U.S. Boiler Company ASPEN ASPN-085 Service manual

1
107362-01 - 8/17 Price - $5.00
9700609
As an ENERGY STAR®Partner, U.S. Boiler Company has determined that the ASPEN™ Series meets the ENERGY
STAR® guidelines for energy efciency established by the United States Environmental Protection Agency (EPA).
INSTALLATION, OPERATING AND
SERVICE INSTRUCTIONS FOR
ASPEN™
CONDENSING HIGH EFFICIENCY
DIRECT VENT
GAS - FIRED HOT WATER BOILER
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.
Space Heating Models:
• ASPN-085
• ASPN-110
• ASPN-155
• ASPN-205
• ASPN-270
Combi Domestic Hot Water
and Space Heating Model:
• ASPNC-155
TO THE INSTALLER: Afx these instructions adjacent to boiler.
TO THE CONSUMER: Retain these instructions for future reference.

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IMPORTANT INFORMATION - READ CAREFULLY
NOTE: The equipment shall be installed in accordance with those installation regulations enforced in the area where the
installation is to be made. These regulations shall be carefully followed in all cases. Authorities having jurisdiction
shall be consulted before installations are made.
All wiring on boilers installed in the USA shall be made in accordance with the National Electrical Code and/or local
regulations.
All wiring on boilers installed in Canada shall be made in accordance with the Canadian Electrical Code and/or local
regulations.
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.
The City of New York requires a Licensed Master Plumber supervise the installation of this product.
The Massachusetts Board of Plumbers and Gas Fitters has approved the ASPEN™ Series boiler. See the Massachusetts Board
of Plumbers and Gas Fitters website, http://license.reg.state.ma.us/pubLic/pl_products/pb_pre_form.asp for the latest Approval
Code or ask your local Sales Representative.
The Commonwealth of Massachusetts requires this product to be installed by a Licensed Plumber or Gas Fitter.
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
Explosion Hazard. DO NOT store or use gasoline or other ammable vapors or liquids in the vicinity of this
or any other appliance.
If you smell gas vapors, DO NOT try to operate any appliance - DO NOT touch any electrical switch or use
any phone in the building. Immediately, call the gas supplier from a remotely located phone. Follow the gas
supplier’s instructions or if the supplier is unavailable, contact the re department.
WARNING
This boiler must only be serviced and repaired by skilled and experienced service technicians.
If any controls are replaced, they must be replaced with identical models.
Read, understand and follow all the instructions and warnings contained in all the sections of this
manual.
If any electrical wires are disconnected during service, clearly label the wires and assure that the wires
are reconnected properly.
Never jump out or bypass any safety or operating control or component of this boiler.
Assure that all safety and operating controls and components are operating properly before placing
the boiler back in service.
Annually inspect all vent gaskets and replace any exhibiting damage or deterioration.

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107362-01 - 8/17
WARNING
Asphyxiation Hazard. This boiler requires regular maintenance and service to operate safely. Follow
the instructions contained in this manual.
Improper installation, adjustment, alteration, service or maintenance can cause property damage,
personal injury or loss of life. Read and understand the entire manual before attempting installation,
start-up operation, or service. Installation and service must be performed only by an experienced,
skilled, and knowledgeable installer or service agency.
This boiler must be properly vented.
This boiler needs fresh air for safe operation and must be installed so there are provisions for
adequate combustion and ventilation air.
Asphyxiation Hazard. The interior of the venting system must be inspected and cleaned before the
start of the heating season and should be inspected periodically throughout the heating season for
any obstructions. A clean and unobstructed venting system is necessary to allow noxious fumes
that could cause injury or loss of life to vent safely and will contribute toward maintaining the boiler’s
efciency.
Installation is not complete unless a safety relief valve is installed in the supply piping. - See the
System Piping Section of this manual for details.
This boiler is supplied with safety devices 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.
Burn Hazard. 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.
Respiratory Hazard. Boiler materials of construction, 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.
Failure to follow all instructions in the proper order can cause personal injury or death. Read all
instructions, including all those contained in component manufacturers manuals which are provided
with the boiler before installing, starting up, operating, maintaining or servicing.
All cover plates, enclosures and guards must be in place at all times.
DANGER
Explosion Hazard. Electrical Shock Hazard. Burn Hazard. This boiler uses ammable gas, high
voltage electricity, moving parts, and very hot water under high pressure. Assure that all gas
and electric power supplies are off and that the water temperature is cool before attempting any
disassembly or service.
Do not attempt any service work if gas is present in the air in the vicinity of the boiler. Never modify,
remove or tamper with any control device.
WARNING
Asphyxiation Hazard. Fire Hazard. Explosion Hazard. This boiler requires regular maintenance and
service to operate safely. Follow the instructions contained in this manual.

