Crown Boiler TWZ Series User manual

TWZ Series
Oil-Fired Hot Water Boilers
INSTALLATION INSTRUCTIONS
These instructions must be axed on or adjacent to the boiler
Models:
• TWZ065
• TWZ075
• TWZ100
• TWZ090
• TWZ125
• TWZ150
• TWZ120
• TWZ175
• TWZ200
DESIGNED TO LEAD
Equipped with Hydrolevel
3250-Plus Control System
WARNING
Improper installation, adjustment, alteration, service or maintenance can cause property damage,
injury, or loss of life. For assistance or additional information, consult a qualied installer, service
agency or the gas supplier. This boiler requires a special venting system. Read these instructions
carefully before installing.
9802705 Rev 0, 03-18
Crown Boiler Company
P.O. Box 14818
3633 I Street
Philadelphia, PA 19134
www.crownboiler.com

1
The following terms are used throughout this manual to bring attention to the presence of hazards of various risk levels,
or to important information concerning product life.
DANGER
Indicates an imminently hazardous situation
which, if not avoided, will result in death, serious
injury or substantial property damage.
CAUTION
Indicates a potentially hazardous situation which,
if not avoided, may result in moderate or minor
injury or property damage.
WARNING
Indicates a potentially hazardous situation which,
if not avoided, could result in death, serious injury
or substantial property damage.
NOTICE
Indicates special instructions on installation,
operation, or maintenance which are important
but not related to personal injury hazards.
DANGER
This boiler is designed for use with #2 fuel oil meeting the specications of ASTM D-396. Attempts to burn
other liquid fuels, or to convert this boiler for use with gaseous fuels, could result in reliability problems,
extensive property damage, or loss of life.
NOTICE
This boiler has a limited warranty, a copy of which is included with this boiler.
The warranty for this boiler is valid only if the boiler has been installed, maintained and operated in
accordance with these instructions.
Surface rust on cast iron sections may be attributed to the manufacturing process as well as condensation
during storage. Surface rust is normal and does not a󰀨ect the performance or longevity of a boiler.
All boilers must be installed in accordance with National, State and Local Plumbing, Heating and
Electrical Codes and the regulations of the serving utilities. These Codes and Regulations may dier
from this instruction manual. Authorities having jurisdiction should be consulted before installations
are made.
In all cases, reference should be made to the following Standards:
USA BOILERS
A. Current Edition of American National Standard ANSI/NFPA 31, “Installation of Oil
Burning Equipment”, for recommended installation practices.
B. Current Edition of American National Standard ANSI/NFPA 211, “Chimneys, Fireplaces,
Vents, and Solid Fuel Burning Appliances”, For Venting requirements.
C. Current Edition of American Society of Mechanical Engineers ASME CSD-1, “Controls and
Safety Devices for Automatically Fired Boilers”, for assembly and operations of controls
and safety devices.
D. All wiring on boilers installed in the USA shall be made in accordance with the National
Electrical Code and/or Local Regulations.
CANADIAN BOILERS
A. Current Edition of Canadian Standards Association CSA B139, “Installation Code for Oil
Burning Equipment", for recommended Installation Practices.
B. All wiring on boilers installed in Canada shall be made in accordance with the Canadian
Electrical Code and/or Local Regulations.
IMPORTANT INFORMATION - READ CAREFULLY

