CleaverBrooks CBH Series Guide

$25.00
CLEAVER-BROOKS MODEL
PACKAGED BOILERS
Manual Part No. 750-99
Printed in
U.S.A.

CLEAVER-BROOKS
MODEL CBH
PACKAGED BOILERS
Operation, Service, and Parts Manual
Please direct purchase orders for replacement manuals
to your local Cleaver-Brooks representative
Manual Part No. 750-99
12/93 Printed in U.S.A

CONTENTS
CHAPTER 1 - GENERAL DESCRIPTION AND PRINCIPLES OF OPERATION .. 1-1
A. The Boiler ...................................................... 1-1
B.
The Burner and Control System ................................. 1-1
C. Control and Component Function ................................ 1-2
D.
Automatic Ignition ............................................... 1-9
E. Combustion Air .................................................. 1-9
F. Oil
Fuel Flow ................................................... 1-9
G.
Gas Fuel Flow .................................................. 1-12
CHAPTER 2 - THE PRESSURE VESSEL ....................................... 2-1
A. General ......................................................... 2-1
B.
Construction ..................................................... 2-1
C. Water Requirements ............................................. 2-1
1. Hot Water Boiler ............................................. 2-1
2. Steam Boiler ................................................. 2-3
D.
Water Treatment ................................................ 2-4
E. Cleaning ........................................................ 2-5
F.
Boil-out of a New Unit .......................................... 2-6
G.
Washing Out .................................................... 2-7
H. Blowdown - Steam Boiler ........................................ 2-7
I. Periodic Inspection .............................................. 2-9
J. Preparation for Extended Lay-up ................................. 2-9
CHAPTER 3 - SEQUENCE OF OPERATION ..................................... 3-1
A.
General .......................................................... 3-1
B.
Circuit and Interlock Controls .................................... 3-1
C. Sequence of Operation - CB-20 -Oil or Gas ...................... 3-2
D.
Sequence of Operation - CB-40 -Oil or Gas ...................... 3-4
E.
Flame Loss Sequence ............................................ 3-6
CHAPTER 4 - STARTING AND OPERATING INSTRUCTIONS ................. 4-1
A. General Preparation - Initial Start-up ............................ 4-1
B.
Control Settings -All Fuels ...................................... 4-1
C. Oil Burner Start-up .............................................. 4-2
D.
Gas Burner Start-up ............................................. 4-3
E. Normal Operation -All Fuels .................................... 4-4
CHAPTER 5 - ADJUSTMENT AND MAINTENANCE ........................... 5-1
A. General ......................................................... 5-1
B.
Periodic Inspection .............................................. 5-2
C. Water Level Controls ............................................ 5-2
D.
Water Gage Glass ............................................... 5-3
E.
Operating Controls ............................................... 5-3
Setting and Adjusting ............................................ 5-4
Pressure Controls - Steam Boiler ................................. 5-4
Temperature Controls - Hot Water Boiler ........................ 5-5
Combustion Air Proving Switch .................................. 5-6
Low
Gas Pressure Switch ........................................ 5-6
High Gas Pressure Switch ........................................ 5-7
Programming Control ............................................ 5-7
Control Operational Test ......................................... 5-7
F. Oil
Burner ...................................................... 5-8
Burner Nozzles .................................................. 5-8
Oil Pump ....................................................... 5-9
Combustion Adjustment .......................................... 5-10
G. Gas Burner ..................................................... 5-11
Gas Pilot Adjustment ............................................ 5-11
Gas Pressure and Flow .......................................... 5-12
Combustion Adjustment .......................................... 5-14
H. Switch and Cam Adjustment ..................................... 5-15
I. Air Damper Adjustment ......................................... 5-18
J. Safety Valves .................................................... 5-18

