CleaverBrooks 4WI Guide

Model 4WI
Operation, Service, and Parts Manual
750-211
12/09
Promethean Boilers
100 to 800 HP Steam and Hot Water
Fuel: Light Oil, Gas or Combination

!DANGER WARNING
If the information in this manual is not fol-
lowed exactly, a fire or explosion may re-
sult causing property damage, personal
injury or loss of life.
— Do not store or use gasoline or other
flammable vapors and liquids in the vicin-
ity of this or any other appliance.
— 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 per-
formed by a qualified Cleaver-Brooks,
service agency or the gas supplier.
Improper installation, adjustment, ser-
vice, or maintenance can cause equip-
ment damage, personal injury, or death.
Refer to the Operation and Maintenance
manual provided with the boiler. Installa-
tion and service must be performed by a
qualified Cleaver-Brooks service provid-
!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
Should overheating occur or the gas sup-
ply valve fail to shut off, do not turn off or
disconnect the electrical supply to the
boiler. Instead turn off the gas supply at a
location external to the boiler.
!DANGER WARNING
Do not use this boiler if any part has been
under water. Immediately call your Cleav-
er-Brooks service representative to in-
spect the boiler and to replace any part of
the control system and any gas control
which has been under water.
!DANGER WARNING
To minimize the possibility of serious per-
sonal injury, fire or damage to the equip-
ment, never violate the following safety
rules.
—Alwayskeeptheareaaroundtheboiler
free of combustible materials, gasoline,
and other flammable liquids 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 legi-
ble condition and kept adjacent to the
boiler or in a safe place for future refer-
ence. Contact your local Cleaver-Brooks
representative if additional manuals 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 installation must conform to the re-
quirements of the authority havingjurisdic-
tion or, in the absence of such
requirements, to UL 795 Commercial-In-
dustrial Gas Heating Equipment and/or
the National Fuel Gas Code, ANSI Z223.1
!DANGER WARNING
The boiler and its individual shutoff valve
must be disconnected from the gas sup-
ply piping system during any pressure
testing of that system at test pressures in
excess of 1/2 psi (3.5 kPa).
!DANGER WARNING

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 care-
fully. 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 under-
stood. Failure to follow all applicable instructions and warnings 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 contractors' personnel who are ser-
vicing, repairing or operating the equipment, in all safety aspects.
Cleaver-Brooks equipment is designed and engineered to give long life and excellent service on the job. The electrical and me-
chanical 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 afford a high degree of pro-
tection 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
of certain repetitive chores and give him more time to 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, main-
tain, 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 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 op-
eration 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 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 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 sub-
stances 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.
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 inconsistency between such
requirements and the warnings or instructions contained herein, please contact Cleaver-Brooks before proceeding.

CLEAVER-BROOKS
Model 4WI, Promethean Boilers
Operation and Maintenance Manual
Manual Number: 750-211
Release Date: December 2009

Copyright © 2009 by Cleaver-Brooks
All rights reserved. No part of this document may be reproduced, stored in a
retrieval system, or transmitted in any form or by any means without the prior writ-
ten consent of Cleaver-Brooks.
Cleaver-Brooks
11950 West Lake Park Drive
Milwaukee, WI 53224
414-359-0600
www.cleaver-brooks.com

750-211 (revised 2009)
Promethean Boilers, Model 4WI Manual i
Promethean Boilers, Model 4WI
750-211
Table of Contents
CHAPTER 1 Firetube Operation Basics 1-1
1.1 — Overview 1-1
1.2 — The Boiler 1-3
1.3 — Construction 1-4
1.4 — Steam Controls (All Fuels) 1-5
1.4.1 — Controls 1-5
1.4.2 — Low Water Cutoff 1-5
1.4.3 — Water Column 1-6
1.4.4 — Steam Pressure Gauge and ALWCO 1-6
1.4.5 — Safety Valve(s) 1-6
1.5 — Hot Water Controls (All Fuels) 1-7
1.5.1 — Pressure and Temperature Gauges 1-7
1.5.2 — Controls 1-7
1.5.3 — Low Water Cutoff and ALWCO 1-8
1.5.4 — Safety Valve(s) 1-8
1.6 — IFGR Components 1-8
CHAPTER 2 Burner Operation and Control 2-1
2.1 — The Burner 2-1
2.2 — Controls Common to all Boilers 2-2
2.3 — Control and Component Function 2-3
2.4 — Components Common to all Boilers 2-3
2.5 — Controls for Gas Firing 2-6

