Navien NP-180 Service Manual page 116

5.23. 39Error
Error occurrence conditions and check items
Error
As one or more units are operating in the cascade system, if no flow is detected
while the system opens the water adjustment valve, the system considers it as a
39E
Flow sensor
defective flow sensor. The system displays 39E (cleared manually) on the remote
error
controller and the PCB, and switches into the Lock-Out mode (gas valve and ignition
transformer locked).
1. Check the supply of cold water. (Frozen / locked valve)
2. Defective flow sensor.
Check items
3. Defective PCB.
Cancelation cascade
system and faucet open
Yes
Water flow out?
Yes
Check connector
Or Replace water flow sensor
©Navien America Inc. 2010
Description
No Check supply cold water
114
NR/NP series service Manual Version 2.0