Unitary products group PxDUA12V06401 series User manual

INSTALLATION
INSTRUCTION
TWO-STAGE ULTRA
MID-EFFICIENCY GAS-FIRED
VARIABLE SPEED FURNACES
Upflow / Horizontal
Models: P*DU - “V” / G8V / L8V
80 To 120 MBH Input
035-17438-001 Rev. A (901)
EFFICIENCY
RATING
CERTIFIED
CAUTION: READ ALL SAFETY GUIDES BEFORE YOU
START TO INSTALL YOUR FURNACE.
SAVE THIS MANUAL
TABLE OF CONTENTS
GENERAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . 2
UNIT INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
VENTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
DUCTWORK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
APPLICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
GAS PIPING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
AIRFLOW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
OPERATION AND MAINTENANCE . . . . . . . . . . . . . . . 18
TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . 22
FURNACE ACCESSORIES . . . . . . . . . . . . . . . . . . . . . 25
WIRING DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

035-17438-001 Rev. A (901)
2Unitary Products Group
GENERAL INFORMATION
DESCRIPTION
This Category I furnace is designed for installation in a resi-
dential or commercial application. A Category I furnace has a
fan assisted combustion system equipped with an integral
mechanical means to draw products of combustion through
the combustion chamber and heat exchanger. It may be
installed in a basement, garage, equipment room, alcove,
attic or any other indoor location where all required clear-
ances to combustibles and other restrictions are met. It is
designed for natural gas fired operation, for use in standard
and Lo Nox applications.
High altitude and propane (LP) changes or conversions
required in order for the appliance to satisfactorily meet the
application must be made by an authorized contractor: in
Canada, a certified conversion station or other qualified
agency, using factory specified and/or approved parts.
The blower in this furnace is programmed to supply a con-
stant volume of airflow to compensate for duct system static.
The furnace must be installed so that all electrical compo-
nents are protected from water.
INSPECTION
As soon as a unit is received, it should be inspected for possi-
ble damage during transit. If the damage is evident, the
extent of the damage should be noted on the carrier’s freight
bill.
A separate request for inspection by the carrier's agent
should be made in writing. Also, before installation, the unit
should be checked for screws or bolts which may have loos-
ened in transit.
IMPROPER INSTALLATION MAY CREATE A CON-
DITION WHERE THE OPERATION OF THE
PRODUCT COULD CAUSE PERSONAL INJURY
OR PROPERTY DAMAGE.
IMPROPER INSTALLATION, ADJUSTMENT,
ALTERATION, SERVICE OR MAINTENANCE CAN
CAUSE INJURY OR PROPERTY DAMAGE.
REFER TO THIS MANUAL FOR ASSISTANCE OR
ADDITIONAL INFORMATION, CONSULT A QUALI-
FIED INSTALLER, SERVICE AGENCY OR THE
GAS SUPPLIER.
THIS PRODUCT MUST BE INSTALLED IN STRICT
COMPLIANCE WITH THE ENCLOSED INSTALLA-
TION INSTRUCTIONS AND ANY APPLICABLE
LOCAL, STATE, AND NATIONAL CODES INCLUD-
ING BUT NOT LIMITED TO, BUILDING, ELECTRI-
CAL AND MECHANICAL CODES.
The furnace area must not be used as a broom
closet or for any other storage purposes, as a fire
hazard may be created. Never store items such as
the following on, near, or in contact with the furnace.
1. Spray oraerosol cans, rags, brooms, dust mops,
vacuum cleaners or other cleaning tools.
2. Soap powders, bleaches, waxes or other clean-
ing compounds; plastic items or containers; gas-
oline, kerosene, cigarette lighter fluid, dry
cleaning fluids or other volatile fluid.
3. Paint thinners and other painting compounds.
4. Paper bags, boxes or other paper products
Never bypass the safety mechanism to operate the
furnace with the blower door removed. To do so
could result in serious personal injury and/or equip-
ment damage.
Lo Nox furnaces requiring propane (LP) gas must
have the Lo Nox screens removed prior to installa-
tion and operation. See propane instruction 035-
14488-000 for instructions on proper removal of the
Nox screens.
This appliance is not to be used for temporary heat-
ing of buildings or structures under construction.
Do not install this furnace in a corrosive or contami-
nated atmosphere.
Do not install this furnace in a mobile home or recre-
ational vehicle.
Furnaces shall not be installed directly on carpeting,
tile or other combustible material other than wood
flooring.

035-17438-001 Rev. A (901)
Unitary Products Group 3
LIMITATIONS AND LOCATION
This furnace should be installed in accordance with all
national/local building/safety codes and requirements, or in
the absence of local codes, with the National Fuel Gas Code,
ANSI Z223.1 (latest edition) or, in Canada, CAN/CGA B149.1
or .2 (latest edition), and other applicable codes.
Use only the type of gas approved for this furnace; refer to
the furnace rating plate.
NOTES, CAUTIONS & WARNINGS
The installer should pay particular attention to the words:
NOTE, CAUTION and WARNING. NOTES are intended to
clarify or make the installation easier. CAUTIONS are given
to prevent equipment damage. WARNINGS are given to alert
the installer that personal injury and/or equipment or property
damage may occur if installation procedures are not handled
properly.
Each furnace in this series is a Category I furnace, suitable
for common venting with other gas-fired appliances as
allowed by the National Fuel Gas Code, NFPA 54/ANSI
Z223.1latest edition.
For installations above 2,000 feet, reduce input 4% for each
1,000 feet above sea level. Canadian installations must be
derated 10% for elevations from 2,000 ft. to 4,500 ft. See
Form 035-14461-000 for information to properly derate fur-
nace.
For installations between 2000 and 4500 feet, it is not
required that the pressure switch be changed. For altitudes
above 4500 feet, the appropriate high altitude kit must be
used.
Furnace shall not be connected to a chimney flue serving a
separate appliance designed to burn solid fuel.
Check the rating plate and power supply to be sure that elec-
trical characteristics match. All models use nominal 115 vac,
1 phase, 60 Hz. power supply.
A furnace installed in a residential garage must be located so
that all burners and burner ignition devices are located no
less than 18" above the garage floor, and located or pro-
tected to prevent damage by vehicles.
The size of the unit should be based on an acceptable heat
loss calculation for the structure. ACCA, Manual J or other
approved methods may be used.
The furnace should be located using these guidelines:
1. Where a minimum amount of vent piping and elbows will
be required.
2. As centralized with the air distribution as possible.
3. Where adequate combustion air will be available.
4. In an area where ventilation facilities provide for safe lim-
its of ambient temperature under normal operating condi-
tions.
5. Where it will not interfere with proper air circulation in the
confined space.
6. Where the vent will not be blocked or restricted.
7. Where sufficient space is provided to allow proper ser-
vice access. Minimum recommended service clearances
are as follows:
Twenty four (24) inches between the front of the furnace
and an adjacent wall or another appliance, when access
is required for servicing and cleaning.
Eighteen (18) inches at the side where access is
required for passage to the front when servicing or for
inspection or replacement of flue/vent connections.
8. Where it will not interfere with the cleaning, servicing or
removal of other appliances.
9. Where the following minimum clearances (in inches) to
combustibles can be maintained. Please see, Table 1 on
page 4.
UNIT INSTALLATION
COMBUSTION AIR
All installations must comply with Section 5.3, Air for Com-
bustion and Ventilation of the National Fuel Gas Code, ANSI
Z223.1 or Sections 7.2, 7.3 or 7.4 of CAN/CGA B149.1 or .2
Installation Code latest editions.
An unconfined space is not less than 50 cubic feet per 1000
Btu/hr input rating for all appliances installed in that area.
Rooms communicating directly with the space containing the
appliances are considered part of the unconfined space, if
openings are not furnished with doors.
A confined space is an area with less than 50 cubic feet per
1000 Btu/hr input rating for all appliances installed in that
area.
The following must be considered to obtain proper air for
combustion and ventilation in confined spaces.
Only use natural gas in furnaces designed for natu-
ral gas. Do not use this furnace with butane. Using
wrong gas could create a hazard, resulting in dam-
age, injury or death.