ii 750-211 (revised 2009)
Promethean Boilers, Model 4WI Manual
2.6 — Controls Common to Oil-Fired Boilers (Including Combination) 2-8
2.7 — Additional Controls for Heavy Oil 2-11
2.8 — Controls for Combination Burners Only 2-13
2.9 — Combustion Air 2-14
2.10 — Automatic Ignition 2-14
2.11 — Atomizing Air 2-15
2.12 — Oil Fuel Flow: Light Oil 2-16
2.13 — Oil Fuel Flow: Heavy Oil 2-17
2.14 — Gas Fuel Flow 2-19
2.15 — Modulating Firing 2-20
CHAPTER 3 Waterside Care and Requirements 3-1
3.1 — Overview 3-1
3.2 — Water Requirements 3-2
3.2.1 — Hot Water Boilers 3-2
3.2.1.1 — Air Removal 3-2
3.2.1.2 — Minimum Water Temperature 3-2
3.2.1.3 — Rapid Replacement of Boiler Water 3-2
3.2.1.4 — Continuous Flow Through the Boiler 3-3
3.2.1.5 — Water Circulation 3-4
3.2.1.6 — Multiple Boiler Installations 3-4
3.2.1.7 — Pump Location 3-5
3.2.1.8 — Pump Operation 3-5
3.2.1.9 — Pressure 3-5
3.2.2 — Steam Boiler 3-6
3.2.2.1 — Feed Pump Operation 3-6
3.2.2.2 — Water Feeder (optional) Operation 3-6
3.3 — Water Treatment 3-6

750-211 (revised 2009)
Promethean Boilers, Model 4WI Manual iii
3.4 — Cleaning 3-7
3.4.1 — Hot Water and Steam Piping 3-7
3.4.2 — Pressure Vessel 3-7
3.5 — Boil-Out of a New Unit 3-8
3.6 — Washing Out 3-10
3.6.1 — Hot Water Boiler 3-10
3.6.2 — Steam Boiler 3-10
3.7 — Blowdown: Steam Boiler 3-11
3.7.1 — Types of Blowdown 3-11
3.7.1.1 — Intermittent Manual Bottom Blowdown 3-11
3.7.1.2 — Continuous Blowdown (Controlling TDS) 3-12
3.7.2 — Frequency of Manual Blowdown 3-12
3.7.3 — Manual Blowdown Procedure 3-13
3.8 — Periodic Inspection 3-13
3.9 — Preparation for Extended Layup 3-14
CHAPTER 4 Sequence of Operation 4-1
4.1 — Overview 4-1
4.2 — Circuit and Interlock Controls 4-2
4.3 — Sequence of Operation: Gas or Oil 4-3
4.3.1 — Pre-Purge Cycle 4-3
4.3.2 — Ignition Cycle 4-4
4.3.3 — Run Cycle 4-4
4.4 — Flame Loss Sequence 4-5
CHAPTER 5 Starting and Operating Instructions 5-1
5.1 — General Preparation for Startup: All Fuels 5-1
5.2 — Control Settings: Steam and Hot Water 5-2
5.3 — Gas Pilot 5-4

