installation, start-up,
373LAV
and operating instructions
DOWNFLOW/HORIZONTAL
GAS-FIRED
INDUCED-COMBUSTION FURNACES
NOTE: Read the entire instruction manual before starting the
installation.
This symbol → indicates a change since the last issue.
Index Page
SAFETY CONSIDERATIONS.....................................................1
Dimensional Drawing...............................................................2
ELECTROSTATIC DISCHARGE (ESD) PRECAUTIONS
PROCEDURE...........................................................................2
INTRODUCTION..........................................................................3
Clearances From Combustible Materials.................................3
LOCATION....................................................................................4
General......................................................................................4
Location Relative to Cooling Equipment ................................4
Hazardous Locations.................................................................4
AIR FOR COMBUSTION AND VENTILATION...................4-5
Unconfined Space..................................................................4-5
Confined Space.........................................................................5
AIR DUCTS...................................................................................5
General Requirements...............................................................5
Ductwork Acoustical Treatment...............................................5
Supply-Air Connections............................................................5
Return-Air Connections............................................................5
DOWNFLOW INSTALLATION..................................................6
HORIZONTAL ATTIC INSTALLATION................................6-7
Construct a Working Platform..............................................6-7
Install Furnace...........................................................................7
HORIZONTAL CRAWLSPACE INSTALLATION....................7
FILTER ARRANGEMENT...........................................................7
GAS PIPING.............................................................................7-10
ELECTRICAL CONNECTIONS................................................10
115-v Wiring...........................................................................10
24-v Wiring.............................................................................10
Accessories ........................................................................10-11
VENTING ....................................................................................11
START-UP, ADJUSTMENT, AND SAFETY CHECK............11
General....................................................................................11
Sequence Of Operation...........................................................11
Heating Mode..........................................................................11
Cooling Mode .........................................................................14
Continuous Blower Mode.......................................................14
Heat Pump Mode....................................................................14
Start-up Procedures.................................................................14
Adjustments .......................................................................14-20
Set Gas Input Rate..................................................................14
Set Temperature Rise..............................................................15
Set Thermostat Heat Anticipator............................................18
Check Safety Controls.......................................................18-19
Checklist ............................................................................19-20
SAFETY CONSIDERATIONS
Installing and servicing heating equipment can be hazardous due to
gas and electrical components. Only trained and qualified personnel should install, repair, or service heating equipment.
Untrained personnel can perform basic maintenance functions
such as cleaning and replacing air filters. All other operations must
Series G
Cancels: II 373L-35-20 II 373L-35-21
ama
CANADIAN GAS ASSOCIATION
®
REGISTERED QUALITY SYSTEM
be performed by trained service personnel. When working on
heating equipment, observe precautions in the literature, on tags,
and on labels attached to or shipped with the unit and other safety
precautions that may apply.
→
In the United States, follow all safety codes including the National
Fuel Gas Code (NFGC) NFPA 54-1996/ANSI Z223.1-1996 and
the Installation Standards, Warm Air Heating and Air Conditioning Systems (NFPA 90B) ANSI/NFPA 90B.
→
In Canada, refer to the CAN/CGA-B149.1- and .2-M95 National
Standard of Canada, Natural Gas and Propane Installation Codes
(NSCNGPIC).
Wear safety glasses and work gloves. Have fire extinguisher
available during start-up and adjustment procedures and service
calls.
Recognize safety information. This is the safety-alert symbol
When you see this symbol on the unit and in instructions or
manuals, be alert to the potential for personal injury.
Understand the signal words DANGER, WARNING, CAUTION,
→
and NOTE. These words are used with the safety-alert symbol.
DANGER identifies the most serious hazards which will result in
severe personal injury or death. WARNING signifies a hazard
which could result in personal injury or death. CAUTION is used
to identify unsafe practices which would result in minor personal
injury or product and property damage. NOTE is used to highlight
suggestions which will result in enhanced installation, reliability,
or operation.
These instructions cover minimum requirements and conform to
existing national standards and safety codes. In some instances,
these instructions exceed certain local codes and ordinances,
especially those that may not have kept up with changing residential construction practices. We require these instructions as a
minimum for a safe installation.
APPROVED
R
7-99
.
—1—
13
⁄16″
39 7⁄8″
20″
INLET
ACCESSORY
3
1
⁄4″ DIA HOLE
GAS ENTRY
28 1⁄2″
7
⁄8″ DIA
VENT CONNECTION
13
⁄16″
9 1⁄8″
10 1⁄4″
1
⁄2″ DIA
D
4 3⁄16″
2 15⁄16″
16 1⁄16″
2″
THERMOSTAT
WIRE ENTRY
7
⁄8″ DIA
ACCESSORY
7
⁄8″ DIA HOLE
POWER ENTRY
1 1⁄2″ DIA
R.H. GAS ENTRY
7
⁄8″ DIA
ACCESSORY
″ TYP
1
11
⁄16″
OUTLET
19″
ADDITIONAL 7⁄8″ DIA K.O. ARE
NOTE:
LOCATED IN THE TOP PLATE
AND BOTTOM PLATE
NOTES:
1. Two additional 7⁄8-in. dia holes are located in the top plate.
2. Minimum return-air openings at furnace, based on metal duct. If flex duct is used,
see flex duct manufacturer's recommendations for equivalent diameters.
a. For 800 CFM–16-in. round or 141⁄2 x 12-in. rectangle.
b. For 1200 CFM–20-in. round or 141⁄2 x 191⁄2-in. rectangle.
c. For 1600 CFM–22-in. round or 141⁄2 x 231⁄4-in. rectangle.
d. For airflow requirements above 1800 CFM, must use entire return air opening.
1 1⁄16″
2 1⁄8″
8 1⁄4″
E
11
⁄16″
A
AIRFLOW
13 5 ⁄16″
10 1⁄4″
11
⁄16″
DIMPLES TO DRILL HOLES
FOR HANGER BOLTS (4 PLACES)
IN HORIZONTAL POSITION
1 1⁄16″
2 1⁄8″
→Fig. 1—Dimensional Drawing
→TABLE 1—DIMENSIONS (IN.)
UNIT SIZE A D E VENT CONN SHIP. WT (LB)
024050 14-3/16 12-9/16 12-11/16 4 121
036050 14-3/16 12-9/16 12-11/16 4 130
024070 14-3/16 12-9/16 12-11/16 4 129
036070 14-3/16 12-9/16 12-11/16 4 138
036095 17-1/2 15-7/8 16 4 150
048095 17-1/2 15-7/8 16 4 152
048115 17-1/2 15-7/8 16 4 158
060115 21 19-3/8 19-1/2 4 175
060135 24-1/2 22-7/8 23 5 192
ELECTROSTATIC DISCHARGE (ESD) PRECAUTIONS
PROCEDURE
CAUTION: Electrostatic discharge can affect electronic
components. Take precautions during furnace installation
and servicing to protect the furnace electronic control.
Precautions will prevent electrostatic discharges from
personnel and hand tools which are held during the
procedure. These precautions will help to avoid exposing
the control to electrostatic discharge by putting the
furnace, the control, and the person at the same electro-
static potential.
3. After touching the chassis you may proceed to service the
control or connecting wires as long as you do nothing that
recharges your body with static electricity (for example; DO
NOT move or shuffle your feet, DO NOT touch ungrounded objects, etc.).
4. If you touch ungrounded objects (recharge your body with
static electricity), firmly touch furnace again before touching control or wires.
5. Use this procedure for installed and uninstalled (ungrounded) furnaces.
6. Before removing a new control from its container, discharge your body’s electrostatic charge to ground to protect
1. Disconnect all power to the furnace. DO NOT TOUCH
THE CONTROL OR ANY WIRE CONNECTED TO THE
CONTROL PRIOR TO DISCHARGING YOUR BODY’S
ELECTROSTATIC CHARGE TO GROUND.
2. Firmly touch a clean, unpainted, metal surface of the
furnace chassis which is close to the control. Tools held in
a person’s hand during grounding will be satisfactorily
the control from damage. If the control is to be installed in
a furnace, follow items 1 through 5 before bringing the
control or yourself into contact with the furnace. Put all
used AND new controls into containers before touching
ungrounded objects.
7. An ESD service kit (available from commercial sources)
may also be used to prevent ESD damage.
discharged.
