Burner Operation and Control
2-2
750-91 (revised 2009)
Model CB-LE Packaged Boiler Manual
Combustion air is provided by a centrifugal blower located in the front head. Combustion air delivery to the burner
is under the control of the modulating motor. The motor also regulates the flow of fuel through a linkage system
connected to the gas butterfly valve and/or oil through a cam operated metering valve. Fuel input and air are thus
properly proportioned for most efficient combustion.
Filtered primary air for atomizing fuel oil is furnished independently of combustion air by a frame mounted air
pump.
The burner control circuit operates on 115 volt, single phase 60 Hz (or 50 Hz if so equipped) alternating current.
The forced draft fan motor is generally operated on 3-phase service at the available main power supply voltage.
Indicator lights signaling load demand, fuel valve, low water, and flame failure conditions are standard equipment.
In addition to the standard basic controls supplied, other devices may be required to meet specific requirements of
an insurance carrier or local code. Refer to the wiring diagram (WD) prepared by Cleaver-Brooks for your specific
installation to determine the specific controls in the burner and limit control circuits. The function of individual
components is outlined in this chapter and the electrical sequence is covered in Chapter 3.
2.2 — Control and Component Function
The term “control” covers the more important valves and components, including, but not limited to, electrical con-
trols or those monitored by the program relay. The operator must become familiar with the individual functioning
of all controls before understanding boiler operation and procedures outlined in this manual.
The actual controls furnished with any given boiler will depend upon the type of fuel for which it is equipped, and
whether it is a hot water or steam boiler. Refer to the applicable group or groups within this chapter that apply to
the particular boiler.
2.3 — Components Common to All Boilers
NOTE: Boilers with optional features may have control components not listed here.
Component Description
Forced Draft Fan Motor Drives forced draft fan directly to provide combustion air. Also
referred to as a blower motor.
Forced Draft Fan Provides all air, under pressure, for combustion of pilot fuel and
main fuel, and for purging.
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.
Modulating Motor Transformer (located in the
modulating motor)
Reduces control circuit voltage (115 Vac) to required voltage (24
Vac) for operation of the modulating motor.
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