035-17438-001 Rev. A (901)
4Unitary Products Group
Air Source from Inside the Building
Two permanent openings, one within 12 inches of the top of
the confined space and one within 12 inches of the bottom,
shall each have a free area of not less than one square inch
per 1,000 Btuh of total input rating of all appliances located in
the space. The openings shall communicate freely with inte-
rior areas having adequate infiltration from the outside.
NOTE: At least 100 square inches free area shall be used
for each opening.
Air Source from Outdoors
1. Two permanent openings, one within 12 inches of the
top ofthe confined space and one within 12inches of the
bottom, shall communicate directly, or by means of
ducts, with the outdoors or to such crawl or attic spaces
that freely communicate with the outdoors.
a. Vertical Ducts: Each opening must have a free
area of not less than one square inch per 4,000 Btuh
of total input of all appliances located in the space.
EXAMPLE:
b. Horizontal Ducts: Each opening must have a free
area of not less than one square inch per 2,000 Btuh
of total input of all appliances located in the space.
NOTE: Ducts must have the same cross sectional area as
the free area in the opening to which they are connected. The
minimum dimension of rectangular ducts shall be three
inches.
2. One permanent opening, commencing within 12 inches
of the top of the enclosure shall be permitted where the
equipment has clearances of at least 1 inch from the
sides and back and 6 inches from the front of the appli-
ance. The opening shall communicate through a vertical
or horizontal duct to the outdoors, or spaces (crawl or
attic)that freely communicatewith the outdoors and shall
have a minimum free area of:
a. 1 sq. in. per 3000 Btu per hr of the total input rating
of all equipment located in the enclosure.
b. Not less than the sum of the areas of all vent con-
nectors in the confined space.
3. Louvers, Grilles and Screens
a. In calculating free area, consideration must be given
to the blocking effects of louvers, grilles and
screens.
b. If the free area of a specific louver or grille is not
known, refer to Table 2 to estimate free area.
NOTE: If mechanically operated louvers are used, a means
to prevent main burner ignition and operation must be pro-
vided should louvers close during startup or operation.
Special Combustion and Ventilation Considerations
Operation of a mechanical exhaust, such as an exhaust fan,
kitchen ventilation system, clothes dryer or fireplace may cre-
ate conditions requiring special attention to avoid unsatisfac-
tory operation of gas appliances.
Total Input of All Appliances = Square Inches Free Area
4000
Table 1: UNIT CLEARANCES TO COMBUSTIBLES
APPLICATION TOP FRONT REAR LEFT
SIDE
RIGHT
SIDE FLUE FLOOR/
BOTTOM CLOSET ALCOVE ATTIC LINE
CONTACT
UPFLOW/HORIZONTAL MODELS - UPFLOW APPLICATION
UPFLOW 1 6 0 0 3
1
6 COMBUSTIBLE YES YES YES NO
UPFLOW B-VENT 1 3 0 0 0 1 COMBUSTIBLE YES YES YES NO
HORIZONTAL APPLICATION
HORIZONTAL 3
2
6 0 1 0 6 COMBUSTIBLE NO YES YES YES
3
HORIZONTAL B-VENT 0 3 0 1 0 1 COMBUSTIBLE NO YES YES YES
3
1.
14 1/2” cabinet models only - all other units “0” clearance
2.
14 1/2” cabinet left airflow applications only - all other units and all right hand air flow applications “0” clearance.
3.
Line contact only permitted between lines formed by the intersection of the rear panel and side panel (top in horizontal position) of the
furnace jacket and building joists, studs or framing.
Table 2: ESTIMATED FREE AREA
Wood or Metal
Louvers or Grilles Wood 20-25%
1
Metal 60-70%
1
Screens
2
1/4 in. mesh or larger 100%
1.
Free area or louvers an grilles varies widely; installer should
follow louver or grille manufacturer’s instructions.
2.
Do not use less than 1/4 in. mesh

035-17438-001 Rev. A (901)
Unitary Products Group 5
Specially Engineered Installations
The above requirements shall be permitted to be waived
where special engineering, approved by the authority having
jurisdiction, provides an adequate supply of air for combus-
tion, ventilation and dilution of flue gases.
Combustion Air Quality
The recommended source of combustion air is to use the out-
door air supply. Excessive exposure to contaminated com-
bustion air will result in safety and performance related
problems. However, the use of indoor air in most applications
is acceptable, except as follows:
1. If the furnace is installed in a confined space it is recom-
mended that the necessary combustion air come from
the outdoors by way of attic, crawl space, air duct or
direct opening.
2. If outdoor combustion air is used, there must be no expo-
sure to the installations or substances listed in number 3
below.
3. The following types of installations may require OUT-
DOOR AIR for combustion, due to chemical exposure.
a. Commercial buildings
b. Buildings with indoor pools
c. Furnaces installed in laundry rooms
d. Furnaces installed in hobby or craft rooms
e. Furnaces installed near chemical storage areas
Exposure to the following substances in the combustion air
supply may also require OUTDOOR AIR for combustion.
f. Permanent wave solutions
g. Chlorinated waxes and cleaners
h. Chlorine based swimming pool chemicals
i. Water softening chemicals
j. De-icing salts or chemicals
k. Carbon tetrachloride
l. Halogen type refrigerants
m. Cleaning solvents (such as perchloroethylene)
n. Printing inks, paint removers, varnishes, etc.
o. Hydrochloric acids
p. Cements and glues
q. Antistatic fabric softeners for clothes dryers
r. Masonry acid washing chemicals
VENTING
CATEGORY I VERTICAL VENTING
Category I venting consists of vertically venting one or more
appliances in B-vent or masonry chimney (as allowed), using
single wall metal pipe or B-vent connectors. Type B-vent sys-
tem extends in a general vertical direction and does not con-
tain offsets exceeding 45 degrees, except that a vent system
having not more than one 60 degree offset is permitted.
NOTE: This appliance may be common vented with another
gas appliance as allowed by the following codes and stan-
dards.
All installations must be vented in accordance with the
National Fuel Gas Code, NFPA 54/ANSI Z223.1 latest edi-
tion. For reference, the National Fuel Gas Code Handbook,
available from NFPA (item JP54HB96) is recommended. The
appliance must also be vented in compliance with all local
utility and code requirements. In Canada, the furnace must
be vented in accordance with the National Standard of Can-
ada, CAN/CGAB149.1 and .2 latest editions.
VENTING INTO AN EXISTING CHIMNEY
Whenever possible, B-1 metal pipe should be used for vent-
ing. Where use of an existing chimney is unavoidable, the fol-
lowing rules must be followed:
1. The masonry chimney must be built and installed in
accordance with nationally recognized building codes or
standards and must be lined with approved fire clay tile
flue liners or other approved liner material that will resist
corrosion, softening, or cracking from flue gases. THIS
FURNACE IS NOT TO BE VENTED INTO AN UNLINED
MASONRY CHIMNEY.
2. This furnace may be vented into a fire clay tile lined
masonry chimney only if a source of dilution air is pro-
vided, such as by common venting with a draft hood
equipped water heater. If no such source of dilution air is
available, Type B vent must be used, or masonry chim-
ney vent kit 1CK0603 or 1CK0604 must be used. See
instruction 035-17452-000 to properly apply these
masonry chimney kits.
3. The chimney must extend at least three feet above the
highest point where it passes through a roof of a building
and at least two feet higher than any portion of the build-
ing within a horizontal distance of ten feet.
4. The chimney must extend at least five feet above the
highest equipment draft hood or flue collar.
It is the responsibility of the installer to verify
proper vent system operation.
A furnace shall not be connected to a chimney flue
serving a separate appliance designed to burn
solid fuel.

