Burner Operation and Control
2-4
750-91 (revised 2009)
Model CB-LE Packaged Boiler Manual
2.4 — 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 items listed below.
Indicator Lights Provide visual information of boiler operation as follows:
• Flame Failure
• Load Demand
• Fuel Valve (valve open)
• Low Water
Program Relay and Flame Safeguard Control Automatically programs each starting, operating, and shutdown
period in conjunction with operating limit and interlock devices.
Includes, in a timed an proper sequence, the operation of the blower
motor, ignition system, fuel valve(s), and the damper motor. The
sequence includes air purge periods prior to ignition and upon
burner shutdown.
The flame detector portion of the control monitors both oil and gas
flames and provides protection in the event of loss of a flame signal.
The control recycles automatically during normal operation, or fol-
lowing a power interruption. It must be manually reset following a
safety shutdown caused by a loss of flame. An internal checking cir-
cuit, effective on every start, prevents burner operation in the event
anything causes the flame relay to hold in during this period.
Component Description
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 regula-
tions.
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.
Gas Pilot Shutoff Cock For manually opening or closing the gas supply to the gas pilot
valve.
Gas Pressure Gauge Indicates gas pressure to pilot.
Gas Pressure Regulating Valve Reduces incoming gas pressure to suit the pilot.
Gas Pilot Aspirator Provides complete mixing of gas and air to the pilot.
Gas Pilot Adjusting Cock Regulates the size of the gas pilot flame.
Component Description
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