736Error - Navien NCB-180 Service Manual

5.2.23 740Error
Error conditions and Check Items
Error
E740
If an error (under 2.2k Ω or over 122.2k Ω ) in the outdoor sensor is detected continuously for 3 seconds, The
Abnormal
system displays the error message E740 on the front panel. If this occurs, the boiler changes the control mode
outdoor sensor
from Reset Curve Mode to Normal Mode.
1. Check the parameter setting. (refer to page 46)
Check items
2. Check the outdoor sensor
116 NCB Service Manual
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 46)
NO
Replace the outdoor thermistor.
Version 1.0