c T
TS (ConUm.med)
K. Motorized Gas Valve ............................................ 5-19
L.
Solenoid Valve .................................................. 5-19
M.
Refractory ....................................................... 5-19
N.
Door Closing and Sealing ........................................ 5-21
0. Forced Draft Fan ................................................ 5-22
P. Fireside Cleaning ................................................ 5-22
Q.
Lubrication ...................................................... 5-22
CHAPTER 6- TROUBLE SHOOTING ........................................... 6-1
A. Burner Does not Start ........................................... 6-1
B. No Ignition ...................................................... 6-1
C. Pilot Flame, But No Main Flame ................................ 6-2
D. Burner Stays in Low Fire . ....................................... 6-2
E. Shutdown Occurs During Firing .................................. 6-2
F.
Damper Motor .................................................. 6-2
CHAPTER 7- PARTS ORDERING INSTRUCTIONS AND PARTS LIST ......... 7-1
ii

WARNING
DO NOT OPERATE, SERVICE, OR REPAIR THIS EQUIPMENT UNLESS YOU FULLY UNDERSTAND
ALL APPLICABLE SECTIONS OF THIS MANUAL.
DO NOT
ALLOW OTHERS TO OPERATE, SERVICE, OR REPAIR THIS EQUIPMENT UNLESS THEY
FULLY UNDERSTAND ALL APPLICABLE SECTIONS
OF THIS MANUAL.
FAILURE
TO FOLLOW ALL APPLICABLE WARNINGS AND INSTRUCTIONS MAY RESULT IN SE-
VERE PERSONAL INJURY OR DEATH.
TO: Owners, Operators and/or Maintenance Personnel
This operating manual presents information that will help to properly operate and care for the equipment. Study its contents
carefully. The unit will provide good service and continued operation
if proper operating and maintenance instructions are
followed.
No attempt should be made to operate the unit until the principles of operation and all of the components are
thoroughly understood. Failure to follow all applicable instructions and warning may result in severe personal injury or death.
It is the responsibility of the owner to train and advise not only his or her personnel, but the contractor's personnel who are
servicing, repairing or operating the equipment, in all safety aspects.
Cleaver-Brooks equipment is designed and engineered to give long life and excellent service on thejob. The electrical and
mechanical devices supplied as part
of the unit were chosen because of their know ability to perform; however, proper operating
techniques and maintenance procedures must be followed at all times. Although these componesnts afford a high degree
of
protection and safety, operation of equipment is not to be considered free from all dangers and hazards inherent in handling and
firing of fuel.
Any
"automatic" features included in the design do not relieve the attendant of any responsibility. Such features merely free
him/her
of certain repetitive chores and give him/her more time tot devote to the proper upkeep of equipment.
It is solely the operator's responsibility to properly operate and maintain the equipment. No amount of written instructions can
replace intelligent thinking and reasoning and this manual is not intended to relieve the operating personnel
of the responsibility
for proper operation.
On the other hand, a thorough understanding of this manual is required before attempting to operate,
maintain, service, or repair this equipment.
Because
of state, local, or other applicable codes, there are a variety of electric controls and safety devices which vary consider-
ably from one boiler to another. This manual contains information designed to show how a basic boiler operates.
Operating controls will normally function for long periods
of time and we have found that some operators become lax in their
daily or monthly tesing, assuming that normal operation will continue indefinitely. Malfunctions
of controls lead to
uneconomical operation and damage and, in most cases, these conditions ca nbe traced directly to carelessness and deficiencies
in testing and maintenance.
It is recommended that a boiler room log or record be maintained. Recording of daily, weekly, nonthly and yearly maintenance
activities and recording
of any unusual operation will serve as a valuable guide to any necessary investigation.
Most instances
of major boiler damage are the result of operation with low water. We cannot emphasize too strongly the need
for the operator to periodically check his/her low water controls and to follow good maintenance and testing practices. Cross-
connecting piping to low water devices must be internally inspected periodically to guard against any stoppages which could
obstruct the free flow
of water to the low water devices. Float bowls of these controls must be inspected frequently to check for
the presence
of foreign substances that would impede float ball movement.
The waterside condition
of the pressure vessel is of extreme importance. Waterside surfaces should be inspected frequently to
check for the presence
of any mud, sludge, scale or corrosion.
The services
of a qualified water treating company or a water consultant to recommend the proper boiler watertreating practices
are essential.
The operation
of this equipment by the owner and his/her operating personnel must comply with all requirements or regulations
of his/her insurance company and/or other authority havingjurisdiction. In the event of any conflict or inconsistency between
such requirements and the warnings or instructions contained herein, please contact Cleaver-Brooks before proceeding.
iii

