Rinnai RH180 Installation Fundamentals page 55

Maintenance Codes
Code Definition
16 Over temperature
warning (safety
shutdown because
unit is too hot).
30 FV sensor
(flammable vapor)
31 Burner Sensor.
32 Heat exchanger
outgoing temp.
thermistor.
35 Tank temperature
thermistor.
55
Remedy
Check for restrictions in air flow around the unit and vent termination.
Licensed
Check for foreign materials in combustion chamber and/or exhaust piping.
professional
Check for clogged heat exchanger.
only
Check that the gas type being used is correct for the unit.
Licensed
Check sensor wiring for damage.
professional
Measure resistance of sensor.
only
Replace sensor.
Licensed
Check sensor wiring for damage.
professional
Measure resistance of sensor.
only
Clean sensor of scale buildup.
Replace sensor.
Licensed
Check sensor wiring for damage.
professional
Measure resistance of sensor.
only
Verify that sensor is properly mounted on the tank surface.
Replace sensor.