Navien NFC-250/175H Installation Manual page 135

Option 2. Using Digital Manometer
a. Open the offset pressure port by loosening
the screw two turns as shown in Figure 9.
Digital pressure
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 Altitude Kit Part No.
0-
5,399 ft NC250/200H Natural
NFC-
250/200H 5,400-
NFC- 10,100 ft NCH250/200H
250/175H
0-
10,100 ft LC250/200H
Table 3. Offset value for low fire
manometer
Gas
Offset
Type
NAC-
-0.03 in ±
Gas 0.01 in
NAC-
NAC- Propane -0.02 in ±
Gas 0.01 in
c. Activate multiple zones and set the boiler
to operate at 1-stage MIN mode (refer
to "11.6.7 Setting the Special Operation
Modes" on page 126). Measure the offset
value at low fire and compare it to the
values in Table 3. If the offset value is out of
range, the gas valve set screw will need to
be adjusted.
If adjustment is necessary, locate the set
screw as shown in Figure 10. Using a
or 4mm Allen wrench, turn the set screw
no more than / turn clockwise to raise or
1
4
counterclockwise to lower the offset value.
Figure 10. Set Screw Location
The set screw is located behind
Note
the screw-on cover. This must be
removed first.
d. At high fire, do not check the offset value
and never adjust the gas valve.
DANGER
Improper gas valve settings can cause severe
personal injury, death or substantial property
damage.
/ in
5
32
Appendixes 135