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Special Installation Requirements for Massachusetts
A. For all sidewall horizontally vented gas fueled equipment installed in every dwelling, building or structure used in whole
or in part for residential purposes and where the sidewall exhaust vent termination is less than seven (7) ft. above grade, the
following requirements shall be satised:
1. If there is no carbon monoxide detector with an alarm already installed in compliance with the most current edition of
NFPA 720, NFPA 70 and the Massachusetts State Building Code in the residential unit served by the sidewall horizontally
vented gas fueled equipment, a battery operated carbon monoxide detector with an alarm shall be installed in compliance
with the most current edition of NFPA 720, NFPA 70 and the Massachusetts State Building Code.
2. In addition to the above requirements, if there is not one already present, a carbon monoxide detector with an alarm
and a battery back-up shall be installed and located in accordance with the installation requirements supplied with the
detector on the oor level where the gas equipment is installed. The carbon monoxide detector with an alarm shall
comply with 527 CMR, ANSI/UL 2034 Standards or CSA 6.19 and the most current edition of NFPA 720. In the event
that the requirements of this subdivision can not be met at the time of the completion of the installation of the equipment,
the installer shall have a period of thirty (30) days to comply with this requirement; provided, however, that during
said thirty (30) day period, a battery operated carbon monoxide detector with an alarm shall be installed in compliance
with the most current edition of NFPA 720, NFPA 70 and the Massachusetts State Building Code. In the event that the
sidewall horizontally vented gas fueled equipment is installed in a crawl space or an attic, the carbon monoxide detector
may be installed on the next adjacent habitable oor level. Such detector may be a battery operated carbon monoxide
detector with an alarm and shall be installed in compliance with the most current edition of NFPA 720, NFPA 70 and the
Massachusetts State Building Code.
3. A metal or plastic identication plate shall be permanently mounted to the exterior of the building at a minimum
height of eight (8) ft. above grade directly in line with the exhaust vent terminal for the horizontally vented gas fueled
heating appliance or equipment. The sign shall read, in print size no less than one-half (1/2) inch in size, “GAS VENT
DIRECTLY BELOW. KEEP CLEAR OF ALL OBSTRUCTIONS”.
4. A nal inspection by the state or local gas inspector of the sidewall horizontally vented equipment shall not be performed
until proof is provided that the state or local electrical inspector having jurisdiction has granted a permit for installation of
carbon monoxide detectors and alarms as required above.
B. EXEMPTIONS: The following equipment is exempt from 248 CMR 5.08(2)(a) 1 through 4:
1. The equipment listed in Chapter 10 entitled “Equipment Not Required To Be Vented” in the most current edition of NFPA
54 as adopted by the Board; and
2. Product Approved sidewall horizontally vented gas fueled equipment installed in a room or structure separate from the
dwelling, building or structure used in whole or in part for residential purposes.
C. When the manufacturer of Product Approved sidewall horizontally vented gas equipment provides a venting system
design or venting system components with the equipment, the instructions for installation of the equipment and the venting
system shall include:
1. A complete parts list for the venting system design or venting system; and
2. Detailed instructions for the installation of the venting system design or the venting system components.
D. When the manufacturer of a Product Approved sidewall horizontally vented gas fueled equipment does not provide the
parts for venting ue gases, but identies “special venting systems”, the following shall be satised:
1. The referenced “special venting system” instructions shall be included with the appliance or equipment installation
instructions; and
2. The “special venting systems” shall be Product Approved by the Board, and the instructions for that system shall include a
parts list and detailed installation instructions.
E. A copy of all installation instructions for all Product Approved sidewall horizontally vented gas fueled equipment,
all venting instructions, all parts lists for venting instructions, and/or all venting design instructions shall remain with the
appliance or equipment at the completion of the installation.

