AHRI APEX Service manual

104707-03 - 4/14 Price - $5.00
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.
INSTALLATION, OPERATING AND
SERVICE INSTRUCTIONS FOR
APEX™
CONDENSING HIGH EFFICIENCY
DIRECT VENT
GAS - FIRED HOT WATER BOILER
9700609

2
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 Apex™ 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.
WARNING
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.

3
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) feet 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) feet 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.

4
TABLE OF CONTENTS
I. Product Description, Specications and Dimensional Data...................... 5
II. Unpacking Boiler........................................................................................ 10
III. Pre-Installation and Boiler Mounting.......................................................... 11
IV. Venting...................................................................................................... 15
A. General Guidelines............................................................................... 15
B. CPVC/PVC Venting.............................................................................. 20
C. Polypropylene Venting......................................................................... 26
D. Stainless Steel Venting........................................................................ 29
E. Removing the Existing Boiler............................................................... 32
F. Multiple Boiler Installation Venting....................................................... 32
V. Condensate Disposal................................................................................. 35
VI. Water Piping and Trim............................................................................... 37
VII. Gas Piping ............................................................................................... 51
VIII. Electrical ................................................................................................... 55
IX. System Start-Up ....................................................................................... 67
X. Operation...................................................................................................... 75
A. Overview.............................................................................................. 75
B. Supply Water Temperature Regulation................................................ 76
C. Boiler Protection Features.................................................................... 77
D. Multiple Boiler Control Sequencer........................................................ 78
E. Boiler Sequence of Operation.............................................................. 79
1. Normal Operation........................................................................... 79
2. Using the Display............................................................................ 80
F. Viewing Boiler Status.......................................................................... 81
1. Status Screens............................................................................... 81
2. Detail Screens................................................................................ 82
3. Multiple Boiler Sequencer Screens................................................ 83
G. Changing Adjustable Parameters........................................................ 84
1. Entering Adjust Mode.................................................................... 84
2. Adjusting Parameters.................................................................... 84
XI. Service and Maintenance ........................................................................ 95
XII. Troubleshooting........................................................................................ 101
XIII. Repair Parts ............................................................................................. 106
Appendix A - Figures................................................................................ 118
Appendix B - Tables.................................................................................. 120
Warranty...........................................................................................Back Page

5
I. Product Description, Specications and Dimensional Data
Apex Series boilers are condensing high efciency gas-red
direct vent hot water boilers designed for use in forced hot
water space or space heating with indirect domestic hot
water heating systems, where supply water temperature
does not exceed 210°F. These boilers have special coil
type stainless steel heat exchangers, constructed, tested and
stamped per Section IV ‘Heating Boilers’ of ASME Boiler
and Pressure Vessel Code, which provide a maximum heat
transfer and simultaneous protection against ue gas product
corrosion. These boilers are not designed for use in gravity
hot water space heating systems or systems containing
signicant amount of dissolved oxygen (swimming pool
water heating, direct domestic hot water heating, etc.).
Table 1B: Dimensions (See Figures 1A, 1B, 1C and 1D)
Dimension
Boiler Model
APX425 APX525 APX625 APX725 APX825
A - Inch
(mm)
28-7/8
(734)
44-7/8
(1140)
50-1/4
(1276)
50-1/4
(1276)
54-9/16
(1384)
B - Inch
(mm)
6-3/16
(157)
22-1/8
(562) N/A N/A 28-3/8 (724)
C - Inch
(mm)
13-1/16
(332)
29
(737)
24
(610)
24
(610)
34-1/4
(876)
D - Inch
(mm)
23-3/4
(602)
39-11/16
(1008)
38-7/8
(987)
38-7/8
(987)
48-1/16
(1226)
E - Inch
(mm)
15-13/16
(402)
29-3/8
(752)
31-5/8
(803)
31-5/8
(803)
33-13/16
(864)
Gas Inlet F
(FPT) 3/4” 3/4” 1” 1” 1”
Return G 1-1/2” (FPT) 2” (MPT) 2” (MPT) 2” (MPT)
Supply H 1-1/2” (FPT) 2” (MPT) 2” (MPT) 2” (MPT)
Condensate Drain J Factory Provided Socket End Compression Pipe Joining Clamp for 3/4” Schedule 40
PVC Pipe
Boiler Two-Pipe
CPVC/PVC Vent Connector
(Figures 1A, 1B, 1C and 1D) -
Inch
4 x 4 6 x 6 6 x 6 6 x 6
Table 1A: Specications
Specication Boiler Model
APX425 APX525 APX625 APX725 APX825
Altitude (ft. above sea level) 0-4500 0-4500 0-2000 0-2000 0-4500
Fuel Shipped for Natural Gas, Field
Converted for LP Gas
Shipped for Natural Gas or Shipped for LP Gas
(no Field Conversion)
Max. Allowable Water Temperature (°F) 210 210 210 210 210
Max. Allowable Working Pressure (psi) 160 160 160 160 160
Factory Supplied Safety Relief Valve (psi)*50 50 60 60 60
Boiler Water Volume (gal.) 3.4 4.2 5.5 5.5 5.0
Heat Transfer Area (sq. ft.) 41.8 50.8 76.2 76.2 65.3
Approx. Shipping Weight (lb.) 304 350 455 455 430
* Optional 80 psi and 100 psi safety relief valves are available for all models.