035-17438-001 Rev. A (901)
6Unitary Products Group
VENT SAFETY CHECK PROCEDURE
The following steps shall be followed with each appliance
connected to the venting system placed in operation, while
any other appliances connected to the common venting sys-
tem are not in operation.
1. Seal any unused openings in the common venting sys-
tem.
2. Inspect venting system for proper size and horizontal
pitch, as required in the National Fuel Gas Code ANSI
Z223.1 or the CAN/CGA B149 Installation Codes and
these instructions. Determine that there is no blockage
or restriction, leakage, corrosion or other deficiencies
which could cause an unsafe condition.
3. Insofar as is practical, close all building doors and win-
dows and all doors between the space in which the appli-
ance(s)connected to the venting systemare located and
other spaces of the building. Turn on clothes dryers and
any other appliances not connected to the common vent-
ing system.
Turn on any exhaust fans, such as range hoods and
bathroom exhausts so they will operate at maximum
speed. Do not operate a summer exhaust fan. Close fire-
place dampers.
4. Follow the lighting instructions. Place the appliance
being operated in operation. Adjust thermostat so appli-
ance will operate continuously.
5. Test for draft hood equipped appliance spillage at the
draft hood relief opening after 5 minutes of main burner
operation. Use the flame of a match or candle.
6. After it has been determined that each appliance con-
nected to the venting system properly vents when tested
as outlined above, return doors, windows, exhaust fans,
fireplace dampers and any other gas burning appliance
to their previous conditions of use.
7. If improper venting is observed during any of the above
tests, the venting system must be corrected.
8. Any corrections or resizing of the common venting sys-
tem must be in accordance with the National Fuel Gas
Code, ANSI Z223.1 or Section 7, Venting Systems and
Air Supply for Appliances, CAN/CGA B149.1 or .2 Instal-
lation Code latest editions. If the common vent system
must be resized, it should be resized to approach the
minimum size as determined using the appropriate
tables in Appendix G of the above codes or the venting
tables supplied with the furnace.
If this furnace is replacing a common vented fur-
nace, it may be necessary to resize the existing
vent line and chimney to prevent oversizing prob-
lems for the new combination of units. Refer to the
National Fuel Gas Code, ANSI Z223.1 or CAN/
CGA B149.1 or .2 Installation Code latest editions.

035-17438-001 Rev. A (901)
Unitary Products Group 7
.
FIGURE 1 : 2-Stage Upflow/Horizontal Furnace Dimensions
FRONT LEFT SIDE RIGHT SIDE
D
B20
40
A28-1/2
3/4
14-3/4
5-3/8
(VENT CONNECTIONS)
POWER WIRING
7/8 HOLE
2-1/2
ACCESS
WIRING
7/8 K.O.
16
8-3/4
T’STAT WIRING
7/8 K.O.
1-1/8
2-1/4
14
23-1/2
20
BC
A
3/4
FLANGE
BOTTOM IMAGE
(FRONT)
TOP IMAGE
(FRONT)
VENT
CONNECTION
(Vent Size)
D
F
E
32-1/2
2
28-1/2
23
13-3/4
GAS INLET
1-1/4 x 2-1/2
MODELS
P*DU-V /
G8V-UH / L8V-UH
80/64/1200/ A
100/80/1600/ B
100/80/2000/ C
120/96/2000/ C
14-1/2
17-1/2
21
21
13-1/4
16-1/4
19-3/4
19-3/4
10-1/8
15-1/4
16-5/8
16-5/8
4
4
4
4
10-1/8
11-5/8
13-3/8
13-3/8
3-3/4
3-3/4
3-3/4
3-3/4
ABCD E F
Table 3: TWO STAGE UPFLOW / HORIZONTAL RATINGS & PHYSICAL/ELECTRICAL DATA
P*DU-V /
G8V-UH
L8V-UH
INPUT
MBH H/L
OUTPUT
MBH
H/L
NOM.
CFM
CABINET
WIDTH
(IN.) AFUE
1
LOW
FIRE
TEMP
RISE °F
HIGH
FIRE
TEMP
RISE °
MAX.
OUTLE
AIR
TEMP. °F
BLOWER
TOTAL
UNIT
AMPS
MAX.
OVER-
CURRENT
PROPECT
2
MIN.
WIRE SIZE
(AWG) @
75 FT.
ONE WAY
OPER.
WGT.
(LBS.)
HP AMPS SIZE
(IN.)
80/59 64/48 1200 A 14-1/2” 80 40 - 70 40 - 70 175 1/2 7.7 10 x 8 9.0 20 14 117
100/65 80/53 1600 B 17-1/2” 80 40 - 70 40 - 70 170 3/4 9.6 10 x 10 12.0 20 14 128
100/65 80/53 2000 C 21” 80 40 - 70 40 - 70 170 1 12.8 11 x 10 14.0 20 12 145
120/78 96/64 2000 C 21” 80 35 - 65 35 - 65 170 1 12.8 11 x 10 14.0 20 12 147
1.
AFUE numbers are determined in accordance with DOE test procedures
2.
Wire size and overcurrent protection must comply with the National Electrical Code (NFPA-70-latest edition).
•For altitudes above 2,000 ft., reduce capacity 4% for each 1,000 ft. above sea level. Refer to instruction 035-14461-000.
•Wire size based on copper conductors, 60°C, 3% voltage drop.
•Continuous return air temperature must not be below 55°F.

035-17438-001 Rev. A (901)
8Unitary Products Group
DUCTWORK
The duct system's design and installation must:
1. Handle an air volume appropriate for the served space
and within the operating parameters of the furnace spec-
ifications.
2. Be installed in accordance with standards of NFPA
(National Fire Protection Association) as outlined in
NFPA pamphlets 90A and 90B (latest editions).
3. Create a closed duct system. The supply system must
be connected to the furnace outlet and the return duct
system must be connected to the furnace inlet. Both sup-
ply and return duct systems must terminate outside the
space containing the furnace.
4. Generally complete a path for heated or cooled air to cir-
culate through the air conditioning and heating equip-
ment and to and from the conditioned space.
When the furnace is used in conjunction with a cooling coil,
the furnace must be installed parallel with, or in the supply air
side of the furnace.
When a parallel flow arrangement is used, the dampers or
other means used to control air flow must be adequate to pre-
vent chilled air from entering the furnace, and if manually
operated, must be equipped with means to prevent operating
of either unit unless the damper is in the full heat or cool posi-
tion.
UPFLOW
Supply Plenum Connection
Attach the supply plenum to the fur-
nace outlet duct connection flanges.
This is typically through the use of S
cleat material when a metal plenum is
used. The use of an approved flexible
duct connector is recommended on all
installations. This connection should be
sealed to prevent air leakage.
If a matching cooling coil is used, it
may be placed directly on the furnace
outlet and sealed to prevent leakage.
Follow the coil instructions for installing
the supply plenum.
On all installations without a coil, a removable access panel
is recommended in the outlet duct such that smoke or
reflected light would be observable inside the casing to indi-
cate the presence of leaks in the heat exchanger. This
access cover shall be attached in such a manner as to pre-
vent leaks.
Return Duct Connection
Return air may enter the furnace through the side(s) or bot-
tom depending on the type of application. Return air may
not be connected into the rear panel of the unit. See the
specific type application installation for details. Be sure to see
the Filters section of this instruction.
FILTERS INSTALLATION
All applications require the use of a filter. A high velocity filter
and retainer are provided for field installation.
Internal Installation
1. Select desired filter position (left/right side, or bottom).
Remove the corresponding cabinet cutouts per instruc-
tions provided. Refer to Figure 4 on page 9.
2. Install snap-in retainer clips into the corresponding slots
from the outside rear of the cabinet, refer to Figure 2 on
page 8. To prevent cabinet air leaks, installsnap-in plugs
(provided) into the unused slots at the outside rear of the
cabinet.
3. Install the wire retainer inside the cabinet. Insert the
open ends of the wire retainer into the clip loops at the
rear of the blower compartment. The retainer wire should
pivot freely like a hinge, on the clips at the rear of the
cabinet. Refer to Figure 3 on page 9.
4. Install the filter(s) provided. Cut filter if necessary to
match air opening in cabinet. Filter should extend
beyond opening edge as much as possible to prevent air
from bypassing the filter. DO NOT remove stiffening rods
from inside the filter. Shorten the rods, if necessary, to
match final filter size.
The cooling coil must be installed in the supply air
duct downstream of the furnace.
FIGURE 2 : Furnace Filter Slot Locations
FURNACE
(REAR CABINET)
RIGHT
SIDE
SLOTS
LEFT
SIDE
SLOTS
BOTTOM SLOTS
CABINET
SLOT
FILTER SUPPORT
CLIPS (PROVIDED)
PLUG UNUSED
CABINET SLOTS
WITH PLUGS
(PROVIDED)