2
WARNING
Improper installation, adjustment, alteration, service or maintenance can cause property damage, personal
injury or loss of life. Failure to follow all instructions in the proper order can cause personal injury or death.
Read and understand all instructions, including all those contained in component manufacturers manuals
which are provided with the boiler before installing, starting-up, operating, maintaining or servicing this
boiler. Keep this manual and literature in legible condition and posted near boiler for reference by owner
and service technician.
This boiler requires regular maintenance and service to operate safely. Follow the instructions contained
in this manual.
Installation, maintenance, and service must be performed only by an experienced, skilled and knowledgeable
installer or service agency.
All heating systems should be designed by competent contractors and only persons knowledgeable in
the layout and installation of hydronic heating systems should attempt installation of any boiler.
Installation is not complete unless a pressure relief valve is installed as shown in Figure 8.1 located in
Section VIII, “System Piping” of this manual.
It is the responsibility of the installing contractor to see that all controls are correctly installed and are
operating properly when the installation is completed.
This boiler is not suitable for installation on combustible ooring. See Figure 3 for means of installing
boiler over a combustible oor. Do not install boiler on carpeting.
Do not tamper with or alter the boiler or controls.
Inspect ueways at least once a year - preferably at the start of the heating season. The inside of the
combustion chamber, the vent system and boiler ueways should be cleaned if soot or scale has accumulated.
When cleaning this boiler, take precaution to avoid damage to burner swing door insulation. If damaged,
or if there is evidence of previous damage, burner swing door insulation must be replaced immediately.
Oil Burner and Controls must be checked at least once a year or as may be necessitated.
Do not operate boiler with jumpered or absent controls or safety devices.
Do not operate boiler if any control, switch, component, or device has been subject to water.
Boiler construction materials, products of combustion and the fuel contain alumina, silica, heavy metals,
carbon monoxide, nitrogen oxides, aldehydes and/or other toxic or harmful substances which can cause
death or serious injury and which are known to the state of California to cause cancer, birth defects and
other reproductive harm. Always use proper safety clothing, respirators and equipment when servicing
or working nearby the appliance.
This boiler contains very hot water under high pressure. Do not unscrew any pipe ttings nor attempt
to disconnect any components of this boiler without positively assuring the water is cool and has no
pressure. Always wear protective clothing and equipment when installing, starting up or servicing this
boiler to prevent scald injuries. Do not rely on the pressure and temperature gauges to determine the
temperature and pressure of the boiler. This boiler contains components which become very hot when
the boiler is operating. Do not touch any components unless they are cool.
DANGER
DO NOT store or use gasoline or other ammable vapors or liquids in the vicinity of this or any other appliance.

3
FOLLOW ALL INSTRUCTIONS and warnings printed
in this manual and posted on the boiler.
INSPECT THE BOILER, BURNER AND CONTROLS
ANNUALLY. To keep your boiler safe and e󰀩cient,
have a service technician follow the Service
checklist near the end of this manual.
IF YOU ARE NOT QUALIFIED to install or service
boilers, do not install or service this one.
THE BOILER MAY LEAK WATER at the end of its
useful life. Be sure to protect walls, carpets, and
valuables from water that could leak from the boiler.
PROTECT YOUR HOME IN FREEZING WEATHER.
A power outage, safety lockout, or component
failure will prevent your boiler from lighting. In
winter, your pipes may freeze and cause extensive
property damage. Do not leave the heating system
unattended during cold weather unless alarms
or other safeguards are in place to prevent such
damage
DO NOT BLOCK AIR FLOW into or around the boiler.
Insu󰀩cient air may cause the boiler to produce
carbon monoxide or start a re.
KEEP FLAMMABLE LIQUIDS AWAY from the boiler,
including paint, solvents, and gasoline. The boiler
may ignite the vapors from the liquids causing
explosion or re.
KEEP CHILDREN AND PETS away from hot surfaces
of the boiler, boiler piping, and vent pipe.
CARBON MONOXIDE (CO) is an odorless, deadly
gas that may be introduced into your home by
any malfunctioning fuel-burning product or vent
system failure. Consider installing CO alarms near
bedrooms in all levels of the building to warn you
and your family of potential CO exposure.
READ THIS ENTIRE MANUAL before attempting
installation, start-up, or service. Improper
installation, adjustment, alteration, service, or
maintenance may cause serious property damage,
personal injury, or death.
DO NOT DISCONNECT PIPE FITTINGS on the boiler
or in the heating system without rst verifying that
the system is cool and free of pressure and that
your clothing will protect you from a release of hot
water or steam. Do not rely solely on the boiler’s
temperature and pressure gauge when making this
judgment.
USE PROPER PERSONAL PROTECTION
EQUIPMENT when servicing or working near the
boiler. Materials of construction, ue products, and
fuel contain alumina, silica, heavy metals, carbon
monoxide, nitrogen oxides, and/or other toxic or
harmful substances that can are hazardous to
health and life and that are known to the State of
California to cause cancer, birth defects, and other
reproductive harm.
INSTALL ALL GUARDS, cover plates, and
enclosures before operating the boiler.
SIZE THE BOILER PROPERLY relative to the design
heat load or, if using domestic hot water priority,
the peak hot water load, whichever is larger. A
grossly oversized boiler will cycle excessively and
this will lead to premature failure of the boiler and
its components. Our warranty does not apply to
damage from excessive cycling.
ADHERE TO ALL LOCAL CODE REQUIREMENTS.
Contact your local code inspector prior to
installation. In the absence of a local code, adhere to
the latest editions of the Installation of Oil Burning
Equipment ANSI/NFPA 31 in the USA or CAN/CSA
B139, Installation Code for Oil Burning Equipment in
Canada.
ALL WIRING must comply with the National
Electrical Code ANSI/NFPA 70 (in the USA) or the
Canadian Electrical Code CSA C22.1 (in Canada)
and any local regulations.
WARNINGS FOR THE HOMEOWNER
WARNINGS FOR THE INSTALLER

