Error - Navien NCB500-2S/37K Service Manual

5.2.5 Error 016

Error Conditions and Checklist
Error
E016
Bi-metal overheated
Checklist
If the overheat controller on the heat exchanger is initiated during boiler combustion
or standby, the system displays 016E (manually cleared) on the front panel. The boiler
switches to Lock-out mode and performs a continuous post-purge and starts the
circulation pump.
1. Check the overheat controller is working correctly.
* Test the resistance or continuity.
2. Check the hot water temperature sensor.
3. Test the circulation pump's supply voltage (AC 230 V).
4. Test the resistance at the pump.
Is HTL* operating
normally?
Yes
Is HTL* operating
normally?
No
Check connection
Description
No
Replace the HTL*
* HTL: High temperature limit switch
Test the resistance
Testing should be performed at least
30 minutes after the error occurred.
YES
Step 1: Flush and clean the filter
Step 2: Restart
Troubleshooting 71