Trane UD2B060ACV32A Series Assembly instructions

Variable Speed, 2-Stage Communicating or 24V
Upflow/ Horizontal and Downflow / Horizontal,
Gas-Fired Furnaces, “Fan Assisted
Combustion System”
A341789P11
Installer’s Guide
Downflow / Horizontal 2
Upflow / Horizontal 1
For VENT SIZING INFORMATION see:
USA —
National Fuel Gas Code........... ANSI Z223.1/NFPA 54 (latest version)
CANADA —
Natural Gas Installation Code ........CAN/CGA-B149.1 (latest version)
Propane Installation Code...............CAN/CGA-B149.2 (latest version)
USA/CANADA ALTERNATE —
Category I Venting Guide ...........Pub. No. 18-CH23D1 (latest version)
1Horizontal Conversion for these furnaces may be left or right side rotation.
2Horizontal Conversion for these furnaces may be left or right side rotation (Important: See venting applications, page 8).
ALL phases of this installation must comply with NATIONAL, STATE AND LOCAL CODES
IMPORTANT — This Document is customer property and is to remain with this unit.
Please return to service information pack upon completion of work.
*First letter may be “A” or “T”
*UD2B060ACV32A
*UD2B080ACV32A
*UD2C080ACV42A
*UD2B100ACV32A
*UD2C100ACV52A
*UD2D120ACV52A
*UD2D140ACV52A
*DD2B060ACV32A
*DD2B080ACV32A
*DD2C100ACV52A
*DD2D120ACV52A
*DD2-ACV
*UD2-ACV
Left Right
18- CD32D1- 3
18- CD32D1- 3

© 2011 Trane All Rights Reserved 18-CD32D1-3
Installer’s Guide
CARBON MONOXIDE POISONING HAZARD
Failure to follow the steps outlined below for each
appliance connected to the venting system being
placed into operation could result in carbon monoxide
poisoning or death.
The following steps shall be followed for each appliance
connected to the venting system being placed into
operation, while all other appliances connected to the
venting system are not in operation:
1. Seal any unused openings in the venting system.
2. Inspect the venting system for proper size and
horizontal pitch, as required in the National Fuel Gas
Code, ANSI Z223.1/NFPA 54 or the CAN/CGA B149
Installation Codes and these instructions. Determine
that there is no blockage or restriction, leakage,
corrosion and other deficiencies which could cause an
unsafe condition.
3. As far as practical, close all building doors and
windows and all doors between the space in which the
appliance(s) connected to the venting system are
located and other deficiencies which could cause an
unsafe condition.
4. Close fireplace dampers.
5. Turn on clothes dryers and any appliance not
connected to the venting system. Turn on any exhaust
fans, such as range hoods and bathroom exhausts, so
they are operating at maximum speed. Do not operate
a summer exhaust fan.
6. Follow the lighting instructions. Place the appliance
being inspected into operation. Adjust the thermostat
so appliance is operating continuously.
7. If improper venting is observed during any of the above
tests, the venting system must be corrected in
accordance with the National Fuel Gas Code,
ANSI Z221.1/NFPA 54 and/or CAN/CGA B149
Installation Codes.
8. After it has been determined that each appliance
connected to the venting system properly vents where
tested as outlined above, return doors, windows,
exhaust fans, fireplace dampers and any other gas-fired
burning appliance to their previous conditions of use.
▲
WARNING
!
Failure to follow safety warnings exactly, could result
in a fire or explosion causing property damage,
personal injury or loss of life.
— 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.
•Immediately call your gas supplier from a
neighbor’s phone. Follow the gas supplier’s
instructions.
•If you cannot reach your gas supplier,
call the fire department.
— Installation and service must be performed by
a qualified installer, service agency or the gas
supplier.
▲WARNING
!
The following warning complies with State of California law, Proposition 65.
Hazardous Gases!
Exposure to fuel substances or by-products of incomplete
fuel combustion is believed by the state of California to
cause cancer, birth defects, or other reproductive harm.
▲
WARNING
!
▲WARNING
!
EXPLOSION HAZARD
Propane gas is heavier than air and may collect in
any low areas or confined spaces. In addition, odor-
ant fade may make the gas undetectable except with
a warning device. If the gas furnace is installed in a
basement, an excavated area or a confined space, it
is strongly recommended to contact a gas supplier
to install a gas detection warning device in case of a
gas leak. Failure to follow this warning could result in
property damage, personal injury or death.
