Reznor CAUA Installation and operating instructions

Shown with model ACU
cased cooling coil.
Revision: CAUA-IOM (05-22) 164771-B
MODEL CAUA
INDOOR UPFLOW HEATER INSTALLATION, OPERATION,
AND MAINTENANCE
Supersedes: I-CAUA (06-21) 164771-A
⚠ DANGER ⚠
FIRE OR EXPLOSION HAZARD
• Failure to follow safety warnings exactly could result in serious injury, death, or property
damage.
• Improper installation,adjustment,alteration, service,or maintenance can cause serious injury,
death, or property damage.
• Installation and service must be performed by a qualified installer, service agency, or the gas
supplier.
• Be sure to read and understand the installation, operation, and service instructions in this
manual.
• Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this or
any other appliance.
WHAT TO DO IF YOU SMELL GAS
• Do not try to light any appliance.
• Do not touch any electrical switch; do not use any phone in your building.
• Leave the building immediately.
• Immediately call your gas supplier from a phone remote from the building. Follow the gas
supplier’s instructions.
• If you cannot reach your gas supplier, call the fire department.
DO NOT DESTROY. PLEASE READ CAREFULLY. KEEP IN A SAFE PLACE FOR FUTURE REFERENCE.

2CAUA-IOM (05-22) 164771-B
TABLE OF CONTENTS
GENERAL INFORMATION .............................................................................4
References ........................................................................................4
Important Safety Information........................................................................... 4
Installation Codes ...................................................................................5
Warranty ..........................................................................................5
Dimensions ........................................................................................6
Weights........................................................................................... 7
Clearances ........................................................................................7
Location ..........................................................................................7
Hazards of Chlorine ................................................................................. 7
INSTALLATION ......................................................................................8
Uncrating/Unpacking................................................................................. 8
Shipped-Separate Parts .............................................................................. 8
Positioning and Mounting ............................................................................. 8
Duct Connections ................................................................................... 8
Requirements and Suggestions for Connecting and Installing Ducts ............................................ 9
Inlet Air Ductwork ................................................................................9
Discharge Air Ductwork ...........................................................................10
Venting/Combustion Air Connections ...................................................................12
Venting/Combustion Air Requirements for Power-Vented Installations ......................................12
Venting/Combustion Air Requirements for Separated-Combustion Installations ...............................19
Vertical Vent Terminal for Separated-Combustion Installations (Option CC2) .................................24
Horizontal Vent Terminal for Separated-Combustion Installations (Option CC6) ...............................29
Piping Connections.................................................................................32
Gas Supply Pressure.............................................................................32
Gas Supply Piping...............................................................................33
Supply Piping Connections ........................................................................33
Condensate Drain Installation ......................................................................34
Electrical Connections ..............................................................................35
Electrical Supply and Control Wiring .................................................................35
Thermostat Wiring ...............................................................................36
CONTROLS ........................................................................................36
Thermostat .......................................................................................37
Combustion Air Proving Switch........................................................................37
Flame Rollout Switch ...............................................................................38
Limit Control ......................................................................................38
Combination Gas Valve .............................................................................38
Venter Assembly...................................................................................38
Ignition System ....................................................................................38
Dirty Filter Switch ..................................................................................39
Transformer ......................................................................................39
Belts, Blowers, and Drives ...........................................................................39
Belt Drive with Optional Variable Frequency Drive .........................................................39
Blower Compartment Door Switch .....................................................................39
Ductstat (Two-Stage, Makeup Air, Option AG3) ...........................................................39
Inlet Air Dampers ..................................................................................40
Two-Position Damper Motor ..........................................................................40
Modulating Damper Motor ...........................................................................40
Modulating Damper Motor with Logic Module.............................................................40
Potentiometer .....................................................................................40
Return Air Controller ................................................................................40
Mixed Air Controller ................................................................................40
Enthalpy Sensor for Two-Position Control ...............................................................40
Enthalpy Sensors for Modulating Control ................................................................40

3
CAUA-IOM (05-22) 164771-B
TABLE OF CONTENTS—CONTINUED
OPERATION .......................................................................................40
Pre-Startup Checklist ...............................................................................40
Startup ..........................................................................................41
Operating Sequences ...............................................................................43
Normal Heat Cycle Operating Sequence .............................................................43
Abnormal Heat Cycle Functions ....................................................................43
Ignition System Operating Sequence ................................................................44
Ignition System Fault Modes .......................................................................44
Vent System Testing................................................................................45
Post-Startup Checklist ..............................................................................45
ADJUSTMENTS.....................................................................................46
Checking and Adjusting Belt Tension ...................................................................46
Adjusting Blower Speed .............................................................................46
Ductstat Adjustment (Two-Stage, Makeup Air, Option AG3) .................................................48
Motor Amp Adjustment ..............................................................................48
Measure and Adjust Manifold (Outlet) Gas Pressure .......................................................49
High Elevation (>2,000 Feet/609 Meters) Installations ...................................................50
Conversion to LP (Propane) .......................................................................50
Dirty Filter Switch Adjustment .........................................................................52
MAINTENANCE.....................................................................................52
Service Checklist ..................................................................................52
Maintenance Procedures ............................................................................53
Vent/Combustion Air System Maintenance ............................................................53
Combination Gas Valve Maintenance ................................................................53
Burner Rack and Manifold Maintenance ..............................................................54
Cleaning Heat Exchanger .........................................................................55
Limit Control Maintenance.........................................................................55
Flame Rollout Switch.............................................................................55
Blower and Blower Motor Maintenance...............................................................55
Filter Maintenance...............................................................................56
Condensate Drain Maintenance ....................................................................56
Combustion Air Proving Switch Maintenance ..........................................................56
Ignition System Maintenance ......................................................................56
Venter Motor and Wheel Maintenance ...............................................................57
Transformer Maintenance .........................................................................58
Blower Compartment Door Switch Maintenance........................................................58
Ductstat Maintenance (Two-Stage, Makeup Air, Option AG3) .............................................58
Inlet Air Damper Maintenance......................................................................58
Two-Position Damper Motor Maintenance ............................................................58
Modulating Damper Motor Maintenance ..............................................................58
Modulating Damper Motor with Logic Module Maintenance ...............................................58
Potentiometer Maintenence........................................................................59
Return Air Controller Maintenence ..................................................................59
Mixed Air Controller Maintenence ...................................................................59
Enthalpy Sensor for Two-Position Control Maintenence ..................................................59
Enthalpy Sensors for Modulating Control Maintenence ..................................................59
TROUBLESHOOTING ................................................................................59
General Troubleshooting ............................................................................59
Unit Troubleshooting Using Ignition Control Module........................................................61
INSTALLATION RECORD (TO BE COMPLETED BY INSTALLER).............................................64