5
⁄8″ TYP
A99109
—2—
MINIMUM INCHES CLEARANCE TO COMBUSTIBLE CONSTRUCTION
This forced air fu rnace is equipped for use with natura l
gas at altitudes0-10,000 ft (0-3,050m).
An accessory kit, supplied by the manufacturer,shall be
used to convert to propane gas use or may be required for
somenatural gas applications.
This furnace is for indoor in stallation in a building
constructedonsite.
This furnace may be installed on combustible flooring in
alcove or closet at minimum clea rance fro m combustible
material.
This furnace may be used with a Type B-1 Vent and may
be ventedin commonwith other gas-firedappliances.
For installation onnon-combustiblefloors only.
†
For installation oncombustibleflooringonlywhen
installedon special base, Part No. KGASB0201ALL,
Coil Assembly, Part No. CD5or CK5, or Coil Casing,
Part No. KCAKC.
For furnaces wider than 14.25 inches (362mm) may
#
be 0 inches.
18 inchesfront clearance required for alcove.
Ø
Indicates supply or returnsides when furnaceis in
*
the horizontal position. Line contact only permissible
betweenlinesformed byintersections of the Top and
two Sides of the furnace jacket, andbuilding joists,
studs or framing.
For single wall vent type 6 inches.
##
For Type B-1 vent type3 inches.
††
Clearance toBack 0 inches indownflow and
horizontal (attic/alcove & crawlspace) positionsand
3 inches in horizontal closet positions.
Fig. 2—Clearances to Combustibles
This f ur nace is approved for DOWNFLOWandHORIZONTAL
installations.
Clearance arrows
do not change with
furnace orientation.
0"
†
†
B
A
C
K
E
D
I
S
1" #
*
Clearance in inches
1"
TOP / PLENUM
E
C
A
N
R
U
F
†
T
N
O
R
F
S
F
R
O
N
T
##
Ø
BOTTOM
#
"
1
1"
#
E
*
D
I
S
E
R
V
I
C
E
30"
Vent Clearance to combustibles:
For Si ngle Wall vents 6 inches.
For Type B-1vent type 1 inch.
322286-101REV.F (LIT )
MIN
A99262
INTRODUCTION
→
The model 373LAV Series G Furnaces are available in sizes
46,000 through 135,000 Btuh input capacities.
The design of the downflow/horizontal gas-fired furnace is
A.G.A./C.G.A. certified for natural and propane gases and for
installation on noncombustible flooring. The furnace is factoryshipped for use with natural gas. A factory accessory gas conversion kit, as listed on the furnace rating plate is required to convert
furnace for use with propane gas.
These furnaces SHALL NOT be installed directly on carpeting,
tile, or any other combustible material other than wood flooring. In
downflow installations, a factory accessory floor base, as listed on
the furnace rating plate MUST be used when installed on combustible materials and wood flooring. A factory floor base is not
required when this furnace is installed on manufacturer’s Coil
Assembly Part No. CD5 or CK5, or when Coil Box Part No.
KCAKC is used. This furnace is for installation in alcoves, attics,
crawlspaces, basements, closets, or utility rooms. The design of
this furnace line is not A.G.A./C.G.A. certified for installation in
mobile homes, recreation vehicles, or outdoors.
→
Before installing the furnace in the United States, refer to the
NFGC and NFPA 90B. For copies of the NFGC and NFPA 90B,
contact the National Fire Protection Association Inc., Batterymarch Park, Quincy, MA 02269; or for only the NFGC contact the
American Gas Association, 400 N. Capitol St., NW, Washington
DC 20001.
→
Before installing the furnace in Canada, refer to the NSCNGPIC.
For a copy of the NSCNGPIC, contact Standard Sales, CSA
International, 178 Rexdale Boulevard, Etobicoke (Toronto), Ontario, M9W 1R3, Canada.
→
Installation must comply with regulations of serving gas supplier
and local building, heating, plumbing or other codes in effect in the
area in which installation is made. In absence of local building
codes, installation must conform with NFGC in the United States
and the NSCNGPIC and all authorities having jurisdiction in
Canada.
These instructions cover minimum requirements for a safe installation and conform to existing national standards and safety codes.
In some instances, these instructions exceed certain local codes
and ordinances, especially those that may not have kept pace with
changing residential construction practices. We require these
instructions as a minimum for a safe installation.
CAUTION: Application of this furnace should be indoors with special attention given to vent sizing and
material, gas input rate, air temperature rise, and unit
sizing. Improper installation or misapplication of the
furnace can require excessive servicing or cause premature component failure.
This furnace is designed for a 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
temperature must not exceed a maximum of 85°F db.
—3—
WARNING: Improper installation, adjustment, alteration, service, maintenance, or use can cause carbon
monoxide poisoning, explosion, fire, electrical shock, or
other conditions which may cause personal injury, loss of
life, or property damage. Consult a qualified installer,
service agency, local gas supplier, or your distributor or
branch for information or assistance. The qualified installer or agency must use only factory-authorized and
listed kits or accessories when modifying this product.
Failure to follow this warning could result in electrical
shock, fire, personal injury, or death.
C. Hazardous Locations
→
For accessory installation details, refer to the applicable installation literature.
NOTE: Remove all shipping brackets and materials before operating the furnace.
I. LOCATION
A. General
CAUTION: Do not install furnace in a corrosive or
contaminated atmosphere. Make sure all combustion and
circulating air requirements are followed, in addition to
all local codes and ordinances.
CAUTION: Do not use this furnace during construction
when adhesives, sealers, and/or new carpets are being
installed. If the furnace is required during construction,
use clean outside air for combustion and ventilation.
Compounds of chlorine and fluorine when burned with
combustion air form acids which cause corrosion of the
heat exchangers and metal vent system. Some of these
compounds are found in paneling and dry wall adhesives,
paints, thinners, masonry cleaning materials, and many
other solvents commonly used in the construction process.
Excessive exposure to contaminated combustion air will
result in safety and performance related problems.
18-IN. MINIMUM
TO BURNERS
A93044
WARNING: When furnace is installed in a residential
garage, it must be installed so that burners and ignition
sources are located a minimum of 18 in. above floor. The
furnace must be located or protected to avoid physical
damage by vehicles. When furnace is installed in a public
garage, airplane hangar, or other building having a
hazardous atmosphere, unit must be installed in accordance with requirements of National Fire Protection
Association, Inc.
II. AIR FOR COMBUSTION AND VENTILATION
Provisions for adequate combustion and ventilation air must be
provided in accordance with Section 5.3 of the NFGC, Air for
Combustion and Ventilation, or applicable provisions of the local
building codes.
Canadian installations must be installed in accordance with NSCNGPIC and all authorities having jurisdiction.
CAUTION: Air for combustion must not be contaminated by halogen compounds, which include fluoride,
chloride, bromide, and iodide. These elements are found
in aerosol sprays, detergents, bleaches, cleaning solvents,
salts, air fresheners, and other household products.
This furnace must be installed so the electrical components are
protected from water.
Locate the furnace as close to the chimney/vent and as near the
center of the air distribution system as possible. The furnace
should be installed as level as possible.
Provide ample space for servicing and cleaning. Always comply
with the minimum fire protection clearances shown on the unit
rating plate. This furnace shall not be installed directly on
carpeting, tile, or any combustible material other than wood
flooring. The furnace may be installed on combustible flooring
when installed with the accessory downflow subbase, which is
available from your distributor or branch when required.
B. Location Relative to Cooling Equipment
The cooling coil must be installed parallel with or on the
downstream side of the furnace to avoid condensation in the heat
exchangers. When installed parallel with a furnace, dampers or
other means used to control the flow of air must prevent chilled air
from entering the unit. If the dampers are manually operated, they
must be equipped with means to prevent operation of either unit
unless the damper is in the full-heat or full-cool position.
CAUTION: The operation of exhaust fans, kitchen ventilation fans, clothes dryers, or fireplaces could create a
NEGATIVE PRESSURE CONDITION at the furnace.
Make-up air MUST be provided for the ventilation
devices, in addition to that required by the furnace.
All fuel-burning equipment must be supplied with air for combustion of the fuel. Sufficient air MUST be provided to ensure there
will not be a negative pressure in the equipment room or space. In
addition, a positive seal MUST be made between the furnace
cabinet and the return-air duct to avoid pulling air from the burner
area and blocked vent safeguard opening.
The requirements for combustion and ventilation air depend upon
whether the furnace is located in an unconfined or confined space.
