750-96 (revised 2010)
Model CB Packaged Boiler Manual
3-1
CHAPTER 3 Sequence of Operation
3.1 — Overview
This chapter outlines the electrical sequencing of various controls through the pre-purge, ignition, run, and shut-
down cycles of the burner.
The program relay establishes the sequence of operation and directs the operation of all other controls and com-
ponents to provide an overall operating sequence.
In the schematic type wiring diagram provided for the boiler, the grounded (common) side of the power supply is
shown as a vertical line on the right side of the diagram. All inductive components (coils, solenoids, transformers,
lights, etc.) are connected to it. The hot side of the power supply is shown as a vertical line on the left side of the
electrical schematic. All the inductive components are connected to it through switches or contacts that permit
the component to function when required.
The burner and control system are in starting condition when the following conditions exist:
• Boiler water is up to 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
• Air compressor motor starter (if provided)
• Oil heater relay (if provided)
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 manufacturer’s bulletin for specific information.
NOTE: For an explanatory booklet on schematic wiring diagrams, request Cleaver-Brooks Bulletin C17-4095.
Courtesy of: C3 Surplus LLC
Surplus Industrial Superstore
305-428-2777
https://www.c3surplus.com
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