035-17438-001 Rev. A (901)
Unitary Products Group 9
5. Position the filter between the wire retainer and the cabi-
net wall (or floor) so it completely covers the cabinet air
opening and secure the filter in place at the front of the
cabinet by fastening the closed (looped) end of the
retainer wire under the flanged edge of the cabinet.
When properly installed the filter should fit flush with all
four sides of the cabinet wall.
NOTE: Air velocity through throwaway type filters may not
exceed 300 feet per minute. All velocities over this require the
use of high velocity filters.
Side Return External Filter
Locate and knock out the square corner locators. These indi-
cate the size of the cutout to be made in the furnace side
panel, refer to Figure 4.
Install the side filter rack following the instructions provided
with that accessory. If a filter(s) is provided at another loca-
tion in the return air system, the ductwork may be directly
attached to the furnace side panel.
NOTE: Some accessories such as electronic air cleaners
and pleated media may require a larger side opening.
The return duct may be attached to the furnace by S-cleat,
bend tabs or other approved methods. Be sure to seal the
duct to the furnace to prevent air leakage.
In order to achieve the airflow indicated in the table, it is rec-
ommended for those applications over 1800 CFM use return
from two sides, one side and the bottom, or bottom only. For
bottom only application, see data and notes on blower perfor-
mance tables in this manual.
Where the return duct system is not complete, the return con-
nection must run full size to a location outside the utility room
or basement. For further details, consult Section 5.3 (Air for
Combustion and Ventilation) of the National Fuel Gas Code,
ANSI Z223.1, or CAN/CGA B149.1 or .2, Installation Code
latest editions.
Bottom Return
Bottom return applications normally pull return air through a
base platform or return air plenum. Be sure the return plat-
form structure is suitable to support the weight of the furnace.
Refer to Figure 1 on page 7 for unit dimensions and Table 3
on page 7 for unit weights. Be sure to seal the furnace to ple-
num connection to prevent air leakage.
The bottom panel is equipped with a perforated opening for
easy removal. Tabs must be cut with sheet metal snips to
allow removing knockout. Scribe marks are included for form-
ing flanges for attachment of the return air ductwork.
NOTE: If an external mounted filter rack is being used, see
the instructions provided with that accessory for proper hole
cut size.
Upflow attic installations must meet all minimum clearances
to combustibles and have floor support with required service
accessibility.
APPLICATION
HORIZONTAL
NOTE:
If an external mounted filter rack is being used, see
the instructions provided with that accessory for proper hole
cut size.
FIGURE 3 : Side Filter Retainer Placement
FIGURE 4 : Side Return Cutout Markings
FILTER
PROVIDED
POSITION WIRE RETAINER
PROVIDED UNDER FLANGE
CLIPS
RIGHT SIDE
INSTALLATION
SHOWN FURNACE
FRONT
CORNER
MARKINGS
FRONT OF
FURNACE
All installations must have a filter installed.

035-17438-001 Rev. A (901)
10 Unitary Products Group
Upflow furnaces may be installed horizontally with the supply
airflow toward the left or right by laying the unit on the left or
right side panel.
After determining the best orientation, lay the unit on top of
the shipping carton to protect the finish.
The appropriate electrical knock-outs for power wiring, con-
trol wiring and gas piping should be removed at this time.
For horizontal application, return air may enter through the
bottom, left side or right side panel or any combination of
these openings. Return air may not be connected into the
rear panel of the unit.
To convert the upflow model furnace to open bottom, see
“Bottom Return” section of this manual.
ATTIC INSTALLATION
This appliance is design certified for line contact for furnaces
installed horizontally. The intersection of the furnace top and
sides form a line. This line may be in contact with combustible
material.
Secure a platform constructed of plywood or other building
material to the floor joists. Sheet metal, 12" in front of the fur-
nace combustion air openings is recommended. Refer to Fig-
ure 6 on page 10.
NOTE: See crawl space installation for suspending the fur-
nace in attic installations.
CRAWL SPACE INSTALLATION
The furnace can be hung from floor hoists or installed on suit-
able blocks or pad. Blocks or pad installations shall provide
adequate height to ensure the unit will not be subject to water
damage.
When suspending the furnace from rafters or floor joists using
rod, pipe or straps, refer to Physical Data, Table 3 on page 7,
for furnace weights to determine suitable means of suspen-
sion.
Do not install the unit on the rear panel.
FIGURE 5 : Typical Attic Installation
RETURN AIR SEDIMENT
TRAP
GAS PIPING
SUPPLY AIR
VENT (Maintain
required clearances
to combustibles)
SHEET METAL
IN FRONT OF
FURNACE
COMBUSTION AIR
OPENINGS IS
RECOMMENDED
LINE CONTACT ONLY PERMISSIBLE
BETWEEN LINES FORMED BY THE
INTERSECTION OF FURNACE TOP
AND TWO SIDES AND BUILDING
JOISTS, STUDS OR FRAMING
12
30 MIN.
WORK AREA
When a furnace is installed in an attic or other insu-
lated space, keep all insulating materials at least 12"
away from furnace and burner combustion air open-
ings.
FIGURE 6 : Typical Furnace Installation Using
Suspension Materials
1 MAX. BETWEEN
ROD & FURNACE
SUPPORT
ROD
6 MIN BETWEEN
ROD & FURNACE
1 MAX. BETWEEN
ROD & FURNACE
ANGLE IRON
BRACKET

