CleaverBrooks CBT User manual

750-382
04/2019
Model CBT
Tubeless Vertical Boiler
Operation and Maintenance Manual
CBT-M — Full Modulation
CBT — On/Off Operation

ii
Should overheating occur or the gas supply valve fail to
shut off, do not turn off or disconnect the electrical sup-
ply to the boiler. Instead turn off the gas supply at a lo-
cation external to the boiler.
!DANGER
WARNING
!DANGER
WARNING
If the information in this manual is not followed exactly,
a fire or explosion may result causing property dam-
age, personal injury or loss of life.
— Do not store or use gasoline or other flammable va-
pors and liquids in the vicinity of this or any other appli-
ance.
— WHAT TO DO IF YOU SMELL GAS
• Do not try to light any appliance.
• Do not touch any electrical switch; do not use
any phone in your building.
• Immediately call your gas supplier from a
neighbor's phone. Follow the gas supplier's
instructions.
• If you cannot reach your gas supplier, call the
fire department.
— Installation and service must be performed by
a qualified Cleaver-Brooks, service agency or the
gas supplier.
Improper installation, adjustment, service, or mainte-
nance can cause equipment damage, personal injury,
or death. Refer to the Operation and Maintenance
manual provided with the boiler. Installation and ser-
vice must be performed by a qualified Cleaver-Brooks
service provider.
!DANGER
WARNING
!DANGER
WARNING
Be sure the fuel supply which the boiler was designed
to operate on is the same type as specified on the boiler
name plate.
!DANGER
WARNING
Do not use this boiler if any part has been under
water. Immediately call your Cleaver-Brooks ser-
vice representative to inspect the boiler and to re-
place any part of the control system and any gas
control which has been under water.
!DANGER
WARNING
To minimize the possibility of serious personal injury,
fire or damage to the equipment, never violate the fol-
lowing safety rules.
— Always keep the area around the boiler free of com-
bustible materials, gasoline, and other flammable liq-
uids and vapors
— Never cover the boiler, lean anything against it,
stand on it, or in any way block the flow of fresh air to
the boiler. This manual must be maintained in legible condi-
tion and kept adjacent to the boiler or in a safe
place for future reference. Contact your local
Cleaver-Brooks representative if additional manu-
als are required.
Notice
Where required by the authority having jurisdiction, the
installation must conform to the Standard for Controls
and Safety Devices for Automatically Fired Boilers,
ANSI/ASME CSD-1.
Notice
The boiler and its individual shutoff valve must be
disconnected from the gas supply piping system
during any pressure testing of that system at test
pressures in excess of 1/2 psi (3.5 kPa).
!DANGER
WARNING The installation must conform to the requirements
of the authority having jurisdiction or, in the ab-
sence of such requirements, to UL 795 Commer-
cial-Industrial Gas Heating Equipment and/or the
National Fuel Gas Code, ANSI Z223.1
!DANGER
WARNING

iii
CLEAVER-BROOKS
Model CBT
Tubeless Vertical Boiler
Operation, Service, and Parts Manual
 Cleaver-Brooks 2019
Manual Part No. 750-382
04/2019

iv
Cleaver-Brooks equipment is designed and engineered to give long life and excellent service on the job. The electrical
and mechanical devices supplied as part of the unit were chosen because of their known ability to perform; however,
proper operating techniques and maintenance procedures must be followed at all times. Although these components af-
ford 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
eliminate certain repetitive chores, providing more time for 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 at-
tempting 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
considerably from one boiler to another. This manual contains information designed to show how a basic burner 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 testing, assuming that normal operation will continue indefinitely. Malfunctions of controls lead to
uneconomical operation and damage and, in most cases, these conditions can be 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, monthly and yearly main-
tenance 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 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 fre-
quently to check for the presence of any mud, sludge, scale or corrosion.
It is essential to obtain the services of a qualified water treating company or a water consultant to recommend the proper
boiler water treating practices.
The operation of this equipment by the owner and his or her operating personnel must comply with all requirements or
regulations of his insurance company and/or other authority having jurisdiction. In the event of any conflict or inconsis-
tency between such requirements and the warnings or instructions contained herein, please contact Cleaver-Brooks be-
fore proceeding.
DO NOT OPERATE, SERVICE, OR REPAIR THIS EQUIPMENT UNLESS YOU FULLY UNDERSTAND ALL APPLI-
CABLE SECTIONS OF THIS MANUAL.
DO NOT ALLOW OTHERS TO OPERATE, SERVICE, OR REPAIR THIS EQUIPMENT UNLESS THEY FULLY UN-
DERSTAND ALL APPLICABLE SECTIONS OF THIS MANUAL.
FAILURE TO FOLLOW ALL APPLICABLE WARNINGS AND INSTRUCTIONS MAY RESULT IN SEVERE PERSONAL
INJURY OR DEATH.
!DANGER
WARNING