iv 750-211 (revised 2009)
Promethean Boilers, Model 4WI Manual
5.4 — Atomizing Air 5-4
5.5 — Firing Preparations for No. 2 Oil (Series 100-200) 5-5
5.6 — Firing Preparation for No. 6 Oil (Series 400-600) 5-7
5.6.1 — Oil Flow 5-8
5.6.2 — Oil Pressure 5-8
5.6.3 — Oil Temperature 5-9
5.7 — Firing Preparations for Gas (Series 200-400-700) 5-10
5.8 — IFGR Setup 5-11
5.9 — Startup, Operating, and Shutdown: All Fuels 5-12
5.9.1 — Operating 5-15
5.9.2 — Shutdown 5-15
5.10 — Control Operational Test and Checks 5-16
CHAPTER 6 Adjustment Procedures 6-1
6.1 — Overview 6-1
6.2 — Linkage: Modulating Motor and Air Damper 6-2
6.3 — Modulating Motor 6-4
6.4 — Modulating Motor Switches: Low-Fire and High-Fire 6-4
6.5 — Burner Operating Controls: General 6-4
6.6 — Modulating Pressure Control: Steam 6-8
6.7 — Operating Limit Pressure Control: Steam 6-8
6.8 — High Limit Pressure Control: Steam 6-9
6.9 — Modulating Temperature Control: Hot Water 6-9
6.10 — High Limit Temperature Control: Hot Water 6-9

750-211 (revised 2009)
Promethean Boilers, Model 4WI Manual v
6.11 — Operating Limit Temperature Control: Hot Water 6-9
6.12 — Low Water Cutoff Devices: Steam and Hot Water 6-10
6.13 — Combustion Air Proving Switch 6-10
6.14 — Atomizing Air Proving Switch 6-11
6.15 — Gas Pilot Flame Adjustment 6-11
6.16 — Gas Pressure and Flow Information 6-13
6.16.1 — Pressure 6-13
6.16.2 — Gas Flow 6-15
6.16.3 — Pressure Correction 6-15
6.16.4 — Checking Gas Flow 6-17
6.17 — Gas Fuel Combustion Adjustment 6-18
6.17.1 — Burner Low-Fire Adjustment 6-20
6.18 — Low-Gas-Pressure Switch 6-21
6.19 — High-Gas-Pressure Switch 6-21
6.20 — Fuel Oil Pressure and Temperature: General 6-21
6.21 — Fuel Oil Combustion Adjustment 6-23
6.21.1 — Standard Burner Low-Fire Adjustment 100-200 HP 6-24
6.21.2 — Burner Low-Fire Adjustment 250-800 HP 6-24
6.22 — Burner Drawer Adjustment 6-24
6.23 — Oil Drawer Switch 6-26
6.24 — Low-Oil-Temperature Switch: Heavy Oil 6-26
6.25 — High-Oil-Temperature Switch: Optional 6-26
6.26 — Low-Oil-Pressure Switch: Optional 6-26
6.27 — Electric Oil Heater Thermostat: 400 and 600 Series (Steam) 6-26
6.28 — Steam Oil Heater Thermostat: No. 6 Oil, 400 and 600 Series (Steam) 6-27

vi 750-211 (revised 2009)
Promethean Boilers, Model 4WI Manual
6.29 — Hot Water Oil Heater Thermostat: 400 and 600 Series 6-27
CHAPTER 7 Troubleshooting 7-1
7.1 — Introduction 7-1
CHAPTER 8 Inspection and Maintenance 8-1
8.1 — Overview 8-1
8.1.1 — Periodic Inspection 8-2
8.2 — Fireside Cleaning 8-3
8.3 — Water Level Controls 8-4
8.3.1 — Steam Boiler 8-4
8.3.2 — Hot Water Boiler 8-5
8.4 — Water Gauge Glass 8-5
8.5 — Electrical Controls 8-6
8.6 — Flame Safety Control 8-8
8.6.1 — Checking Pilot Flame Failure 8-9
8.6.2 — Checking Failure to Light Main Flame 8-10
8.6.3 — Checking Loss of Flame 8-10
8.7 — Oil Burner Maintenance 8-11
8.7.1 — Light Oil Strainers 8-11
8.7.2 — Heavy Oil Strainers 8-11
8.7.3 — Cleaning the Oil Nozzle 8-12
8.7.4 — Cleaning Air Purge Nozzle (No. 6 Oil) and Back Pressure Orifice Nozzle (No. 2 Oil) 8-12
8.7.5 — Ignition System 8-13
8.8 — Gas Burner Maintenance 8-14
8.9 — Motorized Gas Valve 8-15
8.10 — Solenoid Valves 8-15
8.11 — Air Control Damper, Linkage and Cam Spring 8-16

