Navien NFC-175 Service Manual page 69

Error Code Sub Code
E030 0
E031 0
E046 2
1
E047
2
1
2
E060
3
E407 -
E421 -
E434 -
E439 -
E441 -
E445 -
E109 0
Version 1.0
Function / Cause
Exhaust Overheat : exhaust limit switch
shuts down the unit when the flue
temperature exceeds 230 °F (110 °C) for more than
10 minutes.
Overheating of burner
Abnormal heat exchanger High Limit Switch (short)
Abnormal exhaust thermistor (open)
Abnormal exhaust thermistor (short)
Abnormal Dual Venturi Limit Switch operation (ON)
Abnormal Dual Venturi Limit Switch operation
(Close OFF)
Abnormal Dual Venturi Limit Switch operation
(Open ON)
Abnormal Hot water outlet 1 sensor
(After mixing valve)
Abnormal Cold water intake sensor
Abnormal operation: Water adjust valve
Abnormal operation: flow sensor
Hot water outlet 2
(before mixing valve)
Abnormal operation: Bypass mixing valve
Abnormal fan motor activity
Self-diagnostic / Action
1. Turn OFF the system for at least 30 minutes then
restart.
2. Ensure all valves and filters on the boiler loop are
open and clean.
3. Check exhaust thermistor and verify #19 value in
the Status Information menu (see page 36).
4. Check for proper DIP switch settings.
5. Check the heat exchanger; a flush may be
necessary.
Check the fuse of burner.
1. Check heat exchanger High Limit Switch
connection.
2. Check for proper connection to the PCB.
Check the exhaust thermistor connection. Check for
proper connection to the PCB.
Check the Dual Venturi connection.
Test Dual Venturi for proper operation using TEST
mode.
Check gas orifice for obstructions.
1. Check for disconnections between the Hot water
outlet 1 sensor and the controller.
2. Check for any shortages in the Hot water outlet
1 sensor.
1. Check for disconnections between the Cold
water intake sensor and the controller.
2. Check for any shortages in the Cold water intake
sensor.
1. Check for disconnections between the water
adjust valve.
2. Check PCB voltage.
1. Check for debris within the water adjust valve
harness.
2. Check for disconnections in the flow sensor.
3. Check for flow sensor operation.
1. Check for disconnections between the mixing
valve and controller harness.
2. Check PCB voltage.
1. Check for disconnections between the bypass
mixing valve and the harness.
2. Check for PCB voltage.
1. Check and clean the intake air filter.
2. Check and clean the fan motor.
3. Check for proper voltage from PCB. Replace fan if
PCB voltage is normal.
NFC Service Manual 69