4CAUA-IOM (05-22) 164771-B
GENERAL INFORMATION
•The instructions in this manual apply to a model CAUA heater.
•Read this booklet and become familiar with the installation requirements of your particular heater. If you do not
have knowledge of local requirements, check with the gas company or any other local agencies who might have
requirements concerning this installation.
•This unit has been tested for capacity and efficiency so as to provide many years of safe and dependable comfort
providing it is properly installed and maintained. With regular maintenance, this unit will operate satisfactorily year
after year. Abuse, improper use, and/or improper maintenance can shorten the life of the appliance and create
unsafe hazards.
•To achieve optimum performance and minimize equipment failure, it is recommended that periodic maintenance
be performed on this unit. The ability to properly perform maintenance on this equipment requires certain tools
and mechanical skills.
•Model CAUA heaters are design-certified by the Canadian Standards Association (CSA) to ANSI Z83.8 and CSA
2.6 for industrial/commercial installations in the United States and Canada. Heaters are available for use with either
natural gas or propane. The type of fuel, the firing rate, and the electrical characteristics are on the unit rating plate.
•A model CAUA heater requires installation of an inlet air duct or an optional inlet air base and a supply duct or an
optional discharge plenum. Installation of an optional mixing box allows for a mixture of return and outside air. If
the air entering the blower will ever be below 35°F, the unit must have been ordered with factory-installed makeup
air option AD4 which includes required stainless steel components and a condensate drain.
•This heater may be installed as a separated-combustion system (taking combustion air from outside) or as a
power-vented system (taking combustion air from the space where the heater is installed). Separated-combustion
units are designed to separate the air for combustion and the flue products from the environment of the building
in which the unit is installed. Separated-combustion appliances are recommended for use in dust laden and some
corrosive fume environments or in buildings with negative pressure (up to 0.15 IN WC). If installed as a separated-
combustion system, the heater must be equipped with both combustion air and exhaust piping to the outdoors. All
Model CAUA heaters must be vented to the outdoors.
•If ordered with an optional cooling coil, follow the instructions provided with the coil to install the coil and the
thermostatic expansion valves. The coil will be operated with R-410A refrigerant. Follow the instructions with the
MASA condenser or other matching condenser.
References
Table 1. Related Technical Manuals Available from Factory Distributor
Type Form PN*
Replacement parts P-CAUA 271166
Gas conversion CAUA-GC 170635
Ignition control replacement CAUA-IGN CNTRL 178435
Mixing box installation CAUA-GA1-GA9 170640
Inlet air mounting base installation CAUA-AVA2 176515
Return air filter cabinet installation CAUA-CW4-CW16 166162
Cased cooling coil installation CAUA-COOLING-COIL 166152
Discharge plenum installation CAUA-CD60,61,62 176514
Burner condensate drain kit installation CAUA-COND-DRAIN 165012
Ignition system and gas valve replacement parts P-VALVES 263995
*Also available at www.reznorhvac.com.
Important Safety Information
Please read all information in this manual thoroughly and become familiar with the capabilities and use of your
appliance before attempting to operate or maintain this unit. Pay attention to all dangers, warnings, cautions, and
notes highlighted in this manual. Safety markings should not be ignored and are used frequently throughout to
designate a degree or level of seriousness.

