CleaverBrooks CBEX Elite Operation And Maintenance page 53

5.7 — Startup, Operating, and Shutdown: All Fuels
After the boiler is thoroughly warmed, turn the manual flame control to high fire. At this point a combustion anal-
ysis should be made, with instruments, and fuel flow regulated as required. Refer to the adjustment procedures
in Chapter 6. After making the high-fire adjustment, manually decrease the firing rate, stopping at each cam
screw to analyze combustion gases, and adjust as required.
To properly perform the testing and adjusting, it is necessary that the burner be allowed to fire at a maximum
rate long enough to achieve desired results.
5.7.1 — Operating
Normal operation of the burner should be with the controls in automatic mode. Manual mode is provided for ini-
tial adjustment of the burner over the entire firing range. When a shutdown occurs while operating in manual 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. The hot flame to cool air cycling subjects the pressure vessel metal and refractory to undesir-
able stresses.
With the controls in AUTO, the burner will operate on a modulating basis according to the load demand.
The burner will continue to operate with modulated firing until the operating limit pressure or temperature is
reached, unless:
The burner is manually turned "off."
1.
The low-water condition is detected by low-water level control.
2.
The electrical or fuel supply is interrupted.
3.
The combustion air pressure or atomizing air pressure drops below minimum level.
4.
NOTE: There can be other reasons for shutdown such as motor overload, flame outage, tripped circuit breakers,
blown fuses, or through other interlock devices in the circuitry.
When the burner is shut down normally, by either the operating limit control or by manually switching the burner
off, the load demand light will turn off.
Shutdown through flame failure will actuate the flame failure light (and alarm, if so equipped) and the load
demand light will remain lit. The cause of this type of shutdown will have to be located, investigated, and cor-
rected before operation can be resumed.
5.7.2 — Shutdown
When the operating limit control setting is reached to open the circuit or if the burner switch is turned "off," the
following sequence occurs:
The fuel valve is de-energized and the flame is extinguished.
1.
The timer begins operation and the blower motor continues running to force air through the furnace in the
2.
post-purge period.
At the end of the programmed post-purge period, the blower motor is turned off. The air pump motor of an oil
3.
fired burner is also turned off.
The timer has returned to its original starting position and stops. The unit is ready to restart.
4.
750-368
CBEX Elite 100-1200 HP
5-9