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Table of Contents
I. Product Description ............................................................................... 5
II. Specications ......................................................................................... 5
III. Before Installing .................................................................................... 6
IV. Locating the Boiler ................................................................................ 7
V. Air for Combustion & Ventilation ......................................................... 9
VI. Venting ................................................................................................... 13
VII. System Piping ........................................................................................ 15
VIII. Tankless Heater Piping .......................................................................... 19
IX. Fuel Line Piping .................................................................................... 20
X. Wiring .................................................................................................... 23
XI. Start-Up & Checkout ............................................................................. 27
XII. Operation ............................................................................................... 30
XIII. Service & Maintenance .......................................................................... 36
XIV. Troubleshooting ..................................................................................... 39
XV. Parts ....................................................................................................... 44
WARNING
This boiler must be properly vented. The chimney must be inspected for any obstructions and cleaned
prior to each heating season. A clean and unobstructed chimney ue is necessary to produce the minimum
draft required to safely evacuate noxious fumes that could cause personal injury or loss of life. Evidence
of loose debris and or condensate induced stains at the base of the chimney ue, connector or smokepipe
joints may be signs of condensing ue gases. Flue gas condensate is corrosive, which requires special
consideration and must be addressed immediately. Refer to Section VII, "Venting" in this manual for
more details.
This boiler needs fresh air for safe operation and must be installed so there are provisions for adequate
combustion and ventilation air.
This boiler is supplied with controls which may cause the boiler to shut down and not re-start without
service. If damage due to frozen pipes is a possibility, the heating system should not be left unattended in
cold weather; or appropriate safeguards and alarms should be installed on the heating system to prevent
damage if the boiler is inoperative.
This boiler is designed to burn No. 2 fuel oil only. Do not use gasoline, crankcase drainings, or any oil
containing gasoline. Never burn garbage or paper in this boiler. Do not convert to any solid fuel (i.e.
wood, coal). Do not convert to any gaseous fuel (i.e. natural gas, LP). All ammable debris, rags, paper,
wood scraps, etc., should be kept clear of the boiler at all times. Keep the boiler area clean and free of
re hazards.
All boilers equipped with burner swing door have a potential hazard which, if ignored, can cause severe
property damage, personal injury or loss of life. Before opening swing door, unplug burner power cord
from receptacle located in lower right corner of jacket front panel and turn o󰀨 service switch to boiler
to prevent accidental ring of burner outside the combustion chamber. Be sure to tighten swing door
fasteners completely when service is completed.

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I Product Description
The TWZ series boiler is a cast iron oil-red water boiler designed for use in closed forced circulation heating systems.
This boiler must be vented by natural draft into a lined masonry or metal chimney, or Type L vent. An adequate supply of
air for combustion, ventilation and dilution of ue gases must be available in the boiler room. An optional tankless heater is
available to generate domestic hot water.
II Specications
FIGURE 2.0: GENERAL CONFIGURATION *
(GAL/HR) (MBH) (MBH) (Gal)
1.25
1.50
1.20
1.75
2.00
BURNER
INPUT
TWZ175
TWZ200
"B" "C"
0.65
0.75
1.00
0.90
84.0
86.0TWZ120
241
TWZ065
TWZ075
TWZ100
TWZ090
TWZ125
TWZ150
212
"A"
86.1
85.8
84.3
86.0
85.1
20.0
20.0
20.0
NET AHRI
RATING,
WATER
147
APPROX.
WATER
VOL. **
AFUE %
DIMENSIONS (in.)
8 5/16 6 16.0
16.0
16.0
24.0
24.0
24.0
80
91
120
111
152
179
210
104
97
132
156
128
184
17-3/8
17-3/8
22-3/8
27-3/885.1
84.7 27-3/8
10 13/16 7
17-3/8 8 5/16 6
8 5/16 6
27-3/8 13 5/16 8
22-3/8 10 13/16 7
22-3/8
10 13/16 7
13 5/16 8
13 5/16 8
NUMBER
OF
SECTIONS
3
3
3
4
4
4
5
5
5
TWZ SPACE HEATING RATINGS
BASIC BOILER
MODEL
DOE
HEATING
CAPACITY
70
79
TABLE 2.1: SPECIFICATIONS