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FOLLOW ALL INSTRUCTIONS and warnings
printed in this manual and posted on the boiler.
MAINTAIN THE BOILER. To keep your boiler safe
and efcient, have a service technician maintain
this boiler as specied in Service and Maintenance
Instructions.
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. Insuf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, vent piping and
vent terminals.
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.
WARNINGS FOR THE HOMEOWNER
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 gage 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 National Fuel Gas
Code ANSI Z223.1/NFPA 54 or CAN/CSA B149.1,
Natural Gas and Propane Installation Code.
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 INSTALLER

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I. Product Description 7
II. Specications 7
III. Before Installing 9
IV. Locating The Boiler 10
V. Mounting The Boiler 12
VI. Air For Ventilation 15
VII. Venting 16
A. Vent System Design 16
B. Design Requirements Unique to Horizontal Twin Pipe Venting Systems 22
C. Design Requirements Unique to Vertical Venting Systems 28
D. Design Requirements Unique to Split Vent Systems 36
E. Assembly of CPVC/PVC Vent Systems 45
F. Assembly of DuraVent PolyPro Vent Systems 52
G. Assembly of Selkirk Polyue Vent Systems 57
H. Assembly of Centrotherm InnoFlue Vent Systems 61
I. Assembly of Stainless Steel Vent Systems 65
J. Condensate Trap and Drain 67
K. Removing An Existing Boiler From Common Chimney 69
VIII. Gas Piping 70
IX. System Piping 72
A. General System Piping Precaution 72
B. Standard Piping Installation Requirements 73
C. Near Boiler Piping Design 75
D. Piping For Special Situations 88
X. Wiring 89
XI. Start-Up and Checkout 100
XII. Operation 107
XIII. Service and Maintenance 137
XIV. Troubleshooting 144
XV. Service Parts 150
Appendix A: Instructions for High Altitude Installation 162
Above 2,000 ft.
Appendix B: ASPNC-155 Combi Instruction Manual
166
Appendix C: Special Requirements For Side-Wall 177
Vented Appliances In The Commonwealth
of Massachusetts
Table of Contents

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This boiler is a stainless steel gas red condensing boiler designed for use in forced hot water heating systems requiring
supply water temperatures of 180°F or less. It is designed for installation on a wall. This boiler may be vented vertically or
horizontally with combustion air supplied from outdoors. It is not designed for use in gravity hot water systems or systems
containing signicant amounts of dissolved oxygen.
Models ASPN-085 through 270 provide central space heating and/or indirect domestic hot water (DHW) heating.
Model ASPNC-155 provides economical tankless domestic hot water (DHW) heating in addition to central space heating.
I. Product Description
II. Specications
Figure 2.1: General Conguration
33 5
16
"
Supply/Outlet
Water Connection
Return/Inlet
Water Connection
Service
Access
Panel
Alternate
Return/Inlet
Water Connection
Alternate
Supply/Outlet
Water Connection
Outside
of Wall
Inside
of Wall
Vent
Connection
Relief Valve
Temperature/
Pressure Gauge
Drain Valve
Control
Access
Panel
Air Intake
Connection
Gas
Connection
Condensate
Trap
19 7
8
"
'A'
Dimensions
085-155 155 Combi 205-270
'A' 20" 23" 21"

8107362-01 - 8/17
Table 2.3: Specications
Model *
Maximum
Input
(MBH)
Minimum
Input
(MBH)
D.O.E.
Heating
Capacity
(MBH)
AHRI Net
Rating *
(MBH)
AFUE
Water
Volume
(Gallon)
Heating Water
Connection
Size (Copper
Sweat)
Gas
Connection
Size
(NPT)
Approx.
Net
Weight
(lb.)
Maximum
Allowable
Working
Pressure
(PSI)
ASPN-085 85 8.5 79 69 96 2.6 1" 1/2" 110 30
ASPN-110 110 11 103 90 96 2.5 1" 1/2" 115 30
ASPN-155 155 15.5 145 126 95 3.0 1" 1/2" 120 30
ASPNC-155 155 15.5 145 126 95 3.0 1" 1/2" 140 30
ASPN-205 205 20.5 189 164 95 5.1 1¼" 1/2" 135 80
ASPN-270 270 27 252 219 95 4.6 1¼" 1/2" 145 80
*The Net AHRI Water Ratings shown are based on a piping and pickup allowance of 1.15. The manufacturer should be consulted
before selecting a boiler for installations having unusual piping and pickup requirements, such as intermittent system operation,
extensive piping systems, etc.
Figure 2.2: Boiler Internal Component Locations
II. Specications (continued)
Flue
Temperature
Sensor
Return Sensor
Supply Sensor
Blocked Vent Switch
Air Proving Switch
Combustion Air Blower
Gas Valve
Programmed
Display
24V Fuse
Low Voltage PCB
Transformer
Circulator Fuse
High Voltage PCB

