Burnham K2WTC Service manual

1
107774-01- 9/17 Price - $5.00
TO THE INSTALLER: Afx 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 qualied installer, service agency or the
gas supplier. This boiler requires a special venting system. Read these instructions carefully before installing.
9700609
As an ENERGY STAR® Partner, U.S. Boiler Company has determined that the K2WTC 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
K2WTC
CONDENSING HIGH EFFICIENCY
DIRECT VENT
GAS - FIRED HOT WATER COMBI BOILER

2107774-01 - 9/17
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 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.

3
107774-01- 9/17
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.

4107774-01 - 9/17
FOLLOW ALL INSTRUCTIONS and warnings
printed in this manual and posted on the boiler.
INSPECT THE BOILER ANNUALLY. To keep
your boiler safe and ef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
WARNINGS FOR THE HOMEOWNER
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.
DANGER
• Water temperature over 125°F (52°C)
can cause severe burns instantly or
death from scalds.
• Children, disabled and elderly are at
highest risk of being scalded.
• Feel water before bathing or showering.
• Installation of an ASSE 1017 or ASSE
1070 certied tempering valve is
REQUIRED as part of this boiler’s
installation. Consult Sections X and
XIII for details on valve installation and
temperature adjustment.

5
107774-01- 9/17
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

6107774-01 - 9/17
Table of Contents
I. Product Description 7
 II.  Specications  7
III. Before Installing 8
IV. Locating The Boiler 9
V. Mounting The Boiler 11
VI. Air For Ventilation 14
VII. Venting 15
A. Vent System Design 15
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 44
F. Assembly of DuraVent PolyPro Vent Systems 51
G. AssemblyofSelkirkPolyueVentSystems 56
H. Assembly of Centrotherm InnoFlue Vent Systems 60
I. Assembly of Stainless Steel Vent Systems 64
J. Condensate Trap and Drain 66
K. Removing An Existing Boiler From Common Chimney 67
VIII. Gas Piping 68
IX. System Piping 70
A. General System Piping Precaution 70
B. Standard Piping Installation Requirements 71
C. Near Boiler Piping Design 73
D. Piping For Special Situations 79
X. Domestic Hot Water Piping 80
XI. Wiring 82
XII. Start-Up and Checkout 93
XIII. Operation 101
XIV. Service and Maintenance 124
XV. Troubleshooting 131
XVI. Repair Parts 140
Appendix A: Instructions for High Altitude Installation Above 2,000 ft. 153
Appendix B: Special Requirements For Side-Wall Vented Appliances
In The Commonwealth of Massachusetts 156

7
107774-01- 9/17
II. Specications
Figure 2.1: General Conguration
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. In addition to providing water for space heat, this boiler also generates domestic
hot water (DHW). 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.
I. Product Description
"A"
SEE TABLE 2.4
INSIDE
OF WALL
OUTSIDE
OF WALL
30
ACCESS
CONNECTION
DOOR
RELIEF
CONDENSATE TRAP
CLEANOUT
(INSIDE CABINET)
PRESSURE GAUGE
AIR INTAKE
CONNECTION
CONNECTION
CONDENSATE
VALVE
BOILER RETURN WATER
CONNECTION
VENT
TEMPERATURE/
BOILER SUPPLY WATER
CONNECTION
DOMESTIC HOT WATER OUTLET DOMESTIC COLD WATER INLET
GAS CONNECTION
17

8107774-01 - 9/17
Table 2.2: Performance Specications
K2WTC Space Heating Ratings Domestic Hot Water (DHW) Ratings1
Input, MBH
Hot Water Draw Limits, GPM
Model Number
Input, MBH Heating
Capacity,
MBH2
Net AHRI
Water,
MBH AFUE, %
Max.3
Min.4 Min Max Min Max
70°F 77°F 90°F
Rise Rise Rise
K2WTC-135B 12 120 112 97 95.0 12 135 3.3 3.0 2.6 0.5
K2WTC-150B 15 150 142 123 95.0 15 150 3.9 3.7 3.1 0.5
K2WTC-180B 18 180 169 147 95.0 18 180 4.5 4.1 3.5 0.5
Notes:
1) DHW ratings are not AHRI certied.
2) 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.
3) Maximum draw rates shown are at sea level and minimum vent length. Under other conditions draw rates will be reduced proportionally to the reduction in input. See
Table 2.4 and Appendix A for input de-rate information.
4) Minimum ow rate shown is that required through the boiler to initiate a call for DHW. A higher ow rate may be required through the xture due to mixing at the
tempering valve and xture itself.
Table 2.3: Physical Specications
Model
Size
Fig 2.1 Dim
“A”, (in)
Connection Size (NPT Male)
Boiler Water
Content,
(Gal.)
Net Weight,
(lbs.)Supply/Return Hot/Cold Gas
135 15 1 3/4 1/2 0.53 109
150 19 1 3/4 1/2 0.79 126
180 19 1 3/4 1/2 0.79 126
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).
III. Before Installing
II. Specications (continued)
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 (%)
135 3 12 135 7
150 3 52 135 7
180 3 52 135 9

9
107774-01- 9/17
WARNING
• 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.
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 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)
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.
• 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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.
Table 3.1: LP Conversion Kit
Model Size LP Conversion Kit PN
135, 150 107874-01
180 107875-01

10 107774-01 - 9/17
Figure 4.1: Minimum Clearances To Combustible Construction
IV. Locating the Boiler (continued)

11
107774-01- 9/17
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
This boiler weighs as much as 126 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 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.