NOTE: The manufacturer of your furnace does NOT test
any detectors and makes no representations regarding
any brand or type of detector.
▲WARNING
!
SAFETY HAZARD
This information is intended for use by individuals
posessing adequate backgrounds of electrical and
mechanical experience. Any attempt to repair a cen-
tral air conditioning product may result in property
damage, personal injury, or death. The manufacturer
or seller cannot be responsible for the interpretation
of this information, not can it assume any liability in
connection with its use. Failure to follow this warn-
ing could result in property damage, personal injury
or death.
▲CAUTION
!
Sharp Edge Hazard. Be careful of sharp edges on
equipment or any cuts made on sheet metal while
installing or servicing. Personal injury may result.
Safety signal words are used to designate a degree or level
of seriousness associated with a particular hazard. The sig-
nal words for safety markings are WARNING and CAUTION.
a. WARNING indicates a potentially hazardous situation
which, if not avoided, could result in death or serious
injury.
b. CAUTION indicates a potentially hazardous situation
which, if not avoided, may result in minor or moderate
injury. It is also used to alert against unsafe practices
and hazards involving only property damage.

18-CD32D1-3 3
Installer’s Guide
Safety Section 2
Installation Instructions 4
General Installation Instructions 4
Location and Clearances 4
Outline Drawing 5-6
Upflow Installation 7
Downflow Installation 7
Horizontal Installation 7
Air for Combustion and Ventilation 9
Duct Connections 10
Return Air Filters 12
General Venting Instructions 15
Venting into a Masonry Chimney 15
Electrical Connections 17
Field Wiring Diagrams 17-20
Gas Piping 22
Combustion and Input Check 22
Gas Valve Adjustment 23
High Altitude Derate 24
Start Up and Adjustment 25
Preliminary Inspections 25
Lighting Instructions 25
User Interface menu - Communicating Mode 27
User Interface menu - 24 VAC Mode 28
Sequence Of Operation 29
Control and Safety Switch Adjustment 32
Conditions Affecting Furnace Operation 33
Furnace Alert Codes 35
Contents
The following safety practices and precautions must be
followed during the installation, servicing, and operation of
this furnace.
1. Use only with the type of gas approved for this furnace.
Refer to the furnace rating plate.
2. Install this furnace only in a location and position as
specified in “Location and Clearances” (page 4), of these
instructions.
3. Provide adequate combustion and ventilation air to the
furnace space as specified in “Air for Combustion and
Ventilation” (pages 9), of these instructions.
4. Combustion products must be discharged outdoors.
Connect this furnace to an approved vent system only,
as specified in the “Venting” section (pages 15-16), of
these instructions.
5. Never test for gas leaks with an open flame. Use a
commercially available soap solution made specifically
for the detection of leaks to check all connections, as
specified in “Gas Piping” (page 22) of these instruc-
tions.
6. Always install the furnace to operate within the fur-
nace’s intended temperature-rise range with a duct sys-
tem which has an external static pressure within the
allowable range, as specified on the unit rating plate.
Airflow with temperature rise for cfm versus static is
shown in the Service Facts accompanying this furnace.
7. When a furnace is installed so that supply ducts carry
air circulated by the furnace to areas outside the space
containing the furnace, the return air shall also be
handled by a duct(s) sealed to the furnace casing and
terminating outside the space containing the furnace.
8. A gas-fired furnace for installation in a residential
garage must be installed as specified in “Location and
Clearances” section (page 4) of these instructions.
▲CAUTION
!
Do not install the furnace in a corrosive or contaminated
atmosphere.
▲WARNING
!
SAFETY HAZARD
Do not install the furnace directly on carpeting, tile or
other combustible material other than wood flooring.
For vertical downflow application, subbase (BAY-
BASE205) must be used between the furnace and
combustible flooring. When the downflow furnace is
installed vertically with a cased coil, a subbase is not
required. Failure to follow this warning could result
in property damage, personal injury or death.
▲CAUTION
!
LABELING WIRES!
Label all wires prior to disconnection when servicing con-
trols. Wiring errors can cause improper and dangerous
operation. Verify Proper Operation after servicing.
▲CAUTION
!