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Table 2.4: Vent Lengths
Model
Size
Nominal
Vent/Intake Size
(in)
Min Vent Length
(in)
Max Vent
Length (ft)
Approx.
Derate at Max Vent
(%)
85 230 60 7.6
3 30 135 3.7
110 2 30 60 9.7
3 30 135 4.2
155 3 30 135 7.2
205 3 30 135 9.7
270 3 30 135 11.3
See Section VII “Venting” for additional requirements and details.
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 National Fuel Gas Code, ANSI Z223.1. In Canada, installation must be in accordance with the B149.1
Installation Code.
• Where required by the authority having jurisdiction, this installation must conform to the Standard for Controls
and Safety Devices for Automatically Fired Boilers (ANSI/ASME CSD-1).
2. Read Section VII “Venting” to verify that the maximum combustion air and exhaust pipe lengths will not be exceeded
in the planned installation. Also verify that the vent terminal can be located in accordance with Section VII “Venting”.
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 system which includes an indirect water heater, make sure the boiler has the output called for by the indirect
water heater manufacturer’s instructions.
4. All boilers are shipped from the factory congured for 0 - 2,000 ft. altitude. For high altitude installation above 2,000
ft., see Appendix A.
5. All boilers are shipped from the factory congured for use with natural gas. They may be converted for use with
LP gas (“propane”) using proper conversion kit per Table 3.1. Use a combustion analyzer and follow all instructions
supplied with conversion kit.
III. Before Installing
II. Specications (continued)
Size LP Conversion Kit
85 107934-01
110 107935-01
115 107936-01
205 107937-01
270 107938-01
Table 3.1 LP Conversion Kits

10 107362-01 - 8/17
DANGER
• Do not attempt to operate this boiler on LP gas without converting it using the proper conversion kit.
• Do not attempt to convert this boiler to LP gas without the use of a combustion analyzer.
• Failure to follow the conversion instructions will result in operation of the boiler at unsafe Carbon
Monoxide (CO) levels and may result in personal injury or loss of life. Improper conversion may also
result in unreliable operation, resulting in property damage.
• Before attempting to operate this boiler at altitudes above 2,000 ft., follow instructions shown in
Appendix A of this manual.
NOTICE
This product must be installed by a licensed plumber or gas tter when installed within the
Commonwealth of Massachusetts. See Appendix C for additional important information about installing
this product within the Commonwealth of Massachusetts.
IV. Locating the Boiler
1. Observe the minimum clearances shown in Figure 4.1. These clearances apply to combustible construction as well as
non-combustible walls, oors, ceilings and doors.
2. Note the recommended service clearances in Figure 4.1. These service clearances are recommended, but may be reduced
to the combustible clearances provided:
a. Access to the front of the boiler is provided through a door.
b. Access is provided to the condensate trap located beneath the boiler.
Note that servicing the boiler will become increasingly difcult as these service clearances are reduced.
3. Observe the following clearances from piping to combustible construction:
Non-concentric vent (exhaust): ¼"
Air intake piping: 0"
Hot water piping: ¼"
4. The relief valve and gauge must be installed in the location shown in Figure 2.1 and must be in the same space as the
boiler.
5. The boiler should be located so as to minimize the length of the vent system.
6. The combustion air piping must terminate where outdoor air is available for combustion and away from areas that will
contaminate combustion air. Avoid areas near chemical products containing chlorine, chloride based salts, chloro/uoro
carbons, paint removers, cleaning solvents and detergents.
III. Before Installing (continued)

