How do you fix the Rinnai error code 55?

Alton Alexander
By Alton AlexanderUpdated on June 4th, 2022

Rinnai error code 55 indicates that the water heater is not receiving enough power. This can be caused by a number of things, including a tripped circuit breaker or a loose wire. If the problem is with the power supply, you will need to contact an electrician to resolve the issue.

1. Check the gas supply

  1. Check the gas supply by turning off the gas at the main valve.
  2. Check the gas supply by checking the pressure reading at the gas meter.
  3. If the gas supply is not working, replace the gas meter.
  4. If the gas supply is working, check the gas supply line by checking for leaks.
  5. If the gas supply line is leaking, replace the line.

2. Check the igniter

  1. Turn off the power to the unit.
  2. Remove the cover on the front of the unit.
  3. Remove the igniter assembly by unscrewing the two screws that hold it in place.
  4. Check the igniter resistance. It should be around 1.5 ohms. If it is not, replace the igniter.
  5. Reinstall the igniter assembly and screw it in place.
  6. Reconnect the power to the unit and turn it on.
  7. Check the igniter resistance again. If it is still not correct, replace the igniter again.

3. Check the flame sensor

  1. Remove the cover on the front of the machine. There are four screws that hold it in place.
  2. Look for the flame sensor. It is a black and silver cone-shaped device about the size of a penny.
  3. If the sensor is not working, you may need to replace it. Check with your rinnai dealer.
  4. Replace the flame sensor if necessary. Replace the cover and screws and reattach it to the machine.

4. Clean the burner

  1. Open the hood and remove the burner.
  2. Clean the burner by using a pipe cleaner and water.
  3. Dry the burner with a cloth.
  4. Replace the burner.

5. Check the thermocouple

  1. Turn off the water supply to the rinnai
  2. Remove the cover on the rinnai
  3. Look for the thermocouple on the side of the rinnai
  4. If the thermocouple is broken, replace it with a new one.
  5. Reinstall the cover on the rinnai

If the answers above didn't work then you should also try:

  1. Check the gas valve.
  2. Check the control board.
  3. Call a technician.