5
CAUA-IOM (05-22) 164771-B
DANGER: A danger statement describes a potentially hazardous situation that if not avoided, will result in severe
personal injury or death and/or property damage.
WARNING: A warning statement describes a potentially hazardous situation that if not avoided, can result in severe
personal injury and/or property damage.
CAUTION: A caution statement describes a potentially hazardous situation that if not avoided, can result in minor
or moderate personal injury and/or property damage.
NOTE: A note provides important information that should not be ignored.
⚠ DANGER ⚠
• Gas-fired appliances are not designed for use in hazardous atmospheres containing flammable
vapors or combustible dust,in atmospheres containing chlorinated or halogenated hydrocarbons,
or in applications with airborne silicone substances.
• Should overheating occur, or the gas supply fail to shut off, shut off the manual gas valve to the
appliance before shutting off the electrical supply.
• Do not use this appliance if any part has been under water. Immediately call a qualified service
technician to inspect the appliance and replace any gas control which has been under water.
⚠ WARNING ⚠
• For your safety, read the warning labels on the unit.
• If you turn OFF the power supply, turn OFF the gas.
NOTES:
• Installation should be done by a qualified agency in accordance with the instructions in this
manual and in compliance with all codes and requirements of authorities having jurisdiction.
• Service work on this heater should only be done by a qualified gas service technician.The service
information and the troubleshooting guides are intended as an aid to a qualified service technician.
Installation Codes
•These units must be installed in accordance with local building codes.
•In the absence of local codes, in the United States, the unit must be installed in accordance with the National Fuel
Gas Code ANSI Z223.1a (latest edition). A Canadian installation must be in accordance with the CSA B149.1
and B149.2 Installation Code for Gas Burning Appliances and Equipment. These codes are available from CSA
Information Services, 1-800-463-6727.
•Local authorities having jurisdiction should be consulted before installation is made to verify local codes and
installation procedure requirements.
• Massachusetts requirement: if being installed in the Commonwealth of Massachusetts, this unit must be installed
by a licensed plumber or licensed gas fitter.
Warranty
Refer to the limited warranty information on the warranty card in the owner’s envelope. Warranty is void if:
a. Wiring is not in accordance with the diagram furnished with the heater.
b. Unit is installed without proper clearance to combustible materials.

6CAUA-IOM (05-22) 164771-B
GENERAL INFORMATION—CONTINUED
Dimensions
Dimensions are shown in Figure 1 and listed in Table 2.
Figure 1. Dimensions (Refer to Table 2)
Top
View
Right
Side
View
Rear View
Front View
Bottom View

7
CAUA-IOM (05-22) 164771-B
Location
⚠ CAUTION ⚠
• The unit must be level for proper operation.
• Do not locate the heater where it may be exposed to water spray, rain, or dripping water.
Check the rating plate for the gas specifications including elevation and the electrical characteristics of the heater to
ensure that they are compatible with the gas and electric supplies and the elevation of the installation site.
Hazards of Chlorine
NOTE: Remember, chlorine is heavier than air.This fact should be kept in mind when determining
the installation location of heaters and building exhaust systems.
The presence of chlorine vapors in the combustion air of heating equipment presents a potential corrosion hazard.
Chlorine, found usually in the form of Freon or degreaser vapors, when exposed to flame will precipitate from the
compound and form a solution with any condensation present in the heat exchanger or associated parts. The result
is hydrochloric acid, which readily attacks all metals, including 300 grade stainless steel. Care should be taken to
separate these vapors from the combustion process. This may be done by wise location of the unit vent terminal
and combustion air inlet with regard to exhausters or prevailing wind directions.
Table 2. Dimensions
Unit
Size
Dimension (See Figure 1)
A B C D E F G H J K M N P
Inches ±1/8 (mm ±3)
150,
200
38
(965)
34-3/4
(883)
36
(914)
21
(533)
7-1/4
(184)
3-3/4
(95)
12-1/2
(318)
24
(610)
33
(838)
31
(787)
19
(483)
34
(864)
4-5/8
(117)
250,
300
50
(1270)
34-3/4
(883)
48
(1219)
21
(533)
7-1/4
(184)
4-3/8
(111)
12-3/4
(324)
27-1/4
(692)
45
(1143)
31
(787)
16
(406)
46
(1168)
4-3/4
(121)
350,
400
50
(1270)
49-3/4
(1238)
48
(1219)
34
(864)
7
(178)
4-3/8
(111)
14-1/8
(359)
26-3/4
(679)
45
(1143)
44
(1118)
32
(813)
46
(1168)
4-7/8
(124)
Air opening dimensions: supply air (discharge with duct flange) = C × D. Inlet air opening (location selected by installer): right side = K × 16
inches (406 mm), left side = K × 16 inches (406 mm), rear = J × 16 inches (406 mm), bottom = M × N.
Clearances
Clearance to combustibles is defined as the minimum distance—from the heater to a surface or object—that is
necessary to ensure that a surface temperature of 90°F (50°C) above the surrounding ambient temperature is not
exceeded. The unit must be installed so that the clearances listed in Table 4 are provided for service and inspection
and for proper spacing from combustible construction.
Weights
Before installation, check the supporting structure to ensure that it has sufficient load-carrying capacity to support
the weight of the unit. Refer to Table 3, which lists unit weight based on unit size.
Table 3. Weights
Unit Size
150 200 250 300 350 400
Net Weight (Pounds (kg))
288 (131) 300 (136) 380 (172) 394 (179) 445 (202) 460 (209)
Table 4. Clearances
Unit Surface Minimum Clearances (Inches (mm))
Right side, left side, rear, and bottom 0 (0)
Front (service side) 36 (914)
Flue connector 6 (152)
To p 1 (25)

