Cleaver-Brooks CBH 40 - C. CONTROL AND COMPONENT FUNCTION

Chapter 1-General Description and Principles of Operation
alternating current. The forced draft fan motor is
generally operated on 3 phase service at the avail-
able main power supply voltage.
The operating limit and other interlock devices
wired into the circuitry provide safe operation of
the burner and protect against incorrect operating
techniques.
The major electrical components included in the
standard control system consist of a programming
control, limit and operating pressure or tempera-
ture controls, low water cut-off, damper motor, fuel
valve(s ), and motor starter.
The sequence of burner operation from start-up
through shutdown is governed by the programming
control in conjunction with the operating, limit
and interlock devices. This programmer contains a
timer that energizes or de-energizes other controls
at the proper time.
The same control monitors the flame to confirm
gas pilot operation prior to allowing main fuel
valves to open. The ignition of low fire flame on a
spark ignited oil burner must likewise be con-
firmed. The control will shut the burner down in
the event of a flame loss or as a result of action by
a
safety interlock.
The safety interlocks include combustion and air
proving equipment and - depending upon insur-
ance company requirements- controls that prove
the presence of adequate fuel pressure.
In addition to the standard basic controls sup-
plied, other devices may be required to meet
specific requirements of an insurance carrier or
local code. Refer to the wiring diagram furnished
with the burner to determine the specific controls
in the burner and limit control circuits. The func-
tion of individual components is outlined in this
chapter and the electrical sequence is covered in
Chapter 3.
C. CONTROL AND COMPONENT
FUNCTION
The term "control" covers the more important
valves and components, including but not limited
to electrical controls or those monitored by the
programming control. The operator must become
familiar with the individual functioning of all con-
trols whether or not outlined before he can under-
stand the boiler's operation, and procedures
outlined in the manual.
Identify and locate each item using the figure call-
out.
The actual controls furnished with any given boiler
will depend upon the type of fuel for which it is
equipped and whether it is a hot water or steam
boiler.
Boilers having optionally ordered features may
1-2
have control components not listed here.
PROGRAMMING AND FLAME SAFEGUARD
CONTROL (Figure 1-1)
Automatically programs each starting, operating,
and shutdown period in conjunction with
operating, limit, and interlock devices. This in-
cludes, in a timed and proper sequence, the
operation of the blower motor, ignition system, fuel
valve(s) and the damper motor. The sequence in-
cludes air purges prior to ignition and upon burner
shutdown.
The flame detector portion of this control monitors
both oil and gas flames and provides protection in
the event of loss of a flame signal.
The control recycles automatically during normal
operation, or following a power interruption. It
must be manually reset following a safety shut-
down caused by loss of flame. Incorporated is an
internal checking circuit effective on every start
which causes a safety lockout in the event anything
causes the flame relay to hold in during this
period.
The control contains the following major integral
components that are referred to in the operating
sequence text.
Master relay (1K): Energized when all the limit
and operating controls and switches are closed
to start program sequencing and to energize the
forced draft fan motor starter.
Flame relay (2K): Energized when the flame de-
tector senses a suitable flame. When de-ener-
gized by a flame loss it routes control circuit
through the lockout switch.
Lockout Switch (LS ): Trips in the event of
failure to ignite the pilot or main burner flame,
or on loss of flame. Additionally, on a CB-40
control, lock-out will occur upon the opening of
inter-locks or a flame simulating condition
during the programmer's checking period. A
short cooling period is required before it can be
reset. CAUTION. The reason for any lockout
should be investigated and corrected before at-
tempting to re-start.
Timer: Actuates cams to open and close swit-
ching contacts in a non-adjustable timed se-
quence to program the burner's operation
through all the functions necessary to operate
the burner.
Timer Position Dial: Indicates the position of
the timer and the stage reached in burner
operating cycle. (Figure 1-1)
Flame Detector: (figure 1-1): Monitors gas or oil
pilot and energizes the programmer's flame re-
lay in response to a flame signal. It continues to
monitor main flame (oil or gas) after expiration
of pilot proving period. A standardly equipped