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
- Check the gas supply by turning off the gas at the main valve.
- Check the gas supply by checking the pressure reading at the gas meter.
- If the gas supply is not working, replace the gas meter.
- If the gas supply is working, check the gas supply line by checking for leaks.
- If the gas supply line is leaking, replace the line.
2. Check the igniter
- Turn off the power to the unit.
- Remove the cover on the front of the unit.
- Remove the igniter assembly by unscrewing the two screws that hold it in place.
- Check the igniter resistance. It should be around 1.5 ohms. If it is not, replace the igniter.
- Reinstall the igniter assembly and screw it in place.
- Reconnect the power to the unit and turn it on.
- Check the igniter resistance again. If it is still not correct, replace the igniter again.
3. Check the flame sensor
- Remove the cover on the front of the machine. There are four screws that hold it in place.
- Look for the flame sensor. It is a black and silver cone-shaped device about the size of a penny.
- If the sensor is not working, you may need to replace it. Check with your rinnai dealer.
- Replace the flame sensor if necessary. Replace the cover and screws and reattach it to the machine.
4. Clean the burner
- Open the hood and remove the burner.
- Clean the burner by using a pipe cleaner and water.
- Dry the burner with a cloth.
- Replace the burner.
5. Check the thermocouple
- Turn off the water supply to the rinnai
- Remove the cover on the rinnai
- Look for the thermocouple on the side of the rinnai
- If the thermocouple is broken, replace it with a new one.
- Reinstall the cover on the rinnai
If the answers above didn't work then you should also try:
- Check the gas valve.
- Check the control board.
- Call a technician.