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IV. Locating the Boiler (continued)
24"
Service
Clearance*
6"
11 5
8
"
*Right side clearance may be reduced to 1/2"
however relief valve must remain in same
space as boiler.
Provide access to this area
for inspection and cleanout
of condensate trap.
Access
Panel
This boiler is listed for closet installation with
the following clearances from the boiler jacket to
combustible construction:
Top: 11-5/8", Sides: 1/2", Front: 1/2", Bottom: 6"
This above clearances also apply to non-combustible
walls, doors, ceilings and oors.
Clearances from piping to combustible construction:
Non-Concentric Vent (Exhaust): 1/4"
Air Intake Piping: 0"
Hot Water Piping: 1/4"
Recommended Service Clearances:
Right Side: 24", Front: 24", Bottom: 24"
1
2
"
Closet Door
1
2
"
1
2
"
Closet Door
Figure 4.1: Minimum Clearances To Combustible Construction

12 107362-01 - 8/17
A. Wall Mounting
1. If the boiler is installed on a framed wall, minimum acceptable framing is 2 x 4 studs on 16" centers. The boiler
mounting holes are on 16" centers for installation between two studs at the standard spacing. In cases where the boiler
cannot be centered between the studs, or where the studs are spaced closer than 16" apart, the boiler may be anchored
to ¾" plywood or horizontal 2 x 4’s anchored to the studs.
2. 5/16" x 2" lag screws and washers are provided for mounting this boiler. These lag screws are intended for mounting
the boiler directly onto studs covered with ½" sheathing. When the boiler is attached to other types of construction,
such as masonry, use fasteners capable of supporting the weight of the boiler and attached piping in accordance with
good construction practice and applicable local codes.
3. Make sure that the surface to which the boiler is mounted is plumb.
4. Before mounting the boiler, make sure that wall selected does not have any framing or other construction that will
interfere with the vent pipe penetration.
5. Once a suitable location has been selected for the boiler, and any needed modications have been made to the wall, use
Figure 5.1 to locate holes “A” and “B”. Make sure that the horizontal centerline of these holes is level. Holes “C” and
“D” may also be drilled at this time or after the boiler is hung on the wall. If the 5/16" x 2" lag screws are used, drill
3/16" pilot holes.
6. The wall mounting hook is used to secure the boiler to the shipping pallet. Remove this hook from the pallet and
secure to the wall using the 5/16" x 2" lag screws and washers, or other suitable anchors as appropriate (Figure 5.2).
Make sure the hook is level.
7. Hang the boiler on the wall hook as shown in Figure 5.2.
8. If not already done in Step (5) locate and drill holes “C” and “D” using the obround slots in the bottom mounting
ange. Secure the bottom ange to the wall using the 5/16"x 2" lag screws, or other fasteners as appropriate (Figure
5.2).
9. Verify that the front of the boiler is plumb. If it is not, install washers at holes “C” and “D” between the bottom
mounting ange and the wall to adjust.
V. Mounting The Boiler
CAUTION
• Two people are required to safely lift this boiler onto the wall mounting hook.
• Make sure that wall mounting hook is anchored to a structure capable of supporting the
weight of the boiler and attached piping when lled with water. Jurisdictions in areas
subject to earthquakes may have special requirements for supporting this boiler. These
local requirements take precedence over the requirements shown below.

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Figure 5.1 Wall Layout / Mounting Hole Location
V. Mounting The Boiler (continued)

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Figure 5.2 Boiler Mounting Bracket Installation / Boiler Wall Mounting
V. Mounting The Boiler (continued)

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107362-01 - 8/17
Air for combustion must always be obtained directly from outdoors. See Section VII “Venting” for intake piping.
Adequate air for ventilation will be present if the clearances specied in this manual are maintained. If this boiler is
installed in a room with other appliances, provide adequate air for combustion and/or ventilation air in accordance with the
manufacturer’s installation manual or applicable code.
VI . Air for Ventilation
WARNING
Outdoor combustion air must be piped to the air intake. Never pipe combustion air from areas containing
contaminates such as swimming pools and laundry room exhaust vents. Contaminated combustion air will
damage the boiler and may cause property damage, personal injury or loss of life.

