Aire-Flo AF80MPA Series User guide

AIRE FLO
PO BOX 794297
DALLAS, TX 75379
AF80MPA SERIES
INSTALLATION AND SERVICING INSTRUCTIONS
UPFLOW, DOWNFLOW OR HORIZONTAL GAS-FIRED
NON-CONDENSING
WARM AIR FURNACE
Issue 0406
TABLE OF CONTENTS
Safety 2
Furnace Specifications 3
Introduction 6
Location/Placement 6
Air for Combustion & Ventilation 8
Ducting n
Venting 12
Electrical Connections 15
RETAIN THESE INSTRUCTIONS FOR FUTURE REFERENCE
Gas Connections
Unit Sequence of Operation ...
Start-Up Operation & Checkout
Sequence of Operation
Servicing The Furnace
Trouble Shooting Guide
Wiring Diagram
16
17
18
22
23
25
26
A WARNING
If the information in this manual is not
followed exactly, a fire or explosion
may result 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.
Installation and service must be performed
by
a qualified installer, service agency or
the gas supplier. Installation by an
unqualified person may lead to equipment
damage and/or a hazardous condition
which may cause bodily injury and harm
and, as such, at the sole discretion of the
manufacturer, the entire warranty may be
voided and be of no further force and
effect.
A DANGER
Electric Shock Hazard
Turn Off All Power
Before Servicing.
WHAT TO DO IF YOU SMELL GAS:
• Do not try to light any appliance.
' Extinguish any open flame.
' 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.
20543402
Issue 0406
Page 1 of 26

SAFETY
The following is a list of safety precautions and their locations in this manual.
These safety rules and precautions must be followed when installing this furnace.
1. Use only with 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 The
Location/Placement Section on page 6 of these instructions.
3. Provide adequate combustion and ventilation air to the furnace space as
specified in Air for Combustion and Ventilation section on page 8 of these
instructions.
4. Combustion products must be discharged outdoors. Connect this furnace to an
approved vent system only, as specified in Venting on page 12 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 The Gas Connection section on page 16 of these
instructions.
6. Always install furnace to operate within the furnace's intended temperature-rise
range with a duct system which has an external static pressure within the
allowable range, as specified in Furnace Specifications on page 3 of these
instructions. See furnace rating plate.
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 duct(s) sealed to the furnace casing and terminating outside
the space containing the furnace. See page 11 for Ducting.
8. A gas-fired furnace for installation in a residential garage must be installed as
specified in The Location / Placement section on page 6 of these instructions.
9. The furnace is not to be used for temporary heating of buildings or structures
under construction. As noted on page 6 under Introduction.
20543402 Issue 0406 Page 2 of 26

FURNACE SPECIFICATIONS
MODEL
A050B3
A075B3
A075B4
A100B3
A100B4
A100B5
A125B5
UNIT DIMENSIONS
LENGTH
A
29 1/2
29 1/2
29 1/2
29 1/2
29 1/2
29 1/2
29 1/2
WIDTH
B
13 1/2
13 1/2
17
17
17
20 1/2
20 1/2
HEIGHT
C
38 1/4
38 1/4
38 1/4
38/14
38 1/4
38 1/4
38 1/4
DUCT SUPPLY
OPENING
D
11 1/2
11 1/2
15
15
15
18 1/2
18 1/2
E
20 3/8
20 3/8
20 3/8
20 3/8
20 3/8
20 3/8
20 3/8
DUCT
RETURN
OPENING
F
12
12
15 1/2
15 1/2
15 1/2
19
19
G
21 5/8
21 5/8
21 5/8
21 5/8
21 5/8
21 5/8
21 5/8
VENT
PIPE
DIA.
H
4
4
4
4
4
4
4
MAX. OVER
CURRENT
PROTECTION
15
15
15
15
15
15
20
MAX.
UNIT
AMPS
9.9
9.9
11.7
6.9
11.7
11.7
11.7
ELECTRICAL
SUPPLY MIN.
WIRE
SIZE(AWG)
14
14
14
14
14
14
14
TEMPERATURE
RISE
RANGE
45-75
45-75
30-60
45-75
45-75
30-60
45-75
NET
WEIGHT
LBS
105
113
134
141
141
159
167
REDUCER SUPPLIED WITH FURNACE WHEN CONNECTION SIZE
IS DIFFERENT THAN PIPE DIA. REQUIRED (H) FOR FLUE VENT
PIPE.
TOP VENT CONNECTION
"H" (FLUE DIA.)* V
LOUVERED
ACCESS -
DOOR
CONTROL BOX
ACCESS PANEL"
"D"O.D.-
— 1
"P"
GAS INLET
(EITHER SIDE)
SIDE VENT CONNECTION-
"H" (FLUE DIA.)*
THERMOSTAT -
CONNECTIONS
(EITHER SIDE)
F0000167
-r
7 3/4
»E"O.D.
0 ELECTRICAL
I \ I CONNECTIONS
(EITHER SIDE)
.23 1/4.
SIDE RETURN
CUT-OUT
(EITHER SIDE)
— 1
15
-^| 7 5/16 |
20543402
Issue 0406
Page 3 of 26

FURNACE BLOWER SPECIFICATIONS AND AIR FLOW DATA
MODEL
A050B3
(10X6 WHEEL)
(1/3HP MOTOR)
BLOWER
SPEED
LOW*
MED
HIGH
EXTERNAL STATIC (IN. W.C.)
0.1
805
1140
1530
0.2
800
1125
1475
0.3
790
1090
1410
0.4
770
1060
1325
0.5
750
1010
1235
0.6
715
955
1155
0.7
685
880
1065
0.8
620
815
985
0.9
535
710
855
1.0
385
580
720
A075B3
(10X6 WHEEL)
(1/3HP MOTOR)
LOW
MED *
HIGH
805
1140
1530
800
1125
1475
790
1090
1410
770
1060
1325
750
1010
1235
715
955
1155
685
880
1065
620
815
985
535
710
855
385
580
720
A075B4
(12X9 WHEEL)
(1/2HP MOTOR)
LOW
MED *
HIGH
1375
1625
2020
1365
1610
1945
1350
1595
1910
1330
1580
1880
1315
1550
1845
1295
1510
1800
1240
1475
1755
1195
1425
1690
1085
1335
1605
975
1225
1470
A100B3
(10X9 WHEEL)
(1/4HP MOTOR)
LOW
MED *
HIGH
1234
1377
1510
1228
1356
1475
1204
1320
1427
1163
1268
1366
1104
1200
1291
1028
1117
1203
934
1018
1102
823
903
987
695
773
859
549
627
718
A100B4
(12X9 WHEEL)
(1/2HP MOTOR)
LOW
MED*
HIGH
1375
1625
2020
1365
1610
1945
1350
1595
1910
1330
1580
1880
1315
1550
1845
1295
1510
1800
1240
1475
1755
1195
1425
1690
1085
1335
1605
975
1225
1470
A100B5
(12X12 WHEEL)
(1/2HP MOTOR)
LOW
MED *
HIGH
1440
2010
2530
1405
1985
2470
1365
1955
2425
1315
1910
2355
1270
1840
2270
1200
1770
2195
1155
1695
2100
1060
1630
1995
985
1535
1880
895
1395
1760
A125B5
(12X12 WHEEL)
(1/2HP MOTOR)
LOW
MED *
HIGH
1440
2010
2530
1405
1985
2470
1365
1955
2425
1315
1910
2355
1270
1840
2270
1200
1770
2195
1155
1695
2100
1060
1630
1995
985
1535
1880
895
1395
1760
NOTES:
1. Air flow values in cubic feet per minute (CFM).
2. Data taken without filters in place or A/C evaporator in place.
3. Factory setting for cooling is High Speed and heating is indicated by "*"
A WARNING
When operating the furnace in the heating mode, the static pressure and the temperature rise (supply air temperature
minus return air temperature) must be within those limits specified on the rating label. Failure to follow this warning
could lead to severe furnace damage.
AWARNING
Turn OFF all gas and electrical power to furnace before performing any maintenance or service on unit. (Unless
specific test requires gas and electrical supplies.) Failure to take this precaution may result in personal injury due
to electrical shock or uncontrolled gas leakage.
20543402
Issue 0406
Page 4 of 26