6
III Before Installing
1) Safe, reliable operation of this boiler depends upon installation by a professional heating contractor in strict accordance
with this manual and the requirements of the authority having jurisdiction.
• In the absence of an authority having jurisdiction, installation must be in accordance with this manual and the latest
edition of Installation of Oil Burning Equipment (ANSI/NFPA31).
• Where required by the authority having jurisdiction, this installation must conform to the latest edition of Standard for
Controls and Safety Devices for Automatically Fired Boilers (ANSI/ASME CSD-1).
2) Make sure that a properly sized chimney is available which is in good condition. Consult the authority having
jurisdiction, Part VI of this manual, and ANSI/NFPA31 for additional information on venting requirements.
3) Make sure that the boiler is correctly sized:
• For heating systems employing convection radiation (baseboard or radiators) use an industry accepted
sizing method such as the I=B=R Guide RHH published by the Air-Conditioning, Heating and Refrigeration
Institute (AHRI).
• For new radiant heating systems refer to the radiant tubing manufacturer’s boiler sizing guidelines.
• For systems including a Crown Mega-Stor indirect water heater, size the boiler to have either the Heating
Capacity required for the Mega-Stor or the I=B=R Net Rating required for the heating system, whichever results
in the larger boiler.
• For systems that incorporate other indirect water heaters, refer to the indirect water heater manufacturer’s
instructions for boiler output requirements.
4) In some cases, boilers installed at altitudes above 2000ft may require a dierent burner conguration from that at sea
level. Consult the local Crown representative for more information.
Notes:
1. Net Ratings are based on piping and pick-up allowances of 1.15.
2. Burner Capacity Rating, GPH is based on #2 oil with a Gross
Heating Value equal to 140000 BTU/Gal.
3. Maximum Working Pressure, Water - 50 PSI.
4. Tankless Heater Ratings based on I=W=H test standard.
TABLE 2.2: OPTIONAL TANKLESS HEATER RATINGS
TWZ065
TWZ075
TWZ100
TWZ090
TWZ125
TWZ150
TWZ120
TWZ175
TWZ200
3.50
Boiler Model
4.25
4.75
Tankless Heater Rating
(Gal/min)
3.25
3.25
3.75
4.00
2.75
3.00
CAUTION
Fuel oil used with this boiler must conform to ASTM D396. The ASTM D396 standard sets a
5% limit on biodiesel concentration, requires that the biodiesel feedstock comply with ASTM
D6751, and also specifies the procedure that must be used to blend the biodiesel feedstock
with the #2 fuel oil. Attempts to use biodiesel blends not meeting all ASTM D396 requirements
may result in unreliable operation or severe property damage.

