Error - Navien NCB300-28K Service Manual

5.2.12 Error 302

Error conditions and checklist
Error
E302
Low water pressure
Checklist
Testing method
Fault
E302
Low water pressure
sensor
76 Troubleshooting
Low pressure faults are monitored by a water pressure sensor and when a fault is detected
the system displays E302 Low water level error is generated if water pressure is 0.5 bar or
less for 3 sec.
The error is automatically cancelled if water pressure returns to 0.5 bar or above.
1. Check if the input water pressure sensor is wet for any reason, including leakage.
2. Check the auto feeder.
3. Check the controller.
Is there a leak inside the
boiler?
No
Is the water
pressure sensor
normal?
Yes
Check connections
Possible causes
Check the water supply pressure (0.5 bar or lower is the error state).
Low water pressure
Check if the safety valve is stuck.
1. Check the output voltage. (Normal state: 0.25-4.93 V)
Water pressure sensor
fault
2. Replace the faulty or open water pressure sensor.
Description
Yes
Repair the leak
No
Replace the water pressure sensor
Testing method