FURNACE WIRING SPECIFICATIONS
a—WHEN
USED
FACTORY SETTING HEAT SPEED
SEE INSTALLATION INSTRUCTIONS RR FACTORY SETTINGS
JUMPER
LED FAULT
STEADY OF
STEADY DN
HEARTBEAT
FAST HEARTBEAT
2 FLASHES
3 FLASHES
4 FLASHES
5 FLASHES
6 FLASHES
7 FLASHES
[DDES
- - - ND POO
- - - CONTROL HARDWARE FAULT
- - - POWER APPLIED
- - - CALL FOR HEAT
- - - FLAME FAILURE LOCKOUT
- - - PRESSURE SWITCH STUCK CLOSED OR DPEW
HIGH LIMIT CIRCUIT OPEN
- - - FLAME SENSE WITH GAS VALVE OFF
- - - ROLLOUT SWITCH OPEN
- - - POLARITY FAULT
F0000398
FACTORY WRING
HIRING
LINE
24 V
O ORANGE WIRE NJT
GROUND
LEGEND
K BLACK
BL BLLE
BR BROWN
GR GREN
DR ORANGE
RD RED
VI VIOLET
WH WHITE
YL YELLOW
1
p
RLE
BI
CU
*
AL
T
Fl
T|
IBS-—
LIMIT
PRESSURE SWITCH
ROLL OUT SWITCH *
blower interlock:
CONDENSING UNIT
MANJAL RESET
AUXILIARY LIMIT
TRANSfKHR
UW VOLT. FUSE
IN LINE [DN1CTIDN
INDUCER HUB? SWITCH
MJIbS:
(1) MAKE FIBJ POe SUPPLY COWECTKNS TD BLACK AND WHITE WIRES
CAPPED WITH DRANE WIRE NUTS,
(2) WARNING—UNIT MUST BE GROUNDS]. WRING MUST CDNRflM JD N.E.C AND
LDCAL CKS,
(3) IF ANY IF THE ORIGINAL VIE, AS SUPPL1E) WITH TfE FURNACE, MUST BE
REPLACED, IT MUST BE RffLACEO WITH WRING MATERIAL HAVING A
TEWERATURE RATING IF AT LEAST 105 C AND BE A MINDiiH LF IB GA.
AWG COPPK STRAND WIRE.
(4) CONNECT REQUIRED MDTDR LEAD TD ei TERMINAL DN CIRQilT BOARD TD
DELIVK A TDiPERATUE RISE WITHIN THE RANE SPECIFIED CN THE
RATING LABB_. CDJNECT MM LEADS TD THE PARK TffiMINALS.
(5) SET THE HEAT ANTICIPATDR ON HE THRMOSTAT AT 0.25 AMPS.
(6) LDV V1T. FUSE 5 AMP AUTOMOTIVE TYPE LITTLffUSE 257005 OR BUSS AT C5.
F0000399
20543402 Issue 0406
Page 5 of 26

A WARNING
The furnace cabinet must have an uninterrupted or unbroken electrical ground to minimize personal injury if an
electrical fault should occur. The unit must also be electrically grounded in accordance with local codes, or in the
absence of local codes, with the latest edition of the (U.S.) National Electrical Code ANSI/NFPA No. 70 or CSA
Standard C22.1: Part 1 Canadian Electrical Code, if an external electrical source is utilized. DO NOT use gas piping
as an electrical ground.
INTRODUCTION
This furnace is design certified by CSA International as a Category I furnace using air from inside the structure for
combustion.
It is shipped as a packaged unit, complete with burners and controls, and requires a line voltage (115V) connection to
the junction box, a thermostat hook-up as per the wiring diagram and a gas line connection, ducting and flue piping. This
furnace can be installed in either upflow, downflow or horizontal airflow positions, at no time should this unit be
operated on its back. The design of this furnace is NOT CSA Certified for installation in recreation vehicles, in
manufactured (mobil) homes, outdoors or for temporary construction heating.
This furnace has been designed to interface with split system cooling equipment (approved by a nationally recognized
testing laboratory) so as to provide "year round air conditioning". The blower has been sized for both heating and cooling
and the furnace controls include a cooling fan relay.
The furnace installation must conform with local building codes or in the absence of local codes, with the latest edition
of the (U.S.) National Fuel Gas Code ANSI Z223.1 (NFPA-54) or Canadian Natural Gas and Propane Installation Codes
CSAB149.1.
For complete information on installation standards consult the (U.S.) National Fuel Gas Code, obtainable from the
National Fire Protection Association, Inc., Batterymarch Park, Quincy, MA 02269 or the American Gas Association, 1515
Wilson Boulevard Arlington, VA 22209 or the Canadian installation codes obtainable from Canadian Standards Association,
178 Rexdale Boulevard, Etobicoke, Ontario, Canada M9W 1R3.
This furnace is designed for minimum continuous return-air temperature of 60°F dB or intermittent operation down to
55°F dB such as when used with a night setback thermostat. Return-air must not exceed a maximum continuous
temperature of 85°F dB.
These instructions are written for individual residential installation only. For multi-unit installation or
commercial applications, please contact manufacturer for recommendations.
LOCATION / PLACEMENT
Site Selection:
Clearances:
This furnace may be located in an attic, closet, basement, crawl space, alcove or suspended from the
ceiling of a utility room or basement. Select a location that will meet all requirements for safety,
clearances, ventilation and combustion air, ductwork design, gas piping, electrical wiring and venting.
The following minimum clearances, or greater, must be provided between the furnace and adjacent
construction.
TABLE 1
MINIMUM INSTALLATION CLEARANCES
"UPFLOW" POSmON
Suitable for alcove or closet
installationt on combustible
flooring at minimum
clearance from adjacent
construction not less than
the following:
Top
2"
2"
Sides
1"
1"
"DOWNFLOW" POSITION
Suitable for alcove or closet installation! on non-
combustible flooring at minimum clearance from
adjacent construction not less than the following:
* Installation on combustible flooring only when
installed on special base (see model & rating label
for proper special base).
Back
1"
1"
Front
6"
3"
"HORIZONTAL" POSITION
Suitable for attic, alcove or closet installationt on
combustible flooring at minimum clearance from
adjacent construction not less than the following:
* Line contact only permissible between lines
formed by intersection of the top and two sides of
the furnace jacket and building joist, studs, or
framing.
Vent
6" with single wall vent
1" with B1 vent
t For closet installation see Air for Combustion and Ventilation.
20543402
Issue 0406
Page 6 of 26