FORCED
DRAFT
FAN
COMBUSTION AIR
INLET VENT
THE FOUR PASS CONSTRUCTION OF A TYPICAL MODEL CB BOILER
Combustion air enters through the air inlet. The forced draft fan forces air through the
rotary air damper and the diffuser into the combustion chamber. The main fire tube or
combustion chamber, constitutes pass one. Baffling allows gases to pass to the front of the
boiler only through P.ass two; here a baffle allows gases to pass to the rear of the boiler
only through pass three. From the rear the gases are forced through pass four to the vent.
iv

CHAPTER 1
GENERAL DESCRIPTION
AND PRINCIPLES OF OPERATION
A. THE BOILER
B. THE BURNER AND CONTROL SYSTEM
C.
CONTROL AND COMPONENT fUNCTION
D. AUTOMATIC IGNITION
IE. COMBUSTION AIR
f. OIL fUEL flOW
G. GAS fUEL flOW
A. THE BOILER
The Cleaver-Brooks Model "CBH" Boiler is a
packaged steel boiler consisting of a pressure
vessel, oil or gas burner, burner controls, forced
draft fan, air control damper, and associated com-
ponents.
The boiler is a four pass horizontal firetube up-
draft boiler. The pressure vessel is constructed in
accordance with the ASME Boiler and Pressure
Vessel Code. Chapter 2 deals with tfiis portion of
the boiler.
This manual covers boilers designed for high or
low pressure steam or hot water generation in
capacities rated from 25 thru 100 horsepower.
The boiler and related equipment installation, by
others, is to be in compliance with the standards of
the National Board of Fire Underwriters. In-
stallation should also conform to state and local
codes governing such equipment. Prior to in-
stallation, the proper authorities having jurisdic-
tion are to be consulted, permits obtained etc. All
boilers in the above series comply, when equipped
with optional equipment, to Factory Insurance
Association Div. of Industrial Risk Insurers
(F.I.A.), Factory Mutual (FM) or other insuring
underwriters requirements.
B. THE BURNER AND CONTROl
SYSTEM
The type of fuel used by the boiler determines the
series classification. These are:
Series 100
Series 200
Series 700
Light oil (No. 2) only
Light oil (No. 2) or gas
Gas only
A boiler equipped to burn oil and gas includes
equipment for each distinct fuel. Since the burner
uses only one type of fuel at a time, a gas/oil selec-
tor switch is incorporated in the combination units.
The Model CBH boiler has the burner assembly
attached to the front head, readily accessible for
inspection
and maintenance.
The oil burner is of the high pressure atomizing
type and the gas burner is of the high radiant
annular entry type. A gas burner is ignited by a gas
pilot which is spark ignited. A burner that uses
light oil fuel only is normally spark ignited. A
combination gas-oil unit uses a gas pilot for
ignition
of both fuels.
The standard burner, whether firing on oil or gas,
operates at two burning rates -high fire and low
fire. An
optionally equipped gas-fired boiler
operates on a modulating firing principle. The bur-
ner and its components are described in detail
later in this manual.
Combustion air is provided by a centrifugal blower
located in the front head. Combustion air delivery
to the burner is under the control of the damper
motor. This same motor regulates the flow of gas
fuel through a linkage system connected to the gas
butterfly valve or by actuating switches that
energize the oil valves. Fuel input and air are thus
properly proportioned for most efficient combus-
tion.
An electronic safety control programs the sequence
of operation and in conjunction with a flame detec•
tor monitors the flame to shut the burner down in
the event of loss of flame. Other safety controls
shut the burner down under low water conditions
or excessive steam pressure or water temperatures.
The burner control circuit operates on 115 volt,
single phase 60 hertz (or 50 hertz when equipped)
1-1