035-17438-001 Rev. A (901)
Unitary Products Group 11
GAS PIPING
NOTE: An accessible manual shutoff valve must be
installed upstream of the furnace gas controls and within 6
feet of the furnace.
The furnace and its individual shutoff valve must be discon-
nected from the gas supply piping system during any pres-
sure testing of that system at test pressures in excess of 1/2
psig (3.48 kPa).
The furnace must be isolated from the gas supply piping sys-
tem by closing its individual external manual shutoff valve
during any pressure testing of the gas supply piping system
at test pressures equal to or less than 1/2 psig (3.48 kPa).
Gas piping may be connected from either side of the furnace.
Sizing and installation of the supply gas line should comply
with the local utility requirements.
The gas supply should be a separate line, installed in accor-
dance with the National Fuel Gas Code, ANSI Z223.1, or
CAN/CGA B149.1 or .2 Installation Codes (latest editions).
Some utility companies, or local codes, require pipe sizes
larger than the minimum sizes listed. Using the properly sized
wrought iron, approved flexible or steel pipe, make gas con-
nections to the unit. Installation of a drop leg and ground
union is required. Refer to Figure 7.
ELECTRICAL POWER CONNECTION
Field wiring to the unit must conform to and be grounded in
accordance with the provisions of the National Electrical
Code ANSI/NFPA No. 70 latest edition, Canadian Electric
Code C22.1 Part 1 (latest edition) and/or local codes. Electri-
cal wires which are field installed shall conform with the tem-
perature limitation for 63F/35C rise wire when installed in
accordance with instructions. Specific electrical data is given
on the furnace rating plate.
Provide a power supply separate from all other circuits. Install
overcurrent protection and disconnect switch per local/
national electrical codes. The switch should be reasonably
close to the unit for convenience in servicing. With the dis-
connect switch in the OFF position, check all wiring against
the unit wiring label. Also, see the wiring diagram in this
instruction.
An overpressure protection device, such as a pres-
sure regulator, which conforms to the National Fuel
Gas Code, ANSI Z223.1 (U.S.) or CANB149.1 or .2
(Canada) and acts to limit the downstream pressure
to value that does not exceed 0.5 PSI (14" w.c.),
must be installed in the gas piping system upstream
of the furnace. Failure to do so may result in a fire or
explosion or cause damage to the furnace or some
of its components.
Never apply a pipe wrench to the body of the combi-
nation automatic gas valve. A wrench must be
placed on the projection or wrench boss of the valve
when installing piping to it.
INLET GAS PRESSURE RANGE
NATURAL GAS PROPANE (LP)
Minimum 4.5 In. W.C. 11 In. W.C.
Maximum 13.8 In. W.C. 13.8 In. W.C.
FIGURE 7 : Gas Piping
Compounds used on threaded joints of gas piping
must be resistant to the action of liquefied petroleum
gases.
NOTE: 1/8” NPT plug is included in the inlet side of
the gas valve for measuring incoming gas pressure.
After all gas piping connections are completed, leak
test all joints, fittings and furnace connections with
rich soap and water solution, commercial available
bubble type leak detection fluid, or other approved
means.
Do not use an open flame or other source of ignition
for leak testing.
GAS VALVE
TO GAS
SUPPLY
EXTERNAL MANUAL
SHUTOFF VALVE
TO GAS
SUPPLY
DROP LEG
GROUND JOINT UNION
MAY BE INSTALLED
INSIDE OR OUTSIDE UNIT

035-17438-001 Rev. A (901)
12 Unitary Products Group
NOTE: The furnace’s control system depends on correct
polarity of the power supply and a proper ground connection.
Refer to the furnace control diagnostics section for symptoms
of reversed power supply polarity.
Connect the power supply as shown on the unit wiring label
on the inside of the blower compartment door and refer to
Figure 8. The black furnace lead must be connected to the L1
(hot) wire from the power supply.
The white furnace lead must be connected to neutral. Also,
the green equipment ground wire must be connected to the
power supply ground.
Remove the screw retaining the junction box cover. Route the
power wiring through the unit side panel with a conduit con-
nector or other proper connection. Make wiring connections:
Refer to Figure 8. Replace the wiring box cover and screw.
An alternate wiring method is to use a field provided 2 x 4 box
and cover on the outside of the furnace. Route the furnace
leads into the box using a protective bushing where the wires
pass through the furnace panel.
NOTE: The power connection leads and wiring box on
upflow units may be relocated to the left side of the furnace.
Remove the screws and cut wire tie holding excess wiring.
Reposition on the left side of the furnace and fasten using
holes provided.
ELECTRICAL CONTROL CONNECTIONS
Install the field supplied thermostat. The thermostat instruc-
tions for wiring are packed with the thermostat. With the ther-
mostat set in the OFF position and the main electrical source
disconnected, complete the low voltage wiring from the ther-
mostat to the terminal board on the CFM programmable
board. Connect Class 2 control wiring: see Figure 9, for sin-
gle stage thermostat wiring: see Figure 10 for two stage ther-
mostat wiring. .
Apply strain relief to thermostat wires passing through the
cabinet.
NOTE: Some electronic thermostats do not have adjustable
heat anticipators. They may have other type cycle rate adjust-
ments. Follow the thermostat manufacturer's instructions.
The 24volt, 40 VA transformer is sized for the furnace compo-
nents only, and should not be connected to auxiliary devices
such as humidifiers, air cleaners, etc. The transformer may
provide power for an air conditioning unit contactor.
Use copper conductors only.
FIGURE 8 : Upflow Models - Electrical Wiring
BLK/BLK
WHT/WHT
GRN/GRN
HUM
EAC
WIRING INSIDE
JUNCTION BOX
BURNER
COMPARTMENT
CFM/TIMER
BOARD
BLOWER
COMPARTMENT
IGNITION MODULE
CLASS 2 SYSTEM
CONTROL WIRING
TO THERMOSTAT
DOOR SWITCH
JUNCTION BOX
EAC (HOT
)
HUM (HOT)
GND.
N
L1
(HOT)
WHT
GRN
BLK
Set the heat anticipator in the room thermostat as
shown below. Setting it lower will cause short cycles.
Setting it higher will cause the room temperature to
exceed the setpoint.
Two-Stage Thermostat First Stage .4 Amps
Second Stage .1 Amps
Single Stage Thermostat .4 Amps
FIGURE 9 : Field Wiring for Single Stage Thermostat
TYPICAL FIELD WIRING - SINGLE STAGE
SINGLE STAGE
THERMOSTAT
HUMY2
Y1
Y
RW1W2G
C
OX/L
Y1
R
W1
G
C
LOW HEAT TIME
ADJUSTMENT
CFM/TIMER BOARD
MINUTE SELECT
10
15
20
TIME OFF
HUM
Y2
Y1
Y
R
W1W2
O
C
O
X/L HUM
HEAT PUMP
HUMDISTAT COOL HEAT DELAY ADJ
P9
P6
W1
W2
10
15
20
MINUTE SELECT

035-17438-001 Rev. A (901)
Unitary Products Group 13
24 Volt Connections
This variable airflow furnace includes a CFM selection board
in the lower part of the electrical control box. All field wiring
connections should be made to this terminal block.
Connection diagrams are shown above in Figures 9 and 10.
Select the correct diagram for your particular heating and
cooling system.
SAFETY CONTROLS
Blower Door Safety Switch
This unit is equipped with an electrical interlock switch
mounted in the blower compartment. This switch interrupts all
power at the unit when the panel covering the blower com-
partment is removed.
Electrical supply to the unit is dependent upon the panel that
covers the blower compartment being in place and properly
positioned.
Rollout Switch Controls
These controls are mounted on the burner assembly. If the
temperature in the burner compartment exceeds its set point,
the ignitor control and the gas valve are deenergized. This is
a manual reset control and must be reset before operation
can continue.
The operation of this control indicates a malfunction in the
combustion air blower or a blocked vent pipe connection.
Pressure Switch
This furnace is supplied with two differential pressure
switches which monitor the flow through the furnace and
venting system. This switch de-energizes the ignition control
module and the gas valve if any of the following conditions
are present:
1. Blockage of internal flue gas passage ways.
2. Blockage of vent piping.
3. Failure of combustion air blower/motor.
Limit Control
The high temperature limit control is located on the furnace
vestibule panel just to the right and above the gas valve. This
is an automatic reset control and provides over temperature
protection due to reduced airflow, such as a dirty filter or
blower motor failure.
Auxiliary Limit Controls
These high temperature limit controls are located in the
blower compartment, one on each side on upflow/horizontal
unit. Downflow units have a single limit mounted on the
blower assembly. These are manual reset controls and give
high temperature protection when the unit is applied in the
horizontal position.
Control Circuit Fuse
A 3 amp fuse is provided to protect the 24 volt transformer
from overload caused by control circuit wiring errors. This is
an ATO 3, automotive type fuse and is located in the unit wir-
ing harness between the control transformer and the furnace
control.
FIGURE 10 : Field Wiring for Two Stage Thermostat
DO NOT connect field wiring to the furnace ignition
control module.
Blower and burner must never be operated without
the blower panel in place.
TYPICAL FIELD WIRING - TWO STAGE
TWO STAGE
THERMOSTAT
Y1
Y2 OUT
R
C
X/L
JUMPER MUST BE IN
TIMER OFF POSITION
CFM/TIMER
BOARD
Y2
Y1
Y
RW1W2
G
COX/L HUM
OUTDOOR
UNIT
Y2
Y1
R
W1
W2
Y2
G
C
X/L
Main power supply to the unit must still be inter-
rupted at the main power disconnect switch before
any service or repair work is to be done to the unit.
Do not rely upon the interlock switch as a main
power disconnect.

