Noritz NR501-OD Service Manual page 52

903 Combustion abnormality
1 Check air inlet for blockage or obstruction.
2 Check exhaust for blockage or obstruction.
3 Check the Fan Motor.
(ex. Clogging of fan blades, etc.)
4 Check for sudden environmental changes.
(ex. Hurricane, Storm, etc.)
Model Name Gas type
Maintenance Monitor #49
Final Fan Speed Correction
NG
NRC711-OD
LP
NG
NRC711-DV
LP
908 Combustion abnormality
(Unit is locked)
The trouble diagnosis for "Error Code 908" is same "Error Code 901".
Basically, replace the Burner.
Error Codes
Display Remote
Window Controller
Improper gas type
91 91
Check gas type.
Error Codes
Display Remote
Window Controller
Exhaust temperature is too high
941, 942 94
1 Check air inlet for blockage or obstruction.
2 Check exhaust for blockage or obstruction.
3 Check for Heat Exchanger-Primary is normal.
4 Check for inlet water temperature is high.
Unit Status
Unit operation
110%
110%
Unit shuts
104%
104%
52
<Condition of occurrence for error code 903>
When the unit is operating,
- Air inlet for blockage or obstruction.
- Exhaust for blockage or obstruction.
- Fan Motor is abnormal.
If 1 to 4 check out okay, replace the Fan Motor.
Replace the Circuit Board set if the error code is displayed again.
* It is not necessary to replace the Display Window Circuit Board.
.
<Condition of occurrence for error code 908>
If the Unit detects "Error Code 901" 6 times,
the Unit is locked* for safety.
* How to reset the lock is described in page 25.
Description
Description
DV model only
<Condition of occurrence for error code 94>
The Unit detects high exhaust temperature.