A. Unconfined Space
An unconfined space must have at least 50 cu ft for each 1000
Btuh of input for all the appliances (such as furnaces, clothes
dryer, water heaters, etc.) in the space.
If the unconfined space is of unusually tight construction, air for
combustion and ventilation MUST come from either the outdoors
or spaces freely communicating with the outdoors. Combustion
—4—
and ventilation openings must be sized the same as for a confined
space as defined below. Return air must not be taken from the
room unless an equal or greater amount of air is supplied to the
room.
For Example:
373LAV FURNACE
INPUT BTUH
46,000 307
69,000 460
92,000 613
115,000 767
135,000 920
MINIMUM SQ FT
WITH
7-1/2 FT CEILING
all vent connectors in the confined space. (See Fig. 4 and
Table 2.) Equipment clearances to the structure shall be
at least 1 in. from the sides and back and 6 in. from the
front of the appliances.
When ducts are used, they must be of the same cross-sectional area
as the free area of the openings to which they connect. The
minimum dimension of ducts must not be less than 3 in. (See Fig.
4.)
→AIR DUCTS
WARNING: Never connect return-air ducts to the back
of the furnace. A failure to follow this warning can cause
a fire, personal injury, or death.
→
B. Confined Space
A confined space is defined as a space whose volume is less than
50 cu ft per 1000 Btuh of total input ratings of all appliances
installed in that space. A confined space MUST have provisions
for supplying air for combustion, ventilation, and dilution of flue
gases using 1 of the following methods. (See Fig. 3, 4, and Table
2.)
NOTE: In determining free area of an opening, the blocking
effect of louvers, grilles, and screens must be considered. If free
area of louver or grille design is unknown, assume that wood
louvers have a 20 percent free area and metal louvers or grilles
have a 60 percent free area. Screens, when used, must not be
smaller than 1/4-in. mesh. Louvers and grilles must be constructed
so they cannot be closed.
The size of the openings depends upon whether air comes from
outside of the structure or an unconfined space inside the structure.
1. All air from inside the structure requires 2 openings (for
structures not usually tight):
a. Each opening MUST have at least 1 sq in. of free area
per 1000 Btuh of total input for all equipment within the
confined space, but not less than 100 sq in. per opening.
(See Fig. 3 and Table 2.) The minimum dimension of air
openings shall not be less than 3 in.
b. If building is constructed unusually tight, a permanent
opening directly communicating with the outdoors shall
be provided. See item 2 below.
c. If furnace is installed on a raised platform to provide a
return-air plenum, and return air is taken directly from
hallway or space adjacent to furnace, all air for combustion must come from outdoors.
2. Air from outside the structure requires 1 of the following
methods:
a. If combustion air is taken from outdoors through 2
vertical ducts, the openings and ducts MUST have at
least 1 sq in. of free area per 4000 Btuh of total input for
all equipment within the confined space. (See Fig. 4 and
Table 2.)
b. If combustion air is taken from outdoors through 2
horizontal ducts, the openings and ducts MUST have at
least 1 sq in. of free area per 2000 Btuh of total input for
all equipment within the confined space. (See Fig. 4 and
Table 2.)
c. If combustion air is taken from outdoors through a single
opening or duct (horizontal or vertical) commencing
within 12 in. of the top of the confined space, opening
and duct MUST have at least 1 sq in. of free area per
3000 Btuh of the total input for all equipment within the
confined space and not less than the sum of the areas of
I. GENERAL REQUIREMENTS
The duct system should be designed and sized according to
accepted national standards such as those published by: Air
Conditioning Contractors Association (ACCA), Sheet Metal and
Air Conditioning Contractors National Association (SMACNA) or
American Society of Heating, Refrigerating and Air Conditioning
Engineers (ASHRAE). Or consult factory The Air Systems Design
Guidelines reference tables available from your local distributor.
The duct system should be sized to handle the required system
design CFM at the design static pressure.
When a furnace is installed so that the supply ducts carry air to
areas outside the space containing the furnace, the return air must
also be handled by a duct(s) sealed to the furnace casing and
terminating outside the space containing the furnace.
Secure ductwork with proper fasteners for type of ductwork used.
Seal supply- and return-air duct connections to furnace with code
approved tape or duct sealer.
Flexible connections should be used between ductwork and
furnace to prevent transmission of vibration. Ductwork passing
through unconditioned space should be insulated to enhance
system performance. When air conditioning is used, a vapor
barrier is recommended.
Maintain a 1-in. clearance from combustible materials to supply air
ductwork for a distance of 36 in. horizontally from the furnace. See
NFPA 90B or local code for further requirements.
II. DUCTWORK ACOUSTICAL TREATMENT
Metal duct systems that do not have a 90 degree elbow and 10 ft
of main duct to the first branch take-off may require internal
acoustical lining. As an alternative, fibrous ductwork may be used
if constructed and installed in accordance with the latest edition of
SMACNA construction standard on fibrous glass ducts. Both
acoustical lining and fibrous ductwork shall comply with NFPA
90B as tested by UL Standard 181 for Class 1 Rigid air ducts.
III. SUPPLY AIR CONNECTIONS
A. Downflow Furnaces
Connect supply-air duct to supply-air opening (outlet) on furnace.
(See Fig. 1.) The supply-air duct attachment must ONLY be
connected to furnace supply/outlet or air conditioning coil casing
(when used), when installed on non-combustible material. When
installed on combustible material, supply-air duct attachment must
ONLY be connected to an accessory subbase or factory approved
air conditioning coil casing. DO NOT cut main furnace casing to
attach supply side air duct, humidifier, or other accessories. All
accessories MUST be connected external to furnace main casing.
B. Horizontal Furnaces
Connect supply-air duct to supply-air (outlet) opening on furnace.
(See Fig. 1.) The supply-air duct attachment must ONLY be
connected to furnace supply/outlet or air conditioning coil casing
(when used). DO NOT cut main furnace casing to attach supply
side air duct, humidifier, or other accessories. All accessories
MUST be connected external to furnace main casing.
—5—
VENT THROUGH ROOF
(CATEGORY I)
DUCTS TO
OUTDOORS
1 SQ IN.
PER 4000
BTUH
*
RETURN
AIR
INTERIOR
HEATED
SPACE
SUPPLY AIR
* Minimum opening size is 100 sq in. with
minimum dimensions of 3 in.
†
Minimum of 3 in. when type B-1 vent is used.
12″ MAX
1 SQ IN.
PER 1000
BTUH* IN DOOR
OR WALL
UNCONFINED
SPACE
6″ MIN
(FRONT)
1 SQ IN.
PER 1000
BTUH* IN DOOR
OR WALL
†
12″ MAX
A93387
Fig. 3—Confined Space: Air for Combustion and Ventilation
from an Unconfined Indoor Space
12″ MAX
1 SQ IN.
PER 2000
BTUH
*
DUCTS
TO
OUTSIDE
1 SQ IN.
PER 2000
BTUH
*
12″ MAX
SUPPLY AIR
Minimum dimensions of 3 in.
*
Use any of the following
NOTE:
combinations of openings:
A & B C & D D & E F & G
RETURN
A
B
AIR
D
VENT
THROUGH
ROOF
(CATEGORY I)
CONFINED
C
DUCT
TO
OUTDOORS
F
SPACE
G
E
12″ MAX
12″
MAX
1 SQ IN.
PER 4000
BTUH
OUTDOORS
1 SQ IN.
PER 4000
BTUH
12″
MAX
1 SQ IN.
PER 4000
BTUH
*
*
A93388
Fig. 4—Confined Space: Air for Combustion and Ventilation
from Outdoors
→TABLE 2—MINIMUM FREE AREA OF COMBUSTION AIR OPENING*
373LAV
FURNACE
INPUT
(BTUH)
46,000 100 11.50 4 23.0 6 15.33 5
69,000 100 17.25 5 34.5 7 23.00 6
92,000 100 23.00 6 46.0 8 30.67 7
115,000 115 28.75 7 57.5 9 38.33 7
135,000 135 33.75 7 67.5 10 45.00 8
* Free area shall be equal to or greater than the sum of the areas of all vent connections in the confined space. Opening area must be increased, if other gas appliances
in the space require combustion air.
AIR FROM INDOOR
UNCONFINED SPACE
Free Area
of Opening
(Sq In.)