8CAUA-IOM (05-22) 164771-B
INSTALLATION
NOTE: Before installation,make preparations for necessary supplies,tools,and manpower.
Uncrating/Unpacking
•This unit was test operated and inspected at the factory prior to crating and was in operating condition. If the
heater has incurred any damage in shipment, document the damage with the transporting agency and contact an
authorized Distributor. If you are an authorized Distributor, follow the FOB freight policy procedures.
•Also, shipped with the heater are the parts needed to install a heat section condensate drain (needed if installing
a cooling coil).
Shipped-Separate Parts
Table 5. Shipped-Separate Options
Option Component*Description
ACUA, ACUB, ACUC, C Cased cooling coil
Coil is shipped separately for installation in discharge opening of heater
Thermostatic expansion valve kit for R410A refrigerant and the size of unit is
shipped loose for field-installation
AVA2 Inlet air mounting base
(unit sizes 350 and 400) Heater ordered with inlet base mounts on base and has bottom inlet air opening
CC2, CC6 Concentric adapter and
vent terminal
If heater is installed as separated-combustion system, concentric adapter
assembly is required
Concentric adapter and parts are shipped in separate carton
CD60, CD61, CD62 Discharge plenum
(unit sizes 350 and 400)
Discharge plenum is shipped separately for installation over discharge opening
of heater
If discharge plenum and cased cooling coil are part of installation, discharge
plenum is attached to cooling coil casing at factory
CW4, CW5, CW6, CW7,
CW8, CW9, CW10, CW11,
CW12, CW13, CW14,
CW15, CW16
Return air filter cabinet
Return air filter cabinet is shipped separately for field-installation over inlet air
opening of heater
Inlet air opening location is determined by application
Filter cabinet can be attached to rear, left side, right side, or bottom of unit
GA1, GA2, GA3, GA4, GA5,
GA6, GA7, GA8, GA9 Mixing box
If application includes bringing in outside supply air, mixing box must be
attached to unit
Mixing box is shipped separately for field-installation on rear of unit
PC Vibration isolators If vibration isolators are part of installation, four pads are shipped separately
and must be field-installed on bottom at each corner of unit
*Refer to the component installation manual listed in Table 1 for kit components and installation instructions.
•If any of these shipped-separate accessories are part of the installation, check to ensure that the required parts
are at the installation site.
•Other shipped-separate options could include a gas shutoff valve, a thermostat, a thermostat guard, and/or a vent
cap. Make sure all parts are at the site before beginning installation.
Positioning and Mounting
•Determine the position of the heater with regard to clearances, venting, combustion air, gas supply connection,
electrical supply connection, and the inlet air opening.
• Vibration isolation pads (option PC4): If the installation includes optional vibration isolation pads, tip the corner
of the unit enough to slide a pad underneath. Remove the access panel and secure the pad to the cabinet with
the screw provided. Repeat the procedure at all four corners.
Duct Connections
⚠ CAUTION ⚠
To prevent possible motor overloading, ensure that the external duct system static pressure is
within the limits shown on the rating plate and that the motor pulley and belt are properly adjusted.

9
CAUA-IOM (05-22) 164771-B
Requirements and Suggestions for Connecting and Installing Ducts
• Type of ductwork: The type of duct installation to be used depends in part on the type of construction of the building.
• Ductwork material: Rectangular duct should be constructed of galvanized iron—not lighter than No. 26 US gauge
—or aluminum—No. 24 B&S gauge.
• Ductwork structure: All duct sections 24 inches (610 mm) or wider and over 48 inches (1,219 mm) in length
should be cross-broken on top and bottom and should have standing seams or angle-iron braces. Joints should
be S and drive strip or locked.
• Through masonry walls: No warm air duct should come in contact with masonry walls. Insulate around all air
duct through masonry walls with 1-inch (not less than 1/2-inch) of insulation.
• Through unheated space: Insulate all exposed warm air ducts passing through an unheated space with 1-inch
(not less than 1/2-inch) of insulation.
• Duct supports: Suspend all ducts securely from adjacent buildings members. Do not support ducts from unit
duct connections.
• Duct sizing: Proper sizing of the supply air ductwork is necessary to ensure a satisfactory heating installation. The
recognized authority for duct size is the Air Conditioning Contractor’s Association, 2800 Shirlington Road, Suite
300, Arlington, VA 22206 (www.acca.org). A manual covering duct sizing in detail may be purchased directly
from them.
• Access panels: Install removable access panels on both the upstream and downstream sides of the furnace. The
access panels must be accessible when the furnace is in service and should be a minimum of 6 ×10 inches (152
×254 mm) in size so smoke or reflected light may be observed inside the casing to indicate the presence of leaks
in the heat exchanger. Ensure that the access panels are installed in such a manner so as to prevent leakage.
Inlet Air Ductwork
•Inlet air ductwork is required unless equipped with inlet base option AVA2. Filters are recommended when a cooling
coil is part of the installation. Inlet air may be 100% return air, a mixture of return and outside air (air entering the
blower must be ≥35°F unless equipped with makeup air option AD4), or 100% outside air if equipped with makeup
air option AD4.
⚠ CAUTION ⚠
Use tin snips or aviation shears to cut the inlet air opening. Use caution as the cut edges of the
metal will be sharp.
•The inlet air opening (refer to Table 6) may be in the right side, in the left side, in the rear, or in the bottom of the
cabinet and must be cut by the installer. Either cut out the inlet air opening now or when attaching the filter cabinet
or mixing box. If the application includes an optional bottom filter cabinet, either lay the heater down and cut the
opening now or cut it out from the inside after the heater is placed on the bottom filter cabinet. Attach the ductwork
to the heater or to the inlet cabinet.
Table 6. Inlet Air Opening Dimensions
Opening Type Location
Unit Size
150, 200 250, 300 350, 400
Dimensions (Inches (mm))
Without optional filter or mixing cabinet
(actual cutout opening on heater)
Right and left sides 31 × 16 (787 × 406) 31 × 16 (787 × 406) 44 × 16 (1118 × 406)
Rear 33 × 16 (838 × 406) 45 × 16 (1143 × 406) 45 × 16 (1143 × 406)
Bottom 25-1/2 × 32 (648 × 813) 37-1/2 × 32 (953 × 813) 37-1/2 × 46 (953 × 1168)
With optional side or rear filter cabinet
(duct opening in top or rear of cabinet)
Attached to heater side 32 × 16 (813 × 406) 45-1/8 × 16 (1146 × 406)
Attached to heater rear 32 × 16 (813 × 406) 45-1/8 × 16 (1146 × 406)
With optional bottom filter cabinet (duct
opening in bottom of cabinet) Under heater 25-1/2 × 32 (618 × 813)
37-1/2 × 32
(953 × 813)
37-1/2 × 46
(953 × 1168)
With optional mixing box (duct opening
in top, bottom, or rear of cabinet) Attached to heater rear 22 × 19-1/2 (578 × 495)
36-1/2 × 19-1/2
(927 × 495)