v
CONTENTS
CHAPTER 1 INTRODUCTION 1-1
Pressure vessel 1-2
Burner 1-4
Gas train 1-5
Controls 1-6
Component/connection locations 1-9
Optional equipment 1-10
CHAPTER 2 INSTALLATION 2-1
Lifting and moving the boiler 2-2
Water treatment 2-2
Boiler room 2-4
Gas piping 2-5
Boiler water-side connections 2-10
Electrical connections 2-11
Wiring diagrams 2-12
CHAPTER 3 FLUE AND COMBUSTION AIR VENTING 3-1
Venting connections — general 3-2
Flue venting 3-2
Vent terminal location 3-2
Horizontal through-wall venting, inside air (Category III) 3-5
Horizontal through-wall direct venting 3-6
Horizontal through-wall flue vent termination 3-7
Vertical venting, inside combustion air (Category III) central heating 3-8
Vertical venting, direct vent combustion air (Category III) 3-9
Flue and combustion air duct design using direct vent combustion 3-9
CHAPTER 4 COMMISSIONING 4-1
Full modulation boilers 4-2
On/off boilers 4-25
Boil-out of a new unit 4-25
Post start-up checkout procedure 4-26
Falcon control functions and customer interface 4-27
CHAPTER 5 MAINTENANCE 5-1
General 5-2
Bottom blowdown 5-2
Water column blowdown 5-3
Fireside cleaning procedure/disassembly 5-5
Ignition electrode 5-7
UV scanner (full modulation only) 5-8
Waterside inspection/cleaning 5-10
Safety valve 5-11
Troubleshooting 5-11
Display diagnostics 5-27
Lay-up 5-27
CHAPTER 6 PARTS 6-1
Recommended spare parts list 6-2
Safety valves 6-3
Control panel 6-4
Burner assembly 6-6
Water Column 6-10
Feedwater piping 6-11
Gas train 6-12
Direct vent kits 6-13

vi

750-382
CBT
1-1
CHAPTER 1 Introduction
Pressure vessel 1-2
Burner 1-4
Gas train 1-5
Controls 1-6
Component/connection locations 1-9
Optional equipment 1-10

Introduction
1-2 750-382
CBT
The Cleaver-Brooks Model CBT is a two-pass vertical tubeless steam boiler with
side-mounted burner.
The CBT features thick pressure vessel plates designed to provide long life.
Full modulation and on/off options are available. On full modulation units, an
ECM variable speed combustion air blower modulates the burner to precisely
match steam production to demand for reduced fuel usage and cycling. The
side-mount burner arrangement allows for a larger steam space to deliver excep-
tionally dry steam quality while allowing easy access for service and mainte-
nance. The Falcon control keeps the boiler and burner consistently operating at
peak efficiency.
On/off burners use the CB780 burner management control.
The CBT is available in 10, 15, 20, 25, and 30 HP sizes. Features include:
•Natural gas and propane fuels
•15 psig or 150 psig design pressure
•Up to 84% efficiency and high turndown with the PID modulating premix
burner.
•Low emissions: less than 20 ppm NOx (full mod, natural gas only)
•Robust pressure vessel, designed to provide long life; 5 year pressure vessel warranty
•Standard integrated control with user-friendly interface for peak operation and efficiency
Quality construction
ASME construction ensures high quality design, safety, and reliability.
UL listed
The Model CBT and CBT-M are UL listed for both the US and Canada.
Premix technology
The Model CBT-M Boiler utilizes “Premix” technology to mix both fuel and combustion air prior to entering the
firing chamber. This technology provides clean, efficient combustion with very low emission levels.
1.1 — Pressure vessel
The boilers are constructed in accordance with the ASME Boiler Construction Code, Section I for high pressure
steam boilers and Section IV for low pressure steam boilers. High pressure steam boilers are stamped with the
ASME “S” symbol. Low pressure steam boilers are stamped with the ASME “H” symbol. The ASME data plate
can be found on the lower portion of the vessel on the front or left side (see Figure 1-2).
The CBT is a vertically oriented 2-pass tubeless pressure vessel design with a water-backed furnace. The first
fireside pass utilizes radiant heat transfer and the second pass uses convection. The second pass flue passage-
ways incorporate extended heating surfaces designed using computational fluid dynamics (CFD) modeling.
The large steam chest volume ensures exceptional dry quality steam at both high and low operating pressures.
FIGURE 1-1. CBT-M boiler