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

boiler has a lead sulfide (infrared sensitive)
detector.
BURNER SWITCH (Figure 1-1)
A
manually operated start-stop switch used for di-
rectly starting and stopping burner operation.
FORCED DRAFT FAN MOTOR (Figure 1-1)
Directly drives a forced draft fan to provide com-
bustion air. Also referred to as blower motor. On
an oil fired unit the oil pump is driven from this
motor by a V -belt.
BLOWER
MOTOR
COMBUSTION
AIR PROVING
SWITCH
DAMPER
MOTOR
AUXILIARY
SWITCH
DAMPER
LINKAGE
BUTTERFLY
GAS
VALVE
BLOWER MOTOR
STARTER
Chapter 1-General Description and Principles of Operation
FORCED DRAFT FAN MOTOR STARTER
(Figure 1-1)
Energizes forced draft fan (blower) motor.
DAMPER MOTOR (Figure 1-1)
A
two position motor that positions the air damper
through a linkage system, to provide proper air-
fuel ratio under low fire and high fire conditions.
The motor is powered to the open position and
spring returned to the closed.
The motor actuates one or more auxiliary switches.
PROGRAMMING
AND FLAME
SAFEGUARD
CONTR.OL
-------mrTIMER
- DIAL
---------!!!!-GAS-OIL
SWITCH
----OIL
PUMP
OIL PRESSURE
GAUGE
FIGURE 1-l. TYPICAL OIL AND GAS FIRED MODEL CBH BOILER
1-3

Chapter 1-General Description and Principles of Operation
It also operates, through linkage, the butterfly gas
valve.
A modulating motor can be supplied as optional
equipment on a gas fired unit. (Figure 1-2) See Sec-
tion G for details.
DAMPER POSITIONING SWITCH
(Manual-Automatic) (Figure 1-1)
A three-position switch for manually setting either
high fire or low fire rate or establishing a circuit
through the high-low fire control for automatic
operation.
AUXILIARY SWITCH(S) (Figure 1-1)
Actuated by damper motor shaft rotation. Each
boiler has a switch that serves as a low fire switch
to prove that the damper is in a closed position
before ignition can take place. An oil fired boiler
has additional switches that control oil solenoid
valves for high fire operation. An optionally equip-
ped boiler has an additional switch to prove dam-
per opening during the pre-purge.
GAS/OIL SWITCH (Figure 1-1)
Toggle switch used to manually select circuitry for
either gas or oil firing.
IGNITION TRANSFORMER (Figure 1-1)
Provides high voltage spark for ignition electrode
of gas pilot or light oil burner ignition.
OPERATING PRESSURE,
HIGH PRESSURE. AND
M lNG
DAMPER
MOTOR
(OPTIONAL FOR
GAS FIRING)
1-4
HIGH-LOW FIRE CONTROLS
MODULATING
CONTROL
(OPTIONAL FOR
GAS FIRING)
CHECK
VALVE
FIGURE 1-2 TYPICAL STEAM BOILER AND CONTROLS
GAGE
GLASS

