Navien NHB-055 Service Manual page 29

c. Activate multiple zones and set the boiler to operate at
1-stage MIN mode.
Measure the CO
2
Switches" on page 19 and "(3) Operation Conditions
Settings" on page 59).
If the CO value is not within 0.5% of the value listed in
2
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 4mm Allen wrench, turn the
set screw NO MORE THAN 1/4 TURN clockwise to raise or
counter clockwise to lower the CO
Figure 10. Set Screw Location
NOTE
The set screw is located behind the screw-on cover. This must
be removed first.
d. Activate multiple zones and set the boiler to operate at
2-stage D. MAX mode (refer to "(3) Operation Conditions
Settings" on page 59). Measure the CO
fire.
If the CO values do not match Table 2 at high fire, do not
2
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.
Version 1.0
value at low fire (refer to "4.1.1 PCB DIP
value.
2
value at high
2
Option 2. Using Digital Manometer
a. Open the Offset pressure port by loosening the screw two
turns as shown in Figure 11.
Figure 11. Connect Digital Pressure Manometer
b. Connect a manometer to the offset pressure port. For dual
port manometers, use the positive pressure side.
Model Kit Part No. Gas Type
NAC-N1
NHB-055
NAC-L1
NAC-N2
NHB-080
NAC-L2
NAC-N3
NHB-110
NAC-L3
NAC-N4
NHB-150
NAC-L4
Table 3. Offset value for low fire
Digital pressure
manometer
Offset
NG -0.04 in ±0.01 in
LP -0.03 in ±0.01 in
NG -0.04 in ±0.01 in
LP -0.02 in ±0.01 in
NG -0.04 in ±0.01 in
LP -0.02 in ±0.01 in
NG -0.04 in ±0.01 in
LP -0.02 in ±0.01 in
NHB Service Manual 29