740Error - Navien NCB-150E Service Manual

5.2.24 740Error

Error conditions and Check Items
Error
E740
Abnormal outdoor sensor
Check items
128 NCB-E Service Manual
If an error (under 2.2kΩ or over 122.2kΩ) in the outdoor sensor is detected continuously for
3 seconds, The system displays the error message E740 on the front panel. If this occurs, the
boiler changes the control mode from Reset Curve Mode to Normal Mode.
1. Check the parameter setting. (refer to page 18)
2. Check the outdoor sensor.
Is the Outdoor sensor
installed properly?
Yes
Is the outdoor thermistor
normal?
Yes
Check connecter
(#1 and #2 of CN11)
Description
No
Change the Outdoor Reset Control
Mode setting. (refer to page 18)
No
Replace the outdoor thermistor.
Version 1.4