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How to fix Rinnai Tankless Water Heater when there is no hot water and there is no error code?

Published on April 1st, 2022

If your Rinnai tankless water heater is displaying the error code "no hot water," it means that the unit is not heating the water to the desired temperature. There are a few possible reasons for this:

  1. The water heater's thermostat may be set too low. Try turning up the thermostat and waiting a few minutes to see if the water heater begins to heat the water.

  2. There may be something blocking the flow of water to the unit, such as a closed valve or a build-up of sediment in the pipes. Check to make sure that all valves are open and that there is no blockage in the pipes.

  3. The water heater may be low on fuel. If you are using a gas-fired water heater, make sure that there is enough gas in the tank. If you are using an electric water heater, make sure that the power is turned on and that there is no tripped circuit breaker.

  4. The water heater may be defective. If you have tried all of the above troubleshooting steps and the water heater still will not heat the water, you may need to call a service technician to diagnose and repair the problem.

1. Check the gas supply to the unit

  1. Open the damper on the gas line to the water heater.
  2. Look for any obstructions in the line.
  3. Clear any obstructions.
  4. Turn on the gas to the water heater.
  5. Check for any leaks in the piping.
  6. Close the damper on the gas line to the water heater.
  7. Wait 10 minutes for the gas to dissipate.
  8. Check for any gas leaks.
  9. If there are no gas leaks, turn off the gas to the water heater.
  10. Check for any errors in the water heater's display.

2. Check the power supply to the unit

  1. Turn off the power to the water heater.
  2. Check to see if the power cord is plugged into an outlet and the unit is turned on.
  3. If the power cord is plugged in and the unit is turned on, check to see if the power is working by pressing the power button.
  4. If the power is working, check to see if the thermocouple is hot by pressing the thermocouple button.
  5. If the thermocouple is hot, check to see if the power supply is working by checking the error code.
  6. If the power supply is not working, replace the power cord.

3. Clean the burner assembly

-Check the gas supply to the burner assembly. Make sure there is enough gas to light the burner. -If the burner assembly is not lit, check the gas supply to the burner and try again. -If the burner assembly is lit, but no water is coming out of the faucet, check the hoses and connections between the faucet and the water heater. -If the hoses and connections are okay, check the water heater burner assembly. -If the burner assembly is not working, replace it.

4. Check the igniter

  1. Shut off the water supply to the rinnai tankless water heater.
  2. Remove the cover on the water heater.
  3. Remove the igniter.
  4. Replace the igniter if necessary.

5. Check the flame sensor

  1. Turn off the power to the water heater.
  2. Remove the access panel to the water heater.
  3. Locate the flame sensor.
  4. Test the flame sensor by igniting a lighter and holding it near the flame sensor. If the sensor detects the flame, the sensor is operational. If the sensor does not detect the flame, the sensor is defective and needs to be replaced.
  5. Replace the flame sensor if it is defective.

If you didn't find success with an option above, then try:

  1. Check the thermocouple.
  2. Check the gas valve.
  3. Check the water flow rate.
  4. Check the temperature setting.
  5. Call a qualified technician.