Version 1.4
30 NCB-E Service Manual
d. Fully open several hot water fixtures and set the boiler to
operate at 2-stage D. MAX mode. Measure the CO
2
value at
high fire.
If the CO
2
values do not match Table 2 at high fire, do not
adjust the gas valve. Check for the proper Gas Orifice.
DANGER
Improper gas valve settings can cause severe personal injury,
death or substantial property damage.
Option 2. Using Digital Manometer
a. Open the offset pressure port by loosening the screw two
turns as shown in Figure 9.
Digital pressure manometer
Figure 9. Connect Digital Pressure Monometer
b. Connect a manometer to the offset pressure port. For dual
port manometers, use the positive pressure side.
Model
Kit Part No.
Gas Type
Offset
NCB-150E
NAC-N5
NG
-0.04 in ±0.01 in
NAC-L5
LP
-0.03 in ±0.01 in
NCB-180E
NAC-400
NG
-0.04 in ±0.01 in
NAC-04
LP
-0.03 in ±0.01 in
NCB-210E
NAC-500
NG
-0.04 in ±0.01 in
NAC-05
LP
-0.02 in ±0.01 in
NCB-240E
NAC-600
NG
-0.04 in ±0.01 in
NAC-06
LP
-0.02 in ±0.01 in
Table 3. Offset value for low fire
Model
Fuel
High fire
Low fire
%CO
2
%CO
2
NCB-150E
NG
8.9
9.5
LP
10.2
10.8
NCB-180E
NG
8.9
9.5
LP
10.2
10.8
NCB-210E
NG
8.9
9.5
LP
10.2
10.8
NCB-240E
NG
8.9
9.5
LP
10.2
10.8
Table 2. CO
2
value
(CO
2
values must be within 0.5% of the values listed.)
c. Fully open several hot water fixtures and set the boiler to
operate at 1-stage MIN mode.
Note
For operation mode selection, refer to “4.4.11
(3) Operation conditions Settings” on page
56.
Measure the CO
2
value at low fire.
If the CO
2
value is not within 0.5% of the value listed in
Table 2, the gas valve set screw will need to be adjusted.
If adjustment is necessary, locate the set screw as shown
in Figure 8. Using a
5
/
32
in or 4 mm Allen wrench, turn
the set screw no more than
1
/
4
turn clockwise to raise or
counterclockwise to lower the CO
2
value.
Figure 8. Set Screw Location
Note
The set screw is located behind the screw-on
cover. This must be removed first.