7
CAUTION
As with all oil-fired appliances, “Power Venting” this boiler creates a number of potential
problems, especially when this is done through a side wall. These include, but are not
necessarily limited to:
• Accelerated rate of soot buildup on the oil burner cad-cell, burner head, and/or in the
boiler itself.
• Odor complaints
• Severe damage to the side of the structure in the event that the boiler operates at a high
smoke level.
These problems can occur for many reasons, some of which are out of the control of both the
installer and the appliance manufacturer. The use of a chimney to vent this boiler is therefore
recommended. If a power venter must be used, it is the responsibility of the installer and power
venter manufacturer to “engineer” the power vent system. CROWN BOILER COMPANY WILL
ASSUME NO RESPONSIBILITY FOR DAMAGE TO SIDING, ETC. FROM A POWER VENTED OIL-
FIRED BOILER. THIS APPLIES REGARDLESS OF THE CAUSE OF THE SOOTING.
IV Locating the Boiler
1) Clearances:
• Observe the minimum clearances shown below. Except as noted, these clearances apply to all combustible con-
struction, as well as noncombustible walls, ceilings and doors. Also see Figure 4.0.
Front – 24”
Left Side – 6”
Right Side – 6”
Rear – 6”
Top – 6”
Single Wall Chimney Connector (to combustible construction) - 18”
• A 24” service clearance from the jacket is recommended from the top of the boiler. This clearance may be
reduced to that shown above; however, servicing the boiler will become increasingly dicult as this clearance is
reduced.
2) If listed Type L vent is used, follow vent pipe manufacturer recommendations for minimum clearances.
3) Do not install this boiler directly on a combustible surface. Where it is desired to install the TWZ over a non-carpeted
combustible surface, install the boiler on the base shown in Figure 4.1.
4) Do not install this boiler in a location where gasoline or other ammable vapors or liquids will be stored or used. Do not
install this boiler in an area where large amounts of airborne dust will be present, such as a workshop.
WARNING
Failure to observe the following location requirements could result in property damage, a fire,
explosion or carbon monoxide (CO) hazard.

8
FIGURE 4.1: INSTALLATION OVER A COMBUSTIBLE FLOOR
FIGURE 4.0: CLEARANCES
`

9
Air for Combustion and Ventilation
Sucient fresh air must be supplied for combustion and ventilation. Provisions for combustion and ventilation air for oil
burning equipment must be made in accordance with Section 1.5, Air for Combustion and Ventilation, in the latest edition of
Installation of Oil Burning Equipment (ANSI/NFPA 31).
To ensure an adequate supply of air for combustion, ventilation and ue gas dilution, start by determining whether the
boiler is to be installed in a building of unusually tight construction. A building of unusually tight construction can be dened
as one having the following features:
• Walls and ceilings exposed to outside atmosphere have a continuous water vapor retarder with a rating of 1 perm or
less with openings gasketed and sealed
• Weather stripping has been added on openable windows and doors
• Caulking and sealants are applied to areas such as joints around window and door frames, between sole plates and
oors, between wall-ceiling joints, between wall panels, at penetrations for plumbing, electrical, and gas lines, and
at other openings.
For Buildings of Other than Unusually Tight Construction
1) Determine whether the boiler is to be installed in a conned space - A conned space is dened as having a volume less
than 50 cubic feet per 1000 BTU/hr input of all appliances installed in that space. To determine whether the boiler room is a
conned space:
a. Total the input of all appliances in the boiler room in thousands of BTU/hr. Round the result to the next highest
1000 BTU/hr.
b. Find the volume of the room in cubic feet. The volume of the room in cubic feet is:
Length (ft) x width (ft) x ceiling height (ft)
In calculating the volume of the boiler room, consider the volume of adjoining spaces only if no doors are installed
between them. If doors are installed between the boiler room and an adjoining space, do not consider the volume of
the adjoining space, even if the door is normally left open.
c. Divide the volume of the boiler room by the input in thousands of BTU/hr. If the result is less than 50, the boiler
room is a conned space.
Example:
A TWZ090 and a water heater are to be installed in a room measuring 6 ft - 3 in x 7 ft with an 8 ft ceiling. The
water heater has an input of 30000 BTU/hr:
Input of TWZ090 = 0.90 Gal/hr x 140000 BTU/Gal = 126000 BTU/hr
Total input in thousands of BTU/hr = (126000 BTU/hr + 30000 BTU/hr)/1000 = 156
Volume of room = 6.25 ft x 7 ft x 8 ft = 350 ft3
350/156 = 2.24. Since 2.24 is less than 50, the boiler room is a conned space.
WARNING
• Insufficient combustion air supply may result in the production and release of soot or
deadly carbon monoxide (CO) into the home which can cause property damage, severe
personal injury or death.
• This boiler is not designed for use in a space that is depressurized relative to the outdoors.
Operating this boiler in a depressurized space may cause property damage, severe
personal injury or death.