750-382
CBT
1-3
Pressure vessel
The pressure vessel is fully insulated with minimal use of refractory to significantly reduce radiation and convec-
tion losses. Refractory is limited to the burner dry oven and a bottom furnace target plate.
FIGURE 1-2. ASME data
FIGURE 1-2. CBT heat flow
Gases of combustion flow downward
through the furnace (1), then upward
through the 2nd pass (2) before exiting
the flue (3).
(1)
(2)
(3)

Introduction
1-4 750-382
CBT
1.2 — Burner
1.2.1 — Full modulation (CBT-M)
Full modulation units use a premix burner with a self-regulat-
ing gas valve-venturi system, ECM variable regulating gas
valve, variable speed blower, and Fecralloy metal fiber
burner canister.
•Full modulation is provided using the integral variable
speed combustion air fan and Falcon control.
•The low temperature, surface combustion burner flame
provides low emissions and optimum combustion effi-
ciency.
•Direct spark ignition with UV flame detection.
•At maximum firing rate, the sound level of the burner is
less than 70 dBA, measured in front of the boiler at a dis-
tance of 3 feet. At reduced firing rates, sound levels are
even lower.
•Provision is made for optional direct vent combustion air
connection.
•Combustion Air Proving Switch standard.
•Combustion air filter is standard.
1.2.2 — On-off firing (CBT)
Gas is introduced into the combustion zone from a circular manifold
through multiple ports in the manifold. Burner firing is regulated by a
main gas regulator operating steam pressure control. Burner includes
microprocessor-based flame supervision control.
•Direct spark ignition with flame rod.
•Provision is made for optional direct vent combustion air connec-
tion.
•Combustion Air Proving Switch standard.
•Combustion air filter is standard.
FIGURE 1-3. Full modulation burner
FIGURE 1-4. On/off burner

750-382
CBT
1-5
Gas train
1.3 — Gas train
The gas train assembly is provided in accordance with UL/cUL certification and is ASME CSD-1 compliant. The
gas train assembly is factory assembled and wired.
Full modulation gas train components:
A. Single body, dual safety shutoff gas valve with integral trim regulator
B. Low Gas Pressure Switch
C. High Gas Pressure Switch
D. (2) Manual Shutoff Valves
E. Test Cocks
F. Venturi
G. Gas supply regulator (optional)
On/off gas train components:
H. Regulator
I. Low Gas Pressure Switch
J. Gas Solenoid Safety Shutoff Valve
K. Gas Diaphragm Safety Shutoff Valve
L. High Gas Pressure Switch
M. (2) Manual Shutoff Valves
VENTURI
OPTIONAL:
GAS PRESSURE REGULATOR
FIGURE 1-5. Gas train
C
B
D
E
D
A
FULL MODULATION (CBT-M) ON/OFF (CBT)
I
H
M
L
K
JM
F
G

Introduction
1-6 750-382
CBT
1.4 — Controls
1.4.1 — Full modulation controls
The CB Falcon steam boiler control is an integrated burner management and modulation control with a color
touch-screen display/operator interface.
The controller is capable of the following functions:
•Burner sequencing with safe start check, pre-purge, direct spark ignition, and post purge.
•Electronic ignition.
•Flame Supervision.
•Safety shutdown with time-stamped display of lockout condition.
•PID modulating steam pressure set point control.
•Supervision of low and high gas pressure, air proving, stack back pressure, high limit, and low water.
•First-out annunciator.
•Real-time data trending.
•(3) pump/auxiliary relay outputs.
•Modbus communication capability.
CONTROLS ABBREVIATIONS:
ALWCO - Auxiliary Low Water Cutoff
HLC - High Limit Control
HWA - High Water Alarm
OLC - Operating Limit Control
LWCO - Low Water Cutoff
(Optional)
(Optional)
(Optional)
FIGURE 1-6. Control panel, full modulation

750-382
CBT
1-7
Controls
•Outdoor temperature reset.
•Remote firing rate or setpoint control
•Setback/time-of-day setpoint
•Built-in Lead-Lag control for multiple boiler systems
•Warm standby-minimum temperature control
1.4.2 — On-off controls
The Burner Control provides burner sequencing control and flame supervision.
A switch/light panel provides functionality similar to full modulation units: indicator lights for demand, fuel valve
open, alarm, low water, and (optional) high water; panel switches for power on/off and ALWCO reset.
H.W.A. OPTION
BURNER
CONTROL
LIGHT/BUTTON
PANEL
ALWCO
CONTROLLER
LWCO CONTROLLER
PUMP CONTROL
TERMINAL STRIP
IGNITION
TRANSFORMER
AIR PRESSURE
SWITCH
FIGURE 1-7. Control panel, on/off boilers