6
I. Product Description, Specications and Dimensional Data (continued)
Figure 1A: Apex - Model APX425

7
Figure 1B: Apex - Model APX525
I. Product Description, Specications and Dimensional Data (continued)

8
I. Product Description, Specications and Dimensional Data (continued)
Figure 1C: Apex - Models APX625 and APX725

9
I. Product Description, Specications and Dimensional Data (continued)
Figure 1D: Apex - Model APX825

10
I. Product Description, Specications and Dimensional Data (continued)
Table 2: Ratings
Apex Series Gas-Fired Boilers
Model
Number
Input (MBH) Gross Output
(MBH)
Net Ratings Water 1
(MBH)
Thermal
Efciency (%)
Combustion
Efciency (%)
Min. Max.
APX425 80 399 375 326 94.1 94.5
APX525 100 500 475 413 95.0 95.0
APX625 125 625 594 516 95.0 96.0
APX725 145 725 689 599 95.0 95.0
APX825 160 800 760 661 95.0 93.0
Ratings shown are for installations at sea level and elevations up to 2000 ft. For elevations above 2000 ft., the boiler will naturally
derate by 2.5% for each 1000 ft. above sea level.
1 Net AHRI Water Ratings based on allowance of 1.15. Consult manufacturer before selecting boiler for installations having
unusual piping and pickup requirements, such as intermittent system operation, extensive piping systems, etc.
II. Unpacking Boiler
NOTICE
Do not drop boiler.
A. Move boiler to approximate installed position.
B. Remove all crate fasteners.
C. Lift and remove outside container.
D. Remove boiler from cardboard positioning sleeve
on shipping skid.
E. Move boiler to its permanent location.

11
WARNING
Explosion Hazard. Asphyxiation Hazard.
Electrical Shock Hazard. Installation of this
boiler should be undertaken only by trained
and skilled personnel from a qualied service
agency. Follow these instructions exactly.
Improper installation, adjustment, service,
or maintenance can cause property damage,
personal injury or loss of life.
NOTICE
Due to the low water content of the boiler, mis-
sizing of the boiler with regard to the heating
system load will result in excessive boiler
cycling and accelerated component failure.
Thermal Solutions DOES NOT warrant failures
caused by mis-sized boiler applications. DO
NOT oversize the boiler to the system. Multiple
boiler installations greatly reduce the likelihood
of boiler oversizing.
WARNING
Asphyxiation Hazard.
Models APX425 and APX525:
Apply supplied dielectric grease to gasket inside
vent section of two-pipe vent connector. Failure
to apply the grease could result in ue gas leaks
from gasket rupture during vent pipe installation
or gasket deterioration due to condensate
exposure.
A. Installation must conform to the requirements
of the authority having jurisdiction in or, in the absence
of such requirements, to the National Fuel Gas Code,
ANSI Z223.1/NFPA 54, and/or Natural Gas and
Propane Installation Code, CAN/CSA B149.1.
Where required by the authority having jurisdiction, the
installation must conform to the Standard for Controls
and Safety Devices for Automatically Fired Boilers,
ANSI/ASME CSD1.
B. Boileriscertiedfor installation on combustible
ooring. Do not install boiler on carpeting.
C. Provide clearance between boiler jacket and
combustible material in accordance with local re
ordinance. Refer to Figure 2 for minimum listed
clearances from combustible material. Recommended
service clearance is 24 in. (610 mm) from left side,
front, top and rear of the boiler. Recommended front
clearance may be reduced to the combustible material
clearance providing:
III. Pre-Installation and Boiler Mounting
1. Access to boiler front is provided through a door or
removable front access panel.
2. Access is provided to the condensate trap located
underneath the heat exchanger.
3. Access is provided to thermal link located at boiler
rear.
D. Protect gas ignition system components
from water (dripping, spraying, rain, etc.) during
boiler operation and service (circulator replacement,
condensate trap, control replacement, etc.).
E. Provide combustion and ventilation air in
accordance with applicable provisions of local building
codes, or: USA - National Fuel Gas Code, ANSI
Z223.1/NFPA 54, Air for Combustion and Ventilation;
Canada - Natural Gas and Propane Installation Code,
CAN/CSA-B149.1, Venting Systems and Air Supply for
Appliances.
WARNING
Asphyxiation Hazard. Adequate combustion and
ventilation air must be provided to assure proper
combustion. Install combustion air intake per
Section IV “Venting”.
F. The boiler should be located so as to minimize
the length of the vent system. The combustion air
piping must terminate where outdoor air is available for
combustion and away from areas that may contaminate
combustion air. In particular, avoid areas near chemical
products containing chlorines, chlorouorocarbons,
paint removers, cleaning solvents and detergents.
Avoid areas containing saw dust, loose insulation bers,
dry wall dust etc.
NOTICE
Avoid operating this boiler in an environment
where sawdust, loose insulation bers, dry wall
dust, etc. are present. If boiler is operated under
these conditions, the burner interior and ports
must be cleaned and inspected daily to insure
proper operation.
G. General.
1. Apex boilers are intended for installations in an
area with a oor drain, or in a suitable drain pan to
prevent any leaks or safety relief valve discharge
resulting in property damage.
2. Apex boilers are not intended to support external
piping and venting. All external piping and venting
must be supported independently of the boiler.
3. Apex boilers must be installed level to prevent
condensate from backing up inside the boiler.