12 107774-01 - 9/17
Figure 5.1 Wall Layout/Mounting Hole Location
V. Mounting The Boiler (continued)

13
107774-01- 9/17
Figure 5.2 Boiler Mounting Bracket Installation / Boiler Wall Mounting
V. Mounting The Boiler (continued)

14 107774-01 - 9/17
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.
Air for combustion must always be obtained directly from outdoors (see Section VII for intake piping). Although combus-
tion air must always be obtained directly from outdoors, ventilation openings may still be required to prevent overheating of
boiler components if the boiler is installed in a small space, such as a closet.
• If the recommended service clearances shown in Figure 4.1 can be maintained (with all doors to the room
closed), no ventilation openings are required for this boiler.
• If the above service clearances cannot be maintained, provide two openings into the 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within12”oftheoor.Eachoftheseopeningsmusthavea 
free area of at least 100 square inches. The “free area” takes into account the blocking effect of mesh
  grillesandlouvers.Wherescreensareusedtheymustbenonerthan¼”(4x4)mesh.
• If this boiler is installed in a room with other appliances, provide adequate air for combustion and/or
ventilation in accordance with the other appliance manufacturer’s installation manual or applicable code.
In cases where such provisions require two openings in excess of 100 square inches, no additional
opening area is required for this boiler.

15
107774-01- 9/17
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
1. Approved 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.
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.
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 chlorine, 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.

16 107774-01 - 9/17
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

17
107774-01- 9/17
• 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 Kit Available for Use with this Boiler - The following vent kit is available for CPVC/PVC vent systems installed with
this boiler in the USA:
• 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 135ft of intake and 135ft 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°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 135 MBH 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 #1 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)

18 107774-01 - 9/17
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 only vent and combustion air terminals and terminal locations shown in Tables 7.1B, 7.5, 7.13
and 7.21.
VII. Venting A. Vent System Design (continued)
4. Vent Side Noise Attenuator - This boiler comes with a vent side noise attenuator. If equivalent vent length is less than 70
equivalent ft., install noise attenuator as described below. Attenuator is not required on size 135 at altitudes above 2000ft.
Refer to Figure 7.1A.
a. To properly install attenuator, insert approximately a 9” length CPVC pipe in vent adaptor.
 b. Fita3”CPVCcouplingonlengthofpipe.Gluecouplingtopipeusingaeldsuppliedcementandprimerthatis
listed for use with materials being joined (CPVC and/or PVC).
c. Insert attenuator in length of pipe. Ensure attenuator tube is pointing down and sits inside 3” CPVC coupling.
d. Install remaining venting as described in this manual. If using one of the polypropylene or stainless steel vent
systems listed described in this manual, use a listed adapter to adapt from CPVC to be the other vent system.
Figure 7.1A: Installation of Vent Side Attenuator
NOTICE
This boiler comes with a vent side noise attenuator. If equivalent vent length is less than 70 equivalent
ft., install vent side noise attenuator as described in this manual. Failure to do so may result in boiler
combustion noise during operation. Attenuator is not required on size 135 at altitudes above 2000ft.

19
107774-01- 9/17
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 only vent and combustion air terminals and terminal locations shown in Tables 7.5, 7.13 and
7.21.
5. Minimum Vent and Air Intake Lengths - Observe the minimum vent lengths shown in Tables 7.5, 7.13 and 7.21.
6. 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”
7. 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.
VII. Venting A. Vent System Design (continued)
Table 7.1B: Vent/ Air Intake Fitting Equivalent Length
CPVC/PVC Fitting Equivalent
Length (ft)
PolyPro, Polyue
or InnoFlue
Vent Fitting
Equivalent
Length (ft) FasNSeal Vent Fitting Equivalent Length (ft)
3” 90° Elbow (“Sanitary Bend”) 4.0 3” 90° Elbow 8.7 3” 90° Elbow 4.0
3” 45° Elbow 2.0 3” 45° Elbow 4.6 3” 45° Elbow 2.0
3” 90° Elbow (“Short Bend”) 10.0 3” Straight Tee 18.0
3” Coupling 0.0 3” Boot Tee 8.0
Figure 7.2: CPVC and PVC Elbows

20 107774-01 - 9/17
VII. Venting A. Vent System Design (continued)
8. 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3”Polyuehorizontallyevery39”.Supportverticalrunsof3”Polyueevery16ft.
• Support DuraVent FasNSeal horizontally every 6ft or less. Support vertical runs at the base and every 12ft or less.
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.
9. 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ttings 
are not permitted.
• Whenproperlyassembled,expansionofPolyPro,Polyue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.
10. 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.
11. 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.