IV. RETURN AIR CONNECTIONS
The return-air duct must be connected to return-air opening (inlet)
provided as shown in Fig. 1. DO NOT cut into casing sides or back
to attach any portion of return-air duct. Bypass humidifier connections should be made at ductwork or coil casing sides exterior to
furnace.
OUTDOOR AIR THROUGH
VERTICAL DUCTS
Free Area of
Opening and Duct
(Sq In.)
Round
Pipe
(In. Dia)
OUTDOOR AIR THROUGH
HORIZONTAL DUCTS
Free Area of
Opening and Duct
(Sq In.)
Round
(In. Dia)
Pipe
OUTDOOR AIR THROUGH
SINGLE DUCT
Free Area of
Opening and Duct
(Sq In.)
3. Construct plenum to dimensions specified in Table 3.
4. If downflow subbase (KGASB) is used, install as shown in
Fig. 6.
If coil assembly CD5, CK5, or Coil Box KCAKC is used,
install as shown in Fig. 7.
VI. HORIZONTAL ATTIC INSTALLATION
Round
Pipe
(In. Dia)
V. DOWNFLOW INSTALLATION
NOTE: This furnace is approved for use on combustible materials
or wood flooring. A factory accessory floor base, as listed on the
furnace rating plate, MUST be used. A factory accessory floor
base is not required when this furnace is installed on manufacturer’s Coil Assembly Part No. CD5 or CK5, or Coil Box Part No.
WARNING: DO NOT install the furnace on its back;
safety control operation will be adversely affected. Never
connect return-air ducts to the sides or back of the
furnace. Failure to follow this warning could result in fire,
personal injury, or death.
KCAKC is used.
1. Determine application being installed from Table 3.
2. Construct hole in floor per dimensions specified in Table 3
and Fig. 5.
The furnace can be installed horizontally on either the left-hand
(LH) or right-hand (RH) side. A typical attic installation is shown
in Fig. 8.
—6—
FURNACE
CASING
WIDTH
14-3/16
17-1/2
21
24-1/2
A
PLENUM
OPENING
B
OPENING
D
FLOOR
C
Fig. 5—Floor and Plenum Opening Dimensions
TABLE 3—OPENING DIMENSIONS (IN.)
APPLICATION
Non-Combustible Flooring 12-11/16 19 13-3/8 19-5/8
Combustible Flooring Using KGASB Subbase 11-13/16 19 13-7/16 20-3/8
Combustible Flooring with CD5 or CK5 Coil Assembly or
KCAKC Coil Box
Non-Combustible Flooring 16 19 16-5/8 19-5/8
Combustible Flooring Using KGASB Subbase 15-1/8 19 16-3/4 20-3/8
Combustible Flooring with CD5 or CK5 Coil Assembly or
KCAKC Coil Box
Non-Combustible Flooring 19-1/2 19 20-1/8 19-5/8
Combustible Flooring Using KGASB Subbase 18-5/8 19 20-1/4 20-3/8
Combustible Flooring with CD5 or CK5 Coil Assembly or
KCAKC Coil Box
Non-Combustible Flooring 23 19 23-5/8 19-5/8
Combustible Flooring Using KGASB Subbase 22-1/8 19 23-3/4 20-3/8
Combustible Flooring with CD5 or CK5 Coil Assembly or
KCAKC Coil Box
PLENUM OPENING FLOOR OPENING
ABCD
12-5/16 19 13-5/16 20
15-1/2 19 16-1/2 20
19 19 20 20
22-1/2 19 23-1/2 20
A96283
A. Construct a Working Platform
Construct working platform on location where all required
furnace clearances are met. (See Fig. 2 and 8.)
B. Install Furnace
1. Position furnace in desired location.
2. Connect gas supply pipe. See Fig. 8 for typical piping entry.
3. Install field-supplied filter retainers as indicated in Fig. 11
and Table 4 before connecting return-air duct to furnace.
4. Connect supply- and return-air ducts.
5. Install 24- X 24-in. sheet metal shield on platform in front
of louvered control panel as shown in Fig. 8.
VII. HORIZONTAL CRAWLSPACE INSTALLATION
The furnace can be installed horizontally with either the LH or RH
side up. In a crawlspace, the furnace can either be installed on
suitable blocks or pad (See Fig. 9.) or hung from the floor joist.
(See Fig. 10). The furnace can be suspended from each corner by
hanger bolts (4 each 3/8-in. all-thread rod) cut to desired length,
1 X 3/8-in. flat washer, 3/8-in. lockwasher, and 3/8-in. nut.
Dimples are provided for hole locations. (See Fig. 1.)
—7—
→
Since horizontal crawlspace installation is very similar to the attic
installation, refer to Section VI. The installation of a sheet metal
shield in front of the louvered control panel is covered in Section
VI. For a crawlspace installation, this same sheet metal shield must
be installed above the louvered control panel. Extend the sheet
metal shield over the furnace top far enough to cover the gas pipe
entry hole.
VIII. FILTER ARRANGEMENT
WARNING: Never operate unit without a filter or with
filter access door removed. Failure to follow this warning
could result in fire, personal injury, or death.
The 2 factory-supplied filters are shipped in the blower compartment. After the return-air duct has been connected to the furnace,
install the filters in a V-formation inside the return-air plenum. See
Fig. 11 and Table 4 for horizontal applications. Horizontal filter
retainers must be field supplied. See Fig. 12 for downflow
applications.
FURNACE
(OR COIL CASING
WHEN USED)
FURNACE
CD5 OR CK5
COIL ASSEMBLY
OR KCAKC
COIL BOX
COMBUSTIBLE
FLOORING
DOWNFLOW
SUBBASE
SHEET METAL
PLENUM
FLOOR
OPENING
Fig. 6—Furnace, Plenum, and Subbase Installed
on a Combustible Floor
LINE CONTACT ONLY PERMISSIBLE BETWEEN
LINES FORMED BY INTERSECTIONS OF
THE TOP AND TWO SIDES OF THE FURNACE
JACKET AND BUILDING JOISTS,
STUDS, OR FRAMING.
A96285
COMBUSTIBLE
FLOORING
SHEET METAL
PLENUM
FLOOR
OPENING
A96284
Fig. 7—Furnace, Plenum, and Coil Assembly or
Coil Box Installed on a Combustible Floor
MANUAL SHUTOFF
GAS VALVE
SEDIMENT
TRAP
GAS
ENTRY
″
6
24
24
″
″
SHEET
METAL
Fig. 8—Typical Attic Installation
MIN
TYPE-B
VENT
30-IN. MIN
WORK AREA
A97516
Fig. 9—Horizontal Installation on Blocks
—8—
A95235
ANGLE
IRON OR
EQUIVALENT
(B)
(A)
ROD LOCATION
USING DIMPLE
LOCATORS
(SEE DIMENSIONAL
DWG FOR
LOCATIONS)
(A) PREFERRED ROD LOCATION
(B) ALTERNATE ROD LOCATION
Fig. 10—Horizontal Crawlspace Installation on Hanger Rods
3
/8-IN. HEX NUT
& WASHER (4)
REQD PER ROD
(B)
(A)
(A)
(B)
NOTES:
3
⁄8-IN. ROD
(A)
(B)
1. A 1 In. clearance minimum between top of
furnace and combustible material.
2. The entire length of furnace must be
supported when furnace is used in horizontal
position.
A96633
AIRFLOW
12″
4″
D
FIELD-SUPPLIED
FILTER RETAINERS
Fig. 11—Horizontal Filter Arrangement
TABLE 4—FILTER RETAINER (IN.)
FURNACE
CASING WIDTH
14-3/16 (2) 14 X 20 X 1 14-3/8
17-1/2 (2) 14 X 20 X 1 13-3/8
21 (2) 16 X 20 X 1 11-5/8
24-1/2 (2) 16 X 20 X 1 10-1/4
FILTER SIZE
AND QUANTITY
A82173
D
IX. GAS PIPING
Gas piping must be installed in accordance with national and local
codes. Refer to the current edition of the NFGC.
Canadian installations must be installed in accordance with NSCNGPIC and all authorities having jurisdiction.
Refer to Table 5 for recommended gas pipe sizing. Risers should
be used to connect to the furnace and to the meter.
CAUTION: If a flexible connector is required or allowed by the authority having jurisdiction, black iron
pipe shall be installed at the gas valve and extend a
minimum of 2 in. outside the furnace casing.
