94 NHB Service Manual
Version 1.0
Fault
Possible Causes
Check method
Flame loss and noise
occurs after ignition
Digital pressure
manometer
Check the offset values for Min fire
Model
Gas Type
Offset
NHB-055
NG
-0.04 in ± 0.01 in
LP
-0.03 in ± 0.01 in
NHB-080
NG
-0.04 in ± 0.01 in
LP
-0.02 in ± 0.01 in
NHB-110
NG
-0.04 in ± 0.01 in
LP
-0.02 in ± 0.01 in
NHB-150
NG
-0.04 in ± 0.01 in
LP
-0.02 in ± 0.01 in
Offset value for Min fire
Model
Gas Type
MAX fire % CO
2
Min fire % CO
2
NHB-055
NG
8.9
9.5
LP
10.2
10.8
NHB-080
NG
8.9
9.5
LP
10.2
10.8
NHB-110
NG
8.9
9.5
LP
10.2
10.8
NHB-150
NG
8.9
9.5
LP
10.2
10.8
CO
2
value
Flame Rod
(Electrode)
Replace the electrode or clean the fire detecting electrode.
-
Cause: Due to the properties of the electrode, the oxide film is created due to
long-term exposure to the high temperature; therefore, errors may be caused
in detecting the fires.
-
Check-up: Use sandpaper to clean the fire detecting electrode covered with
oxide film or replace it.
Tightness of Screw or
Ground Bolt
Check the tightness of the screw or ground bolt in the C SC heat
exchanger.
-
Cause: Screw or ground bolt in the chamber and SC heat exchanger can be
loosened by the vibration or external impact when operating the boiler (water
heater).
-
Check-up: A failure in the current flow between the chamber and burner may
cause the flame-out; therefore, the tightness (fastened) of the screw needs to
be checked. [Fasten the ground screw (2EA) after fastening the assembly screw
(3EA) in the front of the heat exchanger]
Summary of Contents for NHB-055
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