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Promethean Boilers, Model 4WI Manual vii
8.12 — Fan/Motor Cassette Removal 8-17
8.13 — Inspection and Adjustment 8-18
8.14 — Fan/Motor Cassette Installation 8-19
8.15 — Safety Valves 8-20
8.16 — Fuel Oil Metering Valve, Adjusting and Relief Valves 8-21
8.17 — Air Pump and Lubricating System 8-23
8.17.1 — Air Pump 8-23
8.17.2 — Lubricating Oil 8-23
8.17.3 — Lubricating Oil Strainer and Cooling Coil 8-24
8.17.4 — Air-Oil Tank 8-24
8.17.5 — Air Cleaner 8-24
8.17.6 — Lube Oil Cooling Coil 8-25
8.17.7 — Flexible Coupling Alignment 8-25
8.17.8 — Air Compressor Replacement 8-26
8.17.8.1 — Dismantling 8-26
8.17.8.2 — Reassembly 8-27
8.18 — Refractory 8-27
8.18.1 — Furnace Liner 8-28
8.18.2 — Throat Tile and Liner 8-29
8.18.3 — Installation 8-29
8.18.4 — Rear Door 8-31
8.19 — Opening and Closing Doors 8-31
8.19.1 — Opening Front or Rear Door 8-31
8.19.2 — Rear Access Plug 8-32
8.19.3 — Closing and Sealing Doors 8-32
8.20 — Lubrication 8-33
8.20.1 — Electric Motors 8-33
8.20.2 — Control Linkage 8-33
8.20.3 — Solenoid and Motorized Valves 8-34
8.20.4 — IFGR Lubrication 8-34
8.21 — Oil Heaters: Electric, Steam, Hot Water 8-34
8.22 — Combustion 8-35
CHAPTER 9 Parts 9-1
9.1 — Ordering Parts 9-1

