750-177 4-1
CHAPTER 4
Sequence of Operation
General 4-1
Circuit And Interlock Controls 4-1
Sequence Of Operation - Oil Or Gas 4-3
Flame Loss Sequence 4-4
A. GENERAL
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
components to provide an overall operating sequence.
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
prepared by Cleaver-Brooks for your specific installation.
Abbreviations for the various electrical components are listed in Table 4-1. The sequences outlined in Chapter
4 employ specific nomenclature to aid in applying the text to the wiring diagram.
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 glows.
All entrance switches are closed and power is present at the line terminals of:
• Blower motor starter
• Oil pump motor starter (if provided).
B. CIRCUIT AND INTERLOCK CONTROLS
The burner control circuit is a two-wire system designed for 115 Vac, 60 Hz, single-phase power.
The electrical portion of the boiler is made up of individual circuits with controls that are wired in a manner designed to
provide a safe workable system. The program relay provides connection points for the interconnection of the various
circuits.
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