To prevent shortening its service life, the Furnace
should NOT be used as a “Construction Heater”
during the finishing phases of construction until the
requirements listed in item 9, a-i of the safety sec-
tion of this publication have been met. Condensate
in the presence of chlorides and fluorides from paint,
varnish, stains, adhesives, cleaning compounds,
and cement create a corrosive condition which may
cause rapid deterioration of the heat exchanger.
▲WARNING
!
SAFETY HAZARD
DO NOT USE SEMI-RIGID METALLIC GAS CONNEC-
TORS (flexible GAS lines) within the Furnace cabinet.
Failure to follow this warning could result in property
damage, personal injury or death.
▲WARNING
!
EXPLOSION HAZARD
NEVER USE AN OPEN FLAME TO DETECT GAS
LEAKS. EXPLOSIVE CONDITIONS MAY OCCUR.
USE A LEAK TEST SOLUTION OR OTHER AP-
PROVED METHODS FOR LEAK TESTING. FAIL-
URE TO FOLLOW THIS WARNING COULD RESULT
IN PROPERTY DAMAGE, PERSONAL INJURY OR
DEATH.

4 18-CD32D1-3
Installer’s Guide
9. The furnace may be used for temporary heating of
buildings or structures under construction only when
the following conditions have been met:
a. The furnace venting system must be complete and
installed per manufacturer’s instructions.
b. The furnace is controlled only by a room thermostat
(no field jumpers).
c. The furnace return air duct must be complete and
sealed to the furnace and clean air filters are in
place.
d. The furnace input rate and temperature rise must
be verified to be within nameplate marking.
e. 100% of the furnace combustion air require-
ment must come from outside the structure.
f. The furnace return air temperature range is be-
tween 55 and 80 degrees Fahrenheit.
g. Clean the furnace, duct work, and components upon
substantial completion of the construction process,
and verify furnace operating conditions including
ignition, input rate, temperature rise and venting,
according to the manufacturer’s instructions.
10. This product must be gas piped by a Licensed Plumber
or Gas Fitter in the Commonwealth of Massachusetts.
▲WARNING
!
FIRE OR EXPLOSION HAZARD
Failure to follow the safety warnings exactly could result
in serious injury, death or property damage. Improper ser-
vicing could result in dangerous operation, serious injury,
death, or property damage.
GENERAL INSTALLATION INSTRUCTIONS
The manufacturer assumes no responsibility for equipment
installed in violation of any code or regulation.
This furnace can be configured for Communicating
or 24 VAC modes. Using fully Communicating or 24
VAC modes, the furnace can support single or multi
stage heat pump, AC, or heating only applications.
Combined with a communicating Comfort Control
only, the furnace will support a single stage 24 VAC
cooling outdoor unit only.
It is recommended that Manual J of the Air Conditioning
Contractors Association (ACCA) or A.R.I. 230 be followed
in estimating heating requirements. When estimating
heating requirements for installation at Altitudes above
2000 ft., remember the gas input must be reduced (See GAS
INPUT ADJUSTMENT).
Material in this shipment has been inspected at the
factory and released to the transportation agency
without known damage. Inspect exterior of carton
for evidence of rough handling in shipment. Unpack
carefully after moving equipment to approximate
location. If damage to contents is found, report the
damage immediately to the delivering agency.
Codes and local utility requirements governing the instal-
lation of gas fired equipment, wiring, plumbing, and flue
connections must be adhered to. In the absence of local
codes, the installation must conform with latest edition of
the National Fuel Gas Code ANSI Z223.1 • National Instal-
lation Code, CAN/CGA B149.1. The latest code may be
obtained from the American Gas Association Laboratories,
400 N. Capitol St. NW, Washington D.C. 20001.
1-800-699-9277 or www.aga.org
These furnaces have been classified as Fan Assisted Com-
bustion system CATEGORY I furnaces as required by
ANSI Z21.47 “latest edition” and CAN/CGA 2.3. Therefore
they do not require any special provisions for venting other
than what is indicated in these instructions. (Category I
defined on page 15).
▲WARNING
!
SAFETY HAZARD
These furnaces are not approved or intended for installa-
tion in manufactured (mobile) housing, trailers, or rec-
reational vehicles. Failure to follow this warning could
result in property damage, personal injury, or death.