12
Figure 2: Clearances To Combustible and Non-combustible Material
III. Pre-Installation and Boiler Mounting G. General (continued)
Boiler Clearances to Combustible (and Non-
Combustible) Material:
Models APX425 and APX525:
These boilers are listed for closet installation with the
following minimum clearances – Top = 1 in. (25 mm),
Front = 1 in. (25 mm), Left Side = 10 in. (250 mm),
Right Side = 2 in. (50 mm), Rear = *6 in. (150 mm)
Models APX625, APX725 and APX825:
These boilers are listed for alcove installation with the
following minimum clearances – Top = 1 in. (25 mm),
Front = Open, Left Side = 10 in. (250 mm), Right Side
= 2 in. (50 mm), Rear = *6 in. (150 mm)
* Note:
When boiler is vented vertically, the minimum
clearance from the rear of the jacket is increased
to 18 in. (460 mm) with a short radius 90° elbow
provided in order to provide adequate space at boiler
rear for installation of vent and air intake piping and
service access.
Boiler Service Clearances – Applicable to all Boiler
Models:
Top = 24 in. (610 mm), Front = 24 in. (610 mm), Left
Side = 24 in. (610 mm), Right Side = 24 in. (610 mm),
Rear = 24 in. (610 mm)
The above clearances are recommended for service
access but may be reduced to the Combustible Material
Clearances provided:
1. The boiler front is accessible through a door.
2. Access is provided to the condensate trap located on
the left side of boiler.
3. Access is provided to thermal link located at the
boiler rear.
4. Boiler Installation:
a. For basement installation provide a solid level
base such as concrete where oor is not level or
where water may be encountered on the oor
around boiler. Floor must be able to support
weight of boiler, water and all additional system
components.
b. Boiler must be level to prevent condensate from
backing up inside the boiler.
c. Provide adequate space for condensate piping or
a condensate pump if required.
Listed Direct
Vent System
Vent Pipe
Material
Vent
Pipe
Direction
Enclosure
Vent Pipe
Nominal
Diameter
Minimum
Clearance to
Combustible
Material
Factory Standard
Two-Pipe CPVC/PVC Vent and PVC
Combustion Air Intake
* CPVC/PVC
Vertical or
Horizontal
Unenclosed
at all Sides
4 in. (100 mm)
or
6 in.( 150 mm)
1 in. (25 mm)
Available Optional
Two-Pipe Rigid Polypropylene Vent
(or, Flexible Polypropylene Liner
for Vertical Venting only) and Rigid
Polypropylene or PVC Combustion
Air Intake
Pipe Rigid
Polypropylene
Vent (or,
Flexible
Polypropylene
Liner for
Vertical
Venting only)
4 in. (100 mm)
or (110 mm)
or
6 in. (150 mm)
or (160 mm)
1 in. (25 mm)
Available Optional
Two-Pipe Stainless Steel Vent and
Galvanized Steel or PVC Combustion
Air Intake
Stainless
Steel
4 in. (100 mm)
or
6 in.( 150 mm)
1 in. (25 mm)
* Do not enclose PVC venting - use CPVC vent pipe in enclosed spaces, or to penetrate through
combustible or non-combustible walls.

