Burnham K2WT Residential Service manual

1
107672-03 - 5/18 Price - $5.00
TO THE INSTALLER:
Affix these instructions adjacent to boiler.
TO THE CONSUMER:
Retain these instructions for future reference.
WARNING: Improper installation, adjustment, alteration, service or maintenance can cause property
damage, injury, or loss of life. For assistance or additional information, consult a qualified installer, service
agency or the gas supplier. This boiler requires a special venting system. Read these instructions care-
fully before installing.
9700609
Installation, Operating and Service Instructions for
Condensing
High Efficiency
Direct Vent
Gas-Fired
Water Boiler
K2WT TM
Residential
As an ENERGY STAR®Partner, U.S. Boiler
Company has determined that the K2WT™
Series meets the ENERGY STAR®guidelines for
energy efficiency established by the United States
Environmental Protection Agency (EPA).

2107672-03 - 5/18
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 K2WT™ 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.
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.
WARNING
Indicates an imminently
hazardous situation which, if not avoided, will
result in death, serious injury or substantial
property damage.
DANGER
Indicates a potentially
hazardous situation which, if not avoided,
could result in death, serious injury or
substantial property damage.
WARNING
CAUTION
Indicates a potentially
hazardous situation which, if not avoided, may
result in moderate or minor injury or property
damage.
NOTICE Indicates special instructions on
installation, operation, or maintenance which
are important but not related to personal injury
hazards.
Explosion Hazard. DO NOT store or use gasoline or other flammable 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 fire department.
DANGER
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107672-03 - 5/18
Explosion Hazard. Electrical Shock Hazard. Burn Hazard. This boiler uses flammable
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.
DANGER
Asphyxiation Hazard. Fire Hazard. Explosion 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 efficiency.
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 fittings
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.
WARNING
•••
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•

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FOLLOW ALL INSTRUCTIONS and warnings
printed in this manual and posted on the boiler.
INSPECT THE BOILER ANNUALLY. To keep
your boiler safe and efficient, 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
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 first
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, flue 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
DO NOT BLOCK AIR FLOW into or around the
boiler. Insufficient air may cause the boiler to
produce carbon monoxide or start a fire.
KEEP FLAMMABLE LIQUIDS AWAY from the
boiler, including paint, solvents, and gasoline.
The boiler may ignite the vapors from the liquids
causing explosion or fire.
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.

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Table of Contents
I. Product Description ..................................................6
II. Specifications .......................................................6
III. Before Installing .................................................... 7
IV. Locating The Boiler ...................................................8
V. Mounting The Boiler .................................................10
VI. Air for Ventilation ....................................................13
VII. Venting ...........................................................14
A. Vent System Design ...............................................14
B. Design Requirements Unique to Horizontal Twin Pipe Venting Systems .......20
C. Design Requirements Unique to Vertical Venting Systems .................26
D. Design Requirements Unique to Split Vent Systems ......................34
E. Assembly of CPVC/PVC Vent Systems .................................43
F. Assembly of DuraVent PolyPro Vent Systems ............................50
G. Assembly of Selkirk Polyflue Vent Systems .............................55
H. Assembly of Centrotherm InnoFlue Vent Systems ........................59
I. Assembly of Stainless Steel Vent Systems ..............................63
J. Condensate Trap and Drain .........................................65
K. Removing An Existing Boiler From Common Chimney.....................66
VIII. Gas Piping.........................................................67
IX. System Piping ......................................................69
A. General System Piping Precaution ....................................69
B. Standard Piping Installation Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70
C. Near Boiler Piping Design ..........................................72
D. Piping For Special Situations ........................................81
X. Wiring ............................................................82
XI. Start-up and Checkout ...............................................95
XII. Operation ........................................................104
XIII. Service and Maintenance ............................................133
XIV. Troubleshooting....................................................140
XV. Service Parts ......................................................146
Appendix A: Instruction for High Altitude Installation Above 2,000 ft. ..........158
Appendix B: Special Requirements For Side Wall Vented Appliances
In The Commonwealth of Massachusetts ................................161