16 107362-01 - 8/17
VII. Venting
A. Vent System Design
There are three basic ways to vent this boiler:
• Horizontal (“Side Wall”) Twin Pipe Venting (Figure 7.0a) - Vent system exits the building through an outside wall.
Combustion air and ue gas are routed between the boiler and the terminal(s) using separate pipes for at least part of the
way. A summary of Horizontal Twin Pipe venting options is shown in Table 7.5.
• Vertical Twin Pipe Venting (Figure 7.0b) - Vent system exits the building through a roof. Combustion air and ue gas
are routed between the boiler and the terminal(s) using separate pipes for at least part of the way. A summary of Vertical
Twin Pipe venting options is shown in Table 7.13
• Split Venting (Figure 7.0c) - Exhaust system exits the building through a roof, and combustion air is drawn from a
terminal mounted on the side wall. A summary of split venting options is shown in Table 7.21
All of these systems are considered “direct vent” because the air for combustion is drawn directly from the outdoors into the
boiler. One of the vent option columns in Tables 7.5, 7.13, 7.21 must match the planned vent and air intake system exactly.
Design details applying to all vent systems are shown in this section. Observe all design requirements in this section, as well as
those unique to the type of system being installed:
• B - Design Requirements Unique to Horizontal Twin Pipe Vent Systems
• C - Design Requirements Unique to Vertical Twin Pipe Vent Systems
• D - Design Requirements Unique to Split Vent Systems
WARNING
Asphyxiation Hazard. Failure to vent this boiler in accordance with these instructions could cause
products of combustion to enter the building resulting in severe property damage, personal injury or
death.
Do not interchange vent systems or materials unless otherwise specied.
The use of thermal insulation covering vent pipe and ttings is prohibited.
Do not use a barometric damper, draft hood or vent damper with this boiler.
When using the CPVC/PVC vent option, the use of CPVC is required when venting in vertical or
horizontal chase ways.
Do not locate vent termination where exposed to prevailing winds. Moisture and ice may form on
surface around vent termination. To prevent deterioration, surface must be in good repair (sealed,
painted, etc.).
Do not locate air intake vent termination where chlorines, chlorouorocarbons (CFC’s), petroleum
distillates, detergents, volatile vapors or other chemicals are present. Severe boiler corrosion and
failure will result.
The use of cellular core PVC (ASTM F891), cellular core CPVC or Radel (polyphenolsulfone) is
prohibited.
Do not locate vent termination under a deck.
Do not reduce specied diameters of vent and combustion air piping.
When installing vent pipe through chimney, as a chase, no other appliance can be vented into the
chimney.
Do not allow low spots in the vent where condensate may pool.
DANGER
Failure to follow this warning could result in asphyxiation and/or carbon monoxide poisoning. Correct
venting material and installation is required for proper vent operation. PVC Vent Systems must include at
least 30 inches of CPVC and one CPVC elbow between the boiler and PVC vent piping. See this Section, VII.
Venting for complete information.

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Figure 7.0c: Split Venting
VII. Venting A. Vent System Design (continued)
Figure 7.0a: Horizontal Twin Pipe
Figure 7.0b: Vertical Twin Pipe