A WARNING
Failure to comply with all of the clearances will
create a fire hazard.
INSTALLATION POSITIONS
AIRFLOW
AIRFLOW
F0000404
The furnace should also be located as near to the
center of the air distribution system as possible, and
should be installed level.
This furnace may be installed on non-combustible
flooring, on wood flooring in the upflow or horizontal
positions, however, it must not be installed directly on
carpeting, tile or any other combustible material. In
the downflow position, it must be installed on non-
combustible flooring, on the special base listed on the
rating label or on a cased coil.
In a horizontal position, line contact with conbustible
is only permissible between lines formed by the
intersection of the furnace top, the front and back sides,
and building joists, studs or framing (See Figure 1).
Figure 1
A clearance of at least 30" should be provided at the
front of the unit for servicing. For attic installations, the
passageway and servicing area adjacent to the furnace
should be floored.
If the furnace is to be installed in a crawl space,
consult local codes. (Use of a concrete pad 1" to 2" thick
is recommended.)
If the furnace is to be suspended from the ceiling, it
will be necessary to use steel pipe straps around each
end of the furnace. These straps should be attached to
the furnace with sheet metal screws and to the rafters
with bolts. The furnace may also be suspended by using
an angle iron frame bolted to the rafters. (See Table on
page 3 for size and weight of furnace.) Care must be
taken to allow for service access.
If a furnace is to be installed in a residential garage,
it must be installed so the burners and the ignition source
are located not less than 18" above the floor and the
furnace must be located or protected to avoid physical
damage by vehicles.
AWARNING
Do not place combustible material on the furnace
jacket. Failure to comply with this warning will
create a fire hazard.
AWARNING
This furnace is not watertight and is not designed
for outdoor installation. This furnace shall be
installed in such a manner as to protect the
electrical components from water. Outdoor
installation would lead to a hazardous electrical
condition and to premature furnace failure.
HORIZONTAL LINE CONTACT
LINE CONTACT ONLY PERMISSIBLE
BETWEEN TOP CORNERS OF FURNACE
AND BUILDING JOISTS, STUDS OR
FRAMING.
KEEP ALL INSULATING MATERIAL
CLEAR OF FURNACE. INSULATING
MATERIALS MAY BE COMBUSTIBLE.
Furnace must not lean back. It must be level or
tilt up to 2° to the front. (See Figure 1.)
20543402
Issue 0406
Page 7 of 26

AIR FOR COMBUSTION AND VENTILATION
Contaminated Combustion Air:
This furnace is not to be installed in a structure
defined as having contaminated combustion air. Allowing
exposure to substances containing chlorine or fluoride
could harm the furnace and void the warranty.
Substances to avoid include, but are not limited to:
Permanent wave solutions
Chlorinated waxes and cleaners
Chlorine based swimming pool chemicals
Water softening chemicals
De-icing salts or chemical
Carbon tetrachloride
Halogen type refrigerants
Cleaning solvents (such as perchloroethylene)
Printing inks, paint removers, varnishes, etc.
Hydrochloric acid
Cements and glues
• Antistatic fabric softeners for clothes dryers
Masonry acid washing materials
Unrefined gases
For purposes of this instruction the following
definitions apply:
AWARNING
Contaminated combustion air may cause premature
failure of the heat exchanger that may lead to a
hazardous condition and/or bodily harm, or loss of
life.
Adequate Ventilation and Combustion Air:
This section is provided to give guidelines for the
introduction of air for ventilation and combustion air. The
total quantity of air provided to the installation area must
equal the requirements of all gas appliances in the area.
Adequate facilities for providing air for combustion
and ventilation must be provided in accordance with the
latest edition of the National Fuel Gas Code ANSI
Z223.1/NFPA54 or CSA B149.1 Natural Gas and Propane
Installation Codes, or applicable provisions of the local
building codes.
The furnace shall be installed in a location in which
the facilities for ventilation permits satisfactory combustion
of gas, proper venting and maintenance of ambient
temperature at safe limits under normal conditions of use.
The furnace shall be located so as not to interfere with
proper circulation of air.
In addition to air needed for combustion, ventilation in
the form of process air must be provided as required for:
cooling of equipment or material, controlling dew point,
heating, drying, oxidation or dilution, safety exhaust and
odor control. Air must be supplied for ventilation,
including all air required for comfort and proper working
conditions for personnel.
Confined Space:
Unconfined Space:
A space whose volume is less
than 50 cubic feet per 1000
Btu/hr of the aggregate input
rating of all appliances installed
in that space.
A space whose volume is not
less than 50 cubic feet per 1000
Btu/hr of the aggregate input
rating of all appliances installed
in that space. Rooms
communicating directly with the
space in which the appliances
are installed, through openings
not furnished with doors, are
considered a part of the
unconfined space.
If the installation area meets the definition of
"Unconfined Space" and does not have additional air
requirements as described, the furnace may be installed
without making special provisions for combustion and
ventilation air.
A CAUTION
Whenever this furnace is installed in an area along
with one or more gas appliances, the total Btu/hr
input of all appliances must be included when
determining the free area requirements for
combustion and ventilation air openings.
AWARNING
Do not block the combustion or ventilation air
openings in the furnace. Any blockage will result in
improper combustion and may result in a fire
hazard or unsafe condition.
20543402
Issue 0406
Page 8 of 26

If ventilation and/or combustion air must be supplied to the "Confined Space" from inside the building structure, two
permanent openings to an additional room of sufficient volume as to combine the volumes of the spaces to meet the
criteria for an "Unconfined Space" must be created. Each opening must have a free area of not less than one square
inch per 1000 Btu per hour of total input of all appliances within the "Confined Space" (but not less than 100 square
inches). These openings must be located 12 inches from the top and bottom of the furnace area respectively and must
be at least 3 inches long on the smaller side of the opening (See Figure 2). Neither opening can be blocked at any time.
Figure 2
CONFINED SPACE / INDOOR AIR
A
FURNACE
DDD
QQD
12" MAX.
. WATER HEATER
OPENINGS TO
ITIONAL ROOMS
ISO- IN./1000 BTUH
OF TOTAL INPUT
TOTAL INPUT
(Btuh)
40,000
60,000
80,000
100,000
120,000
140,000
160,000
MIN. FREE AREA
(Sq. In.)
100
100
100
100
120
140
160
ROUND DUCT
(Dia. In.)
12
12
12
12
13
14
15
MAX.
EXAMPLE:
50,000 Btuh Furnace & 10,000 Btuh Water
Heater = 60,000 Btuh Total Input = 12"
Dia. Round Duct.
F0000264
If ventilation and/or combustion air must be supplied to the "Confined Space" from outside the building structure,
two permanent openings to the outdoors must be created. Each opening must have a free area of not less than one
square inch per 4000 Btu per hour of total input of all appliances within the "Confined Space". These openings must
be located 12 inches from the top and bottom of the furnace area respectively (See Figures 3, 4, and 5). Neither
opening can be blocked at any time.
Figure 3
CONFINED SPACE / OUTDOOR AIR
12" MAX:
OPENINGS TO
OUTDOORS
1SQ. IN./4000 BTUH
OF TOTAL INPUT
12" MAX.
TOTAL INPUT
(Btuh)
40,000
60,000
80,000
100,000
120,000
140,000
160,000
MIN. FREE AREA
(Sq. In.)
10
15
20
25
30
35
40
ROUND DUCT
(Dia. In.)
4
5
5
6
6
7
8
EXAMPLE:
50,000 Btuh Furnace & 10,000 Btuh Water
Heater = 60,000 Btuh Total Input = 5" Dia.
Round Duct.
F0000265
WATER HEATER
20543402
Issue 0406
Page 9 of 26

