Chapter 2 — Burner Operation and Control
Part No. 750-184 2-5
subsequent setting of fuel input throughout the firing range. It
has no control over the firing rate when the manual-automatic
switch is set on “automatic.”
11.Burner Switch (Figure 2-8): A manually operated start-stop
switch for directly starting and stopping operation of burner.
12.Flame Detector: Monitors gas or oil pilot and energizes the
programmer flame relay in response to a flame signal. It
continues to monitor main flame (oil or gas) after expiration of
pilot providing period. A standard equipped boiler has a lead
sulfide (infrared sensitive) detector.
13.Combustion Air Proving Switch: A pressure-sensitive switch
actuated by air pressure from the forced draft fan. Its contacts
close to prove presence of combustion air. The fuel valves cannot
be energized unless this switch is satisfied. The combustion air
proving switch is provided on all gas fired or combination gas-oil
burners. An oil fired boiler does not normally have a separate
switch but utilizes the atomizing air proving switch to the same
effect, since the presence of atomizing air from the air pump,
which is belt driven from the blower motor, is evidence of blower
operation.
14.Alarm: Sounds to notify the operator of a condition requiring
attention. The alarm is available as optional equipment.
15.Stack Thermometer (Figure 2-6): Indicates temperature of
vented flue gases.
16.Diffuser (Figure 2-7): A circular plate, located at the furnace end
of the burner drawer, that imparts a rotary swirling motion to
combustion air immediately prior to its entering the flame, thus
providing a thorough and efficient mixture with the fuel.
17.Rotary Air Damper (Figure 2-7): Provides accurate control of
combustion air in proportion to fuel input for various load
demands. It consists of two concentric cylinders with openings.
The outer is stationary. The inner is rotated, under control of the
modulating motor, to vary the effective size of the openings
where they overlap.
18.Indicator Lights (Figure 2-8): Provide visual information of boiler
operation as follows (indicator lights vary with controls
provided):
• Flame Failure
•Load Demand
• Fuel Valve (valve open)
• Low Water
Figure 2-6 Stack Thermometer
Figure 2-7 Diffuser & Damper
Figure 2-8 Control Panel
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