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1. Listed Vent Systems and Materials – The following materials and vent systems may be used to vent this boiler:
• CPVC – Use only CPVC listed to ASTM F441. In Canada, this pipe must also be listed to ULC S636.
• PVC – PVC may be used only as permitted in this manual. All PVC must be listed to ASTM D2665. At least 30" of
CPVC pipe, and at least one CPVC elbow, must be installed between the boiler’s vent connection and the PVC pipe. Use
of foam core PVC is not permitted for venting. PVC vent pipe may not be used to vent this boiler in Canada.
• DuraVent PolyPro - ULC S636 listed PolyPropylene special gas vent system.
• Selkirk Polyue - ULC S636 listed PolyPropylene special gas vent system.
• Centrotherm InnoFlue SW - ULC S636 listed PolyPropylene special gas vent system.
• DuraVent FasNSeal Flex-UL 1738 listed Stainless Steel Special gas vent system.
• Use PVC and/or CPVC for the air intake system. PVC may be used for all air intake piping between the intake terminal
and the boiler.
• When CPVC and/or PVC pipe is used, it must be joined using primer and cement that is listed for use with the pipe
material being joined (PVC, CPVC, or CPVC to PVC).
2. Vent Kits Available for Use with this Boiler - The following vent kits are available for CPVC/PVC vent systems installed
with this boiler in the USA:
• 107039-01 - 2" CPVC/PVC Vent Kit
• 107039-02 - 3" CPVC/PVC Vent Kit
These kits include the following:
(1) 30" CPVC Straight Pipe
(1) 90 degree short bend CPVC Elbow
(1) Straight PVC Coupling (for exhaust terminal)
(1) 90 degree PVC Elbow (for intake terminal)
(2) Rodent screens
The CPVC Pipe and elbow supplied with these kits are not listed to ULC S636 and may not be used in Canada.
3. Maximum Vent and Air Intake Lengths - The maximum length of the vent air intake piping depends upon the vent option
selected and the boiler size. See Tables 7.5, 7.13 or 7.21 for the maximum vent lengths. These maximum lengths apply
to both the vent and intake piping (e.g. Option 1 may have up to 60ft of intake and 60ft of vent piping). For all vent
systems, the lengths shown in Tables 7.5, 7.13 and 7.21 are in addition to the rst 90° elbow. If more elbows are desired,
the maximum allowable vent length must be reduced by the amount shown in Table 7.1 for each additional elbow used.
Termination ttings are never counted.
It is recommended that all eld supplied PVC or CPVC elbows be “1/4 Bend” (Sanitary 90° El) or “Long Sweep 1/4
Bend” type elbows (Figure 7.2). In this manual “sanitary” and “long sweep” elbows are treated as having the same equivalent
length.
Example:
A 3" twin pipe horizontal CPVC/PVC vent system is planned for a horizontally vented 155MBH model which has the
following components in the vent system:
• 1 ft CPVC Straight Pipe
• 90 CPVC Elbow (short bend)
• 1-1/2 ft CPVC Straight Pipe
• Coupling
• 10 ft PVC Straight Pipe
• 90 PVC Elbow (Sanitary Elbow Design)
• 15 ft PVC Straight Pipe
• PVC Coupling Terminal
The Vent Option #2 column in Table 7.5 describes a horizontal direct vent system using 3" CPVC and PVC pipe. From this
column,weseethattheboilermayhaveaventlengthofupto135ft.TherstCPVC90degreeelbowisnotconsidered.From
Table 7.1, we see that the equivalent length of the 90 PVC elbow is 4ft and that the equivalent length of the coupling is 0ft.
The total equivalent length of the planned venting system is therefore:
1ft(StraightCPVC)+0ft(rstshortbendCPVC90Elbow)+1.5ft(StraightCPVC)+0ft(Coupling)+10ft(StraightPVC)
+ 4ft (PVC 90 Sanitary Elbow) + 15ft (Straight PVC) + 0ft (Coupling Terminal) = 31.5ft.
Since Table 7.1 shows a maximum allowable vent length of 135ft, the planned vent system length is acceptable
The ex venting used on some of the Vertical Twin Pipe and Split Vent Options also reduces the maximum allowable vent
length. See Sections VII-C or VII-D for details.
VII. Venting A. Vent System Design (continued)

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NOTICE
Do not exceed maximum vent/combustion air system length. Refer to Tables 7.1 and 7.13 in this
section for maximum vent/combustion air system length.
Use only vent and combustion air terminals and terminal locations shown in Tables 7.5, 7.13, and
7.21 and related Figures in this section.
4. Minimum Vent and Air Intake Lengths - Observe the minimum vent lengths shown in Tables 7.5, 7.13 and 7.21.
5. Clearances to Combustibles - Maintain the following clearances from the vent system to combustible construction:
• Vent - 1/4" (also observe clearances through both combustible and non-combustible walls - see 9 below)
• Air Intake - 0"
• Concentric Portion of Concentric Terminals - 0"
6. Pitch of Horizontal Vent Piping - Pitch all horizontal vent piping so that any condensate which forms in the piping will run
towards the boiler.
• Pitch CPVC/PVC vent piping 1/4" per foot.
• Pitch PolyPropylene vent piping 5/8" per foot.
For Category I, II, and IV boilers, have horizontal runs sloping upwards not less than 1/4 inch per foot (21 mm/m) from the
boiler to the vent terminal.
Les chaudières de catégories I, II et IV doivent présenter des tronçons horizontaux dont la pente montante est d’au moins
1/4 po par pied (21 mm/m) entre la chaudière et l’évent.
VII. Venting A. Vent System Design (continued)
Table 7.1: Vent/ Air Intake Fitting Equivalent Length
CPVC/PVC Fitting Equivalent Length (ft) PolyPro, Polyue or InnoFlue
Vent Fitting Equivalent Length (ft)
2" 90° Elbow (“Sanitary Bend”) 2.6 2" 90° Elbow 4.5
3" 90° Elbow (“Sanitary Bend”) 4.0 3" 90° Elbow 8.7
2" 90° Elbow (“Short Bend”) 6.0 2" 45° Elbow 2.5
3" 90° Elbow (“Short Bend”) 10.0 3" 45° Elbow 4.6
2" 45° Elbow 1.5
3" 45° Elbow 2.0
2" Coupling 0.0
3" Coupling 0.0
Figure 7.2: CPVC and PVC Elbows

