensor Fault
Same as above. Carefully examine the sensor and wiring. Look for damage and scale build up. You probably have to replace the sensor if cleaning it doesn’t help.
Error Code 52: Modulating Solenoid Valve Signal Abnormal
You probably need to replace the solenoid valve. First:
- Check modulating gas solenoid valve wiring harness for loose or damaged terminals.
- Measure resistance of valve coil.
You may be able to resolve the problem by tightening loose terminals.
Error Code 61: Combustion Fan Failure
Examine the combustion fan to see:
- Can the fan turn freely?
- Any problems with the wiring harness? Maybe it has been damaged or has loose connections?
- Is there a problem with the motor winding resistance?
Error Code 65: Water Flow Control Fault
You definitely need to call a plumber for this one. The water flow control valve has failed to close during the bath fill function. Immediately turn off the water and discontinue the bath fill function. Then call a plumber.
Error Code 71: Solenoid Valve Circuit Fault
You probably need to replace the solenoid valve. First:
- Check wiring harness to all solenoids.
- Measure resistance of each solenoid valve coil.
Error Code 72: Flame Sensing Device Fault
Before you call a plumber, you can try the following:
- Check to see if the flame rod is touching flame when the unit fires.
- Examine the wiring to flame rod for damage.
- Clean the flame rod with sandpaper.
- Examine inside the burner chamber for debris or gunk that might be blocking the flame at the flame rod.
- Replace flame rod.
Error Code 00 or “LC”: Scale build up in heat exchanger.
Call a plumber and have them flush the heat exchanger or replace the heat exchanger.
Note: A lot of customers ignore this code because it still allows the tankless water heater to continue running. You will see the display alternates between the LC code and the temperature setting. Make sure you get the heat exchanger serviced and don’t ignore this code just because it allows you to still run the unit or you may have more serious problems down the line.
Need a Charlotte Area Plumber for Tankless Water Heater Help?
This post is about Rinnai tankless water heater troubleshooting because that’s the brand we install the most often, but we have deep experience with all brands of tankless (on demand) water heaters. Give us a call at 704.846.5371 to service your tankless water heater. We look forward to working with you!
Quick question & answer: Why is my Rinnai tankless water heater showing an error code?
Rinnai tankless water heaters show error codes for various reasons. Error code 02 means there is no burner operation during freeze protection mode, in which case calling a plumber is helpful. Error code means there is an over temperature warning. Check for clogs or obstructions in the combustion chamber, exhaust piping, and heat exchanger. Removing obstruction should resolve the problem.