OPERATING LIMIT PRESSURE CONTROL
Steam Boiler (Figure 1-2)
OPERATING LIMIT TEMPERATURE CON-
TROL - Hot Water Boiler (Figure 1-3)
Breaks a circuit to stop burner operation on a rise
of boiler pressure or temperature above a selected
setting. It is adjusted to start or stop the burner at
a pre-selected pressure or temperature setting.
HIGH LIMIT PRESSURE CONTROL
Steam Boiler (Figure 1-2)
HIGH LIMIT TEMPERATURE CONTROL
Hot Water Boiler (Figure 1-3)
Breaks a circuit to stop burner operation at a pre-
selected pressure or temperature above the opera-
ting limit control setting. This control must be
manually reset to restore the circuit.
HIGH-LOW FIRE CONTROL (Figures 1-2 & 1-3)
A pressure or temperature control which, when
placed into the circuit by proper setting of the
damper positioning switch, makes or breaks the
circuit to the damper motor causing the burner to
Chapter !-General Description and Principles of Operation
operate at either high or low fire rate in accord-
ance with load requirements.
MODULATING CONTROL (Figure 1-2)
Senses changing boiler pressures, or temperatures,
and transmits this information to the modulating
damper motor to change the firing rate. Provided
only as optional equipment for a gas fired boiler.
When installed on a 200 Series boiler, it is re-
moved from the operating circuitry while the boiler
is fired on oil.
LOW WATER CUT-OFF AND PUMP CONTROL
(Steam Boiler) (Figure 1-2)
This float-operated control responds to the water
level in the boiler. It performs two distinct func-
tions:
(a) Stops firing of the burner if water level lowers
below the safe operating point and low water light
in the control panel; also causes low water alarm
bell (optional equipment) to ring. Code require-
ments for some models require a manual reset type
of low water cutoff. This type requires manual
OPERATING TEMPERATURE,
HIGH LIMIT TEMPERATURE
AND HIGH-LOW FIRE
CONTROLS
FIGURE 1-3. TYPICAL HOT WATER BOILER AND CONTROLS
1-5

Chapter 1-General Description and Principles of Operation
resetting to start the burner after a low water shut-
down.
(b) Starts and stops the feedwater pump (if used)
to maintain water at the proper operating level.
NOTE; Determine that control is plumb after
shipment and installation and throughout
operating life.
AUXILIARY LOW WATER CUTOFF
(Not shown) (Optional equipment)
This float-operated control breaks the circuit to
stop burner operation in the event boiler water
drops below the master low water cutoff point.
Manual reset type (optional equipment) requires
manual resetting in order to start the burner after
a low water condition.
LOW WATER CUT-OFF
(Hot Water Boiler) (Figure 1-3)
A
float operated control that breaks a circuit to
stop burner operation if water level in the boiler
drops below a safe operating point.
WATER COLUMN (Figure 1-2)
This assembly houses the low water cutoff and
pump control and includes the water gage glass,
gage glass shutoff cocks, and trycocks. The gage
glass provides a means for visually determining
water level.
WATER COLUMN DRAIN VALVE (Figure 1-2)
The water column drain valve is provided so that
the water column and its piping can be flushed
regularly to assist in maintaining cross-connecting
piping and float bowl clean and free of sediment. A
LOW GAS
PRESSURE SWITCH GAS PILOT
PRESSURE REGULATOR
similar drain valve is furnished with auxiliary low
water cutoff (optional equipment) for same pur-
pose.
WATER GAGE GLASS DRAIN VALVE
(Figure 1-2)
This valve is provided to flush the gage glass.
TEST VALVE (Figure 1-2)
This valve allows the boiler to be vented during
filling, and facilitates routine boiler inspection.
PRESSURE GAUGE
(Stearn Boiler) (Figures 1-1 & 1-2)
Indicates boiler's internal pressure.
TEMPERATURE/PRESSURE GAUGE
(Hot Water Boiler) (Figure 1-3)
A
compound gauge that indicates boiler's internal
water temperature and water pressure.
STACK THERMOMETER (Figure 1-2)
Indicates temperature of vented flue gases. (Op-
tional)
SAFETY OR RELIEF VALVE (Figures 1-2 & 1-3)
A
safety valve(s) is used on a steam boiler to re-
lieve the boiler of pressures higher than the de-
signed pressure or the pressure designated by the
purchaser. A relief valve(s) is used on a hot water
boiler for the same purpose.
Safety and relief valves and their escape and drain
piping are to be installed to conform to the ASME
Code requirements. (Figure 1-7)
WARNING: Only the valve manufacturer or his
HIGH GAS
PRESSURE SWITCH
MAIN GAS VALVE
WITH INTEGRAL
PROOF OF CLOSURE
SWITCH
GAS PILOT
SOLENOID VALVE
FIGURE 1-4. GAS TRAIN WITH TWO VALVES
1-6

