750-368
CBEX Elite 100-1200 HP
2-1
CHAPTER 2 Burner and Fuel System
2.1 — The Burner
The oil burner is of the low pressure, air atomizing (nozzle) type. The gas burner is of the non-premix orifice type.
The burners are ignited by a spark ignited interrupted type gas pilot. The pilot is extinguished after the main
flame is established.
Burners equipped to burn oil and gas (combination burners) include equipment for each fuel. Since the burner
uses only one type of fuel at a time, a gas/oil selector switch is incorporated.
Regardless of which fuel is used, the burner operates with full modulation (within its rated operating range). The
burner returns to minimum firing position for ignition.
A flame detector is present to supervise both oil and gas flames, and to shut the burner down in the event of loss
of flame.
The control sequence provides a pre-purging period, proving of the pilot and main flame, and a period of contin-
ued blower operation to post-purge the boiler of all unburned fuel vapor. Other safety controls shut down the
burner under low-water conditions or excess steam pressure (water temperature).
Safety interlock controls include combustion and atomizing air proving switches and, depending upon the fuel
and insurance carrier requirements, controls that prove the presence of adequate fuel pressure.
The sequence of burner operation from startup through shutdown is governed by the Hawk controls in conjunc-
tion with the operating, limit, and interlock devices. The devices are wired into the circuitry to provide safe oper-
ation and protect against incorrect operating techniques.
All CBEX Elite boilers have the burner assembly integral with the front head. The entire head may be swung open
for inspection and maintenance.
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 damper actuator.
Filtered primary air for atomizing fuel oil is furnished independently of combustion air by an air pump.
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