10 CAUA-IOM (05-22) 164771-B
INSTALLATION—CONTINUED
Duct Connections—Continued
Discharge Air Ductwork—Continued
NOTE: Refer to the inlet air option installation manual listed in Table 1 for kit components and
installation instructions.
• Filter cabinet (option CW, return air only): All of the filter cabinets have a duct flange for attaching the inlet air
duct. For inlet duct dimensions, refer to Table 6.
• Outside air and return air mixing box (option GA): All mixing box inlet air openings have duct flanges for
attachment of ductwork. Ductwork must be attached to the outside air opening. Removable door panels provide
for filter access from either end of the cabinet. If the mixing box was ordered with optional filters, it is shipped with
the filters installed. For inlet duct dimensions, refer to Table 6.
NOTE: If ordered with an optional inlet base, the heater is shipped with a factory-provided opening
in the bottom.
• Inlet air mounting base (option AVA2): The optional inlet air mounting base is designed to support a model
CAUA 350 or 400 heater while providing an inlet for return air. The mounting base is designed to be used with an
optional discharge plenum to create packaged stand-alone heating or heating/cooling upflow system which can
be used in an air turnover application. However, if the installation requires it, the mounting base may also be used
with discharge ductwork.
Discharge Air Ductwork
NOTE: If the unit is being installed as a makeup air unit with two-stage control (option AG3), refer
to the Ductstat (Two-Stage, Makeup Air, Option AG3) section for instructions on installing the duct
sensor.
•The discharge duct connects to the top of the heater or to the outlet of the optional cooling coil cabinet. Connect
the ductwork plenum to the duct flange as shown in Figure 2. The duct connection on the top of the heater has a
90° flange. The duct may either have no flange or a 90° flange. Position ductwork around the outside of the heater
flange. If the ductwork has a flange, drill holes vertically through duct flange into the top of the heater and secure
using sheet metal screws. If the ductwork does not have a flange, drill holes horizontally through the ductwork and
the heater flange and secure using sheet metal screws.
• Removable access panel in ductwork (see Figure 2): Minimum size is 6 inches × 10 inches (152 mm × 254
mm). Panel must be sealed.
NOTE: Refer to the discharge air option installation manual listed in Table 1 for kit components
and installation instructions.
• Discharge plenum (option CD): The optional discharge plenum is designed to be used with a screened mounting
base to create a packaged stand-alone upflow system that circulates building air. However, the discharge plenum
may also be used in place of ductwork in applications that do not have an optional mounting base. The discharge
plenum is available in three types. Options CD60 and CD61 are for a heater without a cooling coil. Option CD60
is designed for an open area. Option CD61 includes field-installed blockoff plates to block off one or two sides.
Option CD62 can only be ordered with a cooling coil and includes blockoff plates to provide higher velocity required
for cooling.

11
CAUA-IOM (05-22) 164771-B
Table 7. Discharge Duct Dimensions
Dimension (See Figure 2)
Unit Size
150, 200 250, 300 350, 400
Dimensions (Inches (mm))
A 36 (914) 48 (1219) 48 (1219)
B 21 (533) 21 (533) 34 (864)
DUCT FLANGE
ACCESS PANEL
HEATER
TOP VIEW
Figure 2. Discharge Duct Connection (Refer to Table 7)

12 CAUA-IOM (05-22) 164771-B
INSTALLATION—CONTINUED
Venting/Combustion Air Connections
⚠ DANGER ⚠
• The vent must be installed in accordance with national and local regulations. Failure to provide
proper venting could result in death, serious injury and/or property damage. This unit must be
installed with a vent to the outside of the building. Safe operation of any power-vented, gas-fired
equipment requires a properly operating vent system, correct provision for combustion air, and
regular maintenance and inspection.
• Units installed in multiples require individual vent pipe runs and vent caps. Manifolding of vent
runs is not permitted due to possible recirculation of combustion products into the building and
back pressure effects on the combustion air proving switch.
• Venting must be in accordance with the National Fuel Gas Code Z223.1 or CSA B149.1 and
B149.2, Installation Code for Gas Burning Appliances and Equipment, and all local codes. Local
requirements supersede national requirements.Combustion air for this heater may be either taken
from the space or may be ducted from the outside using the concentric adapter combustion air/
vent system. Flue products must always be vented to the outdoors.
⚠ CAUTION ⚠
Products of combustion can cause discoloration of some building finishes and deterioration of
masonry materials. A clear silicone sealant normally used to protect concrete driveways may be
used to protect masonry materials from discoloration and deterioration. If discoloration is an
esthetic problem relocate the vent or install a vertical vent.
NOTES:
• Installation should be done by a qualified agency in accordance with these instructions. The
qualified service agency installing the vent or vent/combustion air system is responsible for the
installation.
• The venting or venting/combustion air systems illustrated in this manual are the only ones
approved for a model CAUA heater.
DECIDE WHICH VENTING SYSTEM TO INSTALL:
• Power-vented: a power-vented installation uses a power venter to draw combustion air from the
indoor space and exhaust flue products to the outdoors. A vent cap (option CC1 or equivalent)
is required.
• Separated-combustion:a separated-combustion installation requires a vent/combustion air system
that uses a power venter to duct combustion air from outdoors and exhaust flue products to the
outdoors. A vent/combustion air kit (option CC2 or CC6) is required.
Venting/Combustion Air Requirements for Power-Vented Installations
⚠ WARNING ⚠
Do not install a unit in a confined space without providing wall openings leading to and from the
space. If the environment has a positive pressure and is such that it is not detrimental to combustion
air, the power-venting system in this section may be installed.