representative should adjust or
repair these valves.
COMBUSTION AIR PROVING SWITCH
(Figure 1-1)
A
pressure sensitive switch, actuated by air pres-
sure, whose contacts close to prove sufficient pres-
sure of combustion air from the forced draft fan.
OIL PUMP (Figure 1-1)
Draws oil from supply tank and delivers it under
pressure to the burner nozzles. The pump contains
an integral adjustable pressure regulator and
rotary filter. The pump is driven by a V -belt con-
nected to the blower motor.
OIL BURNER PRESSURE GAUGE (Figure 1-1)
Indicates the fuel pump discharge pressure to noz-
zle.
FUEL OIL VALVES (Figures 1-1 & 1-6)
Electrically operated to open in a controlled se-
quence to allow oil flow from the pump to the bur-
ner nozzles. The function of the valves is described
INTERMEDIATE
FRONT HEAD
HEAD
GASKET
Chapter !-General Description and Principles of Operation
in the oil fuel flow section later in this chapter.
FUEL OIL SHUT-OFF COCK (Figure 1-1)
For manually shutting off oil supply to burner.
LOW OIL PRESSURE SWITCH (Optional)
(Figure 1-3)
Switch contacts open when fuel oil pressure drops
below selected pressure. Switch will interrupt the
limit circuit upon loss of sufficient fuel oil pressure
for correct combustion.
AIR DAMPER (Figure 1-5)
Controls the amount of combustion air admitted to
the burner in proper proportion to fuel input for ef-
ficient combustion at high or low firing rates.
NOTE: Depending upon the requirements of
the insurance carrier or other governing agen-
cies, the gas flow control system, or gas train,
may consist of some, or all, of the following
items. Refer to your boiler to determine those
that are applicable. A typical gas train is
shown in figure 1-4.
AIR BAFFLE
PLATE
NOTE: Burner shown in place for illus-
tration purposes only. Burner drawer
must be removed prior to opening
head.
FIGURE 1-5. BOILER WITH FRONT HEAD OPEN, CBH 50-100A OIL AND GAS FIRED
1-7

Chapter 1-General Description and Principles of Operation
GAS PILOT VALVE (Figure 1-4)
A
solenoid valve that opens during the ignition
period to admit fuel to the pilot. It closes after
main flame is established. The sequence of energiz-
ing and de-energizing is controlled by the program-
ming relay.
GAS PILOT SHUT-OFF COCK (not shown)
For manually opening or closing the gas supply to
gas pilot valve.
GAS PRESSURE GAUGE (not shown)
Indicates gas pressure to pilot. (Optional)
GAS PRESSURE REGULATING VALVE
(Figure 1-4)
Reduces incoming gas pressure to suit the pilot's
requirement of between 5" to 10" W.C.
BUTTERFLY GAS VALVE (Figure 1-l)
The pivoted disc in this valve is actuated by con-
necting linkage from the damper motor to regulate
the rate of gas flow to the burner.
MAIN GAS VALVE (Figure 1-4)
An
electrically actuated shutoff valve. When open,
it admits main flame gas through the butterfly gas
valve. The valve may be equipped with a "proof of
closure" switch connected into a pre-ignition inter-
lock circuit. A second motorized shutoff gas valve
is often used.
GAS VENT VALVE: (Figure 1-4)
(Optional)
A normally open solenoid valve installed between
the two main gas valves to vent gas to the at-
mosphere should any be present in the main gas
FIGURE 1-6. FUEL OIL CONTROL VALVES
1-8