10
FIGURE 5.0: BOILER INSTALLED IN CONFINED SPACE, ALL AIR FROM INSIDE
2) Unconned Space - Natural inltration into the boiler room will normally provide adequate air for combustion and venti-
lation without additional louvers or openings into boiler room.
3) Conned Space - Provide two openings into the boiler room, one near the oor and one near the ceiling. The top edge of
the upper opening must be within 12” of the ceiling and the bottom edge of the lower opening must be within 12” of the oor
(Figure 5.0).
• Each opening must have a free area of 1 square inch per 1000 BTU/hr input of all fuel burning appliances in the boiler
room. The minimum opening dimension is 3 inches. Minimum opening free area is 100 square inches per opening.
• If the total volume of both the boiler room and the room to which the openings connect is less than 50 cubic feet per
1000 BTU/hr of total appliance input, install a pair of identical openings into a third room. Connect additional rooms
with openings until the total volume of all rooms is at least 50 cubic feet per 1000 BTU/hr of input.
• The “free area” of an opening takes into account the blocking eect of mesh, grills, and louvers. Where screens are
used, they must be no ner than ¼” (4 x 4) mesh.
For Buildings of Unusually Tight Construction:
1) Openings must be installed between the boiler room and the outdoors or a ventilated space, such as an attic or crawl
space, which communicates directly with the outdoors.
2) Two openings are required. The top edge of the upper opening must be within 12 inches of the ceiling. The bottom
edge of the lower opening must be within 12 inches of the oor.
3) Size openings and ducts as follows:
• Vertical ducts or openings directly outdoors (Figure 5.1, Figure 5.2, and Figure 5.3) - Each opening must have
a free cross sectional area of 1 square inch per 4000 BTU/hr of the total input of all fuel red appliances in the
boiler room but not less than 100 square inches. Minimum opening size is 3 inches.
• Openings to outdoors via horizontal ducts (Figure 5.4) - Each opening must have a free cross sectional area of 1
square inch per 2000 BTU/hr of the total input of all fuel red appliances in the boiler room but not less than 100
square inches. Minimum opening size is 3 inches.
• The “free area” of an opening takes into account the blocking eect of mesh, grills, and louvers. Where screens
are used, they must be no ner than ¼” (4 x 4) mesh.

11
FIGURE 5.1: ALL AIR FROM OUTDOORS, VENTILATED CRAWL SPACE AND ATTIC
FIGURE 5.2: ALL AIR FROM OUTDOORS, VIA VENTILATED ATTIC

12
FIGURE 5.3: ALL AIR FROM OUTDOORS, USING OPENINGS INTO BOILER ROOM
FIGURE 5.4: ALL AIR FROM OUTDOORS, USING HORIZONTAL DUCTS INTO BOILER ROOM

13
VI Venting
Vent installation must be in accordance with local building codes, or the local authority having jurisdiction.
Typical vent installation is illustrated by Figure 6.0. The components of vent installation are the vent connector (breeching),
barometric draft regulator, and chimney.
1) Acceptable Chimneys - The following chimneys may be used to vent a TWZ series boiler:
• Listed Type L vent - Install in accordance with the manufacturer’s instructions, the terms of its listing, and applicable
codes.
• Masonry Chimney - The masonry chimney must be constructed in accordance with the latest edition of Standard
for Chimneys, Fireplaces, Vents, and Solid Fuel Burning Appliances (NFPA 211) and lined with a clay liner or other
listed lining system. Do not vent a TWZ series boiler into an unlined chimney.
FIGURE 6.0: TYPICAL VENT SYSTEM INSTALLATION AND COMPONENTS
WARNING
• Improper venting may result in property damage and/or the release of flue gases, which
contain deadly carbon monoxide (CO), into the home, which can cause severe personal
injury or death.
• Inspect existing chimney before installing boiler. Failure to clean or replace damaged pipe
or tile lining will cause property damage, severe personal injury or death.