13
CAUA-IOM (05-22) 164771-B
•To provide combustion air to the heater, sufficient air must enter the equipment location to replace that exhausted
through the heater vent system. In the past, the infiltration of outside air assumed in heat loss calculations (one
air change per hour) was assumed to be sufficient. However, current construction methods using more insulation,
vapor barriers, tighter fitting and gasketed doors and windows, weather-stripping, and/or mechanical exhaust fans
may now require the introduction of outside air through wall openings or ductwork to the equipment room.
•Under all conditions, enough air must be provided to ensure there will not be a negative pressure condition within
the equipment room or space.
•Requirements for combustion air and ventilation air depend upon whether the unit is located in a confined or
unconfined space. A confined space is defined as a space whose volume is <50 cubic feet per 1,000 BTUh of
the installed appliance input rating. An unconfined space is defined as a space whose volume is ≥50 cubic feet
per 1,000 BTUh of the installed appliance input rating.
•Provide openings (depending on the combustion air source) near the floor and ceiling for ventilation and air for
combustion, as shown in Figure 3 and as listed in Table 8.
NOTE: For further details on supplying combustion air to a confined space, refer to the National
Fuel Gas Code ANSI Z223.1a (latest edition).
Figure 3. Confined Space Combustion Air Openings (Refer to Table 8)
Table 8. Determining Confined Space Combustion Air Requirements
Letter*Air Source Required Opening Size Calculate Combustion Air
Requirements
A Air inside building 1 square inch free area per 1000 BTUh Add total BTUh of all appliances in
confined space and divide by figures
at left for square inch free area size of
each (top and bottom) opening
Never <100 square inches free area for each opening
B Outside air through duct 1 square inch free area per 2000 BTUh
C Direct outside air 1 square inch free area per 4000 BTUh
*See Figure 3.
CONFINED
SPACE
A
A
B
B
C
C
• Type of pipe: All pipe is field supplied. Use either vent pipe approved for a Category III appliance or single-wall,
26-gauge or heavier galvanized (or a material of equivalent durability and corrosion resistance) vent pipe.
NOTE: If local code requires, a double-wall terminal section may be installed with a single-wall
or Category III vent pipe run OR if at least 1/2 of the equivalent vent length is vertical, vent pipe
approved for a Category I heater may be used. Single-wall pipe or double-wall (Type B) vent pipe
is suitable for use with a Category I heater.
• Venter (flue) outlet: A minimum of 12 inches (305 mm)of straight pipe is required at the venter outlet (refer to
Table 9) before installing an elbow in the vent system. An elbow should never be attached directly to the venter.
An elbow attached to the straight pipe can be in any position at or above horizontal (see Figure 4, DETAIL A).

14 CAUA-IOM (05-22) 164771-B
INSTALLATION—CONTINUED
Venting/Combustion Air Connections—Continued
Venting/Combustion Air Requirements for Power-Vented Installations—Continued
Table 9. Venter Outlet Size
Unit Size
150–250 300–400
Diameter (Inches (mm))
5 (127) 6 (152)
Figure 4. Vent Pipe for Power-Vented Installations
NOTES:
• Do not install dampers or any other type of flue restrictor device.
• If installing a double-wall vent run (allowed if half of the vent length is vertical), see Figure 4,
DETAIL B.
DETAIL A: ALTERNATE VENT DIRECTIONS
VENT IN ANY POSITION
ABOVE HORIZONTAL
STEP 1: PLACE CONTINUAL 1/4-INCH BEAD OF
SILICONE SEALANT AROUND CIRCUMFERENCE
OF VENTER OUTLET COLLAR.
STEP 2: SLIDE DOUBLE-WALL PIPE OVER COLLAR SO THAT COLLAR IS
INSIDE INNER PIPE. PUSH DOUBLE-WALL PIPE TIGHT TO HEATER CABI-
NET. TO SECURE CONNECTION, SPACED EQUAL DISTANCE AROUND
PIPE, DRILL AND INSERT THREE 3/4-INCH-LONG SHEET METAL
SCREWS THROUGH PIPE AND INTO COLLAR. DO NOT OVER TIGHTEN
SCREWS.
DETAIL B: CONNECTING DOUBLE-WALL (TYPE B) VENT PIPE TO VENTER OUTLET
PERFORM STEP 2 IMMEDIATELY AFTER STEP 1.

