Water Temperature Issue - Navien NCB-180 Service Manual

5.3.2 Water Temperature Issue

Error type
Front panel power
Defective flow
Boiler is not
operating
properly.
Defective hot water
temperature sensor
Hot water setting
Low hot water
temperature
Water mixed with
cold water.
No hot water
Check the pipe
from the valve
Cold water flows Pre-heating does
temporally
Cause
Hot water does not run if the front panel is switched off.
off
The boiler 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.
sensor If the impeller rotates normally, replace the flow sensor back into the boiler.

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 boiler.

The cold water temperature sensor may not work be working properly.

Check the hot water temperature setting on the front panel.
error
The temperature of hot water at the tap is low while the temperature is high at the hot
water outlet.
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. Check if the cold water / hot water pipes are frozen during the winter.
4. The main heat exchanger is clogged (by scale).
5. 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 switch
not work
settings.
Check method