Figure 4
CONFINED SPACE / OUTDOOR AIR
FROM ATTIC
VENTILATI'
TOP AIR OPENING
SQ. IN./4000 BTUH
OF TOTAL INPUT
DUCT
I MUST EXTEND
ij ABOVE ATTIC
" INSULATION
BOTTOM AIR OPENING
1 SQ. IN./4000 BTUH
OF TOTAL INPUT
MAX.
When horizontal ducts are used to supply air from the
outdoors, they must be of the same cross sectional area
as the free area of the openings to which they connect.
The minimum dimension of rectangular air ducts must not
be less than 3 inches. Each opening must have a free
area of not less than one square inch per 2,000 Btu per
hour of total input of all appliances within the "Confined
Space". These openings must be located 12 in. from the
top and bottom of the furnace area. Neither opening can
be blocked at any time (See Figure 6).
Figure 6
CONFINED SPACE / OUTDOOR
AIR THROUGH HORIZONTAL DUCTS
F0000266
Figure 5
CONFINED SPACE / OUTDOOR AIR
FROM ATTIC & CRAWL SPACE
VENTILATION
LOUVERS
TOP AIR OPENING
1 SQ. IN./4,000 BTUH
OF TOTAL INPUT.
BOTTOM AIR OPENING
1 SQ.IN/4,000 BTUH
OF TOTAL INPUT
1
|_DUCT
MUST EXTEND
ABOVE ATTIC
INSULATION
WAT!
WATER HEATER
1 SQ. IN./2000 BTUH
OF TOTAL INPUT
F0000268
A WARNING
Furnaces installed with combustion air drawn from
a heated space which includes exhaust fans,
fireplaces, or other devices that may produce a
negative pressure should be considered confined
space installations.
F0000267
CRAWL SPACE
A CAUTION
For an attic installation it is important to keep
insulation 12" or more away from any furnace
openings. Some types of insulating materials may
be combustible.
20543402
Issue 0406
Page 10 of 26

DUCTING
The proper sizing of warm air ducts is necessary to insure satisfactory heating operation. Ductwork should be in
accordance with the latest editions of (U.S.) NFPA-90A (Air Conditioning Systems) and NFPA-90B (Warm Air Heating
and Air Conditioning Systems) or Canadian equivalent.
Ductwork Recommendation:
The supply duct work should be attached to the
flanged opening provided at the discharge end of the
furnace. See page 3 "Furnace Specificatons" for the
dimensions of this opening.
A left, right, or bottom return air opening must be
used as determined by the layout of the installation. An
externally mounted air filter is required.
This furnace has a two piece bottom panel. For
bottom or end duct return, remove the back portion of the
bottom panel by removing the four (4) screws - two (2) on
each side toward the back of the furnace (See Figure 7).
Tilt furnace toward the front, the back portion of the panel
will drop down. Then the back portion can be removed
by pulling toward the back of the furnace.
Figure 7
BOTTOM PANEL REMOVAL
FRONT-
FRONT
REMOVE SCREWS - 2 EACH SIDE
F0000024
Knockouts are provided on both sides of the furnace
to facilitate the cutout required to the return air ductwork.
Furnace cutouts must be the full size specified by the
corner markers. Undersized cutouts will adversely
affect the airflow capability of the furnace and could
cause overheating of the heat exchanger.
The following recommendations should be followed
when installing the ductwork:
1. Install locking-type dampers in all branches of the
individual ducts to balance out the system. Dampers
should be adjusted to impose the proper static at the
outlet of the furnace.
2. Noncombustible flexible duct connectors are
recommended to connect both the supply and return
ducts to the furnace.
In cases where the return air grille is located close to
the blower inlet, there should be at least one 90° air
turn between blower and return grille. Further
reduction in sound can be accomplished by installing
acoustical air turning vanes and/or lining the inside of
the duct with acoustical material.
It is recommended that the supply duct be provided
with a removable access panel. This opening shall
be accessible when the furnace is installed and shall
be of such a size that the heat exchanger can be
3.
4.
viewed for possible openings using light assistance or
a probe can be inserted by sampling the air stream.
The access panel shall be designed so as to prevent
leaks when locked in position. If an air conditioning
coil is installed, the access panel to the coil can be
used for this purpose.
A WARNING
When supply ducts carry air circulated by the
furnace to areas outside the spaces containing the
furnace, the return air shall also be handled by a
duct sealed to the furnace casing and terminating
outside the space containing the furnace. Incorrect
ductwork termination and sealing will create a
hazardous condition that could lead to bodily harm.
A CAUTION
Air openings, intake and outlet pipes, return air
grilles and warm air registers must not be
obstructed.
To Convert to Downflow Position:
1. Convert the combustion blower to side flue exit, as
outlined on page 14.
2. Install proper special base per Table 2 for installation
on combustible flooring (follow instructions supplied
with special base).
3. It is recommended that the return air be connected to
the bottom panel of the furnace when it is installed in
the downflow position.
NOTE: SPECIAL SUB-BASE NOT REQUIRED WHEN
FURNACE IS MOUNTED ON A METAL CASED
EVAPORATOR COIL
Table 2
SPECIAL BASE INSTALLATION
MODEL
A050B3
A075B3
A075B4
A100B3
A100B4
A100B5
A125B5
SPECIAL BASE
NUMBER
20066501
20066502
20066503
CAT. NO.
68L77
68L78
68L79
NOTE: Installation on combustible flooring only when
installed on one of the above listed special bases
or as identified on the furnace model and rating
label.
20543402
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Page 11 of 26