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II. Specications
Figure 2.1: General Configuration
This boiler is a stainless steel gas fired condensing boiler designed for use in forced hot water heating systems
requiring supply water temperatures of 180°F or less. 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 significant amounts of dissolved oxygen.
I. Product Description
15
"A"
SEE TABLE 2.3
26 1/8
INSIDE
OF WALL
SERVICE
ACCESS
PANEL
SUPPLY WATER
CONNECTION
TEMPERATURE/
PRESSURE GAUGE
DRAIN
VALVE
RETURN WATER
CONNECTION
OUTSIDE
OF WALL
GAS
CONNECTION
RELIEF
VALVE
VENT
CONNECTION
CONDENSATE
TRAP CLEANOUT
CONDENSATE
CONNECTION
CONTROL
ACCESS
PANEL
AIR INTAKE
CONNECTION

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Table 2.3: Vent Lengths
Table 2.2: Specifications
Model*
Maximum
Input
(MBH)
Minimum
Input
(MBH)
D.O.E.
Heating
Capacity
(MBH)
AHRI Net
Rating *
(MBH)
Water
Volume
(gal.)
Dim.
“A”
Supply
& Return
Connection
Size (NPT)
Gas
Connection
Size (NPT)
Approx.
Net
Weight
(lb.)
Altitude Range (ft)
NG LP
K2WT-080B 80 8 74 64 0.430 17” 1” 1/2” 100 0-10100 0-2000
K2WT-100B 100 10 94 82 0.547 17” 1” 1/2” 102 0-10100
K2WT-120B 120 12 112 97 0.650 17” 1” 1/2” 105 0-10100 0-7800
K2WT-150B 150 15 142 123 0.956 21” 1” 1/2” 119 0-10100
K2WT-180B 180 18 169 147 0.956 21” 1” 1/2” 119 0-2000
K2WT-180M 180 18 168 146 0.790 21” 1” 1/2” 119 2001-10100
* 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.
Model
Nominal
Vent/Intake Size
(in)
Min Vent Length
(in) Max Vent Length
Approx.
Derate at Max Vent
(%)
K2WT-080B 2 12 60 ft 9
K2WT-080B 3 12 135 ft 2
K2WT-100B 2 12 60 ft 15
K2WT-100B 3 12 135 ft 3
K2WT-120B 3 12 135 ft 7
K2WT-150B 3 52 135 ft 7
K2WT-180B 3 52 135 ft 9
K2WT-180M 3 52 135 ft 9
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 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.
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.
III. Before Installing
II. Specifications (continued)
See Section VII (Venting) for additional requirements and details.

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4. All boilers are shipped from the factory configured for use with natural gas. They may be converted for use
with LP gas (“propane”) using a proper conversion kit per Table 3.1. Use a combustion analyzer and follow all
instructions supplied with conversion kit.
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, floors, 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 difficult 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/fluorocarbons, paint removers, cleaning solvents and detergents.
III. Before Installing (continued)
Model Size LP Conversion Kit
080B-100B 107873-01
120B-150B 107874-01
180B 107875-01
180M 108101-01
Table 3.1: LP Conversion Kits
NOTICE This product must be installed by a licensed plumber or gas fitter when installed within the
Commonwealth of Massachusetts. See Appendix B for additional important information about installing
this product within the Commonwealth of Massachusetts.
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 2000 ft., follow instructions shown in Appendix
A of this manual.
WARNING

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Figure 4.1: Minimum Clearances To Combustible Construction
IV. Locating the Boiler (continued)
*LEFT SIDE CLEARANCE MAY BE REDUCED TO 1/2"
HOWEVER RELIEF VALVE MUST REMAIN IN SAME
SPACE AS BOILER.