WARNING: Use the proper length of pipes to avoid
stress on the gas control manifold. Failure to follow this
warning could result in a gas leak, causing fire, explosion,
personal injury, or death.
CAUTION: Connect the gas pipe to the furnace using a
backup wrench to avoid damaging gas controls.
—9—
INSTALLATION
POSITION
OF FILTERS
RETURN-AIR
PLENUM
ACCESS DOOR
AIRFLOW
GAS
SUPPLY
MANUAL
SHUTOFF
VALVE
(REQUIRED)
SEDIMENT
TRAP
UNION
A89414
Fig. 13—Typical Gas Pipe Arrangement
Fig. 12—Downflow Filter Arrangement
TABLE 5—MAXIMUM CAPACITY OF PIPE *
NOMINAL IRON
PIPE SIZE
(IN.)
1/2 0.622 175 120 97 82 73
3/4 0.824 360 250 200 170 151
1 1.049 680 465 375 320 285
1-1/4 1.380 1400 950 770 660 580
1-1/2 1.610 2100 1460 1180 990 900
* Cubic ft of gas per hr for gas pressures of 0.5 psig (14-in. wc) or less, and a
pressure drop of 0.5-in. wc (based on a 0.60 specific gravity gas). Ref: Table
10-2 NFPA 54/ANSI Z223.1-1996.
→
WARNING: Never purge a gas line into a combustion
INTERNAL
DIAMETER
(IN.)
LENGTH OF PIPE (FT)
10 20 30 40 50
chamber. Never use matches, candles, flame, or other
sources of ignition to check for gas leakage. Use a
soap-and-water solution to check for gas leaks. Failure to
follow this warning could result in fire, explosion, personal injury, or death.
Joint compounds (pipe dope) should be applied sparingly and only
to the male threads of the joints. This pipe dope must be resistant
to the action of propane gas.
An accessible manual shutoff valve MUST be installed upstream
of the furnace gas controls and within 72 in. of the furnace. A
1/8-in. NPT plugged tapping, accessible for test gage connection,
MUST be installed immediately upstream of the gas supply
connection to the furnace and downstream of the manual shutoff
valve. Place a ground joint union between the gas control manifold
and the manual shutoff.
Install a sediment trap in the riser leading to the furnace. The trap
can be installed by connecting a tee to the riser leading from the
furnace. Connect a capped nipple into the lower end of the tee. The
capped nipple should extend below the level of the gas controls.
(See Fig. 13.)
A88486
Piping should be pressure tested in accordance with local and
national plumbing and gas codes before the furnace has been
attached. If the pressure exceeds 0.5 psig (14-in. wc), the gas
supply pipe must be disconnected from the furnace and capped
before the pressure test. If the test pressure is equal to or less than
0.5 psig (14-in. wc), turn off electric shutoff switch located on the
gas valve before the test. It is recommended that the ground joint
union be loosened before pressure testing.
After all connections have been made, purge the lines and check
for gas leakage with regulated gas supply pressure.
X. ELECTRICAL CONNECTIONS
A. 115-v Wiring
Refer to the unit rating plate or Table 6 for equipment electrical
requirements. The control system requires an earth ground for
proper operation.
CAUTION: Do not connect aluminum wire between
disconnect switch and furnace. Use only copper wire.
Make all electrical connections in accordance with the current
→
edition of the National Electrical Code (NEC) ANSI/NFPA
70-1999, and any local codes or ordinances that might apply. For
Canadian installations, all electrical connections must be made in
accordance with Canadian Electrical Code CSA C22.1, or authorities having jurisdiction.
NOTE: Proper polarity must be maintained for 115-v wiring. If
polarity is incorrect, control center fault code indicator light will
flash rapidly and furnace will not operate.
—10—
→
WARNING: The cabinet MUST have an uninterrupted
or unbroken ground according to NEC ANSI/NFPA
70-1999 and Canadian Electrical Code CSA C22.1 or
local codes to minimize personal injury if an electrical
fault should occur. This may consist of electrical wire or
conduit approved for electrical ground when installed in
accordance with existing electrical codes. Do not use gas
piping as an electrical ground. Failure to follow this
warning could result in electrical shock, fire, or death.
B. 24-v Wiring
Make field 24-v connections at the 24-v terminal strip. (See Fig.
14.) Connect terminal Y as shown in Fig. 15 for proper operation
in cooling mode. Use AWG No. 18 color-coded wire only.
The 24-v circuit contains an automotive-type, 3-amp fuse located
on the main control board. Any direct shorts during installation,
service, or maintenance could cause this fuse to blow. If fuse
replacement is required, use ONLY a 3-amp fuse of identical size.
C. Accessories
1. Electronic air cleaner (EAC)
Two quick-connect terminals, marked EAC-1 and EAC-2,
are provided for EAC connection. (See Fig. 14.) These
terminals are energized with 115v (1.0-amp maximum)
during blower motor operation.
2. Humidifier (HUM)
Quick-connect terminal (HUM) and screw terminal (C
are provided for 24-v humidifier connection. The terminals
are energized with 24V (0.5-amp maximum) after inducer
motor prepurge period.
OM)
→
After fully assembling the vent connector to the furnace flue collar,
securely fasten the vent connector to the collar with two fieldsupplied, corrosion-resistant, sheet metal screws located 180° apart
and midway up the collar.
The horizontal portion of the venting system shall maintain a
minimum of 1/4-in. upward slope per linear ft and it shall be
rigidly supported every 5 ft or less with hangers or straps to ensure
that there will be no movement after installation.
XII. START-UP, ADJUSTMENT, AND SAFETY CHECK
A. General
NOTE: Proper polarity must be maintained for 115-v wiring. If
polarity is incorrect, control center fault indicator light will flash
rapidly and furnace will not operate.
The furnace must have a 115-v power supply properly connected
and grounded. Proper polarity must be maintained for correct
operation. Thermostat wire connections at R, W, C, and Y must be
made at the 24-v terminal block on the control board. The gas
service pressure must not exceed 0.5 psig (14-in. wc), but must be
no less than 0.16 psig (4.5-in. wc).
Before operating the furnace, check each manual reset switch for
continuity. If necessary, press the button to reset the switch.
The blower compartment door must be in place to complete the
115-v circuit to the furnace.
CAUTION: This furnace is equipped with 2 manual
reset limit switches in the gas control area. The switches
will open and shut off power to the gas valve if a flame
rollout or an overheating condition occurs in the gas
control area. DO NOT bypass the switches. Correct
inadequate combustion air supply problem and reset the
switches.
→
WARNING: DO NOT connect furnace control HUM
terminal to HUM (humidifier) terminal on
B. Sequence of Operation
Thermidistat™, Zone Controller, or similar device. See
Thermidistat, Zone Controller, thermostat, or controller
manufacturer’s instructions for proper connection. A
failure to follow this warning could result in fire.
CAUTION: Furnace control must be grounded for
proper operation or control will lockout. Control is
grounded through green wire routed to gas valve and
burner bracket screw.
NOTE: A field-supplied, 115-v controlled relay connected to
EAC terminals may be added if humidifier operation is desired
during blower operation.
XI. VENTING
Refer to the national or local installation code such as NFGC in the
→
United States, or the NSCNGPIC in Canada for proper vent sizing
and installation requirements. Use the enclosed Installation In-
Using the schematic diagram shown in Fig. 16, follow the
sequence of operation through the different modes. Read and
follow the wiring diagram very carefully.
NOTE: If there is a power interruption and any thermostat call,
the control will initiate a 90-sec blower only on period before
starting another cycle.
structions (Single-Stage Vent Tables for Category I Fan-Assisted
Furnaces) for a quick, easy reference.
TABLE 6—ELECTRICAL DATA
UNIT SIZE
024050 115—60—1 127 104 6.6 14 42 15
036050 115—60—1 127 104 8.1 14 34 15
024070 115—60—1 127 104 6.7 14 42 15
036070 115—60—1 127 104 8.4 14 33 15
036095 115—60—1 127 104 9.2 14 30 15
049095 115—60—1 127 104 10.2 14 28 15
048115 115—60—1 127 104 10.1 14 28 15
060115 115—60—1 127 104 13.3 12 33 20
060135 115—60—1 127 104 14.3 12 31 20
* Permissible limits of the voltage range at which the unit will operate satisfactorily.
† Time-delay type is recommended.