viii 750-211 (revised 2009)
Promethean Boilers, Model 4WI Manual
9.2 — Parts 9-2
9.2.1 — Front Door Insulated Head 9-2
9.2.2 — Front Door Exterior Insulation Component List 9-3
9.2.3 — Rear Door Insulated Assembly 9-4
9.2.4 — Rear Door Insulation Component List 9-5
9.2.5 — Rear Door Insulated Access Plug 9-6
9.2.6 — Front Head Assembly 60” Diameter 9-7
9.2.7 — Front Davit Assembly 9-8
9.2.8 — Rear Door Davit Parts List 9-9
9.2.9 — Refractory Throat Materials for 60” 9-10
9.2.10 — Refractory Throat Materials 67”-106” 9-11
9.2.11 — Motor Cartridge Assembly: 60” 9-12
9.2.12 — Motor Cartridge Assembly: 67” 9-13
9.2.13 — Motor Cartridge Assembly: 78” 9-14
9.2.14 — Motor Cartridge Assembly: 85” 9-15
9.2.15 — Motor Cartridge Assembly: 96” 9-16
9.2.16 — Motor Cartridge Assembly: 106” 9-17
9.2.17 — Front Head Linkage: 60”-106” 9-18
9.2.18 — Front Head, FGR Linkage: 60”-85” 9-20
9.2.19 — Front Head, FGR Linkage: 96” & 106” 9-22
9.2.20 — 60” Burner Drawer, Gas Pilot, Models 100-600, 100-125 HP 9-24
9.2.21 — 67” Burner Drawer, Gas Pilot, Models 101-600, 150-200 HP 9-26
9.2.22 — 78” Burner Drawer, Gas Pilot, HI-TD, 250-300 HP 9-28
9.2.23 — 85” Burner Drawer, Gas Pilot, Models 100-200, 350-400 HP 9-30
9.2.24 — 96”-106” Burner Drawer, Gas Pilot, Models 101 & 200, 500-800 HP 9-32
9.2.25 — Burner Housing Support: 60” 9-34
9.2.26 — Burner Housing Support: 67”-106” 9-36
9.2.27 — General Control Panel: 60”-106”, 100-800 HP 9-38
9.2.28 — Entrance Box & Fuses: 60”-1-6”, 100-800 HP 9-39
9.2.29 — Main Gas Train: 60”-106”, 100-800 HP 9-42
9.2.30 — Pilot Gas Train: 60”-106”, 100-800 HP 9-43
9.2.31 — Front Head #2 Oil/Air Piping: 60”-67”, 100-200 HP 9-44
9.2.32 — Front Head #2 Oil/Air Piping: 78”-85”, 250-400 HP 9-45
9.2.33 — Front Head #2 Oil/Air Piping: 96”-106”, 500-800 HP 9-46
9.2.34 — Air Compressor Piping: 60”-106”, 100-800 HP 9-47
9.2.35 — Air Compressor: 60”-85”, 100-400 HP 9-48
9.2.36 — Air Compressor: 96”-106”, 500-800 HP 9-49
9.2.37 — Light Oil Piping: 78”-106”, 250-800 HP 9-50
9.2.38 — Light Oil Piping: 60”-67”, 100-200 HP 9-51
9.2.39 — Hot Water Temperature Controls: 60”-106”, 100-800 HP 9-52
9.2.40 — Steam Pressure Controls: 60”-106”, 100-800 HP 9-53
9.2.41 — Water Column Piping: 60”-67”, 100-200 HP 9-54
9.2.42 — Water Column Piping: 78”-85”, 250-400 HP 9-56
9.2.43 — Water Column Piping: 96”-106”, 500-800 HP 9-58
9.2.44 — Front Door 60”-106” Air Duct Gasket 9-60
9.2.45 — Pressure Vessel Manway Components 9-61
9.2.46 — Pressure Vessel Handhole Components 9-61
9.2.47 — Pressure Vessel Handhole Components 9-62

750-211 (revised 2009)
Promethean Boilers, Model 4WI Manual 1-1
CHAPTER 1 Firetube Operation Basics
1.1 — Overview
Firetube boilers are available for low or high pressure steam, or for hot water applications. Firetube boilers are typ-
ically used for applications ranging for 15 to 1800 horsepower. A firetube boiler is a cylindrical vessel, with horizon-
tal tubes passing through and connected to the front and rear tube sheets. The vessel contains the water and
absorbs the energy generated from the flame.
The front door and rear door provide the seal to con-
tain the hot combustion gases. Baffles designed into
the doors serve to redirect the combustion gases
through the various firetube passages. The flame orig-
inates in the furnace. As the combustion gases travel
down the furnace and through the various firetube
channels, heat from the flame and combustion gases is
transferred to the water.
FIGURE 1-1. Open Front and Rear Doors
Transferred energy develops into the required steam or hot water. The primary purpose of the boiler is to supply
energy to the facility’s operations — for heat, manufacturing processes, laundry, kitchen, etc. The nature of the
facility’s operation will dictate whether a steam or hot water boiler should be used.
The general information in this manual applies directly to Cleaver-Brooks Promethean boilers ranging from 100
through 800 boiler horsepower for the following fuels:
Series 100 Light Oil (No. 2)
Series 200 Light Oil (No. 2) or Gas
Series 400 Heavy Oil (No. 6) or Gas
Series 600 Heavy Oil (No. 6)
Series 700 Gas

Firetube Operation Basics
1-2 750-211 (revised 2009)
Promethean Boilers, Model 4WI Manual
FIGURE 1-2. Firetube Boiler Cutaway View
The low emission option for the Promethean line of Firetube Boilers reduces Nitrogen
Oxide (NOx) emissions, a major contributor to ozone pollution (smog). Carbon Monox-
ide (CO) emissions also tend to be lower due to increased turbulence caused by the addi-
tion of the flue gases into the combustion air stream, thereby improving combustion.
The Promethean Firetube Boiler line is designed to incorporate Induced Flue Gas Recir-
culation (IFGR) when firing either natural gas and/or light oil, and is compatible with
both hot water and steam systems.
The IFGR system mixes a portion of the relatively cool flue gas from the exit of the
fourth-pass tubes with the incoming combustion air to reduce the furnace flame temper-
ature, thereby reducing NOx emissions. In this approach, the combustion air fan handles
both the combustion air and the recirculated flue gases.
FIGURE 1-3. Induced Flue Gas Recirculation (IFGR)

