Navien NCB300-28K Service Manual page 70

5.2.6 Error 030
Error occurrence conditions and check items
Error
E030
Exhaust gas temperature error
Checklist
If the overheat controller on the top of the exhaust duct is initiated, the system displays
the heat exchanger bimetal overheat message 030E (cleared manually) on the front panel.
The boiler switches into Lock-Out, and performs post-purge continuously and operates
the pump.
Overheating controller operates when the temperature exceeds 110°C for 10 minutes or
over.
1. When the controller detects the exceeding temperature of 110°C for 10 minutes or
more E030 is displayed and a post-purge will be performed. → Automatically cleared.
2. When the controller detects the exceeding temperature of 60°C while performing
post-purge. → Manually cleared.
3. When the controller detects the exceeding temperature of 110°C for 10 seconds or
over three times or more after the error is automatically cleared. → Manually cleared.
1. Check if the overheat controller operates normally.
2. Check if the PCB works properly.
Is exhaust thermistor
normally operating?
Yes
Check the heat exchanger
Check for leakage in the
combustion chamber
Flush heat exchanger
Description
No
Check the exhaust thermistor
Check the resistance
Troubleshooting 69