Rinnai Error Code 18: Rinnai Code 18 - Exhaust Thermistor Fault
How to Fix Rinnai Code 18
- Step 1: Turn the unit off and then back on again. This may reset the system and clear a temporary error.
- Step 2: Check the wiring connections on the outside of the unit for any obvious damage or corrosion. Do not open the unit.
- Step 3: If the error persists after resetting, contact a qualified HVAC technician to diagnose and repair the problem.
What Does Rinnai Error Code 18 Mean?
Rinnai error code 18 indicates a fault with the exhaust thermistor, which is a temperature-sensitive resistor that monitors the temperature of the exhaust gases leaving your tankless water heater. The unit's control board relies on accurate readings from this thermistor to ensure safe and efficient operation. If the thermistor is faulty, sending incorrect or no data, the unit will shut down to prevent potential overheating or other problems. This shutdown is a safety measure. The control board needs to know the exhaust temperature to properly modulate the burner and fan speed. A faulty thermistor can lead to the unit running too hot, potentially damaging components or creating unsafe exhaust conditions. It's important to address this issue promptly to restore hot water and ensure the continued safe operation of your Rinnai tankless water heater.
Common Causes of Rinnai Code 18
- Faulty exhaust thermistor
- Loose or corroded wiring connections to the exhaust thermistor
- Damage to the thermistor wiring harness
- Problem with the main control board
Applicable Rinnai Models
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