Navien NR-20DU User Manual page 30

Error Code
E060 Abnormal operation: dual venturi
E109 Abnormal operation: fan motor
E110 Abnormal air pressure
E407 Hot water outlet: thermostat
open or short circuit
E421 Cold water inlet1: thermostat
open or short circuit
E432 Cold water inlet2: thermostat
open or short circuit
E434 Abnormal operation: water
adjustment valve
E438 Abnormal operation: circulation
pump
E439 Abnormal operation: flow sensor
Reason
Check the Dual Venturi connection.
Clean the intake air filter. See the Operation manual.
• Ensure that the exhaust pipe is free of obstructions.
• Clean the intake air filter. See the Operation manual.
Contact Technical Support at 1-800-519-8794.
Contact Technical Support at 1-800-519-8794.
Contact Technical Support at 1-800-519-8794.
Contact Technical Support at 1-800-519-8794.
• External: Ensure that all water supply and return lines are
open.
• Internal: Check the direction of the 2-way valve.
Contact Technical Support at 1-800-519-8794.
Self-diagnostic / Action
29