Water Temperature Issue - Navien NFC-175 Service Manual

5.3.2 Water Temperature Issue

Error type
Boiler is not operating
properly.
Low hot water
temperature
No hot water from the
valve
Cold water flows
temporally
120 NFC Service Manual
Cause
Front panel power off Hot water does not run if the front panel is switched off.
The temperature is sensed higher than the actual temperature due to a defective
hot water (cold water) sensor.
Defective heating supply
thermistor
●
●
Hot water setting error 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 mixed with cold
●
water.
●
1. The cold water valve is closed.
2. Check if the cold water filter (external) is clogged with foreign substance.
Check the pipe 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
Pre-heating does not The system initiates the external circulation preheating when a recirculation mode
work is selected on the front panel DIP switches. Confirm the DIP switch settings.
Hot water temperature is low although hot water is recognized by the boiler.
The cold water temperature sensor may not work be working properly.
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.
Check method
Version 1.0