13
III. Pre-Installation and Boiler Mounting G. General (continued)
H. Boiler Stacking
1. For installations with unusually high space heating
and/or domestic hot water heating loads, where
employing 2 Apex boilers will offer the benets
of greater operational efciency, oor space
savings and boiler redundancy, Apex boilers may
be installed stacked maximum one boiler on top
of another. Refer to Table 3 “Apex Boiler Model
Stacking Combinations” for details.
Table 3: Apex Boiler Model Stacking
Combinations
Bottom Boiler
Model Top Boiler Model
APX425 APX425
APX525 APX425 or APX525
APX625 APX425, APX525 or APX625
APX725 APX425, APX525, APX625 or APX725
APX825 APX425, APX525, APX625, APX725 or APX825
2. To eld assemble individual Apex boilers into a
stackable conguration, use the steps below:
a. Position the bottom boiler rst. Refer to Sections
II “Unpacking Boiler” and III “Pre-Installation
& Boiler Mounting” of the manual for details.
Always position higher input boiler model as
bottom boiler.
b. Each Apex boiler is factory packaged with
2 stacking boiler attachment brackets (P/N
101679-01) and the bracket mounting hardware
[six (6) self-drilling hex washer head plated #8
x ½” long screws, P/N 80860743]. Locate and
remove the brackets and the hardware. The
stacking boiler attachment bracket has three
7/32” diameter holes punched in a triangular
pattern. See Figure 3 “Stacking Boiler
Attachment Bracket Placement”.
c. Apex boiler left and right side panels have a
series of dimples at panel top and bottom. These
dimples are positioning dimples for stacking
boiler attachment bracket mounting screws. Side
panel bottom positioning dimples are evenly
spaced from boiler front and back, while side
panel top positioning dimples follow specic
pattern to compensate for Apex boiler model
variable depth.
d. Position the upper boiler on top of the bottom
boiler and align boiler front doors and sides ush
with each other.
• Place rst stacking boiler attachment bracket
onto the upper boiler left side panel, at the
panel lower left corner and align bracket two
upper holes with corresponding side panel
lower dimples.
• The remaining lower bracket hole must align
with a matching bottom boiler left side panel
top positioning dimple.
• Once bracket holes and side panel dimple
alignment is veried, attach the bracket to
top and bottom boiler left side panels with
the mounting screws.
e. Repeat above procedure to install second
stacking boiler attachment bracket and secure the
stacked boiler right side panels together at the
front right corner.
f. Install the third stacking boiler attachment
bracket to secure top and bottom boiler left side
panels at the rear left corner. Align the bracket
holes with corresponding positioning dimples in
the top boiler and bottom boiler left side panels,
then secure bracket with the screws.
g. Repeat above procedure to install the fourth
stacking boiler attachment bracket to secure
stacked boiler right side panels at the rear right
corner.
3. When installing stackable boiler combinations
observe the following guidelines:
a. Venting - Top and bottom boilers must have their
individual vent piping and vent terminals.
WARNING
Asphyxiation Hazard. No common manifold
venting is permitted. Each boiler must have its
own individual vent and combustion air pipes
and terminals.
For sidewall venting individual model vent
terminals must terminate no closer than 12
in. (300 mm) horizontally and 3 ft. (900 mm)
vertically from each other in order to prevent
combustion air contamination. For vertical
through the roof venting, individual vertical
vent terminals, if level with each other, must
be spaced no closer than 12 in. (300 mm)
horizontally. If vertical terminals cannot end in
one plane, they must be spaced no closer than 3
ft. (900 mm) horizontally.
Follow instructions in Section IV “Venting”
of the manual for specics of individual boiler
vent termination. Follow instructions in Section
V “Condensate Disposal” for each individual
boiler ue gas condensate line construction and
condensate disposal. Terminating individual
boiler condensate lines into common pipe prior
to drain disposal is permissible, providing
common pipe has sufcient ow capacity
to handle combined condensate volume of
stackable combination.

