750-91 (revised 2009)
Model CB-LE Packaged Boiler Manual
5-15
5.10 — Control Operational Test and Checks
• The burner is manually turned “off.”
• The low-water condition is detected by low-water level control.
• The electrical or fuel supply is interrupted.
• The combustion air pressure or atomizing air pressure drops below minimum level.
When the burner is shut down normally, by either the operating limit control or by manually switching the burner
off, the load demand light no longer glows.
Shutdown through conditions causing safety or interlock controls to open 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 corrected before operation can be resumed. Refer to the “troubleshooting” section in
Chapter 7.
5.9.2 — 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. The timer begins operation and the blower motor con-
tinues running to force air through the furnace in the 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-
fired burner is also turned off. The timer has returned to its original starting position and stops. The unit is ready to
restart.
5.10 — Control Operational Test and Checks
Proper operation of the various controls should be verified and tested when the boiler is initially placed into ser-
vice, or whenever a control is replaced. Periodic checks should be made thereafter in accordance with a planned
maintenance program.
The operating limit control may be checked by allowing steam pressure or water temperature to increase until the
burner shuts down. Depending upon the load, it may be necessary to manually increase the firing rate to raise steam
pressure to the burner shut off point. If the load is heavy, the header valve can be closed or throttled until the pres-
NOTE: There can be other reasons for shutdown, such as motor overload, flame outages, tripped circuit breakers,
blown fuses, or through other interlock devices in the circuitry.
It is advisable to check for tight shut-off of fuel valves. Despite precautions and strainers, foreign material in either new
or renovated fuel lines may lodge under a valve seat and prevent tight closure. The situation is especially true in new
installations. Promptly correct any conditions causing leakage. Failure to follow these instructions could result in seri-
ous injury or death.
!
Warning
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