Water Temperature Issue - Navien NCB-150E 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
132 NCB-E Service Manual
Cause
Front panel power off Hot water does not run if the front panel is switched 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.
Defective flow 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.
Defective hot water
temperature 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.
●
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. 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.
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 internal/external circulation preheating when a recirculation
work mode is selected on the front panel DIP switches. Confirm the DIP switch settings.
Check method
Version 1.4