‡ Length shown is as measured 1 way along wire path between unit and service panel for maximum 2 percent voltage drop.
VOLTS—
HERTZ—
PHASE
OPERATING VOLTAGE RANGE
Maximum* Minimum*
MAXIMUM
UNIT AMPS
MINIMUM
WIRE GAGE
MAXIMUM WIRE
LENGTH FT‡
MAXIMUM
FUSE OR CKT BKR
AMPS†
—11—
GRYW
24-V THERMOST AT
TERMINALS
TEST/TWIN
3-AMP FUSE
115-VAC (L1)
POWER SUPPLY
HOT SURFACE
IGNITOR CONNECTOR
SEC-1
COOL
HEAT
OM
C
HUM
24V
HUMIDIFIER TERMINAL
(24-VAC 0.5 AMP MAX)
LED OPERATION &
DIAGNOSTIC LIGHT
HARNESS CONNECTOR
24-V TRANSFORMER SEC-2
SP ARE-1
BLOWER SPEED
SELECTION TERMINALS
SP ARE-2
EAC-1
EAC-ELECTRONIC AIR CLEANER
TERMINALS (115-VAC 1.0 AMP MAX)
EAC-2
115-VAC (L2) NEUTRAL
CONNECTION
INDUCER MOTOR
CONNECTOR
→Fig. 14—Furnace Control
A99255
BLK
WHT
WHT
GND
115-V
FIELD-SUPPLIED
DISCONNECT
THREE-WIRE
BLK
AUXILIARY
J-BOX
FIELD 24-V WIRING
FIELD 115-, 208/230-, 460-V WIRING
FACTORY 24-V WIRING
FACTORY 115-V WIRING
FIVE
WIRE
NOTE 2
WCR GY
THERMOSTAT
TERMINALS
HEATING-
ONLY
W
R
GND
CONTROL
BOX
FURNACE
G
C
Y
24-V
TERMINAL
BLOCK
NOTE 1
CONDENSING
UNIT
TWO
WIRE
NOTES: Connect Y-terminal as shown for proper operation.
1.
2.
Some thermostats require a "C" terminal connection as shown.
3.
If any of the original wire, as supplied, must be replaced, use
same type or equivalent wire.
Fig. 15—Heating and Cooling Application Wiring Diagram
FIELD-SUPPLIED
DISCONNECT
208/230- OR
460-V
THREE
PHASE
208/230-V
SINGLE
PHASE
GND
A98209
—12—
TO 115VAC FIELD DISCONN ECT
(WHEN USED)
(WHEN USED)
SCHEMATIC DIAGRAM
GRY
SW2
L2
CAP
BLWM
START
OL
LO
LGPS
PRS
ALS
BVSS
DSS
NOTE #9
PCB
HI
MED LO
MED HI
COM
NOTE #7
COM
COOL
HEAT
SPARE-1
SPARE-2
ILK
ORN
ORN
ORN
ORN
SW1
(NOT ON ALL MODELS)
HI/LO
BLWR
L1
YEL
3-P
NOTE #13
1-M
NOTE #14
LS
ORN
OM
C
BLOWER OFF DELAY
HUM
BLU
RED
LED
TEST/TWIN
90 SEC
135 SEC
180 SEC
SELECTION CHART
EQUIPMENT GROUND
W
OFF
DELAY
(NATURAL GAS & PRO PANE)
NOTE # 4
NEUTRAL
L1
(WHEN USED)
NOTE #11
NOTE #14
BLOWER
IDM
HSI
2
1
PL52
1
PL2
EAC-2
EAC-1
IDR
HSIR
GV
NOTE #5
2-C
GRN
FL
BLK
FRS2
WHT
4
BLU
FRS1
FSE
RED
SEC-2
5
987
6
SEC-1
(WHEN USED)NOTE #11
321
PL1
HI/LO
GVR
225 SEC
NOT USED
PL3
2
1
3
PR2
24VAC
115VAC
TRAN
PR1
GRN
WHT (COM )
WHT
BRN
TRAN
RED
BLK (HI)
FUSE
24 VAC-3A
FU1
BLOWER
RELAY
NOTE #6
FU1
TEST/TWIN
OL
SPARE-1
COOL
SPEED
SELECT
HSIR IDR BLWR
FL
PRS
NOTE #13
LS
(WHEN USED)
LGPS
(WHEN USED)
NOTE #11
FRS1 FRS2
(WHEN USED)
7
SEC-2
SEC-1
GVR-2
HUM
NOTE #12
CAP
START
NOTE #7
BLU (MED LO)
YEL (MED HI)
SPARE-2
EAC-1
HEAT
L2
PR2
123
PL3
PL2
VAC
120
PL1
NOTE #13
1
4
HI/LO
BLWR
HSIR
W
R
BRN
BLWM
BLK
WHT
RED (LO)
WHT (CO M)
1.5 AMP
EAC-2
OM
C
WHT
2
1
PR1
WHT
BLK
BLK
BLK
L1
ALS
NOTE #5
NOTE #11
(WHEN USED)
3
L1
FU2
BLK
IDM
BLK
12
GV
NOTE #14
3-P
2
GVR-1
CPU
NEUTRAL
GRN
WHT
GRN
HSI
BVSS
NOTE #14
DSS
GVR
IDR
NOTE #4
FUSED DISCONNECT
SWITCH (WHEN REQ'D)
JB
ILK
WHT
PL5
FSE
2-C
1-M
NOT USED
G
PCB PRINTED CIRCUIT BOARD
BLWR BLOWER MOTOR RELAY, SPST-(N.O.)
NOT USED
9
6
5
OM
C
PL1 9-CIRCUIT CONNECTOR
PL2 2-CIRCUIT PCB CONNECTOR
PL3 3-CIRCUIT IDM CONNECTOR
PL5 2-CIRCUIT HSI/PCB CONNECTOR
BLWM BLOWER MOTOR
BVSS BLOCKED VENT SHUTOFF SWITCH, SPST - (N.C.)
CAP CAPACITOR
CPU MICROPROCESSOR AND CIRCUITRY
DSS DRAFT SAFEGUARD SWITCH
optimum speed selection.
1. If any of the original equipment wire is replaced use wire rated for 105˚C.
2. Inducer (IDM) and blower (BLWM) motors contain internal auto-reset thermal overload switches (OL).
3. Blower motor speed se lections are for average conditions, see installation instructions for details on
4. Use only copper wire between the disconnect switch and the furnace junction box (JB).
NOTES:
JUNCTION
UNMARKED TERMINAL
PCB TERMINAL
PRS PRESSURE SWITCH, SPST-(N.O.)
TEST/TWIN COMPONENT TEST & TWIN TERMINAL
TRAN TRANSFORMER-115VAC/24VAC
(FIELD INSTALLED & SUPPLIED)
EAC-1 ELECTRONIC AIR CLEANE R C O N NE CTION (115 VAC 1.5 AMP MA X .)
EAC-2 ELECTRONIC AIR CLEANER CONNECTION (COMMON)
FL FUSIBLE LINK
FRS FLAME ROLLOUT SW. -MANUAL RESET, SPST-(N.C.)
FSE FLAME PROVING ELECTRODE
FU1 FUSE, 3 AMP, AUTOMOTIVE BLADE TYPE, FACTORY INSTALLED
FU2 FUSE OR CIRCUIT BREAKER CURRENT INTERRUPT DEVICE
(135 seconds only on some models)
after three hours.
9. Blower-off delay, gas heating 90, 135, 180 or 225 seconds, cooling or heat pump 90 seconds.
FIELD WIRING (24VAC)
HSIR HOT SURFACE IGNITOR RELAY, SPST-(N.O.)
10. Ignition-lockout will occur after four consecutive unsuccessful trials-for-ignition. Control w ill auto-reset
CONDUCTOR ON PCB
FIELD WIRING TERMINAL
HUM 24VAC HUMIDIFIER CONNECTION (.5 AMP. MAX.)
IDM INDUCED DRAFT MOTOR
IDR INDUCED DRAFT RELAY, SPST-(N.O.)
models only.
11. When used, auxiliary limit switch (ALS) is on some downflow models only. When used, FL is on upflow
12. Some models may have spade quic k connect terminals.
13. Factory c onnected when LGPS is not used.
FIELD GROUND
EQUIPMENT GROUND
FIELD SPLICE
ILK BLOWER ACCESS PANEL INTERLOCK SWITCH, SPST-(N.O.)
