CleaverBrooks CBEX-DE User Manual

Startup and Operation
4-4
750-392
CBEX-DE
With a proven pilot, the man fuel valves (OV or MGV) are energized and the main fuel valve light (FVL) in the
panel is lit. The main flame is ignited and the trial period for proving the main flame begins. It lasts 10 seconds
for light oil and natural gas. At the end of the proving period, if the flame detector still detects main flame, the
ignition transformer and pilot valve are de-energized and pilot flame is extinguished.
NOTE: Depending upon the requirements of the regulatory body, insurer, or fuel being burned, either the 10 or
15 second pilot ignition terminal may be used. Both provide the same function but differ in time interval allowed
for proving main flame ignition. Refer to the boiler wiring diagram.
The cause for loss of flame or any other unusual condition should be investigated and corrected before attempt-
ing to restart. Failure to follow these instructions could result in serious injury or death.
4.1.3 — Run Cycle
With main flame established, the Release to Modulate Relay (RMR) switches operation to the Hawk firing rate
controls. Depending on the selection AUTO or MANUAL, control is accomplished through the Hawk HMI (man-
ual mode) or automatically based on the modulation signal and the current Hawk combustion settings.
The actuators for fuel, air, and FGR are positioned independently via Modbus signal.
The burner starting cycle is now complete. the LDL and FVL lights on the panel remain lit. Demand firing contin-
ues as required by load conditions.
4.1.4 — Burner Shutdown: Post-Purge
NOTE: Normal operation of the burner should be with the controls in the automatic mode and under the direc-
tion of the modulating signal. The manual mode is provided for initial adjustment of the burner over the entire fir-
ing range. When a shutdown occurs while operating in the manual mode at other than low fire, the damper will
not be in a closed position, thus allowing more air than desired to flow through the boiler. Excess air flow sub-
jects the pressure vessel metal and refractory to undesirable conditions.
The burner will fire until steam pressure or water temperature in excess of demand is generated. With modulated
firing, the actuators should return to their low fire positions before the operating limit control (OLC) opens. When
the limit control circuit is opened, the following sequence occurs:
The main fuel valve circuit is de-energized, causing the main fuel valve (MGV or OV) to close. The flame is extin-
guished. The control panel lights (LDL and FVL) are turned off. The blower motor continues to run to force air
through the boiler for the post-purge period.
The blower motor start circuit is de-energized at the end of the post-purge cycle and the shutdown cycle is com-
plete.
The program relay is now ready for subsequent recycling, and when steam pressure or water temperature drops
to close the contacts of the operating control, the burner again goes through its normal starting and operating
cycle.
4.2 — Flame Loss Sequence
The program relay will recycle automatically each time the operating control closes, or after a power failure. It
will lock out following a safety shutdown caused by failure to ignite the pilot or the main flame, or by loss of
flame. Lockout will also occur if flame or flame simulating condition occurs during the pre-purge period.
The control will prevent startup or ignition if limit circuit controls or fuel valve interlocks are open. The control
will lock out upon any abnormal condition affecting air supervisory controls wired in the running interlock circuit.

CleaverBrooks CBEX-DE Specifications

General

Brand	CleaverBrooks
Model	CBEX-DE
Category	Boiler
Language	English