Navien NCB500-2S/37K Service Manual page 59

Error Code Sub Code
1
E205
2
1
E218
2
E291 3
E302 0
E352 0
1
E353
2
1
E407
2
1
E421
2
E434 1
E441 1
E445 1
1
E480
2
E515
E517 0
E594 0
E615
E740 1
E782 0
58 Troubleshooting
Function
Heating supply thermistor open
error
Heating supply thermistor short
error
Heating return thermistor open
error
Heating return thermistor short
error
Supply / Return inversion limit
Low water pressure
High water pressure
Water pressure sensor open error
Water pressure sensor short error
Hot water outlet thermistor open
error
Hot water outlet thermistor short
error
Cold water inlet thermistor open
error
Cold water inlet thermistor short
error
Abnormal operation: Flow control
value
DHW Outlet 2 thermistor open or
short circuit
Abnormal operation: Mixing valve
DHW tank thermistor open circuit
DHW tank thermistor short circuit
Abnormal operation: Relay
feedback (PCB)
Abnormal operation: DIP switch
setting (PCB)
Abnormal operation: EEPROM
(PCB)
Abnormal operation: Input and
memory (MCU)
Abnormal operation: Outdoor
temperature sensor
Abnormal operation: Main panel
communication
Diagnosis/Actions
1. Check the thermistor.
2. Check pump wiring connections.
1. Check the thermistor.
Check the direct water connection.
1. Check filling link and pressurise system to 1.0 - 1.3 bar.
2. Check the incoming water pressure and activity at the PRV.
1. Check filling link is not open and filling the system.
2. Check the incoming water pressure and activity at the PRV.
Check the water pressure sensor.
1. Check the thermistor.
2. Replace the thermistor.
1. Check the thermistor.
2. Replace the thermistor.
Check the dip switches on the front panel and the PCB.
Check the PCB.
1. Ensure that outdoor reset curve is correctly configured.
2. Check the outdoor temperature sensor's wiring connections.
Check the PCB.