28
l. Turn on the gas shutoff valve and the boiler
service switch.
m. Start the boiler and check for fuel gas odor around
the gas valve. If an odor is evident, check to make
sure that the pressure tap fitting is closed.
4. All gas piping must be leak tested prior to placing the
boiler in operation.
a. If the required leak test pressure is higher than
13.5 in. w.c., the boiler must be isolated from the
gas supply piping by closing the service valve.
b. If the gas valves are exposed to pressure
exceeding 13.5 in. w.c., both gas valves must be
replaced.
5. Install the boiler such that the gas ignition system
components are protected from water (dropping,
spraying, rain, etc.) during operation and service
(circulator replacement, condensate collector and
neutralizer clean out, control replacement, etc.).
E. MAIN GAS VALVES - OPERATION
1. Figure 5.2 is an illustration of the main gas valves,
venturi and blower assembly for the Series PFC
TM
boiler.
2. Do not make adjustments to the gas valves without
instrumentation to measure carbon dioxide (CO
2
) and
carbon monoxide (CO) emissions in the exhaust vent
pipe.
3. Turning the throttle screw clockwise will decrease
the gas flow (decreasing CO
2
) and turning it
counterclockwise will increase the gas flow rate
(increasing CO
2
). Markings adjacent to the throttle
screw show + and – indicating this operation.
a. Throttle adjustments should be made only at full
input rate.
b. See Section 9, Start-Up Procedure for specific
information about commissioning and adjusting
the boiler.
4. The recommended CO2 settings are given in Table
5.5 and Table 5.6 for PFC-625 and PFC-750,
respectively. In no case should the boiler be allowed
to operate with CO emissions higher than 200 ppm.
5. Refer to Section 3, Venting and Air Inlet Piping for
information on obtaining exhaust vent samples from
this boiler.
FUEL PIPING
VENTURI
INLET
NOTE:
* DO NOT ADJUST THE THROTTLE OR OFFSET SCREW
WITHOUT THE PROPER COMBUSTION TESTING EQUIPMENT.
INLET PRESSURE TAP
* THROTTLE
SCREW
* OFFSET SCREW
* OFFSET SCREW
* THROTTLE
SCREW
Figure 5.2: Gas Valve, Venturi, Blower Assembly –
PFC-625/750
PFC-625
Natural Gas
Propane (LP)
Low Fire
High Fire
Low Fire
High Fire
Carbon
Monoxide
(CO)
< 50 ppm < 200 ppm < 50 ppm < 200 ppm
Carbon
Dioxide
(CO
2
)
8.6% to 9.2%
10.3% to
10.7%
9.8% to
10.2%
Excess
Oxygen
(O
2
)
4.8% to 5.8%
4.6% to
5.2%
5.4% to
6.0%
Excess Air
26.5% to 34.1%
25.1% to
29.4%
31.0% to
35.8%
Table 5.5: PFC-625 Combustion Settings
PFC-750
Natural Gas
Propane (LP)
Low Fire
High Fire
Low Fire
High Fire
Carbon
Monoxide
(CO)
< 50 ppm < 200 ppm < 50 ppm < 200 ppm
Carbon
Dioxide
(CO
2
)
8.6% to 9.2%
9.8% to 10.2%
Excess
Oxygen
(O
2
)
4.8% to 5.8%
5.4% to 6.4%
Excess Air
26.5% to 34.1%
31.0% to 39.2%
Table 5.6: PFC-750 Combustion Settings
PFC-625 and PFC-750 boilers utilize a dual gas valve
system. When making combustion adjustments,
throttle and offset changes
MUST
be made equally
on both valves.
Reference Section 9.G of this IOM for valve
adjustment and zeroing procedure.
NOTICE