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Promethean Boilers, Model 4WI Manual 1-3
1.2 — The Boiler
The low emission design, with its various levels of IFGR systems, can affect the selection of the combustion air fan,
motor, burner, and other components. Several different system configurations are available, depending on the
requirements for NOx emissions and the fuels used. All systems use similar primary components, but may have dif-
ferent linkage controls, IFGR damper fan, and motor sizes.
The boiler and related equipment installation are to be in compliance with the standards of the National Board of
Fire Underwriters. Installation should also conform to state and local codes governing such equipment. Prior to
installation, the proper authorities having jurisdiction are to be consulted, permits obtained, etc.
All Promethean boilers in the series comply, when equipped with optional equipment, to Industrial Risk Insurers
(IRI), Factory Mutual (FM), or other insuring underwriters requirements.
1.2 — The Boiler
The Promethean boiler is a packaged firetube boiler of welded steel construction and consists of a pressure vessel,
burner, burner controls, forced draft fan, damper, air pump, refractory, and appropriate boiler trim.
FIGURE 1-4. Typical Steam Boiler
The horsepower rating of the boiler is indicated by the numbers following the fuel series. For example, CB700-600
indicates a gas-fired 600 hp boiler.
The firetube construction provides some characteristics that differentiate it from other boiler types. Because of its
vessel size, the firetube contains a large amount of water, allowing it to respond to load changes with minimum
variation in steam pressure.

Firetube Operation Basics
1-4 750-211 (revised 2009)
Promethean Boilers, Model 4WI Manual
Firetube boilers are rated in boiler horsepower (BHP), which should not be confused with other horsepower mea-
surements.
Hot water is commonly used in heating applications with boiler supplied water to the system at 180º F to 220º F.
The operating pressure for hot water heating systems usually is 30 psig to 125 psig.
Steam boilers are designed for low or high pressure applications. Low pressure boilers are limited to 15 psig design,
and are typically used for heating applications. High pressure boilers are typically used for process loads and can
have a design pressure of 75 psig to 350 psig.
Steam and hot water boilers are defined according to design pressure and operating pressure.
Design pressure is the maximum pressure used in the design of the boiler for the purpose of calculating the mini-
mum permissible thickness or physical characteristics of the pressure vessel parts of the boiler. Typically, the safety
valves are set at or below design pressure.
Operating pressure it the pressure of the boiler at which it normally operates. The operating pressure usually is
maintained at a suitable level below the setting of the pressure relieving valve(s) to prevent frequent valve opening
during normal operation.
The type of service that your boiler is required to provide has an important bearing on the amount of waterside
care it will require.
Feedwater equipment should be checked and ready for use. Be sure that all valves, piping, boiler feed pumps, and
receivers are installed in accordance with prevailing codes and practices.
Water requirements for both steam and hot water boilers are essential to boiler life and length of service. Constant
attention to water requirements will pay dividends in the form of longer life, less downtime, and prevention of
costly repairs.
Care takin in placing the pressure vessel into initial service is vital. The waterside of new boilers and new or remod-
eled steam or hot water systems may contain oil, grease, or other foreign matter. A method of boiling out the vessel
to remove accumulations is described in Chapter 3.
1.3 — Construction
Steam boilers designed for 15 psig and hot water boilers designed for 250º F at 125 psi or less are constructed in
accordance with Section IV, Heating Boilers, of ASME Code.
Steam boilers designed for operating pressures exceeding 15 psig are constructed in accordance with Section I,
Power Boilers, of the ASME Code. Hot water boilers designed for operating temperatures above 250º F or 125 psi
are likewise built to Section I of the ASME Code.