Introduction
1-8 750-382
CBT
1.4.3 — Water level and limit controls, all boilers
The pressure transmitter provides an analog steam
pressure signal to the controller for modulated firing
(full modulation units) or on/off operation.
The high limit control (HLC) provides safety shutdown
when steam pressure exceeds the maximum operating
range of the boiler. It includes a manual reset switch
and adjustable set point.
The operating control (OLC) is set below the maximum
pressure setting of the HLC. This control is auto reset
and includes adjustable set point
Standard water level controls comprise an automatic
reset primary low water cutoff (LWCO) and a manual
reset auxiliary low water cutoff (ALWCO). A manual
reset LWCO is available where required by code.
Four individual conductance probes are mounted
within the LWCO water column to indicate levels for
low water, pump on, pump off, and high water alarm
(optional). The solid-state level control boards reside in
the boiler control enclosure.
A panel mounted ALWCO reset/test switch is provided.
The water column blowdown should be piped to a
boiler blowdown system. Please refer to service and
maintenance section for blowdown procedures.
FIGURE 1-8. Low water and limit controls
Steam pressure gauge
Manual valve
ALWCO probe
HLC
OLC
LWCO/pump control
Gauge glass
Gauge glass
Pressure transmitter
blowdown valve
WC blowdown valve
(modulating burner
only)
holder

750-382
CBT
1-9
Component/connection locations
1.5 — Component/connection locations
Refer to Chapter 3 for recommended vent sizes and lengths.
FIGURE 1-9. Boiler components/connections, CBT-M
PRESSURE RELIEF VALVE
STACK
OUTLET
AUX. LOW WATER CUTOFF
SURFACE BLOWOFF PIPING
FEEDWATER PIPING
BLOWDOWN PIPING
LEVEL CONTROL
GAUGE GLASS
GAS
TRAIN
BURNER
CABINET
CONTROL
PANEL
AIR
INLET
(OPTIONAL)
FIGURE 1-10. Boiler components/connections, CBT
GAS TRAIN
SURFACE
BLOWOFF
PIPING
ALWCO
FEEDWATER PIPING
BOTTOM BLOWDOWN (OPTIONAL)
STACK OUTLET
LWCO
AIR INLET
BURNER
SIGHT GLASS

Introduction
1-10 750-382
CBT
1.6 — Optional equipment
Certain options are available for the Model CBT Boiler; normally these will have been specified at the time of
order entry. In addition, some options may have been provided (by others) that are not part of Cleaver-Brooks
scope of supply. In either case, the Cleaver-Brooks authorized representative should be consulted regarding
specific project requirements.
Model CBT optional features:
• Gas pressure regulator (>1/2 psig supply)
• Gas pressure relief valve (>1 psig supply)
• Minimum Temperature/Warm Standby
• Direct vent kit combustion air adapter
• Chemical feed system
• Surface blow-off conductivity control
• Feedwater system (includes tank, pump, and control) - shipped separately
• Feedwater valves
• Blowdown valves
• Steam header valves
• High water alarm
• Time clock for setback control
• Stack temperature limit control
• Stack thermometer
• Alarm horn
• Lead-Lag steam pressure header transmitter
• Feedwater sets and condensate receivers
• Blowdown separators and tanks
• Economizers
• Complete steam skid or field-installed solutions
• Factory mounted valves
• Communications gateway
• Boiler Monitor (remote connectivity)

750-382
CBT
2-1
CHAPTER 2 Installation
Lifting and Moving the Boiler 2-2
Water Treatment 2-2
Boiler Room 2-4
Gas Piping 2-5
Boiler Waterside Connections 2-10
Electrical Connections 2-11
Wiring Diagrams 2-12
Provisions for combustion and ventilation air must
be in accordance with UL 795, Commercial-
Industrial Gas Heating Equipment, cUL, or
applicable provisions of the local building codes.
Failure to follow this warning could result in
personal injury or death
The boiler must be installed such that the gas
ignition system components are protected from
water (dripping, spraying, rain, etc.) during
appliance operation and service. Failure to follow
this warning could result in equipment failure.
!Warning !Caution
If an external electrical source is utilized, the boiler,
when installed, must be electrically bonded to
ground in accordance with the requirements of the
authority having jurisdiction or, in the absence of
such requirements, with the National Electrical
Code and/or UL 795, Commercial-Industrial Gas
Heating Equipment.
!Warning