LOCATION AND CLEARANCES
The location of the furnace is normally selected by the
architect, the builder, or the installer. However, before the
furnace is moved into place, be sure to consider the follow-
ing requirements:
1. Is the location selected as near the chimney or vent and
as centralized for heat distribution as practical?
2. Do all clearances between the furnace and enclosure
equal or exceed the minimums stated in Clearance
Table on the Outline Drawings.
3. Is there sufficient space for servicing the furnace and
other equipment? A minimum of 24 inches front acces-
sibility to the furnace must be provided. Any access
door or panel must permit removal of the largest com-
ponent.
4. Are there at least 3 inches of clearance between the
furnace combustion air openings in the front panel and
any closed panel or door provided?
5. Are the ventilation and combustion air openings large
enough and will they remain unobstructed? If outside
air is used, are the openings set above the highest snow
accumulation level? (See the Air for Combustion and
Ventilation section.)
6. Allow sufficient height in supply plenum above the
furnace to provide for cooling coil installation, if the
cooling coil is not installed at the time of this furnace
installation.
7. A furnace shall be installed so electrical components
are protected from water.
8. If the furnace is installed in a residential garage, it
must be installed so that the burners, and the ignition
source are located not less than 18 inches above the
floor and the furnace must be located or protected to
avoid physical damage from vehicles.

18-CD32D1-3 5
Installer’s Guide
*UD2B060ACV32A *UD2B080ACV32A *UD2B100ACV32A *UD2C080ACV42A *UD2C100ACV52A
*UD2D120ACV52A *UD2D140ACV52A
From Dwg. C341699 Rev. 9
*UD-ACV OUTLINE DRAWING
(ALL DIMENSIONS ARE IN INCHES)

6 18-CD32D1-3
Installer’s Guide
From Dwg. C341700 Rev. 5
*DD2-ACV OUTLINE DRAWING
(ALL DIMENSIONS ARE IN INCHES)
MODEL A B C D
*DD2B060ACV32A *DD2B080ACV32A 17-1/2" 9-5/8" 16-1/4" 16"
*DD2C100ACV52A 21" 13-1/16" 19-3/4" 19-1/2" *DD2D120ACV52A 24-1/2" 15-5/16" 23-1/4" 23"
* - The First Letter May Be "A" or "T"

18-CD32D1-3 7
Installer’s Guide
FURNACE
FRONT
A (width)
B (depth)
C
D
3
UPFLOW
FURNACE
CASED
COIL
SCREWS
(BOTH SIDES)
STANDOFFS
(BOTH SIDES)
STANDOFFS (4) DRILL SCREWS (4)
FOR VERTICAL
INSTALLATIONS:
1
2
UPFLOW INSTALLATION
Standoffs and screws (See Figure 1) are included with the
cased coils for attachment to the furnace. There are clear-
ance alignment holes near the bottom of the coil wrapper.
Drill screws are used to engage the furnace top flanges.
The standoff is inserted into the cabinet alignment hole.
The drill screws are inserted through the standoffs then
screwed into the furnace flange. The coil is always placed
downstream of the furnace airflow. The above instructions
apply only if the coil is on top of an upflow furnace.
DOWNFLOW INSTALLATION
▲WARNING
!
FIRE HAZARD
Do not install the furnace directly on carpeting, tile or
other combustible material other than wood flooring.
For vertical downflow application, subbase (BAY-
BASE205) must be used between the furnace and
combustible flooring. When the downflow furnace is
installed vertically with a cased coil, a subbase is not
required. Failure to follow this warning could result
in property damage, personal injury or death.
REQUIRED FLOOR OPENING: (DOWNFLOW)
See Figure 3 and Table 1
TABLE 1
CABINET
WIDTH
RETURN
DUCT WIDTH
FLOOR OPENING PLENUM OPENING
"A" "B" "C" "D"
17-1/2" 16-1/4" 16-5/8" 20-1/8" 15-5/8" 19-3/8"
21" 19-3/4" 20-1/8" 20-1/8" 19-1/8" 19-3/8"
24-1/2" 23-1/4" 23-5/8" 20-1/8" 22-5/8" 19-3/8"
HORIZONTAL INSTALLATION
The coil and furnace must be fully supported when used in
the horizontal.
Three brackets (with screws) are included with downflow
furnaces for installation to stabilize and secure the furnace
and TXC cased coil in the horizontal position. See Fig-
ure 4.