14
2) Acceptable Vent Connectors - The following may be used for vent connectors:
• Listed Type L vent.
• Single Wall Galvanized Pipe - Use 0.018” (26 gauge) or heavier.
3) Chimney and Vent Connector Sizing - See Table 6.1 for minimum vent connector and chimney sizing. The vent
connector size must not be smaller than boiler ue collar diameter.
4) Do not vent this appliance into any portion of a mechanical vent system operating under positive pressure.
5) Do not connect the boiler into a chimney ue serving an open replace or other solid fuel appliance.
6) Prior to boiler installation, inspect chimney for obstructions or other defects and correct as required. Clean chimney as
necessary.
7) Vent pipe should slope upward from boiler not less than one inch in four feet. No portion of vent pipe should run
downward or have sags. Vent pipe must be securely supported.
8) The vertical section of vent pipe coming o the boiler should be as tall as possible, while still maintaining the proper
clearance from the horizontal vent connector to combustibles and the proper pitch called for in (7) above.
9) Vent pipe should be installed above the bottom of the chimney to prevent blockage.
10) Vent pipe must be inserted ush with inside face of the chimney liner and the space between vent pipe and chimney
sealed tight. A thimble permanently cemented in place can be used to facilitate removal of chimney connector for cleaning.
11) Install the barometric draft regulator in accordance with the regulator manufacturer’s instructions.
12) Secure all joints in the vent connector system with sheet metal screws. This includes the joint between the vent
connector and the boiler collar, as well as the barometric draft regulator. Use at least three screws at each joint.
TABLE 6.1: MINIMUM RECOMMENDED BREECHING AND CHIMNEY SIZE
Round I.D. (in) Rectangular I.D. (in) Height (ft)
TWZ065 6 6 8 x 8 15
TWZ075 6 6 8 x 8 15
TWZ100 6 6 8 x 8 15
TWZ090 7 7 8 x 8 15
TWZ125 7 7 8 x 8 15
TWZ150 7 7 8 x 8 15
TWZ120 8 8 8 x 8 15
TWZ175 8 8 8 x 8 15
TWZ200 8 8 8 x 8 15
Boiler
Model
Min Breeching
Dia. (inches)
Min. Recommended Chimney Size and Height

15
FIGURE 7.1: STANDARD BOILER PIPING
Standard Piping
Figure 7.1 shows typical boiler system connections on a single zone system. Additional information on hydronic system
design may be found in the I=B=R Guide RHH published by the Air-Conditioning, Heating and Refrigeration Institute
(AHRI). The components in this system and their purposes are as follows:
VII System Piping
WARNING
• Install boiler so that the electrical components are protected from water (dripping,
spraying, rain, etc.) during appliance operation and service (circulator replacement,
etc.).
• Operation of this boiler with continuous return temperatures below 120°f can cause
severe heat exchanger corrosion damage.
• Operation of this boiler in a system having significant amounts of dissolved oxygen can
cause severe heat exchanger corrosion damage.
• Do not use toxic additives, such as automotive antifreeze, in a hydronic system.
• Pipe relief valve discharge to a safe location. The relief valve may discharge scalding
hot water.
• Do not install a valve in the relief valve discharge line.
• Do not move relief valve from factory location.
• Do not plug relief valve discharge. Blocking the relief valve may result in boiler
explosion.

16
1) Relief valve (Required) - Mount the relief valve on the top left side of the boiler as shown in Figure 7.1 using the 3/4”
nipple provided. The relief valve shipped with the boiler is set to open at 30 psi. This valve may be replaced with one
having a pressure up to the “Maximum Allowable Working Pressure” shown on the rating plate. If the valve is replaced,
the replacement must have a relief capacity in excess of the DOE heating capacity for the boiler.
Pipe the discharge of the relief valve to a location where water or steam will not create a hazard or cause property damage
if the valve opens. The end of the discharge pipe must terminate in an unthreaded pipe. If the relief valve discharge is not
piped to a drain, it must terminate at least 6 inches above the oor. Do not run relief valve discharge piping through an
area that is prone to freezing. The termination of the relief valve discharge piping must be in an area where it is not likely
to become plugged by debris.
2) Circulator (Required) - Figure 7.1 shows the ideal location of the circulator which is in the supply piping immediately
downstream of the expansion tank. A less ideal, but acceptable, location for most residential circulators is in the return (if
this is done, be sure that adequate clearance exists to open the door.
3) Expansion Tank (Required) - If this boiler is replacing an existing boiler with no other changes in the system, the
old expansion tank can generally be reused. If the expansion tank must be replaced, consult the expansion tank
manufacturer’s literature for proper sizing.
4) Fill Valve (Required) - Either a manual or automatic ll valve may be used. The ideal location for the ll is at the
expansion tank.
5) Automatic Air Vent (Required) - At least one automatic air vent is required. Manual vents will usually be required in
other parts of the system to remove air during initial ll.
6) Low Water Cut-O (Required by some codes) - The 3250-Plus control supplied with this boiler will prevent burner
operation in the event that there is insucient water in the boiler. It can be set for either automatic or manual reset
operation (see Part XII for more details)
7) Manual Reset High Limit (Required by some codes) - This control is required by ASME CSD-1 and some other codes.
Install the high limit in the boiler supply piping just beyond the boiler with no intervening valves. Set the manual reset
high limit as far above the operating limit setting as possible, but not over 240°F. Wire the control to break the 120 VAC
electrical supply to the boiler.
8) Flow Control Valve (Required under some conditions) - The ow control valve prevents ow through the system unless
the circulator is operating. A ow control valve may be necessary on converted gravity systems to prevent gravity
circulation. Flow control valves are also used to prevent “ghost ows” in circulator zone systems through zones that are
not calling for heat.
9) Isolation Valves (Optional) - Isolation valves are useful if the boiler must be drained, as they will eliminate having to drain
and rell the entire system.
10) Drain Valve - The drain valve is shipped in the boiler parts bag. Install it in the tee on the boiler return as shown in
Figure 1.
NOTICE
The 1-1/2” plugged tapping on the bottom rear section is present for manufacturing purposes
only. Do not attempt to use this tapping as a return connection.