Filters:
Air filters must be used in every Installation. For side
return installations, air filters must be installed external to
the furnace casing. An external filter rack kit with filter
(parts No. 20069901 or Cat. No. 68L75 12 / 151/2" x 25"
sizes and 20069902 or Cat. No. 68L76 for 151/2" / 19" x
25" sizes) is available as an optional accessory.
For bottom (end) return installations, the above
optional external rack may be used, if the unit was not
provided with a internal filter. Minimum filter size and
suggested filter materials are shown in Table 3. (If
different type filter is used, it must be an equivalent high
airflow capacity.)
Table 3 EXTERNAL FILTER RACK SIZE
MODEL
050-3
075-3
075-4
100-3
100-4
100-5
125-5
SIDE
RETURN
15 1/2 X25
15 1/2 X25
151/2 X25
BOTTOM/END
RETURN
12X25
15 y2 X25
19X25
This furnace may use either a disposable filter,
permanent filter, electronic or high efficiency media air
cleaner. Consult filter/cleaner manufacturers for
maintience service and static pressure drop for air moving
requirements.
When installing the furnace with cooling equipment for
year round operation, the following recommendations
must be followed for series or parallel air flow:
1. In series flow applications, the evaporator coil is
mounted after the furnace in an enclosure in the
supply air stream. The furnace blower is used for
both heating and cooling airflow.
2. In parallel flow installation, dampers must be provided
to direct air over the furnace heat exchanger when
heat is desired and over the cooling when cooling is
desired. At no time may the evaporator coil be
located on the return air side of the heat exchanger.
IMPORTANT: The dampers should be adequate to
prevent cooled air from entering the
furnace, and if manually operated, must
be equipped with means to prevent
operation of either the cooling unit or
furnace unless the damper is in the full
cool or full heat position.
A WARNING
The coil MUST be installed on the air discharge
side of the furnace. Under no circumstances
should the air flow be such that cooled, conditioned
air can pass over the furnace heat exchanger. This
will cause condensation in the heat exchanger and
possible failure of the heat exchanger that could
lead to a fire hazard and/or hazardous conditions
that may lead to bodily harm. Heat exchanger
failure due to improper installation will not be
covered by warranty.
VENTING
Venting for this category I furnace must be to the
outside and in accordance with local codes or
requirements of the local utility. In the absence of local
codes, venting must conform to the applicable sections of
the latest edition of the (U.S.) National Fuel Gas Code
ANSI Z223.1/NFPA54. and/or CSA B149.1 Natural Gas
and Propane Installation Codes, and the vent
manufacturers instructions.
This furnace is CSA International certified as a
Category I forced air appliance and can not be vented
into a vent system with any Category II, III or IV
appliance. It must be vented vertically, or nearly
vertically, unless installed with a listed mechanical venter
in accordance with horizontal venting instructions. It must
not be connected to any portion of a mechanical draft
system operating under positive pressure
The 3" (in.) to 4" (in.) vent adaptor coupling (supplied
with unit) MUSTBEUSED. It must be connected directly
to the outlet of the combustion blower using a field
supplied corrosion resistant sheet metal screw (See
Figure 8).
Figure 8
VENT ADAPTOR MOUNTING
REDUCER
(SUPPLIED WITH UNIT)
SCREW
(FIELD SUPPLIED)
Pre-lnstallation Vent System Inspection:
Before this furnace is installed, it is highly
recommended that any existing vent system be
completely inspected.
For a chimney or "B" vent, this should include the
following:
1. Inspection for any deterioration in the chimney or "B"
20543402
Issue 0406
Page 12 of 26

vent. If deterioration is discovered, the chimney must
be repaired or the "B" vent must be replaced.
2. Inspection to ascertain that the vent system is clear
and free of obstructions. Any blockage must be
cleared before installing this furnace.
3. Cleaning the chimney or "B" vent if previously used
for venting a solid fuel burning appliance or fireplace.
4. Confirming that all unused chimney or "B" vent
connections are properly sealed.
5. Verification that the chimney is properly lined and
sized per the applicable codes.
Masonry Chimney:
This furnace can be common vented into an existing
tile lined masonry chimney provided:
1. The chimney is currently serving at least one
drafthood equipped appliance.
2. The vent connectors and chimney are sized in
accordance with the applicable sections of the (U.S.)
National Fuel Gas Code ANSI Z223.1/NFPA54.
and/or CSA B149.1 Natural Gas and Propane
Installation Codes.
This furnace must NOT vented ALONE into an
existing masonry chimney (either tile lined or unlined)
unless the chimney is also lined with either a type B vent
system or a listed single wall, metal lining system. Both
of these systems must be sized in accordance with the
applicable sections of the (U.S.) National Fuel Gas Code
ANSI Z223.1/NFPA54. and/or CSA B149.1 Natural Gas
and Propane Installation Codes.
Before venting this furnace into a chimney, check the
chimney for deterioration and repair if necessary. This
furnace must not be vented into a chimney serving a
separate appliance designed to burn solid fuel. Type"B"
vent connectors must be used on all installations and it
must be sized per the applicable sections of the (U.S.)
National Fuel Gas Code ANSI Z223.1/NFPA54. and/or
CSA B149.1 Natural Gas and Propane Installation Codes.
Type "B" Vent:
The furnace is also approved for use with a "B" vent
that terminates through the roof. Refer to the applicable
sections of the (U.S.) National Fuel Gas Code ANSI
Z223.1/NFPA54. and/or CSA B149.1 Natural Gas and
Propane Installation Codes for proper sizing and set-up
of this furnace with "B" vent for a dedicated vent system
or a common vented system.
Horizontal Venting:
This furnace is design certified by CSA International
for horizontal venting through an outside wall by use of
one of the following auxiliary draft inducer kits:
Table 4 AUXILIARY DRAFT INDUCERS
Vent Kit MFR
Field Controls Co.
Tjernlund Products Inc.
Model
SWG-4G
SS1 OR SS1C
GPAK-J
GPAK-1
* Furnace Input
50000, 75000, 100000 or
125000
50000, 75000, 100000 or
125000
50000, 75000 or 100000
100000 or 125000
* See rating label on this furnace for input
Vent Length: Max. 60 ft. - Min. 12 ft.
Vent Diameter: 4 in.
Follow instructions included with venting kit for proper installation and setup.
Location Requirements for Horizontal Venting:
Locate the vent terminal adhering to the following
minimum clearances and as specified in the auxiliary draft
inducer vent kit:
1. Vent terminal must be located at least one (11) foot
above the grade or at least one (11) foot above the
normal expected snowfall.
2. Avoid installing vent terminal above public walkways.
If this is not possible, install the terminal at least
seven (71) feet above the walkway.
3. Vent terminal should be at least four (41) feet to the
side of and at least one (11) foot above doors and
windows.
4. Vent terminal should be at least three (3f) feet above
any forced air inlet located within ten (10') feet.
5. Vent terminal should be located at least six (61) feet
from the combustion air intake of another appliance.
6. Vent terminal should be located at least four (41) feet
above any electric or gas meters, regulators, and
relief equipment.
General Venting Requirements:
This furnace may be common vented only with other
Category I appliances. Common venting is allowed as
permitted by National and/or local codes. Refer to the
applicable sections of the (U.S.) National Fuel Gas Code
ANSI Z223.1/NFPA54. and/or CSA B149.1 Natural Gas
and Propane Installation Codes for proper sizing and set
up.
The vent must be terminated with a listed vent cap or
roof assembly. This venting must be installed in
accordance with the vent manufacturer's instructions and
be in accordance with all local codes and/or National
Codes. Follow Figure 9 for vent exit options.
The following requirements are provided for a proper
venting system:
1. Be sure that the chimney flue is clear of any dirt or
debris.
2. Be sure that the chimney is not servicing an open
fireplace.
3. Never reduce the pipe size below the outlet size of
the furnace without checking the applicable sections
of the (U.S.) National Fuel Gas Code ANSI
Z223.1/NFPA54. and/or CSA B149.1 Natural Gas and
Propane Installation Codes.
20543402
Issue 0406
Page 13 of 26