14
III. Pre-Installation and Boiler Mounting G. General (continued)
b. Gas Piping - Follow instructions in Section
VII “Gas Piping” of the manual for sizing
and installation of an individual boiler. When
common gas piping is sized, insure it will
have adequate capacity for combined input
(CFH gas ow) of the selected stackable boiler
combination.
c. Water Piping and Trim - Follow instructions
in Section VI “Water Piping and Trim” of the
manual for system piping and boiler secondary
piping selection/sizing based on combined
heating capacity and/or gross output of the
selected stackable boiler combination. Follow
instructions of Section VI “Water Piping
and Trim” for each individual boiler trim
installation.
d. Electrical - Follow instructions in Section VIII
“Electrical” of the manual to wire individual
boilers.
Figure 3: Stacking Boiler Attachment Bracket Placement

15
IV. Venting
A. General Guidelines
1. Listed Vent/Combustion Air Systems
a. Install vent system in accordance with National
Fuel Gas Code, ANSI Z223.1/NFPA 54 or
Natural Gas and Propane Installation Code,
CAN/CSA B149.1 Installation Code for Canada,
or, applicable provisions of local building codes.
Contact local building or re ofcials about
restrictions and installation inspection in your
area.
b. The Apex is a Direct Vent (sealed combustion)
boiler. Combustion air must be supplied directly
to the burner enclosure from outdoors and ue
gases must be vented directly outdoors.
c. The following combustion air/vent system
options are listed for use with the Apex boilers
(refer to Table 4):
i. Two-Pipe CPVC/PVC Vent/Combustion
Air System - Separate CPVC/PVC pipe
serves to expel products of combustion and
separate PVC pipe delivers fresh outdoor
combustion air. Refer to Part B for specic
details.
ii. Two-Pipe Polypropylene Vent/Combustion
Air System - Separate rigid or exible
polypropylene pipe serves to expel
products of combustion and separate rigid
polypropylene or PVC pipe delivers fresh
outdoor combustion air. Refer to Part C for
specic details.
iii. Two-Pipe Stainless Steel Vent/Combustion
Air System - Separate stainless steel pipe
serves to expel products of combustion
and separate PVC or galvanized steel pipe
delivers fresh outdoor combustion air. Refer
to Part D for specic details.
2. Vent/Combustion Air Piping
a. Do not exceed maximum vent/combustion air
lengths listed in Table 5. Vent/combustion air
length restrictions are based on equivalent length
of vent/combustion air pipe (total length of
straight pipe plus equivalent length of ttings).
Table 6A lists equivalent lengths for ttings.
Do not include vent/combustion air terminals
in equivalent feet calculations. Use vent/
combustion air equivalent length worksheet
provided in Table 6B.
b. Maintain minimum clearance to combustible
materials. See Figure 2 for details.
c. Enclose vent passing through occupied or
unoccupied spaces above boiler with material
having a re resistance rating at least equal to the
rating of adjoining oor or ceiling.
Note: For one or two family dwellings, re
resistance rating requirement may not need to be
met, but is recommended.
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 use a barometric damper, draft hood or vent damper with this boiler.
Do not locate vent termination under a deck.
Do not locate vent termination where exposed to prevailing winds.
Do not locate combustion air termination where chlorines, chlorouorocarbons (CFC’s), petroleum
distillates, detergents, volatile vapors or other chemicals are present. Severe boiler corrosion and
failure will result.
Use outdoor air for combustion. Do not obtain combustion air from within the building.
Use specied vent and combustion air pipe diameters. Do not reduce specied diameters of vent and
combustion air piping.
Do not interchange vent systems or materials unless otherwise specied.
Do not apply thermal insulation to vent pipe or ttings.
Moisture and ice may form on surface around vent termination. To prevent deterioration, surface must
be in good repair (sealed, painted, etc.).
Do not allow low spots in the vent where condensate may pool.
The CPVC vent materials supplied with this boiler do not comply with Natural Gas and Propane
Installation Code, CAN/CSA 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 either
stainless steel Special Gas vent or a listed ULC S636 Class IIB venting system.