15
CAUA-IOM (05-22) 164771-B
Table 10. Vent Pipe Diameter and Length for Power-Vented Installations
Description Unit Size
150–250 300–400
Diameter (Inches (mm))
Vent pipe 5 (127) 6 (152)
Length (Feet (Meters))
Minimum 5 (1.5)
Maximum 50 (15.2)
Equivalent straight length for 45-degree elbow 2.5 (0.8)*
Equivalent straight length for 90-degree elbow 5 (1.5)*
*Reduce by this amount for each elbow.
• Joints and sealing:
a. If using single wall, 26-gauge or heavier galvanized pipe, secure slip-fit connections using sheet metal screws or
rivets. Seal pipe joints either with tape suitable for 550°F (such as option FA1, PN 98266) or high-temperature
silicone sealant.
b. If using Category III vent pipe, follow pipe manufacturer's instructions for joining pipe sections. When attaching
Category III pipe to the venter outlet or the vent cap, make secure, sealed joints following a procedure that
best suits the style of Category III pipe being used.
c. If installing a double-wall (Type B) terminal pipe, follow the instructions in Figure 5 to join the double-wall pipe
to a single-wall or Category III vent pipe run. To attach the vent cap, follow instructions in Figure 6.
d. If using double-wall (Type B) vent pipe in the vent pipe run (at least half of the equivalent vent length must be
vertical), follow the pipe manufacturer's instructions for joining pipe sections. For attaching double-wall pipe
to the heater, see Figure 4, DETAIL B). To attach the vent cap, see Figure 6.
STEP 1
On single-wall or Category III vent
pipe or taper-type reducer, place
continual 1/4-inch bead of silicone
sealant around circumference.
Perform STEP 2 immediately fol-
lowing STEP 1.
STEP 2
Insert pipe with bead of sealant into
inner pipe of double-wall pipe until bead
of sealant contacts inner pipe to create
sealed joint.
STEP 3
Double-
Wall Pipe
Single-wall
or Category
III vent pipe
or taper-type
reducer
Spaced equally around double-wall
pipe, drill three small holes below
sealant ring. Insert 3/4-inch-long
sheet metal screws to secure joint.
Do not overtighten screws.
Figure 5. Joining Double-Wall (Type B) Pipe to Single-Wall or Category III Vent Pipe
• Vent pipe diameter and length (refer to Table 10): If the system contains all vertical pipe or a combination of
horizontal and vertical vent pipe, the maximum permissible vent length may be increased 1 foot (305 mm) for each
foot (305mm) of vertical rise up to a maximum increase of 10 feet (3 meters).

16 CAUA-IOM (05-22) 164771-B
INSTALLATION—CONTINUED
Venting/Combustion Air Connections—Continued
Venting/Combustion Air Requirements for Power-Vented Installations—Continued
Figure 6. Joining Double-Wall (Type B) Pipe to Vent Cap
• Vent system support: Use non-combustible supports on vent pipe. Support horizontal runs every 6 feet (1.8
meters). Support vertical runs of Type B double-wall or Category III vent pipe in accordance with the requirements
of the pipe manufacturer. Support vertical single-wall pipe in accordance with accepted industry practices. Do not
rely on the heater for support of either horizontal or vertical vent pipe.
• Condensation: Any length of single-wall vent pipe exposed to cold air or run through an unheated area or an
area with an ambient temperature of 45°F or less must be insulated along its entire length with a minimum of 1/2
inch foil-faced fiberglass, 1-1/2# density insulation. Where extreme conditions are anticipated, install a means of
condensate disposal.
• Vent terminal (pipe and vent cap): The vent system must be terminated with the type of vent cap approved for
use with this heater. The vent cap must be the same size as the vent pipe. Use of the vent cap available with the
heater (option CC1) is recommended. A different style vent cap could cause nuisance problems or unsafe conditions.
NOTE: The vent terminal pipe may be either single-wall or double-wall (Type B).
• Vent terminal options: Vent terminals for power-vented installations using the option CC1 vent cap are shown
in Figure 7 (vertical vent configurations) and Figure 8 (horizontal vent configurations). Refer to Table 11 for
horizontal vent terminal clearances.
NOTE: A vent cap is required. Maintain a clearance of 12”(305mm) from the wall to the vent terminal
cap for stability under wind conditions.
STEP 1: PLACE CONTINUAL
3/8-INCH BEAD OF SILICONE
SEALANT AROUND
CIRCUMFERENCE OF VENT CAP
COLLAR TO PREVENT ANY WATER
INSIDE VENT CAP FROM RUNNING
DOWN DOUBLE-WALL PIPE.
STEP 3: SECURE VENT CAP
TO DOUBLE WALL PIPE BY
DRILLING AND INSERTING
3/4-INCH-LONG SHEET
METAL SCREW INTO VENT
CAP COLLAR. DO NOT OVER
TIGHTEN SCREW.
STEP 2: INSERT COLLAR ON VENT CAP AS FAR
AS POSSIBLE INSIDE INNER WALL OF DOUBLE-
WALL PIPE. ADD ADDITIONAL SILICONE
SEALANT TO FULLY CLOSE ANY GAPS
BETWEEN VENT CAP AND DOUBLE-WALL PIPE
TO PREVENT WATER FROM ENTERING DOUBLE-
WALL PIPE.
PERFORM STEP 2 IMMEDIATELY
FOLLOWING STEP 1.