4. All pipe should be supported using the proper clamps
and/or straps. These supports should be at least
every four (41) feet.
5. All horizontal runs of pipe should have at least a 1/4"
(in.) per foot of upward slope from the furnace to the
vent terminal.
6. All runs of pipe should be as short as possible with
as few turns as possible.
7. Seams should be tightly joined and checked for
leaks.
8. The flue pipe must not extend into the chimney but
be flush with the inside wall.
9. The chimney or vent pipe must extend at least three
(31) feet above the highest point where it passes
through a roof of a building and at least two (21) feet
higher than any portion of a building within a
horizontal distance of ten (10') feet. It shall also
extend at least five (51) feet above highest connected
equipment flue collar.
Figure 9
VENT EXIT OPTIONS
HORIZONTAL
RIGHT
AIR FLOW
DOWNFLOW
OR-
r\
UPFLOW
F0000261
HORIZONTAL
LEFT
AIR FLOW
10. The 3" to 4" vent adaptor coupling must be used to
connect to the combustion blower outlet. It must be
installed directly to the combustion blower outlet (See
Figure 8).
To Convert to Side Flue Exit:
1. Remove the louver door from the furnace. (Be sure
the side vent exit knock-out is removed from the right
side panel of the cabinet. See Figure 9.)
2. Disconnect the pressure switch tubing from the
combustion blower.
3. Remove the four (4) screws that secure the
combustion blower adaptor plate to the flue collector
box, taking care to support the blower assembly so
that it does not fall.
4. Rotate the blower 90° (degrees) clockwise, so that
the outlet of the blower is pointing toward the right
side panel of the furnace.
5. Insure that the gasket is in place between the blower
adaptor plate and the flue collector box. Reattach the
blower assembly to the flue collector box, using the
four (4) screws removed in step 3. Be sure that the
screws are properly tightened and that the gasket
seals the plate to the box.
6. Reconnect the pressure switch tubing to the
combustion blower.
7. (Optional) Install vent pipe guard.
Kit Number 20284801.
Figure 10
VENT PIPE GUARD KIT
For Horizontal Positions:
It is not necessary to reposition any of the
components of the furnace in order to install it in either
horizontal position. As outlined above, it is permissible to
use the side vent exit for the horizontal-left position, if
desired.
Checking For Vent Oversizinq:
If this furnace is replacing a furnace that is attached
to a venting system serving other appliances, the venting
system is likely to be too large to properly vent all of the
attached appliances. An improperly sized venting system
can lead to condensation, leakage, or spillage.
20543402
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Page 14 of 26

AWARNING
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 CSA B149.1. Natural Gas and Propane 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 spaces of the building.
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. Test for spillage from draft hood equipped appliances at the draft hood relief opening after 5 minutes of main
burner operation. Use the flame of a match or candle.
8. 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 Z223.1/NFPA 54 and/or CSA B149.1. Natural Gas and
Propane Installation Codes.
9. After it has been determined that each appliance connected to the venting system properly vents when
tested as outlined above, return doors, windows, exhaust fans, fireplace dampers and any other gas-fired
burning appliance to their previous conditions of use.
ELECTRICAL CONNECTIONS
When installed, the furnace must be electrically
grounded in accordance with local codes or, in the
absence of local codes, with the (U.S.) National Electrical
Codes. ANSI/NFPA 70 or CSA Standard C22.1: Part 1
Canadian Electrical Code. For proper installation refer to
furnace rating label for electrical ratings and for the field
wiring of this unit refer to furnace wiring specifications on
page 5 or alternately from the wiring diagram on page 28.
In all instances, other than wiring for the thermostat, the
wiring to be done and any replacement of wire shall
conform with the temperature limitation for Type T wire
[63°F rise (35°C)].
The electrical connections and the thermostat
connections are made at the openings on either side
panel of the unit in the control box area. Either side may
be used as convenient, but the provided hole plugs must
be inserted in the unused holes.
The control system depends on the correct polarity of
the power supply. Connect "Hot" (H) wire and "Ground"
(G) wire as shown in furnace wiring specification on
wiring diagram. Use reference Table on page 3 (Furnace
Specifications), for over current protection, max unit amp
rating and wire size. Use copper wire only for 115V-
supply service to unit. When replacing any original
internal wiring, use only 105°C, 16 AWG copper wire.
Instructions for wiring the thermostat are packed in
the thermostat (field supplied) box. Make the thermostat
connections as shown in furnace wiring specifications at
the 24-volt terminal board located in the control box.
When installing optional accessories to this appliance,
follow the manufacturer's installation instructions included
with the accessory.
AWARNING
The unit cabinet must have an uninterrupted or
unbroken electrical ground to minimize personal
injury if an electrical fault should occur. This may
consist of electrical wire or approved conduit when
installed in accordance with existing electrical
codes. Do not use gas piping as an electrical
ground. Failure to follow this warning can result in
an electrical shock, fire, bodily harm, or loss of life.
20543402
Issue 0406
Page 15 of 26

GAS CONNECTIONS
Gas piping shall be of such size and so installed as
to provide a supply of gas sufficient to meet maximum
demands without undue loss of pressure between the gas
meter and the furnace. It is recommended that the gas
line to the furnace shall be a separate line direct from the
meter, unless the existing gas line is of ample capacity.
Refer to gas pipe capacity table in the National Fuel Gas
Code ANSI Z223.1/NFPA54. and/or CSA B149.1 Natural
Gas and Propane Installation Codes.
If local codes allow the use of a flexible gas appliance
connector, always use a new listed connector. Do no use
a connector which has previously serviced another gas
appliance.
Use a joint compound (pipe dope) that is resistant to
the action of liquefied petroleum gases or any other
chemical constituents of the gases to be conducted
through the piping.
For proper furnace operation the maximum gas
supply pressure is 14" w.c. and the minimum gas
supply pressure is 4.5" w.c. - Natural (11" w.c. - LP)
as shown on rating label.
Before any system of gas piping is finally put into
service, it should be carefully tested to determine if it is
gas tight. Check all piping for leaks using soapy water
and a brush. The piping must stand a pressure of six (6)
inches of mercury (3 PSIG) for a period of ten (10)
minutes or as required by local authority.
AWARNING
FIRE OR EXPLOSION HAZARD
Failure to follow the safety warnings exactly
could result in serious injury, death or property
damage.
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. A fire or explosion may result causing
property damage, personal injury or loss of life.
AWARNING
The furnace and its individual shutoff valve
must be disconnected from the supply piping
system during any pressure testing of that system
at test pressures in excess of 1/2 PSIG (3.5kPa or
14"w.c).
The furnace must be isolated from the gas
supply piping system by closing its individual
manual shutoff valve during any pressure testing of
the gas supply piping system at pressures equal to
or less than 1/2 PSIG (3.5kPa or 14"w.c). Failure
to follow the above procedures could lead to a
hazardous condition and bodily harm.
Figure 11
GAS CONTROL PIPING
WHEN FLANGE IS NOT USED
APPLY WRENCH
FROM TOP OR
BOTTOM OF GAS
CONTROL TO
EITHER SHADED
AREAS.
Figure 12
TYPICAL GAS SERVICE CONNECTION
FIELD SUPPLIED MAIN
MANUAL SHUT-OFF
VALVE
>r
i
This furnace is manufactured for use with Natural gas
and must be converted using the proper LP conversion kit
for use with LP (Propane) gas. For LP (Propane) gas, a
tank regulator is required to reduce supply pressure to
12"-13"w.c. For manifold pressure see Table 6.
A main manual shut off valve must be used in the
gas piping. The shut off type and location must follow
local codes and should always be in an accessible but
protected location. In the absence of local codes the
recommended methods for installing the gas piping to the
furnace are shown in Figures 11 and 12.
The gas valve contains two threaded ports for a 1/8"
NPT tap in order to test incoming gas pressure and
outgoing manifold pressure (See Figure 13).
A CAUTION
Many soaps used for leak testing are corrosive to
certain metals. Piping must be rinsed thoroughly
with clean water after leak check has been
completed.
AWARNING
Never use an open flame when testing for gas
leaks! Use of an open flame could lead to a fire or
explosion.
20543402
Issue 0406
Page 16 of 26