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FIGURE 7.3: BOILER BYPASS PIPING
FIGURE 7.2: INDIRECT WATER HEATER BOILER SIDE PIPING
Piping for Special Situations
Certain types of heating systems have additional requirements. Some of the more common variations follow:
1) Indirect Water Heaters - Figure 7.2 shows typical indirect water heater piping. Boiler piping is the same as for any two-
zone system. Figure 7.2 shows circulator zoning, which is usually preferred for indirect water heaters. Size the circulator
and indirect water heater piping to obtain the boiler water ow through the indirect water heater called for by the indirect
water heater manufacturer.
2) Large Water Volume Systems - The piping shown in Figure 7.3 will minimize the amount of time that the boiler operates
with return temperatures below 120°F on these systems. A bypass is installed as shown to divert some supply water
directly into the return water. The bypass pipe should be the same size as the supply. The two throttling valves shown are
adjusted so that the return temperature rises above 120°F during the rst few minutes of operation. A three-way valve can
be substituted for the two throttling valves shown.

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FIGURE 7.4: ISOLATION OF BOILER FROM SYSTEM WITH A HEAT EXCHANGER
3) Low Temperature Systems - Some systems, such as radiant tubing systems, require the system water temperature to
be limited to a value below the temperature of the water leaving the TWZ. These systems also typically have return
temperatures well below the 120°F minimum.
Figure 7.4 illustrates the use of a heat exchanger to connect the TWZ boiler to this type of system. The heat exchanger
will permit the transfer of heat from the boiler water to the low temperature system while holding the system supply and
boiler return temperatures within their limits. For this system to work properly, the heat exchanger must be properly sized
and the correct ow rates are required on either side of the heat exchanger. Consult the heat exchanger manufacturer for
sizing information. The water in the boiler is completely isolated from the water in the system. This means that separate
ll and expansion tanks are required for the heating system loop.
There are several other ways to connect low temperature systems to the non-condensing boilers like the TWZ such as four
way mixing valves and variable speed injection pumping systems.
4) Systems containing oxygen - Many hydronic systems contain enough dissolved oxygen to cause severe corrosion damage
to a cast iron boiler such as the TWZ. Some examples include:
• Radiant systems that employ tubing without an oxygen barrier.
• Systems with routine additions of fresh water.
• Systems which are open to the atmosphere.
If the boiler is to be used in such a system, it must be separated from the oxygenated water being heated with a heat
exchanger as shown in Figure 7.4.
Consult the heat exchanger manufacturer for proper heat exchanger sizing as well as ow and temperature requirements.
All components on the oxygenated side of the heat exchanger, such as the pump and expansion tank, must be designed for
use in oxygenated water.
5) Air Handlers - Where the boiler is connected to air handlers through which refrigerated air passes, use ow control valves
in the boiler piping or other automatic means to prevent gravity circulation during the cooling cycle.