line when the gas valves are de-energized. The
vent valve closes when the gas valves are
energized.
MAIN GAS COCK (Figure 1-4)
For manually opening and closing the main fuel
gas supply downstream of the main gas line
pressure regulator. A second shut-off cock, down-
stream of the main gas valve(s), may be installed
to provide a means of shutting off the gas line
whenever a test is made for leakage across the
mam gas valve.
LOW GAS PRESSURE SWITCH (Figure 1-4)
A
pressure actuated switch that is closed whenever
main gas line pressure is above a preselected
pressure. Should the pressure drop below this set-
ting, the switch contacts will open a circuit causing
the main gas valve(s) to close, or prevent the bur-
ner from starting. This switch is usually equipped
with a device that must be manually reset after
being tripped.
HIGH GAS PRESSURE SWITCH (Figure 1-4)
A
pressure actuated switch that is closed whenever
main gas line pressure is below a preselected pres-
sure. Should the pressure rise above the setting, the
switch contacts will open a circuit causing the
main gas valve(s) to close, or prevent the burner
from starting. The switch is usually equipped with
a device that must be manually reset after being
tripped.
LEAKAGE CONNECTION
The body of the gas valve has a plugged opening
that is used whenever it is necessary or desirous to
conduct a test for possible leakage across the
closed valve.
D. AUTOMATIC IGNITION
A gas burner (and an oil burner on a combination
unit), is ignited by an interrupted type gas pilot.
Some insurance regulations require that a light oil
burner (Model 100) be ignited with a gas pilot al-
though standardly this model has spark ignition.
The gas pilot flame is ignited automatically by an
electric spark. Fuel for the pilot is supplied from
the utility mains or from a tank (bottle) supply.
Flow rate (flame size) is regulated by a pressure
regulator (Figure 1-4 ). The burner is designed to
have combustion air flow into and mix with the
pilot gas stream to provide a suitable flame.
At the beginning of the ignition cycle, the pilot gas
solenoid valve and ignition transformer are
simultaneously energized. The ignition trans-
former supplies high voltage current for the
igniting spark which arcs between the single elec-
trode within the pilot tube and the wall of the tube
itself. The gas pilot solenoid and transformer are
de-energized after main flame is ignited.
Chapter 1-General Description and Principles of Operation
On a Model 100 boiler with spark ignition, the low
fire oil
nozzle is ignited by a spark arcing between
two electrodes supplied with high voltage current
from the ignition transformer. At the beginning of
the ignition cycle, the low fire oil solenoid valve
and ignition transformer are simultaneously ener-
gized. The ignition transformer is de-energized af-
ter low fire is established and proven.
E. COMBUSTION AIR
Air for the combustion of fuel, (also called "sec-
ondary" air) is furnished by the forced draft fan
(Figure 1-3) mounted in the front head. In oper-
ation, air pressure is built up in the entire head
and forced through a diffuser plate for a thorough
mixture with the fuel for proper combustion.
The supply of combustion air is governed by auto-
matically throttling the output of the fan by
regulating the air damper to furnish the proper
amount of air for correct ratio of air to fuel for ef-
ficient combustion at both low and high firing
rates.
F. Oil FUEl FlOW
An oil fired boiler is equipped with a belt driven
fuel pump (Figures 1-1 & 1-5) that withdraws fuel
oil from a storage tank. The pump has a greater
capacity than the maximum burning rate and all
oil not delivered to the burner nozzles is returned
to the storage tank.
The pump has an integral pressure regulator that
can be adjusted to provide the necessary atomizing
SUPPORT FROM BUILDING
CONSTRUCTION
Discharge opening
MUST be larger than
inlet
TO STEAM
VENT
WATER LEVEL
NOTE: Back-pressure of steam exhaust system MUST
be less than 10% of safety valve setting-!--
FIGURE 1-7. RECOMMENDED
SAFETY VALVE INSTALLATION PROCEDURE
1-9

Chapter 1-General Description and Principles of Operation
HIGH FIRE ORIFICE
OIL VALVE BLOCK
(HFOV)
OIL PRESSURE
GAUGE
OIL SHUTOFF SOLENOID
VALVE
(LFOV-1)
t OIL
TERMINAL
BLOCK
CHECK
VALVE OIL
-sUPPLY
__.OIL
RETURN
FIGURE 1-8. SCHEMATIC OIL FLOW DIAGRAM, MODEL CBH 25-40 AND 50A
MANIFOLD BLOCK
MANUAL OIL
SHUTOFF VALVE
INTERMEDIATE ~- --- \----1---L_j------j__J.-----\
HIGH FIRE I
OIL VALVE :
(HFOV-1)
HIGH FIRE
OIL VALVE !
(HFOV-2) )J
HIGH FIRE
OIL NOZZLE
-·
LOW FIRE
OIL NOZZLE
ORIFICE
FITTING
t OIL
STRAINER
FIGURE 1-9 SCHEMATIC OIL FLOW DIAGRAM, MODEL CBH 50-100
1-10
OIL
SUPPLY
OIL
RETURN