035-17438-001 Rev. A (901)
14 Unitary Products Group
STARTUP AND ADJUSTMENTS
The initial startup of the furnace requires the following addi-
tional procedures.
1. When the gas supply is initially connected to the furnace,
the gas piping may be full of air. In order to purge this air,
it is recommended that the ground joint union be loos-
ened until the odor of gas is detected. When gas is
detected, immediately retighten the union and check for
leaks. Allow five minutes for any gas to dissipate before
continuing with the startup procedure.
2. All electrical connections made in the field and in the fac-
tory should be checked for proper tightness.
IGNITION SYSTEM CHECKOUT/ADJUSTMENT
1. Turn the gas supply ON at external valve and main gas
valve.
2. Set the thermostat above room temperature to call for
heat.
3. System startup will occur as follows:
a. The ventor motor will start and operate on low
speed. Shortly after ventor startup, the hot surface
ignitor will glow for about 17 seconds.
b. After this warm-up cycle, the ignition module will
energize (open) the main gas valve on low fire for
seven seconds.
c. After flame is established, the supply air blower will
start within 30 seconds.
NOTE: Burner ignition may not be satisfactory on first star-
tup due to residual air in gas line, or until gas pressure (mani-
fold) is adjusted.
4. With the furnace in operation, paint the pipe joints and
valve gasket lines with a rich soap and water solution.
Bubbles indicate a gas leak. Take appropriate steps to
stop the leaks. If the leak persists, replace the compo-
nent.
Gas Valve Operation
The manual switch is a two-position (ON-OFF) type. To turn
the valve on, move switch to the “ON” position. Refer to Fig-
ure 11 on page 15.
CHECKING GAS INPUT
1. Turn off all other gas appliances connected to gas meter.
2. With the furnace turned on, measure the time neededfor
one revolution of the hand on the smallest dial on the
meter. A typical domestic gas meter usually has a 1/2 or
1 cubic foot test dial.
3. Using the numberof seconds for each revolution and the
size of the test dial increment, find the cubic feet of gas
consumed per hour from Table 4 on page 15.
NOTE: To find the Btuh input, multiply the number of cubic
feet of gas consumed per hour by the BTU content of the gas
in your particular locality. Contract your gas company for this
information, as it varies widely from city to city.
EXAMPLE: It is found by measurement that it takes 26 sec-
onds for the hand to turn on the 1 cubic foot dial to make a
revolution with only a 120,000 Btuh furnace running. Using
this information, locate 26 seconds in the first column of.
Read across to the column headed 1 Cubic Foot where you
will see that 138 cubic feet of gas per hour are consumed by
the furnace at that rate. Multiply 138 by 850 (the BTU rating
of the gas obtained from the local gas company). The result is
117,300 Btuh, which is close to the 120,000 Btuh rating of the
furnace.
If the actual input is not within +2% of the furnace rating, with
allowance being made for the permissible range of the regu-
lator setting (0.3 inches W.C.), replace the orifice spuds with
spuds of the proper size.
ADJUSTMENT OF MANIFOLD GAS PRESSURE
The regulated outlet pressures, both low and high, have been
calibrated at the factory. Additional pressure adjustment
should not be necessary. If adjustment is necessary, set to
the following specifications. Check high pressure before
checking or adjusting low pressure. After adjustment, check
for gas leakage.
High Outlet Pressure Adjustment
1. Turn off all electrical power to the system at main fuse or
circuit breaker. Close manual gas valve.
2. Attach a manometer to the outlet pressure tap of the
valve.
3. Turn on power and energize main and redundant (P.M.)
solenoids as well as the HI terminal. Open manual gas
valve.
4. Remove high adjustment seal screw to expose the 3/32”
set screw, see Figure 11 on page 15.
5. To increase outlet pressure, turn the 3/32” set screw
clockwise. To decrease outlet pressure, turn the set
screw counterclockwise. Adjust regulator until pressure
shown on manometer matches the pressure specified on
the appliance rating plate.
DO NOT omit this test! NEVER use a flame to check
for gas leaks.
Be sure to relight any gas appliances that were
turned off at the start of this input check.
NATURAL GAS
Low Fire 1.6 IWG
High Fire 3.5 IWG

035-17438-001 Rev. A (901)
Unitary Products Group 15
6. Replace high adjustment seal screw and tighten
securely. Cycle the valve two or three times to verify reg-
ulator setting.
7. Once the correct high outlet gas pressure to the burners
has been set adjust the low outlet pressure per the
adjustment procedure detailed in the next section..
Low Outlet Pressure Adjustment
1. Adjust the thermostat so the furnace will operate at low
fire.
2. Refer to Figure 11, for the location of the pressure regu-
lator adjustment cap and screw on main gas valve.
3. Remove low adjustment seal screw, see Figure 11.
4. To increase outlet pressure, turn the 3/32” set screw
below the low adjustment seal screw clockwise. To
decrease outlet pressure, turn the set screw counter-
clockwise. Adjust regulator until pressure shown on
manometer matches the pressure specified on the appli-
ance rating plate.
5. Replace low adjustment seal screw and tighten securely.
Cycle the valve several times to verify regulator setting.
6. Turn off gas and electricity and remove manometer and
gas valve tap and replace the outlet pressure tap plug.
7. Turn the electrical and gas supplies back on, and with
the burners in operation, check for gas leakage around
the plug with a soap and water solution.
ADJUSTMENT OF TEMPERATURE RISE
Direct Drive Motors (only applies to PSC replacement)
The temperature rise, or temperature difference between the
return air and the heated air from the furnace, must be within
the range shown on the furnace rating plate. Application limi-
tations are shown in Table 1 or 2. After the temperature rise
has been determined, the cfm can be calculated.
After about 20 minutes of operation, determine the furnace
temperature rise. Take readings of both the return air and the
heated air in the ducts, about six feet from the furnace where
they will not be affected by radiant heat.
Table 4: GAS RATE (CUBIC FEET PER HOUR)
SECONDS FOR
ONE REVOLUTION SIZE OF TEST DIAL
1/2 CUBIC FT 1 CUBIC FT
10 180 360
12 150 300
14 129 257
16 113 225
18 100 200
20 690 180
22 82 164
24 75 150
26 69 138
28 64 129
30 60 120
32 56 113
34 53 106
36 50 100
38 47 95
40 45 90
42 43 86
44 41 82
46 39 78
48 37 75
50 36 72
52 35 69
54 34 67
56 32 64
58 31 62
60 30 60
The manifold pressure must be checked with the
screw-off cap in place on the pressure regulator.
If manifold pressure is too high, an overfire condition
exists which could cause heat exchanger failure. If
the manifold pressure is too low, sooting and even-
tual clogging of the heat exchanger could occur.
Be sure that the gas valve pressure regulator cap is
replaced.
FIGURE 11 : Gas Valve - (Top) Manual On/OFF Switch
(Bottom) Regulator Adjustments
R
E
P
L
A
C
E
R
E
P
L
A
C
E
S
C
R
E
W
S
C
R
E
W
INLET
OUTLET
ON / OFF SWITCH
WRENCH
BOSS
LOW FIRE
REGULATOR
ADJUSTMENT
SEAL SCREW
HIGH FIRE
REGULATOR
ADJUSTMENT
SEAL SCREW
HI ADJUST
LO ADJUST
PM
C
HI
O
F
F
ON

