Navien NP-180 Service Manual page 117

Check method
Error type
No hot water
cold water
supply error
flows
Water heater
Defective
not working flow sensor
Defective
Other trouble
Emergency measures
against defective
flow sensor
©Navien America Inc. 2010
Cause
1. Check if the system opens/closes the cold water valve and the
hot water output valve properly.
2. Check if the cold water line is frozen.
3. Check if the cold water filter is clogged.
5. Check the current flow displayed on the PCB
(15.66 15.66 gal/min).
If the flow sensor is defective, the displayed flow value is 00.0
while water flows from the hot water tap.
Disassemble the flow sensor, blow air with mouth. The hall sensor
of the flow sensor is defective if the impeller rotates and display
remains 0.00.
6. Check connector assembly and contact of the flow sensor.
7. Check the input voltage of the flow sensor.
Operating voltage (Black+Red) : Defective PCB if DC 5 V is
not supplied.
8. Replace the flow sensor if no flow is detected while the operating
voltage is normal.
If the trouble continues despite the checking of above items,
the PCB is defective
PCB
Replacement of part takes the priority if an error occurs in the flow sensor.
If it is impossible to replace the part, take the following emergency measures
The CH flow sensor rotor is compatible with the NR/NP flow sensor.
If the flow sensor rotor is stuck due to foreign substance
Disassemble the flow sensor, blow with mouth to the right direction.
If the impeller does not rotate, disassemble the impeller, and remove foreign
substance before reassembling it.
If the flow displayed on the PCB is 00.0, and the impeller rotates when you
blow it, the hall sensor of the flow sensor is defective.
The hall sensor is substituted by the CH flow sensor.
>> Please clarify this procedure
115
NR/NP series service Manual
Check method
Version 2.0