UNIT SEQUENCE OF OPERATION
Here's How Your System Works:
Call For Heat
The thermostat calls for heat by energizing the "W"
terminal. The control checks to see the limit circuit is
closed and pressure switch is open. If the limit circuit is
open, the control responds per the Open Limit section
following. If the pressure switch is closed, the control will
flash "3" on the LED and wait indefinitely for the pressure
switch to open. If the pressure switch is open, the control
proceeds to pre-purge.
Pre-Purge
The control energizes the induced draft motor and
waits for the pressure switch to close. The control
flashes "3" on the LED while the pressure switch is open.
If the pressure switch does not close within 60 seconds
of the inducer energizing, the control will de-energize the
inducer for 300 seconds, and then re-energize the
inducer. This cycle shall continue as long as a call for
heat exists until the pressure switch is proven.
When the pressure switch is proven closed, the
control begins the pre-purge time. If flame is present any
time while in pre-purge, the control will flash "5" on the
LED and go into soft lockout. The control runs the
inducer for a 15 second pre-purge time, then proceeds to
the ignition trial period.
Ignition Trial Period
The control energizes the HSI for a 7 second warmup
period (12 seconds for retries) then energizes the main
gas valve. The inducer remains energized. If flame has
not been sensed within the 7 second ignition trial, the
control de-energizes the gas and HSI outputs and
proceeds with ignition retires. If flame is not established
after three (3) trials for ignition, the control will flash "2" on
the LED and goes into lockout.
Blower On Delay
The control waits for 30 seconds from the time the
gas valve opened and then energizes the indoor blower
heat speed. The gas valve and inducer remain
energized. The control proceeds to steady heat mode.
Steady Heat
Control inputs are continuously monitored to ensure
limit and pressure switches are closed, flame is
established, and the thermostat call for heat remains.
When the thermostat call for heat is removed, the control
de-energizes the gas valve and begins post-purge and
blower off delay time.
Open Limit
Any time the limit switch is open, the control de-
energizes the gas valve and runs the indoor blower motor
on heat speed. While the Ilimit switch is open, the control
flashes "4" on the LED. Check for a restriction in the duct
system (i.e. dirty filters, blocked ductwork, closed
registers ) .
When the switch re-closes, the control runs the indoor
blower through the selected fan off delay. If the call for
heat is still present when the limit switch closes, the
control will begin an ignition sequence while the blower
off delay continues. Note: Cycling on the limit is an
abnormal condition and a corrective action must be taken.
Failure to correct this condition could damage the heat
exchangers and void the warranty.
Post Purge
The inducer output remains on for a 15 second post-
purge period after the thermostat is satisfied.
Blower Off Delay
The indoor blower motor is de-energized after a delay
time as selected by the movable shunt. The off delay
may be set to 60, 90, 120 or 180 seconds. The blank
default blank setting is 180 seconds. Blower timing begins
when the thermostat is satisfied or heat cycle interupted.
If the thermostat calls for heat while in the blower off
delay, the control immediately restarts the ignition
sequence while the blower off delay continues.
AWARNING
Should overheating occur, or the gas supply fail to
shut OFF, turn OFF the manual gas valve to the
appliance BEFORE turning OFF the electrical
supply. A failure to adhere to this warning can
result in a fire or explosion and bodily harm.
Call for Cool
For cooling operation, when the inside temperature
exceeds the thermostat setting, the thermostat will turn
ON the cooling system.
When the thermostat calls for cooling, power from the
transformer energizes the fan control board (for blower
operation) and the outdoor condensing unit (for air
conditioning).
The fan control board will automatically turn on the
blower and condensing unit. The air moving over the
indoor coil by the blower is cooled (and dehumidified) and
passes through the ducts to the room registers.
When the thermostat is satisfied, the fan control
board is de-energized and the condensing unit is shut-off.
The blower will continue to operate for an additional 30
seconds for added cooling efficiency.
Call for Fan
When the thermostate calls for continuous fan (G)
without a call for heat or cool, the outdoor blower is
immediately energized on the COOL speed.
A call for COOL or HEAT has priority over continuous
fan operation.
20543402
Issue 0406
Page 17 of 26

STARTUP AND OPERATIONAL CHECKOUT
AWARNING
Do not use this furnace as a construction heater.
Use of this furnace as a construction heater
exposes the furnace to abnormal conditions,
contaminated combustion air and the lack of air
filters. Failure to follow this warning can lead to
premature furnace failure and/or vent failure which
could result in a fire hazard and/or bodily harm.
1. Be sure all electrical power is OFF.
2. Check all wiring using proper wiring diagram on
inside of the control box cover.
3. Turn ON the electrical power.
4. Set the ignition system control switch in the "ON"
position.
5. Set the thermostat above room temperature.
6. The hot-surface ignitor will heat-up to an "orange"
glow, the main burners will ignite.
The automatic gas valve controls the flow of gas to
the main burners. The control circuit built into the
automatic valve body has 2 positions: "OFF" and "ON"
(Figure 13). To shut off gas manually: Switch from "ON"
to "OFF" position. When in "OFF" position, the main
burners are extinguished.
This furnace is equipped with an automatic hot-
surface ignition control and does not require the manual
lighting for furnace operation.
Figure 13
GAS CONTROL DIAGRAM
Figure 14
TYPICAL FLAME APPEARANCE
(Main Burners)
BURNER
HEAT
EXCHANGER
GAS
MANIFOLD
F0000258
BURNER
FLAME
(Blue Only)
PRESSURE REGULATOR
ADJUSTMENT (UNDER
CAP SCREW)
INLET
PRESSURE
TAP
INLET
VR8205
GAS CONTROL
r-KNOB
WIRING
TERMINALS (2)
MANIFOLD
/■PRESSURE
TAP
^OUTLET
OFF
ON
F0000319
AWARNING
Do not attempt to manually light the burners.
Failure to follow this warning can lead to electrical
shock that could result in bodily harm.
7. Recheck for leaks in the manual shut off valve, gas
control valve and gas connections using a soap
solution.
AWARNING
Never use an open flame when testing for gas
leaks! Use of an open flame could lead to a fire or
explosion.
A CAUTION
Many soaps used for leak testing are corrosive to
certain metals. Piping must be rinsed thoroughly
with clean water after leak check has been
completed.
After the ductwork connections have been made, gas
piping and electrical wiring completed and the furnace
has been properly vented, the unit should be started and
adjusted for proper operation. Check off the following
steps as they are completed.
Manifold Pressure Adjustment:
Turn OFF the gas and electrical before
preceeding! Remove the manifold pressure tap pipe
plug from the gas valve (Figure 13 outlet pressure tap)
and install a pressure tap and connect it to a manometer.
Turn on the gas and electrical supplies, then measure the
manifold pressure with the furnace in operation.
20543402
Issue 0406
Page 18 of 26