035-17438-001 Rev. A (901)
16 Unitary Products Group
Increase the blower speed to decrease the temperature rise;
decrease the blower speed to increase the rise.
All direct-drive blowers have multi-speed motors. The blower
motor speed taps are located in the control box in the blower
compartment.
You may select a heating speed and a cooling speed. They
may be the same speed or a different speed.
To use the same speed tap for heating and cooling, the heat
terminal and cool terminal must be connected using a jumper
wire and connected to the desired motor lead. Place all
unused motor leads on Park terminals. Two Park terminals
are provided.
Variable Speed Motors
The temperature rise, or temperature difference between the
return air and the heated air from the furnace, must be within
the range shown on the furnace rating plate and within the
application limitations shown in Table 3 on page 7.
HEATING AIRFLOW
The heating airflow has been preset at the factory to provide
maximum CFM. If a lesser CFM is required for a specific
HVAC system the “JUMPER” on the HEAT selection pins on
the CFM-Timer Board may be moved to tap “B” or “C”, or “D”.
Pins “A” will provide the highest CFM and “D” the lowest
CFM. Refer to Table 6 on page 17 for CFM options.
NOTE: Power to the blower must be removed for at least 4
seconds after a heat or cool tap selection change, in order for
the motor to recognize an adjustment.
The fixed blower on delay and adjustable blower-off delay will
function as described in the “OPERATION AND
MAINTENANCE" Section on page 18 of this instruction.
NOTE: When changing jumper positions, make sure that
the jumper is pushed all the way on the pins. If the jumper is
not making good contact or is left off completely, the blower
will operate as if the jumper were in the “A” position.
COOLING AIRFLOW
The Cooling airflow is preset at the factory to provide approx-
imately 90% of the maximum CFM and must be adjusted in
the field to match the HVAC system at installation. Refer to
the outdoor unit installation instruction for the recommended
airflow and Table 6 on page 17.
The "DELAY" Tap should be set in the "B" position for a two-
stage condenser. This results in a 45 second off delay at 82%
of the programmed cooling airflow with a 15-second coast to
stop. It should be set in the "C" position for a system with a
TXV or solenoid valve. This results in a 45 second off delay at
75% of the programmed cooing airflow with a 15-second
coast to stop. It should be set in the "D" position for a system
without a TXV or solenoid valve. This results in a 60 second
off delay at 82% of the programmed cooling airflow with a 15-
second coast to stop. The "A" position is the factory setting
and is used for test purposes. With the delay set in the “A”
position, the blower will operate at 100% of the programmed
cooling air flow for 60 seconds, with a 15 second coast to
stop.
NOTE: When changing jumper positions, make sure that
the jumper is pushed all the way on the pins. If the jumper is
not making good contact or is left off completely, the blower
will operate as if the jumper were in the “A” position.
ADJUSTMENT OF FAN-OFF CONTROL SETTINGS
This furnace is equipped with a time-on/time-off heating fan
control. The fan-on is fixed at 30 seconds. The fan-off delay is
factory set to 60 seconds, however, it is field adjustable to 90,
120, or 180 seconds. The fan-off setting must be long enough
to adequately cool the furnace, but not so long that cold air is
blown into the heated space.
The continuous fan speed and the fan-off timing may be
adjusted by setting the DIP switches located on the control
board as follows: (See Figure 12 and Table 5).
This continuous fan speed dip switch (switch 3) on the igni-
tion control has no effect on setting and should be left in the
“OFF” position, as continuous fan speed is determined by the
variable speed motor program.
Do not energize more than one motor speed at a
time or damage to the motor will result.
Table 5: FAN CONTROL SETTINGS
IGNITION CONTROL
To Delay Fan-Off By: Set Switch
1-2
60 Sec. On-On
90 Sec. Off-On
120 Sec. On-Off
180 Sec. Off-Off
FIGURE 12 : Typical Heat/Cool Speed Tap
Connections
OFF ON
SWITCH 3 SHOULD
BE LEFT IN “OFF
POSITION
COOL
HEAT LO
HEAT HI
LINE
WI W2 YRGB
FAN OFF
ADJUSTMENT
SWITCHES

035-17438-001 Rev. A (901)
Unitary Products Group 17
AIRFLOW
All CFM’s are shown at 0.5” w.c. external static pressure.
These units have variable speed motors that automatically
adjust to provide constant CFM from 0.0” to 0.6” w.c. static
pressure. From 0.6” to 1.0” static pressure, CFM is reduced
by 2% per 0.1” increase in static. Operation on duct systems
with greater than 1.0” w.c. external static pressure is not rec-
ommended.
At some settings, LOW COOL and/or LOW HEAT air flow
may be lower that what is required to operate an airflow
switch on certain models of electronic air cleaners. Consult
the instructions for the electronic air cleaner for further
details.
FIGURE 13 : CFM Selection board
Table 6: AIRFLOW DATA - MID EFFICIENCY 2 STAGE CFM/TAP SELECTION - VARIABLE SPEED
HIGH/LOW SPEED COOLING AND HEAT PUMP CFM
MODEL JUMPER SETTINGS
P*DUA12V06401
G8V08012UHA11
L8V08012UHA11
P*DUB16V08001
G8V10016UHB11
L8V10016UHB11
P*DUC20V08001
G8V1002UHC11
L8V1002UHC11
P*DUC20V09601
G8V12020UHC11
L8V12020UHC11 COOL TAP ADJ TAP
High Low High Low High Low High Low
1340 740 1675 920 2050 1135 2020 1130 A B
1155 635 1555 850 1860 980 1855 960 B B
1220 671 1525 830 1945 1035 1920 1010 A A
1050 578 1410 795 1665 910 1680 850 B A
1100 605 1355 760 1740 950 1765 910 A C
913 502 1330 750 1575 880 1630 820 C B
945 520 1280 710 1440 830 1485 760 B C
726 400 1145 625 1325 760 1355 720 D B
830 456 1235 680 1410 820 1465 745 C A
660 400 1035 555 1190 725 1210 650 D A
747 411 1105 600 1245 745 1260 695 C C
594 400 920 495 1065 690 1080 595 D C
HIGH/LOW HEAT CFM
MODEL JUMPER SETTINGS
P*DUA12V06401
G8V08012UHA11
L8V08012UHA11
P*DUB16V08001
G8V10016UHB11
L8V10016UHB11
P*DUC20V08001
G8V1002UHC11
L8V1002UHC11
P*DUC20V09601
G8V12020UHC11
L8V12020UHC11 HEAT TAP ADJ TAP
High Low High Low High Low High Low
1315 880 1490 990 1480 975 1950 1330 A Any
1185 795 1350 900 1350 900 1840 1165 B Any
1075 720 1240 820 1235 815 1705 1055 C Any
990 665 1140 760 1140 770 1535 960 D Any
CFM SELECTION BOARD
TAP SELECTION
D
C
B
A
D
C
B
A
COOL HEAT ADJ DELAY
REMOVE FOR
HEAT PUMP HUMIDISTAT

