CleaverBrooks 4WI, Operation, Service And Parts Manual

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Burner Operation and Control
2-4 750-211 (revised 2009)
Promethean Boilers, Model 4WI Manual
3. Modulating Motor Operates the rotary air damper and fuel metering valves through a cam and linkage
system to provide proper air/fuel ratios under all boiler load conditions.
4. Modulating Motor Trans-
former Reduces control circuit voltage (115 Vac) to required voltage (24 Vac) for operation
of the modulating motor.
5. Forced Draft Fan Motor
Starter Energizes forced draft fan (blower) motor.
6. Ignition Transformer Provides high voltage spark for ignition of gas pilot or light oil pilot.
7. Low Fire Switch An internal auxiliary switch, cam actuated by the motor shaft, which must be closed
to indicate that the air damper and fuel metering valve are in the low fire position
before an ignition cycle can occur.
8. Atomizing Air Proving
Switch A pressure sensitive switch actuated by air pressure from the Air Pump. Its contacts
close to prove presence of atomizing air. The fuel valves cannot be energized unless
this switch is satisfied.
9. Manual-Automatic Switch When set at “automatic,” subsequent operation is at the command of the modulat-
ing control, which governs the position of the modulating motor in accordance
with load demand.
When set at “manual,” the modulating motor, through the manual flame control,
can be positioned at a desired burner firing rate. The primary purpose of the “man-
ual” position is for testing and setting the air/fuel ratio through the entire firing
range.
10. Manual Flame Control A manually operated potentiometer that permits the positioning of the modulating
motor to a desired burner firing rate when the manual-automatic switch is set on
“manual.” It is used primarily for initial or subsequent setting of fuel input through-
out the firing range. It has no control over the firing rate when the manual-auto-
matic switch is set on “automatic.”
11. Burner Switch A manually operated start-stop switch for directly starting and stopping operation
of the 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 ener-
gized unless this switch is satisfied.
14. Alarm Sounds to notify the operator of a condition requiring attention. The alarm is avail-
able as optional equipment.
15. Stack Thermometer Indicates temperature of vented flue gases.
16. Diffuser 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 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.
Component/Control Description