16
Table 4: Vent/Combustion Air System Options
IV. Venting A. General Guidelines (continued)
Approved Direct
Vent System
Vent
Material Orientation Termination Description Figures Component Table Part
Factory Standard
Two-Pipe,
CPVC/PVC Vent and
PVC Air Intake
CPVC/PVC
Horizontal
Standard
(through sidewall)
The system includes separate CPVC vent
pipe and PVC air intake pipe terminating
through sidewall with individual
penetrations for the vent and air intake
piping and separate terminals (tees).
4, 5A, 5B
9 through 13 7A
B.
Optional
Snorkel
(through sidewall)
Same as above but separate snorkel type
terminals.
4, 6A, 6B
9 through 13 7B
Optional
Vertical
Vertical
(through roof)
The system includes separate CPVC vent
pipe and PVC air intake pipe terminating
through roof with individual penetrations
for the vent and air intake piping and
separate vertical terminals.
7 through 11
13 7C
Available Optional
Two-Pipe, Rigid
Polypropylene Vent (or
Flexible Polypropylene
Liner for Vertical
venting only) and Rigid
Polypropylene or PVC
Pipe Air Intake
Rigid
Polypropylene
(or Flexible
Polypropylene
Liner for vertical
Venting only)
Horizontal
Standard
(through sidewall)
The system includes separate Rigid
Polypropylene vent pipe and Rigid
Polypropylene or PVC air intake pipe
terminating through sidewall with individual
penetrations for the vent and air intake
piping and separate terminals (tees).
4, 5A, 5B
9, 12, 14 10A, 10B
C.
Optional Snorkel
(through sidewall)
Same as above but separate snorkel type
terminals.
4, 6A, 6B
9, 12, 14 10A, 10B
Optional
Vertical
Vertical
(through roof or
chimney/chase)
The system includes separate Flexible
Polypropylene vent liner and Rigid
Polypropylene vent pipe combination for
venting and Rigid Polypropylene or PVC
air intake pipe terminating through roof
with individual penetrations for the vent
and air intake and separate terminals.
7 through 9
14, 15 10A, 10B
Available Optional
Two-Pipe,
Stainless Steel Vent and
PVC/Galvanized Steel
Air Intake
Stainless Steel
Horizontal
Standard
(through sidewall)
The system includes separate stainless
steel vent pipe and PVC/galvanized
steel air intake pipe terminating through
sidewall with individual penetrations for
the vent and air intake piping and separate
terminals.
4, 5A, 5B
9, 12, 16
11A, 11B D.
Optional Snorkel
(through sidewall) Same as above but separate snorkel type
terminals.
4, 6A, 6B
9, 12, 16
Vertical Vertical (through
roof)
The system includes separate stainless
steel vent pipe and PVC/galvanized
steel air intake pipe terminating through
roof with individual penetrations for the
vent and air intake piping and separate
terminals.
7 through 9
16
Table 5: Vent/Combustion Air Pipe Length – Two-Pipe Direct Vent System Options
CPVC/PVC
Polypropylene (PP) or Polypropylene (PP)/PVC
Stainless Steel/PVC or Galvanized Steel)
Boiler
Model
Combustion Air Vent
Nominal
Pipe
Diameter
Minimum
Equivalent
Length
Maximum
Equivalent
Length
Nominal
Pipe
Diameter
Minimum
Equivalent
Length
Maximum
Equivalent
Length
APX425 4 in.
(100 mm or 110 mm)
2.5 ft.
(760 mm)
100 ft.
(30.5 m)
4 in.
(100 mm or 110 mm)
2.5 ft.
(760 mm)
100 ft.
(30.5 m)
APX525
APX625
6 in.
(150 mm or 160 mm)
2.5 ft.
(760 mm)
200 ft.
(61.0 m)
6 in.
(150 mm or 160 mm)
2.5 ft.
(760 mm)
200 ft.
(61.0 m)
APX725
APX825

17
Figure 4: Location of Vent Terminal Relative to Windows, Doors, Grades, Overhangs, Meters and Forced Air
Inlets - Two-Pipe System Vent Terminal (Shown), Two-Pipe System Air Intake Terminal (Not Shown)
IV. Venting A. General Guidelines (continued)
d. Slope horizontal vent pipe minimum 1/4 in/ft
(21 mm/m) downward towards the boiler.
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.
e. If possible, slope horizontal combustion air
pipe minimum 1/4 in/ft (21 mm/m) downward
towards terminal. If not, slope towards boiler.
f. Use noncombustible ¾ in. pipe strap to support
horizontal runs and maintain vent location and
slope while preventing sags in pipe. Do not
restrict thermal expansion or movement of vent
system. Maximum support spacing 4 ft. (1.2 m).
Avoid low spots where condensate may pool.
Do not penetrate any part of the vent system with
fasteners.
Les instructions d´installation du système
d´évacuation doivent préciser que les sections
horizontales doivent être supportées pour
Table 6A: Vent System and Combustion Air System Components Equivalent Length
vs. Component Nominal Diameter
Vent or Combustion Air System
Component Description
Equivalent Length for Vent or Combustion Air System Component
vs. Component Nominal Diameter
Component Nominal Diameter 4 in. (100 mm or 110 mm) 6 in. (150 mm or 160 mm)
90° Elbow (Short Radius) 13 ft. (4.0 m) 22 ft. (6.7 m)
45° Elbow (Short Radius) 4.5 ft. (1.4 m) 7.5 ft. (2.3 m)
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.
g. For multiple boiler installations with vertical
roof terminals, separate vent pipes from multiple
boilers may be piped through a common conduit
or chase so that one roof penetration may be
made.
3. Vent/Combustion Air Terminals
Install venting system components on exterior
of building only as specically required by these
instructions (refer to Figure 4).