035-17438-001 Rev. A (901)
18 Unitary Products Group
ACCESSORY CONNECTIONS
The furnace control will allow power switching control of vari-
ous accessories. Refer to Figure 14 for connection details.
Electronic Air Cleaner Connection
Two 1/4” spade terminals (EAC and EAC N) for electronic air
cleaner connections are located on the control board. The
terminals provide 115 VAC (1.0 amp maximum) during circu-
lating blower operation. These terminals are energized in
continuous fan mode only if the green wire labeled “G Cool
Speed” is connected as described below. A high voltage con-
nection lead is routed to the junction box for easy connection.
Humidifier Connection
Two 1/4” spade terminals (HUM and HUM N) for humidifier
connections are located on the control board. The terminals
provide 115 VAC (1.0 amp maximum) during heating system
operation. A high voltage connection lead is routed to the
junction box for easy connection.
OPERATION AND MAINTENANCE
SEQUENCE OF OPERATION
The following describes the sequence of operation of the fur-
nace as it relates to a furnace equipped with a variable speed
blower. Refer to the schematic wiring diagram on page 26 for
component location.
CONTINUOUS BLOWER
There are two modes of continuous blower operation. In one
mode the blower is controlled directly through the blower
motor. In the second mode the blower is controlled through
the ignition control. In the first mode, when the thermostat
fan-switch is set to the ON position a circuit is completed
between terminals “R” and “G” of the thermostat. The contin-
uous fan speed will be 63% of the high cool speed. If more air
is desirable the green wire labeled (G Cool Speed) may be
connected to the “G” terminal of the ignition control to achieve
HIGH COOL speed (DIP switch number 3 on the ignition con-
trol must be in the OFF position).
Intermittent Blower Cooling
On cooling/heating thermostats with fan switch, when the fan
switch is set in the auto position and the thermostat calls for
cooling, a circuit is completed between the R, Y and G termi-
nals. The motor is energized through the Y1 cool terminal
and runs on the speed selected on the CFM / Timer board.
The fan off setting is fixed at 60 seconds for SEER enhance-
ment.
HEATING OPERATIONAL SEQUENCE
Two Stage Thermostat
The ignition control in this furnace is unique to this product.
The control allows for a 24 volt or a 115 volt circulator input/
output. This allows for the replacement of the variable speed
motor with a multi-speed PSC motor in the event a variable
speed motor is not available at the time of servicing.
In a typical system, a call for first stage heat is initiated by
closing the W1 thermostat contacts. The inducer blower is
energized at high speed and the control waits for the low
pressure switch contacts to close. The inducer blower is
energized at low speed and the 120 VAC silicon carbide igni-
tor is powered.
At the end of the ignitor warmup time, the first stage of the
two stage gas valve is energized (low fire). Flame must be
detected within 7 seconds. If flame is detected, the delay-to-
fan-on period begins. After the delay-to-fan-on period ends,
the circulator fan is energized at low heat speed and the air
cleaner and humidifier are energized.
A call for second stage heat (W1 and W2) after a call for first
stage heat will energize the inducer at high speed and ener-
gize the circulator at high heat speed. The circulator will ener-
gize at high heat speed after 30 seconds with a call for
second stage heat. If the furnace has been operating in first
stage heat for more than 30 seconds and the control receives
a call for second stage heat, the blower will immediately
switch to high speed. The second stage pressure switch con-
tacts will close and energize the second stage gas valve (high
fire).
If a call for second stage heat occurs at the same time as a
call for first stage heat, the second stage heat is energized
immediately after flame rectification is sensed on fist stage.
When the second stage of the thermostat is satisfied, the
inducer motor is reduced to low speed and the 2nd stage gas
valve is de-energized to 1st stage. The circulator remains on
high heat speed for 30 seconds then de-energizes to low
heat speed.
FIGURE 14 : Accessory Connections
115 VOLT
HUMIDIFIER
115 VOLT
ELECTRONIC
AIR CLEANER
BLK
WHT
EAC HOT
HUM. HOT
BLK
WHT
EAC
HUM
EAC
HUM NEUTRALS
SWITCHED
CIRCUITS
Label all wires prior to disconnecting when servicing
controls. Wiring errors can cause improper and dan-
gerous operation. Verify proper operation after ser-
vicing.

035-17438-001 Rev. A (901)
Unitary Products Group 19
When the first stage of the thermostat is satisfied, the gas
valve is deenergized and the heat delay to fan off begins tim-
ing. The inducer will postpurge for an additional 15 seconds,
then the inducer and humidifier will deenergize. Upon com-
pletion of the heat delay-to-fan-off, the circulator and air
cleaner are deenergized. For control timing, refer to Figure
15 on page 20.
If flame is not detected during the trial for ignition period, the
gas valve is de-energized, the ignitor is turned off and the
ignition control goes into the “re-try” sequence.
The ”re-try” sequence provides a 60 second wait with inducer
interpurge following an unsuccessful ignition attempt (flame
not detected). After this wait, the ignition sequence is
restarted with an additional 10 seconds of ignitor warmup
time. Two retries will be attempted before the control goes
into system lockout. If flame is established for more than 10
seconds after ignition, the ignition controller will clear the igni-
tion attempt (or retry) counter.
If flame is detected, then lost, the ignition control will repeat
the initial ignition sequence. After 5 attempts to sustain flame,
the control will go into system lockout.
During burner operation, a momentary loss of power of 50
milliseconds or longer will deenergize the main gas valve.
When power is restored, the gas valve will remain deener-
gized and a restart of the ignition sequence will begin imme-
diately.
A momentary loss of gas supply, flame blowout, or a shorted
or open condition in the flame probe circuit will be sensed
within 0.8 seconds. The gas valve will deenergize and the
control will restart the ignition sequence.
Recycles will begin and the burner will operate normally if the
gas supply returns, or the fault condition is corrected, before
the last ignition attempt. Otherwise, the control will go into
system lockout.
If the control has gone into system lockout, it may be possible
to reset the control by a momentary power interruption of one
second or longer. Refer to the “FURNACE CONTROL DIAG-
NOSTICS” on page 24 of this instruction for reset informa-
tion.
Single Stage Thermostat
If a single stage thermostat is used the unit will be controlled
through the CFM Timer board timer adjust pins (refer to Fig-
ure 9 on page 12). For the furnace to operate on High Fire
the timer jumper must be placed on the 10, 15 or 20 minute
adjustment terminals. On a call for heat the unit will operate
on low fire as detailed above. If the heating requirements
cause the cycle to exceed the jumper settings, the high fire
timer will energize the second stage heat. The second stage
operation will function as detailed above. The heating cycle
will be completed in high fire operation. If the timer jumper is
in the “TIME OFF” position with a single-stage thermostat, the
unit will stay in low fire operation.

035-17438-001 Rev. A (901)
20 Unitary Products Group
FIGURE 15 : Sequence Timing For Ignitor Control
W2 SIGNAL
ON
CLOSED
OPEN
OPEN
CLOSED
ABSENT
PRESENT
HIGH INDUCER
HIGH STAGE PRESSURE
SWITCH AND 2ND STAGE
MAIN VALVE
CIRCULATOR HIGH
HEAT SPEED
2ND STAGE
CALL HIGH HEAT AFTER LOW
HEAT IS ESTABLISHED
HIGH
HEAT
OFF
DELAY
30 SEC.
HIGH LIMIT
W1 SIGNAL
LOW
INDUCER
LOW STAGE
PRESSURE
SWITCH
HSI
1ST STAGE
MAIN VALVE
FLAME
SENSE
LOW CIRCULATOR
HEAT SPEED
1ST STAGE LOW PRESSURE
SWITCH CLOSE
RECOGNITION
HSI
WARM
UP
17 SEC.
IGNITION
ACTIVATION
PERIOD
4 SEC.
TRIAL FOR
IGNITION
7 SEC.
INTER-
PURGE
60 SEC.
HSI
WARM
UP
27 SEC.
IGNITION
DEACTIVATION
PERIOD
3 SEC.
HEAT FAN
DELAY ON
30 SEC.
BURN
TIME
POST
PURGE
15 SEC.
HEAT FAN DELAY OFF
SELECTABLE
60,90,120,180 SEC.
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
NOTE:
1. THIS DIAGRAM SHOWS TWO IGNITION ATTEMPTS
2. TIMING LENGTHS ARE NOT TO SCALE