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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 modifications 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 flange. Secure the bottom flange 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 flange and the wall to adjust.
V. Mounting The Boiler
CAUTION
This boiler weighs as much as 119 pounds:
• 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 filled 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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Air for combustion must always be obtained directly from outdoors. See Section VII for intake piping.
Adequate air for ventilation will be present if the clearances specified 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
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.
WARNING

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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 flue 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 flue 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
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.
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 specified.
The use of thermal insulation covering vent pipe and fittings 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.
Any CPVC vent materials supplied with this boiler do not comply with B149.1.S1-07 and are not approved
for use in Canadian jurisdictions that require vent systems be listed to ULC S636-2008. In these
jurisdictions, vent this boiler using a listed ULC S636 Class IIB venting system.
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, chlorofluorocarbons (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 specified 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.
WARNING
•
•
•
•
•
•
•
•
•
•
•
•

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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
BOILER

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• DuraVent PolyPro - ULC S636 listed Polypropylene special gas vent system.
• Selkirk Polyflue - 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 kit 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 termination)
(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 first 90° elbow.
If more elbows are desired, the maximum allowable vent length must be reduced by the amount shown in Table
7.1B for each additional elbow used. Termination fittings are never counted.
It is recommended that all field supplied PVC or CPVC elbows be “1/4 Bend” (Sanitary 90° Elbow) 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 120MBH 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 first CPVC 90 degree elbow
is not considered. From Table 7.1B, 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 (first 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 7.1B shows a maximum allowable vent length of 135ft, the planned vent system length is acceptable
The flex 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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Figure 7.2: CPVC and PVC Elbows
Table 7.1B: Vent/ Air Intake Fitting Equivalent Length
CPVC/PVC Fitting Equivalent
Length (ft)
PolyPro, Polyflue
or InnoFlue
Vent Fitting
Equivalent
Length (ft)
FasNSeal
Vent Fitting
Equivalent
Length (ft)
2” 90° Elbow (“Sanitary Bend”) 2.6 2” 90° Elbow 4.5 3” 90° Elbow 4.0
3” 90° Elbow (“Sanitary Bend”) 4.0 3” 90° Elbow 8.7 3” 45° Elbow 2.0
2” 90° Elbow (“Short Bend” ) 6.0 2” 45° Elbow 2.5 3” Straight Tee 18.0
3” 90° Elbow (“Short Bend”) 10.0 3” 45° Elbow 4.6 3” Boot Tee 8.0
2” 45° Elbow 1.5
3” 45° Elbow 2.0
2” Coupling 0.0
3” Coupling 0.0
VII. Venting A. Vent System Design (continued)
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)
• 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” 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.
NOTICE Do not exceed maximum vent/combustion air system length. Refer to Tables 7.1B, 7.5, 7.13, and
7.21 in this section for maximum vent/combustion air system length.
Use Use only vent and combustion air terminals and terminal locations shown in Tables 7.1B, 7.5, 7.13 and
7.21.

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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 Polyflue horizontally every 30”. Support 3” Polyflue horizontally every 39”. Support vertical
runs of both 2” and 3” Polyflue every 16 ft.
• Support DuraVent FasNSeal horizontally every 6ft or less. Support vertical runs at the base and every 12ft or
less.
The 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 specified.
These instructions shall also specify that the venting system:
• For Category II and IV boilers, be installed so as to prevent accumulation of condensate; and
• 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 fléchissement. Les méthodes et les intervalles de support doivent être
spécifiés. 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 shall 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 fittings are not permitted.
• When properly assembled expansion of PolyPro, Polyflue and InnoFlue vent systems is accommodated at the
joints. See Section VII - F, G & H of this manual for details.
• Stainless steel vent systems must be free to expand and contract 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
conflict arises between the two sets of instructions, the more restrictive requirements shall govern.