750-211 (revised 2009)
Promethean Boilers, Model 4WI Manual 1-5
1.4 — Steam Controls (All Fuels)
1.4 — Steam Controls (All Fuels)
1.4.1 — Controls
1.Operating Limit Pressure Control: Breaks a circuit to stop
burner operation on a rise of boiler pressure at a selected set-
ting. It is adjusted to stop or start the burner at a preselected
pressure setting.
2.High Limit Pressure Control: Breaks a circuit to stop
burner operation on a rise of pressure above a selected setting.
It is adjusted to stop the burner at a preselected pressure above
the operating limit control setting. The high limit pressure con-
trol is normally equipped with a manual reset.
FIGURE 1-5. Steam Controls
3. Modulating Pressure Control: Senses changing boiler pressures and transmits the information to the modu-
lating motor to change the burner firing rate when the manual-automatic switch is set on “automatic.”
1.4.2 — Low Water Cutoff
The style of Low Water Cutoff is determined by the design pressure of the vessel or by cus-
tomer preference. The Level Master (for operation and maintenance information, consult
the Level Master manual that accompanied the boiler) is used on all steam boilers 150 psig
to 250 psig. The McDonnell-Millar (MM) LWCO is available on low pressure steam boilers
to 15 psig and hot water boilers to 250º F and to 125 psi. For additional information on the
Level Master, refer to the Level Master Operation and Maintenance manual, manual number
750-192.
FIGURE 1-6. Level Master Low Water Cutoff (LWCO)
1. Low Water Cutoff and Pump Control: Float-operated control responds to the water level in the boiler. It per-
forms two distinct functions:
•Stops firing of the burner if water level lowers below the safe operating point. Energizes the low-water light in
the control panel; also causes low-water alarm bell (optional equipment) to ring. Code requirements of some
models require a manual reset type of low water cutoff.
•Starts and stops the feedwater pump (if used) to maintain water at the proper operating level.

Firetube Operation Basics
1-6 750-211 (revised 2009)
Promethean Boilers, Model 4WI Manual
2. Water Gauge Glass Drain Valve: Provided to flush the gauge glass.
3. Vent Valve: Allows the boiler to be vented during filling and facilitates routine boiler inspection as required by
ASME Code.
4. Water Column Drain Valve: Provided so that the LWCO and its piping can be flushed regularly to assist in
maintaining cross-connecting piping and in keeping the float bowl clean and free of sediment. A similar drain
valve is furnished with auxiliary low water cutoff for the same purpose.
1.4.3 — Water Column
1.Water Column Assembly: Houses the low water cutoff and pump control and
includes the water gauge glass and shutoff cocks.
FIGURE 1-7. Water Column Assembly
1.4.4 — Steam Pressure Gauge and ALWCO
1.Steam Pressure Gauge: Indicates boiler
internal pressure.
2.Auxiliary Low Water Cutoff: Breaks the
circuit to stop burner operation in the event
boiler water drops below the master low
water cutoff point. Manual reset type
requires manual resetting in order to start
the burner after a low water condition.
FIGURE 1-8. Steam Pressure Gauge and ALWCO (Hot Water)
1.4.5 — Safety Valve(s)
Safety Valves: Prevent buildup over the design pressure of the pressure vessel. The size, rating, and number of
valves on a boiler is determined by the ASME Boiler Code. The safety valves and the discharge piping are to be
installed to conform to the ASME Code requirements. The installation of a valve is of primary importance to its
service life. A valve must be mounted in a vertical position so that discharge piping and code-required drains can be
properly piped to prevent buildup of back pressure and accumulation of foreign material around the valve seat area.
Apply only a moderate amount of pipe compound to male threads and avoid over-tightening, which can distort the
seats. Use only flat-jawed wrenches on the flats provided. When installing a flange connected valve, use a new gas-
ket and draw the mounting bolts down evenly. Do not install or remove side outlet valves by using a pipe or wrench
in the outlet.