Sequence Of Operation; General; Circuit And Interlock Controls - CleaverBrooks FLX Operation, Service And Parts Manual

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 (WD)
prepared by Cleaver-Brooks for your
specific installation.
Abbreviations for the various electrical components are listed
in Figure 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).
The sequences do not attempt to correlate the action of the
fuel supply system or feedwater system except for the
750-177
CHAPTER 4

Sequence Of Operation

A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1
B. Circuit And Interlock Controls . . . . . . . . . . . . . . . . 4-1
C. Sequence Of Operation - Oil Or Gas. . . . . . . . . . . . 4-2
D. Flame Loss Sequence . . . . . . . . . . . . . . . . . . . . . . . 4-3
interlock controls that directly relate to the action of the
program relay. Chapters 5 and 6 contain operating
instructions and specific information on setting and adjusting
the controls.
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.
The controls used vary depending upon the fuel oil or gas and
the specific requirement of applicable regulatory bodies.
Refer to the boiler wiring diagram to determine the actual
controls provided. The circuits and controls normally used in
the circuits follow and are referred to in the following
sequence of operation.
Limit Circuit:
• Burner switch (BS)
• Operating limit control (OLC) - pressure or temperature
• High limit control (HLC) - pressure or temperature
• Low-water cutoff (LWCO)
• Gas-oil selector switch (GOS) - (Combination burner
only)
• Low gas pressures switch (LGPS)
• High gas pressure switch (HGPS)
Fuel valve interlock circuit
• Main gas valve auxiliary switch (MGVAS)
• Oil valve auxiliary switch (OVAS)
4-1