IBC VFC 15-150 Installation And Operating Instructions Manual page 41

Zero-offset adjustment screw
Gas:Air ratio adjustment screw
MODEL
VFC 15-150 (Natural Gas)
VFC 15-150 (Propane)
VFC 45-225 (Natural Gas)
VFC 45-225 (Propane)
Table 8: Combustion test target ranges - CO
STARTUP AND COMMISSIONING
VFC 15-150, VFC 45-225 MODULATING GAS BOILERS
procedure. Pressure may droop up to 1" to 2" w.c. at high fire but under no
circumstances should it drop below 3" w.c. at the gas valve inlet test port.
2. Allow the boiler to ignite / run against a large load, to maintain high fire
3. With the boiler at maximum output, use a 2 mm hex key to adjust the zero-
offset (see Figure 32, "A") as required to achieve -0.2 to -0.3" wc. This
adjustment should only be necessary if this screw has been tampered with.
4. With a combustion analyzer probe in the flue gas test port, turn the Gas:Air
Ratio Adjustment screw (see Figure 32, "B") to achieve the appropriate Table
8 mixture target at High Fire. This screw offers very fine adjustment, and
may require several turns.
changing direction of turn, it may take up to a full turn before any change
is indicated on the analyzer reading. Clock the gas meter to confirm full
maximum rating plate input.
To confirm or adjust the minimum fire level settings, Re-define the load as
5.
"Manual Control". Use Heat Output in "Configure Load x" to control the output
as needed.
At the minimum firing rate, adjust the zero-offset screw (see Figure 32, "A")
6.
to obtain the target CO
stages if this adjustment has been tampered with.
Turn boiler off by removing the call for heat (use the Heat Load Configuration
7.
screen to turn load to off if no other ready means available); turn OFF gas
supply to boiler, then remove the manometer connections, and turn the
centre-screw in the manifold pressure test port 1 full turn clockwise. Ensure
fully closed, but not over-tightened. Restore gas and soap test for leaks.
HIGH FIRE
RANGE TARGET
8.9 to 9.5% CO 9.2% CO
2
10.4 to 10.7% CO 10.6% CO
2
8.9 to 9.5% CO 9.2% CO
2
10.4 to 10.7% CO 10.6% CO
2
/ Maximum CO
2
Removal of flue gas test port plug
This screw has significant backlash. When
NOTE:
value. It may be necessary to reduce the output in
2
LOW FIRE
RANGE
7.9 to 8.6% CO
2 2
9.0 to 9.8% CO
2 2
7.9 to 8.6% CO
2 2
9.0 to 9.8% CO
2 2
Insertion of flue gas analyzer probe
CO MAX PPM
TARGET
8.4% CO < 100
2
9.6% CO < 150
2
8.4% CO < 120
2
9.6% CO < 180
2
3-3