pressure to the burner nozzles. This pressure is
read on the oil pressure gauge.
Oil flow to the burner nozzles is controlled by sole-
noid valves. At the proper time in the operating se-
quence, the primary, or safety, shut-off valve
(LFOV-1) and the low fire valve (LFOV-2) are
energized by the programming control. The open-
ing of these valves allows the oil to flow to the low
fire nozzle.
When the damper motor moves to the high fire
position, an auxiliary switch actuated by the
motor, energizes a high fire valve.
PILOT GAS
MAIN GAS
MAIN GAS
SHUTOFF VALVE
Chapter 1-General Description and Principles of Operation
Figure 1-8 shows the valves used on the 25 through
40 and 50A size boilers. The orifice block between
the valves prevents a sudden pressure drop when
the high fire valve opens.
The oil discharge from the pump on the 50 through
100 size flows into a manifold block (Figure 1-9).
The intermediate valve is energized prior to the
high fire valve. The purpose for this is to make the
change from low to high fire smoother by balanc-
ing the oil input with the increasing flow of air as
the damper opens. The return line from the mani-
fold is orificed to maintain a constant pressure.
I
MAIN GAS
VALVE(S)
FIGURE 1-10. SCHEMATIC GAS FLOW DIAGRAM
1-11

Chapter !-General Description and Principles of Operation
G. GAS fUEl flOW
The gas flow system is shown with the direction of
flow indicated by arrows. (Figure 1-10)
Metered gas from the utility flows into the burner's
gas piping through a main gas shut-off cock;
through a pressure regulator where the pressure is
reduced to the pressure suitable to the burner's re-
quirements; through an electrically operated main
gas valve and through a butterfly gas valve to the
burner. Gas required for pilot operation is taken
from this line prior to the main gas shut-off cock.
Gas for the pilot operation flows through a shut-off
cock into a pressure regulator where the pilot oper-
ating pressure is established. A solenoid valve con-
trols the flow of the gas and when energized
(opened) allows the gas to flow to the pilot where it
is mixed with combustion air. This mixture is
ignited by a controlled electric spark to establish
the pilot flame. The pilot burns only during the
time required for main flame ignition.
At the beginning of the ignition cycle, the pilot
solenoid valve is energized through circuitry in the
programmer control and the pilot ignited. When
pilot flame is proven, the programming control
energizes the electrically operated main gas valve
allowing flow through the butterfly valve to the
burner. The rate of flow to the burner depends
upon the position of the vane in the butterfly valve.
This is mechanically controlled by the damper
motor and varied in the same maimer as the air
damper, thus properly proportioning gas and com-
bustion air.
1-12
High-Low Burner Operation
The standard burner is equipped for two position
firing; either low or high. A pressure control on a
steam boiler, or a temperature control on a hot
water boiler, makes or breaks the circuit to the
damper motor causing the burner to operate at
either the high fire or the low fire rate in accord-
ance with load requirements.
Modulating Burner Operation
An optionally equipped gas fired boiler has a
modulating damper motor. This type of motor is
reversible and will move in either direction or stop
at any position within its range.
Through a linkage arrangement it controls the air
damper and the butterfly gas valve to maintain a
constant air-fuel ratio throughout the firing range.
Gas flows through the burner orifice ring to enter
the combustion zone where it is intimately mixed
with combustion air to produce main flame.
The main gas valve cannot be energized (opened)
unless the combustion air proving switch is closed
to indicate a sufficient supply of combustion air.
Some insurance requirements specify two main gas
valves. Additional requirements call for a nor-
mally open vent valve to be placed between them
for venting gas should any be present in main gas
line when main gas valves are de-energized. The
vent valve closes when the main gas valves open.