JB JUNCTION BOX
LED LIGHT-EMITTING DIODE FOR STATUS CODES
LGPS LOW G AS PR ESSURE SW ITCH, SPST-(N.O.)
5. This wire must be connected to furnace sheetmetal for control to detect flame.
6. Replace only with a 3 amp fuse.
7. Yellow lead not on all motors.
8. Blower-on delay, gas heating 45 seconds, cooling or heat pump 2 seconds.
FACTORY WIRING (115VAC)
FACTORY WIRING (24VAC)
FIELD WIRING (115VAC)
GV GAS VALVE-REDUNDANT OPERATORS
GVR GAS VALVE RELAY, DPST-(N.O.)
HI/LO BLOWER MOTOR SPEED CHANGE RELAY, SPDT
HSI HOT SURFACE IGNITOR (115 VAC )
8
Y
ALS AUXILIARY LIMIT SWITCH , OVERTEM P. -MANUAL RESET, SPST-(N.C.)
LEGEND
A98200e
322869-101 REV. E
installed.
14. Factory c onnected when BVSS is not used. BVSS used when Chimney Adapter Accessory Kit is
PLUG RECEPTACLE
Fig. 16—Furnace Wiring Diagram
LS LIMIT SWITCH, AUTO RESET, SPST(N.C.)
OL AUTO-RESET INTERNAL MOTOR OVERLOAD TEMP. SW.
—13—
1. Heating mode
When the thermostat "calls for heat," R-W circuit closes.
The furnace control performs a self-check, verifies the
pressure switch contacts are open, and starts the inducer
motor.
a. Prepurge period—As the inducer motor comes up to
speed, the pressure switch contacts close to begin a
15-sec prepurge period.
b. Igniter warm-up—At the end of the prepurge period, the
igniter is energized for a 17-sec igniter warm-up period.
c. Ignition sequence—When the igniter warm-up period is
completed, the gas valve opens, permitting gas flow to
the burners where it is ignited. After 5 sec, the igniter is
de-energized and a 2-sec flame-sensing period begins.
d. HUM terminal is energized with the gas valve. See
Accessories in Electrical Connections section.
e. Flame-sensing—When burner flame is sensed, the con-
trol begins the blower on delay period and continues
holding the gas valve open. If burner flame is not sensed,
the control closes the gas valve and repeats the ignition
cycle.
NOTE: Ignition sequence will repeat 3 additional times before a
lockout occurs. Lockout automatically resets after 3 hrs, or can be
manually reset by turning 115v off (not at thermostat) for 3 sec
minimum, then on again.
→
→
f. Blower on delay—Forty-five sec after burner flame is
proven, the blower motor is energized on heating speed.
Simultaneously, the humidifier and electronic air cleaner
terminals (HUM and C
and EAC-2 for electronic air cleaner) are energized.
g. Blower off delay—When the thermostat is satisfied, the
circuit between R and W is broken, de-energizing the gas
valve and stopping gas flow to the burners. The blower
motor, and EAC remain energized for 135 sec.
h. Post-purge—The inducer motor remains energized 5 sec
after the burners are extinguished.
2. Cooling mode
When the thermostat "calls for cooling," R-G and R-Y
circuits close. The R-Y circuit starts the outdoor condensing
unit and combined R-Y and R-G circuits start the furnace
blower motor on cooling speed. The EAC-1 terminal is
energized with 115v whenever the blower is operating on
cooling speed.
When the thermostat is satisfied, R-G and R-Y circuits are
broken. Furnace blower and EAC continue operating on
cooling speed for an additional 90 sec.
3. Continuous blower mode
NOTE: EAC-1 terminal is energized with 115v whenever blower
is operating.
When the R-G circuit is made, the blower motor operates on
heating speed. During a call for heat, the blower stops,
allowing the furnace heat exchangers to heat up more
quickly, then restarts at the end of the 45-sec blower on
delay period.
The blower reverts to continuous operation after the heating
cycle is completed.
When the thermostat "calls for cooling," the blower operates on cooling speed. When the thermostat is satisfied, the
blower operates an additional 90 sec before reverting back
to continuous operation on heating speed.
OM-24V for humidifier, EAC-1
4. Heat pump mode
When installed with a heat pump, the furnace control
automatically changes the timing sequence to avoid long
blower off time during demand defrost cycles. When the
W-Y or W-Y-G thermostat inputs are received at the same
time, the control changes the blower to heating speed or
starts the blower if it was off, and begins a heating cycle.
The blower remains on until the end of the prepurge period,
then shuts off until the end of the ignition warm up and trial
for ignition periods (a total of 24 sec). The blower then
comes back on at heating speed.
When the W input signal disappears, the control begins the
normal inducer post-purge period and the blower changes to
cooling speed after a 1-sec delay. If the W-Y-G signals
disappear at the same time, the blower remains on for the
selected heating blower off delay period and the inducer
goes through its normal post-purge period. If the W-Y
inputs should disappear, leaving the G signal input, the
control goes into continuous blower and the inducer remains on for the normal post-purge period.
Anytime the control senses false flame, the control locks
out of the heating mode. This occurs because the control
cannot sense the W input due to the false flame signal and,
as a result, sees only the Y input and goes into cooling mode
blower off delay. All other control functions remain in
standard format.
NOTE: EAC-1 terminal is energized whenever blower operates.
HUM terminal is only energized when gas valve is energized.
C. Start-up Procedures
1. Purge gas lines—After all connections have been made,
purge the lines and check for leaks.
→
→
→
→
→
WARNING: Never purge a gas line into a combustion
chamber. Never use matches, candles, flame, or other
sources of ignition to check for gas leakage. Use a
soap-and-water solution to check for gas leaks. Failure to
follow this warning could result in fire, explosion, personal injury, or death.
2. Component test—The furnace control allows all components, except gas valve, to be run for a short period of time.
This feature helps diagnose a system problem in case of a
component failure. To initiate component test procedure,
short (jumper) the TEST 3/16-in. quick connect terminal on
control (adjacent to diagnostic light) and the C
terminal on furnace thermostat connection block for approximately 2 sec. (See Fig. 14.)
NOTE: Component test feature will not operate if any thermostat
signal is present at control.
Component test sequence is as follows.
a. Momentarily jumper TEST and C
LED goes off.
b. LED will display previous status 4 times.
c. Inducer motor starts and continues to run for entire
component test.
d. Hot surface igniter is energized for 15 sec, then de-
energized.
e. Blower motor operates on cooling speed for 10 sec, then
stops.
f. Blower motor operates on heating speed for 10 sec, then
stops.
g. Inducer motor stops.
OM-24V terminals until
OM-24V
—14—
3. To operate furnace, follow procedures on operating instruction label attached to furnace.
4. With furnace operating, set thermostat below room temperature and observe that furnace goes off. Set thermostat
above room temperature and observe that furnace restarts.
D. Adjustments
1. Set gas input rate
Furnace gas input rate on rating plate is for installations at
altitudes up to 2000 ft. Furnace input rate must be within ±2
percent of input on furnace rating plate.
a. Determine natural gas orifice size and manifold pressure
for correct input.
→
(1.) Obtain average yearly gas heat value (at installed
altitude) from local gas supplier.
→
(2.) Obtain average yearly gas specific gravity from
local gas supplier.
(3.) Verify furnace model. Table 8 can only be used for
model 373LAV Furnaces.
(4.) Find installation altitude in Table 8.
NOTE: For Canada altitudes of 2000 to 4500 ft, use U.S.A.
altitudes of 2001 to 3000 ft in Table 8.
(5.) Find closest natural gas heat value and specific
gravity in Table 8.
(6.) Follow heat value and specific gravity lines to point
of intersection to find orifice size and manifold
pressure settings for proper operation.
EXAMPLE: (0—2000 ft altitude)
Heating value = 1050 Btu/cu ft
Specific gravity = 0.62
Therefore: Orifice No. 43*
Manifold pressure 3.6-in. wc
* Furnace is shipped with No. 43 orifices. In this example
all main burner orifices are the correct size and do not need
to be changed to obtain proper input rate.
b. Adjust manifold pressure to obtain input rate.
(1.) Remove regulator adjustment seal cap. (See Fig.
17.)