Installation
2-2 750-382
CBT
2.1 — Lifting and Moving the Boiler
The boiler should be lifted by the base using a suitable fork lift, or by the top using the lifting lugs provided. For
fork truck lifting, ensure the forks extend through the length of the base.
Note: The boiler should not be moved by pushing, prying, or pulling on any part of the casing.
The boiler must be installed on a non-combustible floor. If the floor is not level, piers or a raised pad slightly larger
in length and width than the boiler base dimensions will make boiler installation and leveling easier.
The boiler must be installed so that all components remain accessible for inspection, cleaning, or maintenance.
Field-installed piping and electrical connections must be arranged so as to avoid interfering with removal of the
casing panels or with the burner door.
2.2 — Water Treatment
Properly treated boiler water will help maximize the effectiveness and lifespan of the pressure vessel. Contact your
local Cleaver-Brooks representative or water management consultant for complete information on how to prevent
damage resulting from inadequate water treatment.
See Table 2-1 for CBT water quality guidelines.
The boiler must not be installed on combustible flooring.
FIGURE 2-1. Lifting boiler
60° min.
!Caution
In order to avoid damage to the unit, lifting or moving the boiler should only be done
by experienced personnel suitably equipped for moving heavy equipment.
!Caution

750-382
CBT
2-3
Water Treatment
The CBT boiler requires soft water. Failure to observe this requirement can lead to dangerous
operating conditions, and may result in damage to the boiler. If necessary, your Cleaver-Brooks representative
can provide additional information regarding your water softening requirements.
The objectives of water treatment in general are to:
1. Prevent hard scale and soft sludge deposits that inhibit heat transfer and that could lead to overheated metal
and costly downtime and repairs.
2. Eliminate corrosive gases in the supply or boiler water.
To accomplish these objectives, the boiler requires proper water treatment before and after introduction of water
into the unit. The selection of pretreatment processes depends upon the water source, its chemical characteristics,
the amount of makeup water needed, system operation practices, etc.
Because of the variables involved, no single boiler compound can be considered a cure-all; nor is it advisable to
experiment with homemade treating methods. A sound treatment program should include a weekly analysis of the
water in the system.
The internal or waterside surfaces of the pressure vessel should be inspected at regular intervals for evidence of
corrosion, pitting, contamination, or accumulations of foreign matter. If any of these conditions are detected,
contact your local Cleaver-Brooks authorized representative for advice on corrective action. It is recommended that
a properly sized water meter be installed in the raw water makeup line to accurately determine the amount of raw
water admitted to the boiler.
Surface blow-off is available for steam boilers. This option allows removal of surface water impurities through a
blowdown line located at the normal operating water level of the boiler. If allowed to accumulate, surface
impurities may impede steam release and could cause foaming, leading to priming and carryover in the steam
lines.
Corrosion and sludge deposits in old systems must be removed prior to installation of a new boiler.
Table 2-1. CBT water quality
QUANTITY LIMITS
Oxygen <0.005 ppm
CO2 0 ppm
Hardness <2.0 ppm
Suspended Solids <300 ppm
pH 8.5 - 10.5
Sulfite >50 ppm
Fe <0.1 ppm
Silica <150 ppm
Total Alkalinity <700 ppm
Dissolved Solids <3,000 ppm
Important
!
!Warning
Inadequate or improper water treatment will shorten the life of the
boiler and could result in a hazardous condition.

Installation
2-4 750-382
CBT
2.3 — Boiler Room
The boiler room must comply with all building codes and regulations. An adequate supply of combustion air and
sufficient ventilation are required for safe operation. If the optional direct vent combustion air kit is not used,
ventilation must be provided to meet applicable regulations for air supply.
Clean combustion air is required for optimum efficiency and boiler operation (minimum combustion air 10 cfm
per boiler horsepower). Dust and airborne contaminants will adversely effect burner performance. See Chapter 3,
Stack and Intake Venting, for more information.
If conditions dictate, a serviceable filter must be placed at the burner inlet to eliminate airborne contamination to
the burner. If a direct vent air intake is used, the intake and flue venting should be terminated so as to prevent
rain, snow, dust, or debris from entering the intake piping.
Observe proper clearances above and around boiler - see Figure 2-2.
TABLE 2- 2. Boiler room ambient conditions
Relative humidity < 85% non-condensing
Ambient temperature range 0 oC to 50 oC / 32oF to 122oF
Storage temperature range -40 oC to 60 oC / -40oF to 140oF
Combustion air temperature 0 oC to 50 oC / 32oF to 122oF
18”
18”
36”
18” 18”
IN FRONT OF
ELECTRICAL
CONTROL PANEL
CLEARANCE
ABOVE BOILER = 18”
FIGURE 2-2. Recommended Clearances