750-91 (revised 2009)
Model CB-LE Packaged Boiler Manual
4-1
CHAPTER 4 Sequence of Operation
4.1 — Overview
Chapter 4 outlines the electrical sequencing of various controls through the pre-purge, ignition, run, and shutdown
cycles of the burner.
The program relay establishes the sequence of operation and directs the operation of all other controls and compo-
nents to provide an overall operating sequence.
The burner and control system are in starting condition when the following conditions exist:
• Boiler water is up to the correct level, closing the low-water cutoff switch.
• The low-water light (panel) is off.
• The operating limit pressure control (steam boiler) or the operating limit temperature control (hot water boiler)
and high limit pressure or temperature control are below their cutoff setting.
• All applicable limits are correct for burner operation.
• The load demand light is on.
All entrance switches should be closed and power should be present at the line terminals of::
• Blower motor starter
• Air compressor motor starter (if provided)
• Oil heater relay (if provided)
• Oil pump motor starter (if provided)
The sequences do not attempt to correlate the action of the fuel supply system or feedwater system except for the
interlock controls that directly relate to the action of the program relay. Chapters 5 and 6 contain operating instruc-
tions and specific information on setting and adjusting the controls.
NOTE: The make or model of the program relay provided will vary depending upon job specifications. The following
sequence applies regardless of the make or model. Please refer to the Wiring Diagram (WD) prepared by Cleaver-
Brooks for your specific installation.
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