Remove the cap to access the screw for input
adjustment (Figure 13 Pressure Regulator). Turn
regulator-adjusting screw IN to increase pressure,
OUT to decrease pressure. Replace the cap. Measure
the manifold pressure.
For Natural gas, best results are obtained with a
manifold pressure of 3.2" to 3.5"w.c. For units that have
been
converted to LP (Propane) gases, a manifold
pressure of 10"w.c. is necessary. After proper
adjustment, turn OFF gas, replace manifold pressure tap
pipe plug and turn ON gas.
TABLE 5
AWARNING
At higher altitudes and varying heating valves,
manifold pressure or orifice changes maybe
required. Consult Tables 7 and 8 for appropriate
values. Failure to follow this warning could lead to
a hazardous furnace operating condition and result
in serious bodily injury or loss of life.
Seconds for
One
Revolution
10
12
14
16
18
20
22
24
26
28
30
32
34
Gas
Rate
(Cubic Feet per
TEST DIAL
1/2
Cubic
Feet
160
150
129
113
100
90
82
75
69
64
60
56
53
1
Cubic
Foot
360
300
257
225
200
180
164
150
138
129
120
113
106
2
Cubic
Feet
720
600
514
450
400
360
325
300
276
258
240
226
212
Seconds for
One
Revolution
36
38
40
42
44
46
48
50
52
54
56
58
60
Hour)
TEST DIAL
1/2
Cubic
Feet
50
47
45
43
41
39
37
36
35
34
32
31
30
1
Cubic
Foot
100
95
90
86
82
78
75
72
69
67
64
62
60
2
Cubic
Feet
200
190
180
172
164
156
150
144
138
134
128
124
120
4. Calculate the furnace input using the following
formula:
Determining Furnace Input:
NOTE: All access doors must be in place when checking
gas input.
1. Turn OFF all other gas appliances (except for pilot
burners) served by the same gas meter.
2. With furnace operating in full heat cycle, note how
many seconds it takes for one full revolution of the
smallest dial on the meter. Typically, this will be a
1/2 - or - 1 - cubic foot test dial.
3. Using the number of seconds for one revolution and
the size of the meter dial, determine the cubic foot
per hour of gas flow by using the formula provided
below or Table 5.
Cubic Ft/Hr
Number of Dial Revolutions x Cubic Foot/Revolution x 3600
Time
(in seconds) Required for Number of Timed Revolutions
BTUH = Cubic Ft/Hr x BTU/Cubic Foot
The local gas supplier should be able to provide the
heating value of the gas, in BTU/cubic foot. If a
specific value is not available, use 1000 BTU/cubic
foot for Natural gas or 2500 BTU/cubic foot for
Propane (LP).
A WARNING
Furnace input should be maintained within ± 2% of
the value on the rating plate or appropriate altitude
derate. Adjust manifold pressure or change
orifices size if required.
5. Calculate the unit's actual input rate.
Example: If the heating value of the natural gas is 1015
Btu/cu. and it takes 60 seconds to burn 2 cu:
ft. of gas then:
Input = 1015 Btu/cu. ft. X 1 rev X 2 cu. ft./rev. X 3600
60 sec.
Input = 121,800 Btu/hr.
20543402
Issue 0406
Page 19 of 26

Burner Orifice Sizing:
The furnace is supplied with standard orifices for the
gas shown on the rating plate. Table 6 shows
combinations of heating values and specific gravities for
various gases, from which proper input can be obtained.
If changing orifices is required, remove the manifold
from the furnace (following the instructions found on page
23) and replace orifices as required by Table 6, the
altitude derating section of this instruction or as local code
dictates.
TABLE 6
Burner Orifice Selection
Type of Gas@Manifold Press.
(Heating Value-Specific Gravity)
Btu per Cu. Ft.
Natural Manifold Press.= 3.5"w.c.
800-0.6
900-0.6
1000-0.6
1100-0.6
Propane Manifold Press. = 10"w.c.
2500-1.53
Orifice
Size
(Drill #)
40
41
42
43
54
After securing the manifold assembly, replace all
other components and/or wiring, being sure that all
connections and screws are tightened properly.
Altitude Derating:
The following information is provided as guidelines for
altitude derating and is not meant to supersede any state
or local codes. Local codes have priority over any others
and in some case might limit your options in dealing with
an altitude derate situation.
NOTE: In Canada for altitudes up to 4500 ft. (1372 m)
see the rating label on this furnace for proper
manifold pressure and orifice size. Certification
for installations at altitudes over 4500 ft. (1372 m)
is the jurisdiction of local authorities.
Check with your local gas company to find out if the
gas supply in your area is derated. Gas deration negates
the necessity of performing any adjustment on the
furnace.
If your gas supply is not derated, regardless of the
type of gas used, installation of this furnace at elevations
above 2,000 ft. requires an input reduction at the rate of
four percent (4%) for each 1,000 ft. above sea level.
Unless an orifice change is specified by an applicable
code, or the furnace is to be installed above 6,999 feet,
the recommended method of altitude derating this furnace
is to appropriately lower your manifold pressure. The
appropriate manifold pressures based on the elevation
and the heating value can be found in Table 7.
TABLE 7
High Altitude Manifold Pressure Derate
(with standard 42 orifice Natural / 54 orifice LP sizes)
Altitude
(Feet)
0-999
1000-1999
2000-2999
3000-3999
4000-4999
5000-5999
6000-6999
"Heating Value of Natural Gas
(BTU/FT3)
900
4.32
4.32
3.67
3.38
3.11
2.88
2.64
950
3.88
3.88
3.29
3.04
2.79
2.58
2.37
1000
3.50
3.50
2.97
2.74
2.52
2.33
2.14
1050
3.16
3.16
2.68
2.47
2.27
2.10
1.93
1100
2.84
2.84
2.41
2.22
2.04
1.89
1.73
LP
Propane
2500
10
10
8.46
7.74
7.05
6.40
5.77
Heating-Value based on atmospheric pressure of 30 inhg and 60°F temperature.
If local codes require an orifices change or if the
furnace installation is above 6,999 feet. The appropriate
orifice size based on the elevation and the heating value
can be found in Table 8. Sizing of the orifice must be
based on the previously mentioned 4% derate for each
1,000 feet for installations at/or above 2,000 feet rule and
the orifices must be drilled in such a way as to assure
concentricity. Hand drilling of orifices is unacceptable.
TABLE 8
High Altitude Orifice Size Derate
Altitude
(Feet)
2000-2999
3000-3999
4000-4999
5000-5999
6000-6999
7000-7999
8000-8999
9000-9999
10000-10999
*Heating Value of Natural Gas
(BTU/FT3)
900
N.C.
N.C.
43
43
44
44
45
46
47
950
N.C.
N.C.
43
44
44
45
46
47
48
1000
43
43
44
44
45
46
47
48
49
1050
43
44
44
45
46
47
48
48
49
1100
44
44
45
46
47
48
48
49
50
LP
Propane
2500
N.C.
N.C.
55
55
55
56
56
56
57
Heating-Value based on atmospheric pressure of 30 inhg and 60°F temperature.
A WARNING
Hand drilling of orifices is never acceptable since it
could lead to delayed ignition, overfiring, improper
combustion, flashback and flame rollout. All these
conditions could lead to a fire hazard and bodily
harm, or loss of life.
Blower Adjustment Checkout:
Prior to any blower adjustment, electrical service must
be turned OFF.
This furnace is equipped with a 3 speed direct drive
motor to deliver a temperature rise within the range
specified on the rating label, between the return and
supply plenums, at the external duct static pressure noted
on the rating label.
20543402
Issue 0406
Page 20 of 26