18
IV. Venting A. General Guidelines (continued)
a. Use only listed vent/combustion air terminals.
i. Horizontal Sidewall Venting: For models
APX425 and APX 525, use tee terminals for
both vent and combustion air as shown in
Figure 5A. For models APX625, APX725,
and APX825, use tee terminals or 90°
elbows for both vent and combustion air as
shown in Figure 5A or Figure 5B. Alternate
snorkel terminations are shown in Figure 6A
and Figure 6B.
ii. Vertical Roof Venting: Use straight
coupling on vent and two 90° elbows turned
downwards for combustion air as shown in
Figure 7 and Figure 8.
b. Maintain correct clearance and orientation
between vent and combustion air terminals.
Table 6B: Vent/Combustion Air Equivalent Length Calculation Work Sheet
Combustion Air Vent
90° Elbow(s) (Installer Supplied) 90° Elbow(s) (CPVC Supplied with Boiler)
Nominal Diameter Quantity
(Pc)
Equivalent
Length, per Pc
Subtotal,
Equivalent
Length (A)
Nominal Diameter Quantity
(Pc)
Equivalent Length,
per Pc
Subtotal,
Equivalent
Length (D)
4 in.
(100 mm or 110 mm) 13 ft. (4.0 m) 4 in. (100 mm or 110 mm) 1 13 ft. (4.0 m) 13 ft. (4.0 m)
6 in.
(150 mm or 160 mm) 22 ft. (6.7 m) 6 in. (150 mm or 160 mm) 1 22 ft. (6.7 m) 22 ft. (6.7 m)
45° Elbow(s) (Installer Supplied) 90° Elbow(s) (Installer Supplied)
Nominal Diameter Quantity
(Pc)
Equivalent
Length, per Pc
Subtotal,
Equivalent
Length (B)
Nominal Diameter Quantity
(Pc)
Equivalent Length,
per Pc
Subtotal,
Equivalent
Length (A)
4 in.
(100 mm or 110 mm) 4.5 ft. (1.4 m) 4 in. (100 mm or 110 mm) 13 ft. (4.0 m)
6 in.
(150 mm or 160 mm) 7.5 ft. (2.3 m) 6 in. (150 mm or 160 mm) 22 ft. (6.7 m)
Straight Pipe, (Installer Supplied) 45° Elbow(s) (Installer Supplied)
Nominal Diameter
Quantity
Length,
ft or m
Equivalent
Length,
ft/ft or m/m
Subtotal,
Equivalent
Length (C)
Nominal Diameter
Quantity
Length,
ft or m
Equivalent Length,
ft/ft or m/m
Subtotal,
Equivalent
Length (B)
4 in.
(100 mm or 110 mm) 14 in. (100 mm or 110 mm) 4.5 ft. (1.4 m)
6 in.
(150 mm or 160 mm) 16 in. (150 mm or 160 mm) 7.5 ft. (2.3 m)
* Total Equivalent Length (A+B+C) = 2.5 Ft. (760 mm) Straight Pipe, (CPVC Supplied with Boiler)
*Notes:
1. Calculated total equivalent length cannot exceed
maximum equivalent length shown in Table 5.
2. Vent and combustion air terminals do not count towards
total equivalent length.
3. Pressure drop for exible polypropylene liner is 20%
greater than for rigid pipe. Multiply measured exible
polypropylene liner length by 1.2 to obtain equivalent
length.
Example
Measure length of exible polypropylene liner = 35 ft.
Equivalent length of exible polypropylene liner = 35 ft.
x 1.2 = 42 ft.
4. Maximum equivalent length of exible polypropylene liner
is 48 ft. (14.6 m).
5. All elbows referenced are short radius.
Nominal Diameter
Quantity
Length,
ft or m
Equivalent Length,
ft/ft or m/m
Subtotal,
Equivalent
Length (E)
4 in.
(100 mm or 110 mm)
2.5 ft.
(0.76 m) 12.5 ft. (0.76 m)
6 in.
(150 mm or 160 mm)
2.5 ft.
(0.76 m)
1 2.5 ft.
(0.76 m)
Straight Pipe, (Installer Supplied)
Nominal Diameter
Quantity
Length,
ft
Equivalent Length,
ft/ft
Subtotal,
Equivalent
Length (C)
4 in.
(100 mm or 110 mm) 1
6 in.
(150 mm or 160 mm) 1
* Total Equivalent Length (A+B+C+D+E) =
Figure 5A: Direct Vent - Sidewall Tee Terminations