IMPORTANT:
The 2/4TXC cased coil must be placed downstream in the
supply air of the furnace. In horizontal installations, the
apex of the coil may point either toward or away from the
furnace. See the 2/4TXC coil Installer's Guide for more
details.
The cased coil is secured to the furnace and both the fur-
nace and the cased coil must be properly supported. The
brackets mount using the rear screws on the coil case and
use the screws provided to secure the bracket to the fur-
nace. The remaining bracket is placed as close to center as
possible (horizontally) between the coil case front and the
furnace bottom channel (for downflow/horizontal furnace).
Use four of the screws provided to secure the bracket.
This furnace may be installed in an attic or crawl space in
the horizontal position by placing the furnace on the left or
right side (as viewed from the front in the upright posi-
tion). The horizontal furnace installation in an attic should
be on a service platform large enough to allow for proper
clearances on all sides and service access to the front of
the furnace (See Clearance Table on Outline Drawings and
Figure 5).
If the furnace is suspended using perforated steel strap
(plumber’s strap), it must be supported at all four corners
and in the middle at the front of the furnace. The forward
most screw on the side of the furnace may be used to con-
nect the strapping (See Figure 7). Line contact is only per-
missible between lines formed by the intersection of the top
and two sides of the furnace casing and the building joists,
studs, or framing.
CASED COIL CONNECTION
BRACKET FOR DOWNFLOW FUR-
NACE IN HORIZONTAL
4
5
Typical Upflow/Horizontal Attic Installation

8 18-CD32D1-3
Installer’s Guide
6
Airflow
Airflow
Airflow
Airflow
Airflow Airflow Airflow
Downflow-Horizontal Furnace Vent Applications
Horizontal
Vertical
NOT APPROVED
NOT APPROVED
APPROVED
APPROVED
APPROVED
APPROVED
APPROVED

18-CD32D1-3 9
Installer’s Guide
7
50 CU. FT. OR MORE
PER 1000 BTU/HR. INPUT
ALL EQUIP. INSTALLED
UNCONFINED
8
CONFINED
LESS THAN 50 CU. FT.
PER 1000 BTU/HR. INPUT
ALL EQUIP INSTALLED
9
Typical Suspended Upflow/Horizontal Furnace
IMPORTANT:
Limited Warranty is conditional upon proper furnace and
vent system application and installation. Downflow fur-
naces installed in the vertical or horizontal position may
be vented through top or right side of the furnace cabinet
only (see figure 6 for defined top, left and right). A 90 de-
gree elbow may be installed inside the cabinet and rotated
so the vent pipe entering through the right side furnace
cabinet cutout can be connected to the elbow. Right side
venting may be used to provide access if an electronic
air cleaner is installed. Left side venting must use a 90
degree elbow outside the cabinet (Figure 6).
AIR FOR COMBUSTION AND VENTILATION
Adequate flow of combustion and ventilating air must not
be obstructed from reaching the furnace. Air openings
provided in the furnace casing must be free of obstructions
which restrict the flow of air. Airflow restrictions affect
the efficiency and safe operation of the furnace. Keep this
in mind should you choose to remodel or change the area
which contains your furnace. Furnaces must have a free
flow of air for proper performance.
Provisions for combustion and ventilation air shall be
made in accordance with “latest edition” of Section 5.3, Air
for Combustion and Ventilation, of the National Fuel Gas
Code, ANSI Z223.1, or Sections 7.2, 7.3 or 7.4 of CAN/CGA
B149 Installation Codes, and applicable provisions of the
local building codes. Special conditions created by mechani-
cal exhausting of air and fireplaces must be considered to
avoid unsatisfactory furnace operation.
Furnace locations may be in “confined space” or “unconfined
space”. Unconfined space is defined in Table 2 and Figure
8. These spaces may have adequate air by infiltration to
provide air for combustion, ventilation, and dilution of
flue gases. Buildings with tight construction (for example,
weather stripping, heavily insulated, caulked, vapor bar-
rier, etc.), may need additional air provided as described for
confined space.
Confined spaces are installations with less than 50 cu. ft. of
space per 1000 BTU/hr input from all equipment installed.
Air for combustion and ventilation requirements can be
supplied from inside the building as in Figure 9 or from the
outdoors, as in Figure 10.
