740Error - Navien NPE-180A Service Manual

5.1.26 740Error

Error occurrence conditions and check items
Error
E740 If an error (under 2.2kΩ or over 122.2kΩ) in the outdoor sensor is detected continuously for 3 seconds, The
Abnormal outdoor system displays the error message E740 on the front panel. If this occurs, the water heater changes the control
sensor mode from Reset Curve Mode to Normal Mode.
1. Check if the outdoor sensor connector is wet due to any reason, including leakage.
2. Check the Resistance of the outdoor sensor.
Check items 3. Check the parameter setting. (refer to page 155)
4. Replace the defected Hot water outlet temperature sensor.
5. Replace the controller.
5.1.27 760Error
Error occurrence conditions and check items
Error
E760 If the water heater operate more than set flushing time(day), The system displays the error message E760 on the
Flushing Alram front panel. If this occurs, the water heater operate with Normal Mode.
1. Check the water heate and flushing the water heate, if it is required.
Check items
2. Reset the timer with reset button on the front panel.
5.1.28 785Error
Error occurrence conditions and check items
Error
E785 If an AHU heating is OFF and Flow Rate is O and Flow Switch is detected continuously for 3 seconds, The system
Abnormal External Flow displays the error message E785. If this occurs, the water heater operate AHU heating Mode and operate DHW
Switch mode when the water heater detect saved flowrate plus 0.4gpm(1.5 lpm) more.
1. Check if the Flow Switch is ON or OFF.
Check items 2. Check the Resistance of the terminal block.
3. Replace the controller.
Description
Description
Description
Troubleshooting 117