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VII. Venting A. Vent System Design (continued)
Figure 7.3: Expansion Loops for CPVC/PVC Pipe
Figure 7.3b
Figure 7.3a
Figure 7.4: Wall Penetration Clearances for PVC Vent Pipe
Figure 7.3c

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B. Design Requirements Unique to Horizontal Twin Pipe Venting Systems
Table 7.5 summarizes all horizontal twin pipe vent options. Illustrations of horizontal twin pipe vent systems are
shown in Figures 7.6 – 7.10. In addition to the requirements in Section VII - A, observe the following design
requirements:
1. Permitted Terminals for Horizontal Venting:
Terminal Option A: Fittings (Acceptable for Vent Options 1-8) – Vent terminates in a plain end (coupling for PVC,
bell end for PolyPro, Polyflue and plain end pipe for InnoFlue). Intake terminates in a PVC 90 sweep elbow
pointing down. Outer edge of both terminals must be within 10” of the wall surface (Figures 7.6, 7.9). The section
of DuraVent PolyPro, Centrotherm InnoFlue or Selkirk Polyflue exposed to the outdoors must be UV resistant.
Use of rodent screens is generally recommended for both terminations. Two rodent screens are included within
the available 2” and 3” vent kits or can be fabricated from 1/2” stainless steel mesh screen. Rodent screens and
are installed as shown in Figure 7.28. Rodent screens (“bird guards”) for PolyPro, InnoFlue and Polyflue are as
follows:
Size/Vent System Rodent Screen (“Bird Guard”)
2” PolyPro DuraVent # 2PPS-BG
3” PolyPro DuraVent # 3PPS-BG
2” Polyflue Selkirk # 2PF-HVST
3” Polyflue Selkirk # 3PF-HVST
2” InnoFlue Centrotherm # IASPP02
3” InnoFlue Centrotherm # IASPP03
If necessary to achieve required clearance above grade, CPVC or CPVC/PVC vent systems may be terminated
using fittings on snorkels as shown in Figure 7.12. When this is done, the equivalent length of all pipe on the
exterior of the building, except for the terminal fittings themselves, must be counted when calculating the
equivalent length. The maximum vertical run of the snorkel is 7 feet. Brace both the vent and inlet piping if
required. PolyPro, InnoFlue and Polyflue may not be snorkeled.
Terminal Option B: Ipex Low Profile Terminal (Acceptable for Vent Options 1,2) – This terminal is shown in Figure
7.7. If the terminal is oriented vertically (alternate orientation shown in Fig 7.7) the exhaust opening must be
on the top as shown. See Section VII - E of this manual and the Ipex instructions provided with the terminal, for
installation details.
Terminal Option C: DiversiTech “Low Profile” Terminal (Acceptable for Vent Options 1,2) – This terminal is shown
in Figure 7.7. If the terminal is oriented vertically (alternate orientation shown in Fig 7.7) the exhaust opening
must be on the top as shown. See Section VII - E of this manual and the DiversiTech instructions provided with
the terminal, for installation details.
Terminal Option D: Ipex FGV Concentric Terminal (Acceptable for Vent Options 1,2) - This terminal is shown in
Figure 7.8 and may be used with CPVC/PVC vent systems. This terminal is available in various lengths and in
both PVC and CPVC. Terminals acceptable for use with these vent options are as follows:
Ipex PN FGV Concentric Terminal Description
196005 2 x 16” PVC
196105 2 x 28” PVC
196125 2 x 40” PVC
196006 3 x 20” PVC
196106 3 x 32” PVC
196116 3 x 44” PVC
197107 3 x 32” CPVC
197117 3 x 44” CPVC
See Section VII - E of this manual and the Ipex instructions provided with the terminal, for installation details.
Terminal Option E: DiversiTech Concentric Terminal (Acceptable for Vent Options 1,2) - This terminal is shown in
Figure 7.8 and may be used with CPVC/PVC vent systems. See Section VII - E of this manual and the DiversiTech
instructions provided with the terminal, for installation details.
Terminal Option F: DuraVent PolyPro Concentric Terminal (Acceptable for Vent Options 3,4) - This terminal is
shown in Figure 7.10 and may be used with DuraVent 2” or 3” PolyPro vent systems. See Section VII - F of this
manual and the DuraVent instructions provided with the terminal, for installation details.
VII. Venting B. Design Requirements Unique to Horizontal Twin Pipe Venting Systems (continued)