20 107362-01 - 8/17
VII. Venting A. Vent System Design (continued)
7. Supporting Pipe - Vertical and horizontal sections of pipe must be properly supported. Maximum support spacing is as
follows:
• Support CPVC/PVC horizontally and vertically every 4 feet.
• Support DuraVent PolyPro horizontally near the female end of each straight section of pipe and vertically every 10 feet.
• Support Centrotherm InnoFlue horizontally every 39 inches with additional supports at elbows and vertically every 78".
• Support 2" Selkirk Polyue horizontally every 30". Support 3" Polyue horizontally every 39". Support vertical runs of
both 2" and 3" Polyue every 16 ft.
• Support DuraVent FasNSeal horizontally every 6 ft. or less. Support vertical runs at the base and every 12 ft. or less.
These instructions for the installation of the venting system shall specify that the horizontal portions of the venting system
shall be supported to prevent sagging; the methods of and intervals for support shall be specied. These instructions shall also
specify that the venting system:
• For category II and IV boilers, be installed so as to prevent accumulation of condensate.
• For category II and IV boilers, where necessary, have means provided for drainage of condensate.
Les instructions d´installation du système d´évacuation doivent préciser que les sections horizontales doivent être
supportées pour prévenir le échissement. Les méthodes et les intervalles de support doivent être spéciés. Les
instructions divent aussi indiquer les renseignements suivants:
• les chaudières de catégories II et IV doivent être installées de façon à empêcher l´accumulation de condensat:
• et si nécessaire, les chaudières de catégories II et IV doivent être pourvues de dispositifs d´évacuation du condensat.
8. Allowing for Thermal Expansion -
• For CPVC/PVC pipe design the vent system to allow 3/8" of thermal expansion for every 10ft of CPVC/PVC pipe.
The boiler will always act as an anchor to one end of the vent system. If at all possible, select and install hangers and
wall thimbles so that the vent system can expand towards the terminal. When a straight run of pipe exceeds 20ft and
must be restrained at both ends, an offset or expansion loop must be provided (Figures 7.3a, 7.3b). When a straight
horizontal run of pipe exceeds 20ft and is restrained at one end with an elbow at the other, avoid putting a hanger or
guide less than “Y” inches from the elbow in the adjoining straight section (Figure 7.3c). Thermal expansion ttings
are not permitted.
• When properly assembled expansion of PolyPro, Polyue and InnoFlue vent systems is accommodated at the joints. See
Part VII-F, G & H of this manual for details.
• Stainless steel vent systems must be free to expand and contact in accordance with manufacturer's installation
instructions.
9. Running PVC Vent Pipe Inside Enclosures and Through Walls - PVC vent pipe must be installed in a manner that permits
adequate air circulation around the outside of the pipe:
• Do not enclose PVC venting - Use CPVC in enclosed spaces, even if PVC is installed upstream.
• PVC venting may not be used to penetrate combustible or non-combustible walls unless all of the following conditions are
met:
a. The wall penetration is at least 66 inches from the boiler as measured along the vent.
b. The wall is 12" thick or less
c. An airspace of at least that shown in Figure 7.4 is maintained around the OD of the vent.
If any of these conditions cannot be met, use CPVC for the wall penetration.
10. Vent Manufacturer’s Instructions – The vent system manufacturer may have additional vent system design requirements.
Read and follow the vent manufacturer’s instructions in addition to those shown here. Where a conict arises between the
two sets of instructions, the more restrictive requirements shall govern.