Navien NPE-180A Service Manual page 120

5.2.2 Water Temperature Issue
Error type
Front panel power off
Defective flow sensor
Water heater is not
operating properly.
Defective hot water
temperature sensor
Hot water setting error
Low hot water
Water mixed with cold
temperature
No hot water from the
Check the pipe
valve
Cold water flows Pre-heating does not
temporally
Cause
Hot water does not run if the front panel is switched off.
The water heater does not work due to the defective flow sensor.
The flow sensor impeller will not rotate if it contains excessive scale or debris. Clean
●
out the flow sensor if possible.
If the impeller rotates normally, replace the flow sensor back into the water heater.
●
The sensor may be reused temporarily after cleaning, but replacement is
●
recommended.
The temperature is sensed higher than the actual temperature due to a defective hot
water (cold water) sensor.
Hot water temperature is low although hot water is recognized by the water heater.
●
The cold water temperature sensor may not work be working properly.
●
Check the hot water temperature setting on the front panel.
The temperature of hot water at the tap is low while the temperature is high at the hot
water outlet.
water. Cold water and hot water are mixed due to improper pipe installation.
●
Cold water and hot water are mixed due to improper piping at the hot water faucet.
●
1. The cold water valve is closed.
2. Check if the cold water filter is clogged with foreign substance.
3. The water adjustment valve is closed. (Refer to E434 on page 102)
4. Check if the cold water / hot water pipes are frozen during the winter.
5. The main heat exchanger is clogged (by scale).
6. Low inlet water pressure
For the A model, the system initiates the internal/external circulation preheating when
a recirculation mode is selected on the front panel DIP switches. Confirm the DIP
work
switch settings.
Check method
Troubleshooting 119