1. All air from inside the building as in Figure 9: The
confined space shall be provided with two permanent
openings connected directly to an additional room(s)
of sufficient volume so that the combined volume of all
spaces meets the criteria for an unconfined space. The
total input of all gas utilization equipment installed in
the combined space shall be considered in making this
determination. Refer to Table 3, for minimum open
areas required.
2. All air from outdoors as in Figure 11: The confined
space shall be provided with two permanent open-
ings, one commencing within 12 inches of the top and
one commencing within 12 inches of the bottom of the
enclosure.
The openings shall be connected directly, or by ducts,
with the outdoors or spaces (crawl or attic) that freely
connect to the outdoors. Refer to Table 3, for minimum
open areas required.
3. The following types of installations will require use
of OUTDOOR AIR for combustion, due to chemical
exposures:
* Commercial buildings
* Buildings with indoor pools
* Furnaces installed in commercial laundry rooms
* Furnaces installed in hobby or craft rooms
* Furnaces installed near chemical storage areas.
Exposure to the following substances in the combustion
air supply will also require OUTDOOR AIR for combus-
tion:
* Permanent wave solutions
* Chlorinated waxes and cleaners
* Chlorine based swimming pool chemicals
* Water softening chemicals
* Deicing salts or chemicals
* Carbon Tetrachloride
* Halogen type refrigerants
* Cleaning solvents (such as perchloroethylene)
* Printing inks, paint removers, varnish, etc.
* Hydrochloric acid
* Cements and glues
* Antistatic fabric softeners for clothes dryers
* Masonry acid washing materials

10 18-CD32D1-3
Installer’s Guide
q
0
TABLE 2
MINIMUM AREA IN SQUARE FEET
FOR UNCONFINED SPACE INSTALLATIONS
FURNACE
MAXIMUM BTUH
INPUT RATING
WITH 8 FT. CEILING
MINIMUM AREA IN SQUARE
FEET OF UNCONFINED SPACE
60,000
80,000
100,000
120,000
140,000
375
500
625
750
875
TABLE 3
MINIMUM FREE AREA IN SQUARE INCHES
EACH OPENING (FURNACE ONLY)
Furnace
Maximum
BTUH/INPUT
Rating
Air
From
Inside
Air From Outside
Vertical
Duct
Horizontal
Duct
60,000
80,000
100,000
120,000
140,000
100
100
100
120
140
15
20
25
30
35
30
40
50
60
70
DUCT CONNECTIONS
Air duct systems should be installed in accordance with
standards for air conditioning systems, National Fire Pro-
tection Association Pamphlet No. 90. They should be sized
in accordance with ACCA Manual D or whichever is appli-
cable. Check on controls to make certain they are correct
for the electrical supply.
Central furnaces, when used in connection with cooling
units, shall be installed in parallel or on the upstream side
of the cooling units to avoid condensation in the heating
element, unless the furnace has been specifically approved
for downstream installation. With a parallel flow arrange-
ment, the dampers or other means used to control flow of
air shall be adequate to prevent chilled air from entering
the furnace, and if manually operated, must be equipped
with means to prevent operation of either unit unless the
damper is in full heat or cool position.
On any job, flexible connections of nonflammable mate-
rial may be used for return air and discharge connections
to prevent transmission of vibration. Though these units
have been specifically designed for quiet, vibration free
operation, air ducts can act as sounding boards and could,
if poorly installed, amplify the slightest vibration to the
annoyance level.
When the furnace is located in a utility room adjacent to
the living area, the system should be carefully designed
with returns which minimize noise transmission through
the return air grille. Although these winter air condition-
ers are designed with large blowers operating at moderate
speeds, any blower moving a high volume of air will pro-
duce audible noise which could be objectionable when the
unit is located very close to a living area. It is often advis-
able to route the return air ducts under the floor or through
the attic. Such design permits the installation of air return
remote from the living area (i.e. central hall).
When the furnace is installed so that the supply ducts carry
air circulated by the furnace to areas outside the space
containing the furnace, the return air shall also be handled
by a duct(s) sealed to the furnace and terminating outside
the space containing the furnace.
Minimum return air/“air entering” temperature for
the furnace is 55° F.
Where there is no complete return duct system, the return
connection must be run full size from the furnace to a
location outside the utility room, basement, attic, or crawl
space.
DO NOT install return air through the back of the
furnace cabinet.