17
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Figure 7. Vertical Vent Terminal—Power-Vented Installations
SINGLE-WALL VENT RUN AND SINGLE-WALL TERMINAL
SINGLE-WALL VENT RUN AND DOUBLE-WALL TERMINAL

18 CAUA-IOM (05-22) 164771-B
INSTALLATION—CONTINUED
Venting/Combustion Air Connections—Continued
Venting/Combustion Air Requirements for Power-Vented Installations—Continued
Figure 8. Horizontal Vent Terminal—Power-Vented Installations
SINGLE-WALL VENT RUN AND DOUBLE-WALL TERMINAL
SINGLE-WALL VENT RUN AND SINGLE-WALL TERMINAL

19
CAUA-IOM (05-22) 164771-B
Table 11. Minimum Clearance Requirements for Horizontal Vent Terminal
Component/Structure Minimum Clearance, All Directions Unless Specified (Feet (Meters))
Forced air inlet within 10 feet (3.1 meters)*3 (0.9) above
Combustion air inlet of another appliance 6 (1.8)
Mechanical air supply inlet to any building Canada: 6 (1.8)
Any building opening (door, window, or gravity air inlet) 4 (1.2) horizontal and below
1 (0.3) above
Gas meter,** electric meter, and relief equipment US: 4 (1.2) horizontal
Canada: 6 (1.8) horizontal
Gas regulator** US: 3 (0.9) horizontal
Canada: 6 (1.8) horizontal
Adjoining building or parapet 6 (1.8)
Adjacent public walkway 7 (2.1) above
Grade (ground level) 3 (0.9) above
*Does not apply to the inlet of a direct vent appliance.
**Do not terminate the vent directly above a gas meter or service regulator.
Venting/Combustion Air Requirements for Separated-Combustion Installations
• Venter outlet and combustion air pipe collars (refer to Table 12): A minimum length of 12 inches (305 mm)
of straight pipe is always required at the venter outlet. For the combustion air inlet collar, use tin snips or aviation
shears to cut out the hole in the top of the heater (see Figure 9). Insert the pipe down through the hole and attach
it to the collar inside the heater. Seal the joint. Larger size heaters have oval collars. If the collar is oval, form the
pipe to fit the collar.
Table 12. Venter Outlet and Combustion Air Inlet Sizes
Collar
Unit Size
150, 200 250 300–400
Diameter (Inches (mm))
Venter outlet 5 (127) 5 (127) 6 (152)
Combustion air inlet 6 (152)
Figure 9. Venter Outlet and Combustion Air Pipe Collars
VENTER OUTLET COLLAR
COMBUSTION AIR
INLET COLLAR
CUT OUT HOLE FOR
COMBUSTION AIR PIPE

20 CAUA-IOM (05-22) 164771-B
INSTALLATION—CONTINUED
Venting/Combustion Air Connections—Continued
Venting/Combustion Air Requirements for Separated-Combustion Installations—Continued
• Piping: All pipe is field-supplied. Requirements for both the vent pipe and the combustion air inlet pipe are as follows:
a. Vent pipe: Vent pipe approved for a Category III appliance OR single-wall, 26-gauge or heavier galvanized
(or a material of equivalent durability and corrosion resistance) vent pipe is required between the heater and
the concentric adapter box. Double-wall (Type B) vent pipe is required for the vent terminal section. The length
of vent pipe that extends through the box and runs concentric through the combustion air pipe must be one
piece with no joints.
b. Combustion air pipe: Sealed, single-wall galvanized pipe is recommended for combustion air.
c. Pipe length and diameter: Vent pipe diameters and maximum indoor vent lengths apply to both horizontal
and vertical vents. Pipe diameter and length requirements are listed in Table 13.
NOTE: Add all straight sections and equivalent lengths for elbows.The total length of the straight
sections and elbows must not exceed the maximum length.
Table 13. Vent Pipe Diameter and Length for Separated-Combustion Installations
Type Description Unit Size
150, 200 250 300–400
Diameter (Inches (mm))
Pipe from heater to concentric
adapter box
Vent pipe 5 (127) 5 (127) 6 (152)
Inlet air pipe 6 (152)
Concentric (outdoor terminal) pipes Vent pipe 4 (102) 5 (127) 5 (127)
Inlet air pipe 6 (152) 8 (203) 8 (203)
Length (Feet (Meters))
Pipe from heater to concentric
adapter box
Minimum 5 (1.5)
Maximum 40 (12.2) 50 (15.2) 50 (15.2)
Equivalent straight length for 45-degree elbow 2.5 (0.8)
Equivalent straight length for 90-degree elbow 5 (1.5)
• Clearance: Do not enclose the vent pipe or place pipe closer than 6 inches (152 mm) to combustible material.
• Condensation: Any length of single-wall vent pipe exposed to cold air or run through an unheated area or an
area with an ambient temperature of 45°F or less must be insulated along its entire length with a minimum of 1/2
inch foil-faced fiberglass, 1-1/2# density insulation. Where extreme conditions are anticipated, install a means of
condensate disposal.
• Joints and sealing: Seal pipe joints as follows:
a. To seal joints in Category III vent pipe: Follow the pipe manufacturer’s instructions for joining and sealing
Category III vent pipe sections.
b. To seal joints in single-wall vent or combustion air pipe: Secure slip-fit pipe connections using sheet metal
screws or rivets. Seal all joints with aluminum tape or silicone sealant.
c. To seal the joint in two terminal sections of double-wall vent pipe in a vertical vent:Follow the pipe
manufacturer’s instructions for joining and sealing double-wall vent pipe sections.
d. To seal the joint between the terminal section of double-wall vent pipe and a single-wall or Category
III vent pipe: follow the illustrated step-by-step instructions in Figure 5. Make this connection no more than
6 inches (152 mm) from the concentric adapter box.
e. To seal the joint between the terminal section of double-wall vent pipe and the vent cap: Follow the
illustrated step-by-step instructions in Figure 10.