19
i. Space centerlines of vent and combustion
air terminals minimum 12 in. (300 mm)
apart. More than 12 in. (300 mm) spacing is
recommended.
ii. If possible, locate vent and combustion
air terminals on the same wall to prevent
nuisance shutdowns. If not, boiler may
be installed with roof vent terminal and
sidewall combustion air terminal.
iii. When installed on the same wall, locate
vent terminal at same height or higher than
combustion air terminal.
iv. When using tee terminals, do not locate vent
terminal directly above air intake as dripping
condensate may freeze on and block intake.
c. Locate bottom of vent and combustion air
terminals at least 12 in. (300 mm) [18 in.
(460 mm) in Canada] above the normal snow line
and at least 12 in. (300 mm) above grade level.
d. Locate vent and combustion air terminals at
least 12 in. (300 mm) from any door, window, or
gravity inlet into the building.
e. Do not install vent terminal directly above
windows or doors.
f. Locate bottom of vent terminal at least 3 ft. (900
mm)above any forced air inlet located within 10
ft. (3.0 m).
g. If window and/or air inlet is within 4 ft. (1.2 m)
of an inside corner, maintain at least 6 ft. (1.8 m)
spacing between terminal and adjoining wall of
inside corner.
h. Locate bottom of vent terminal at least 7 ft.
(2.1 m) above a public walkway.
i. Maintain minimum clearance of at least 4 ft.
(1.2 m) [3 ft. (900 mm)in Canada] horizontally
between vent terminal and gas meters, electric
meters, regulators, and relief equipment. Do
not install vent terminal above or below this
equipment.
j. Do not locate the vent terminal under decks or
similar structures.
k. For horizontal wall terminals, maintain minimum
clearance of at least 12 in. (300 mm) vertically
between vent terminal and eave, soft, or roof
overhang 12 in. (300 mm) or less wide. If eave,
soft, or roof overhang is wider than 12 in. (300
mm), increase vertical clearance to 5 ft. (1.5 m)
to avoid ue vapor condensation. Maximum
width of overhang is 3 ft. (900 mm).
l. Maintain minimum 12 in. (300 mm) horizontal
spacing between vent terminal and a building
corner.
m. Under certain conditions, water in the ue gas
may condense, and possibly freeze, on objects
around the terminal including on the structure
IV. Venting A. General Guidelines (continued)
Figure 6B: Direct Vent - Optional Vent and
Combustion Air Sidewall Snorkel Terminations
Figure 5B: Direct Vent - Sidewall Elbow Terminations,
Size 625 through 825 Only
Figure 6A: Direct Vent - Optional Vent Sidewall
Snorkel Termination

20
IV. Venting A. General Guidelines - B. CPVC/PVC Venting (continued)
Figure 7: Direct Vent - Vertical Terminations
Extend vent/combustion air piping to maintain minimum vertical (‘X’) and minimum horizontal (‘Y’) distance
of 12 in. (300 mm) [18 in. (460 mm) Canada] from roof surface. Allow additional vertical (‘X’) distance for
expected snow accumulation.
itself. If these objects are subject to damage by
ue gas condensate, they should be moved or
protected.
n. If possible, install the vent and combustion air
terminals on a wall away from the prevailing
wind. Reliable operation of this boiler cannot be
guaranteed if terminals are subjected to winds in
excess of 40 mph (64 km/hr).
o. Do not locate combustion air terminal in areas
that might contain combustion air contaminates,
such as near swimming pools.
p. For multiple boiler installations with horizontal
wall terminals, maintain minimum 12 in.
(300 mm) horizontal distance between adjacent
boiler vent terminals. Maintaining greater
spacing is recommended to avoid frost damage
to building surfaces where vent terminations are
placed.
q. For multiple boiler installations with vertical
roof terminals, maintain minimum 12 in.
(300 mm) horizontal distance between adjacent
boiler vent terminals.
B. CPVC/PVC Venting
WARNING
Asphyxiation Hazard. Failure to follow
these instructions could cause products of
combustion to enter the building, resulting
in severe property damage, personal injury,
or death.
Use all CPVC vent components (supplied
with boiler) for near-boiler vent piping before
transitioning to Schedule 40 PVC pipe
(ASTM 2665) components for remainder of
vent system.
Use CPVC vent components within any
interior space where air cannot circulate
freely, including through vertical or
horizontal chase ways, inside a stud wall, in
closets, and through wall penetrations.
The use of cellular core PVC (ASTM
F891), cellular core CPVC or Radel
(polyphenolsulfone) is prohibited.
All condensate that forms in the vent must
be able to drain back to the boiler.
Figure 8: Direct Vent - Vertical Terminations
with Sloped Roof