CleaverBrooks CBLE, Operation And Maintenance Manual

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750-91 (revised 2009)
Model CB-LE Packaged Boiler Manual 2-1
CHAPTER 2
Burner Operation and
Control
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 gas pilot. The pilot is of the interrupted type and is extinguished after
main flame is established.
Burners equipped to burn oil and gas (combination burners) include equipment for each distinct 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. High-pressure boilers (above 15 psi) can be wired for both
low-pressure and high-pressure modulation, which enables the boiler to operate at lower pressure during off-load
hours, but at a somewhat reduced steam output, dependent upon lower steam pressure and steam nozzle sizing.
The flame safeguard and program relay include a flame detector to supervise both oil and gas flames, and to shut
the burner down in the event of loss of flame. The programming portion of the control provides a pre-purging
period, proving of the pilot and main flame, and a period of continued blower operation to post-purge the boiler of
all unburned fuel vapor. Other safety controls shut down the burner under low-water conditions, excess steam
pressure, or 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, plus temperature prov-
ing controls when heated fuel oil is used.
The sequence of burner operation from startup through shutdown is governed by the program relay in conjunction
with the operating, limit, and interlock devices. The devices are wired into the circuitry to provide safe operation
and protect against incorrect operating techniques.
All CBLE boilers have the burner assembly attached to the front head. The entire head may be swung open for
inspection and maintenance.