Burner Operation and Control
2-6
750-211 (revised 2009)
Promethean Boilers, Model 4WI Manual
2.5 — Controls for Gas Firing
Depending upon the requirements of the insurance carrier or other governing agencies, the gas flow control sys-
tem, or gas train, may consist of some, or all, of the following items. Refer to the Dimension Diagram (DD) pre-
pared by Cleaver-Brooks for the installation.
FIGURE 2-6. Pilot Gas Train and Main Gas Train
Component/Control Description
1. Gas Pilot Valve A solenoid valve that opens during the ignition period to admit fuel to the pilot. It
closes after main flame is established. The sequence of energizing and de-energizing
is controlled by the programming relay. A second gas pilot valve may be required by
insurance regulations.
2. Gas Pilot Vent Valve When a second gas pilot valve is required, a normally open vent valve (optional
equipment) is installed between them. Its purpose is to vent gas to the atmosphere,
should any be present in the pilot line when the pilot valves are closed. The valve
closes when the pilot valves are energized.
3. Gas Pilot Shutoff Cock For manually opening or closing the gas supply to the gas pilot valve.
4. Gas Pressure Gauge Indicates gas pressure to pilot.
5. Gas Pressure Regulating
Valve
Reduces incoming gas pressure to suit the pilot.
6. Main Gas Valves Electrically actuated shutoff valves that open simultaneously to admit gas to the
burner. The downstream valve is equipped with a “proof of closure” switch that is
connected into the pre-ignition interlock circuit.
7. Main Gas Cock For manually opening and closing the main fuel gas supply downstream of the main
gas line pressure regulator. A second shutoff cock, downstream of the main gas
valve(s), is installed to provide a means of shutting off the gas line whenever a test is
made for leakage across the main gas valve.
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