ON AND
OFF SWITCH
GAS
PRESSURE
REGULATOR
ADJUSTMENT
INLET
PRESSURE TAP
MANIFOLD
PRESSURE TAP
A95618
Fig. 17—Redundant Automatic Gas Control Valve
(2.) Turn adjusting screw, counterclockwise (out) to
decrease manifold pressure or clockwise (in) to
increase manifold pressure.
NOTE: This furnace has been approved for a manifold pressure
of 3.2-in. wc to 3.8-in. wc when installed at altitudes up to 2000 ft.
For altitudes above 2000 ft, the manifold pressure can be adjusted
from 2.0-in. wc to 3.8-in. wc.
CAUTION: DO NOT bottom out gas valve regulator
adjusting screw. This can result in unregulated manifold
pressure and result in excess overfire and heat exchanger
failures.
(7.) Check and verify burner orifice size in furnace.
NEVER ASSUME ORIFICE SIZE. ALWAYS
CHECK AND VERIFY.
BURNER
ORIFICE
→
CAUTION: Do not redrill orifices. Improper drilling
(burrs, out-of-round holes, etc.) can cause excessive
burner noise and misdirection of burner flames. This can
result in flame impingement of burners and heat exchangers, causing failures.
NOTE: If orifice hole appears damaged or it is suspected to have
been redrilled, check orifice hole with a numbered drill bit of
correct size. Never redrill an orifice. A burr-free and squarely
aligned orifice hole is essential for proper flame characteristics.
A93059
(3.) After correct manifold pressure is obtained, replace
gas valve regulator adjustment screw cap and verify
adjusted gas input rate using method outlined in
item c.
(4.) Burner flame should be clear blue, almost transpar-
ent. (See Fig. 18.)
c. Verify natural gas input rate by clocking gas meter.
NOTE: High-Altitude Adjustment
UNITED STATES
At installation altitudes above 2000 ft, this furnace has been
approved for a 4 percent derate for each 1000 ft above sea level.
See Table 7 for derate multiplier factor.
TABLE 7—ALTITUDE DERATE MULTIPLIER FOR U.S.A.
ALTITUDE
(FT)
0—2000 0 1.00
2001—3000 8—12 0.90
3001—4000 12—16 0.86
4001—5000 16—20 0.82
5001—6000 20—24 0.78
6001—7000 24—28 0.74
7001—8000 28—32 0.70
8001—9000 32—36 0.66
9001—10,000 36—40 0.62
* Derate multiplier factor is based on midpoint altitude for altitude range.
%OF
DERATE
DERATE MULTIPLIER
FACTOR FOR U.S.A*
—15—
TABLE 8—MODEL 373LAV ORIFICE SIZE† AND MANIFOLD PRESSURE FOR CORRECT INPUT
(Tabulated Data Based on 23,000 BTUH Per Burner, Derated 4 Percent per 1000 Ft Above Sea Level)*
ALTITUDE
RANGE
(FT)
0 925 42 3.4 42 3.5 42 3.6 42 3.7 42 3.8
to 975 43 3.7 43 3.8 42 3.2 42 3.3 42 3.4
2000 1025 43 3.3 43 3.4 43 3.6 43 3.7 43 3.8
U.S.A. and Canada
ALTITUDE
RANGE
(FT)
U.S.A 775 42 3.7 42 3.8 41 3.5 41 3.6 41 3.8
Altitudes 800 42 3.4 42 3.6 42 3.7 42 3.8 41 3.5
2001 825 42 3.2 42 3.3 42 3.5 42 3.6 42 3.7
to 850 43 3.7 43 3.8 42 3.3 42 3.4 42 3.5
3000 875 43 3.5 43 3.6 43 3.7 42 3.2 42 3.3
or 900 43 3.3 43 3.4 43 3.5 43 3.7 43 3.8
Canada 925 43 3.1 43 3.2 43 3.4 43 3.5 43 3.6
Altitudes 950 43 3.0 43 3.1 43 3.2 43 3.3 43 3.4
U.S.A. and Canada
2000 975 43 2.8 43 2.9 43 3.0 43 3.1 43 3.2
to 1000 43 2.7 43 2.8 43 2.9 43 3.0 43 3.1
4500 1025 43 2.6 43 2.6 43 2.7 43 2.8 43 2.9
ALTITUDE
RANGE
(FT)
3001 825 43 3.5 43 3.6 43 3.7 43 3.8 42 3.2
to 875 43 3.1 43 3.2 43 3.3 43 3.4 43 3.5
U.S.A. Only
4000 925 43 2.8 43 2.9 43 3.0 43 3.0 43 3.1
ALTITUDE
RANGE
(FT)
4001 800 43 3.2 43 3.3 43 3.5 43 3.6 43 3.7
to 850 43 2.9 43 3.0 43 3.1 43 3.2 43 3.3
U.S.A. Only
5000 900 43 2.6 43 2.6 43 2.7 43 2.8 43 2.9
* For size 060135 only, input is 22,500 Btuh per burner. Deduct 0.1-in. wc from manifold pressure shown in table. Change orifice size if manifold pressure falls below 3.2-in.
wc on altitudes up to 2000 ft, otherwise change orifice size if manifold pressure falls below 2.0-in. wc.
† Orifice sizes shown in BOLD are factory installed.
AVG GAS
HEAT VALUE
AT ALTITUDE
(BTU/CU FT)
850 41 3.6 41 3.7 41 3.8 40 3.6 40 3.8
875 42 3.8 41 3.5 41 3.6 41 3.7 41 3.8
900 42 3.5 42 3.7 42 3.8 41 3.5 41 3.6
950 42 3.2 42 3.3 42 3.4 42 3.5 42 3.6
1000 43 3.5 43 3.6 43 3.7 42 3.2 42 3.3
1050 43 3.2 43 3.3 43 3.4 43 3.5 43 3.6
1075 44 3.5 44 3.6 43 3.2 43 3.3 43 3.4
1100 44 3.3 44 3.4 44 3.5 43 3.2 43 3.3
AVG GAS
HEAT VALUE
AT ALTITUDE
(BTU/CU FT)
AVG GAS
HEAT VALUE
AT ALTITUDE
(BTU/CU FT)
750 42 3.4 42 3.6 42 3.7 42 3.8 41 3.5
775 42 3.2 42 3.3 42 3.5 42 3.6 42 3.7
800 43 3.7 43 3.8 42 3.2 42 3.3 42 3.4
850 43 3.3 43 3.4 43 3.5 43 3.6 43 3.7
900 43 2.9 43 3.0 43 3.1 43 3.2 43 3.3
950 43 2.6 43 2.7 43 2.8 43 2.9 43 3.0
975 43 2.5 43 2.6 43 2.7 43 2.7 43 2.8
1000 43 2.4 43 2.4 43 2.5 43 2.6 43 2.7
AVG GAS
HEAT VALUE
AT ALTITUDE
(BTU/CU FT)
725 42 3.2 42 3.3 42 3.5 42 3.6 42 3.7
750 43 3.7 43 3.8 42 3.2 42 3.3 42 3.4
775 43 3.4 43 3.6 43 3.7 43 3.8 42 3.2
825 43 3.0 43 3.1 43 3.2 43 3.4 43 3.5
875 43 2.7 43 2.8 43 2.9 43 3.0 43 3.1
925 43 2.4 43 2.5 43 2.6 43 2.7 43 2.8
950 43 2.3 43 2.4 43 2.5 43 2.5 43 2.6
0.58 0.60 0.62 0.64 0.66
Orifice
No.
Orifice
No.
Orifice
No.
Orifice
No.
Manifold
Pressure
0.58 0.60 0.62 0.64 0.66
Manifold
Pressure
0.58 0.60 0.62 0.64 0.66
Manifold
Pressure
0.58 0.60 0.62 0.64 0.66
Manifold
Pressure
Orifice
No.
Orifice
No.
Orifice
No.
Orifice
No.
SPECIFIC GRAVITY OF NATURAL GAS
Manifold
Pressure
SPECIFIC GRAVITY OF NATURAL GAS
Manifold
Pressure
SPECIFIC GRAVITY OF NATURAL GAS
Manifold
Pressure
SPECIFIC GRAVITY OF NATURAL GAS
Manifold
Pressure
Orifice
No.
Orifice
No.
Orifice
No.
Orifice
No.
Manifold
Pressure
Manifold
Pressure
Manifold
Pressure
Manifold
Pressure
Orifice
No.
Orifice
No.
Orifice
No.
Orifice
No.
Manifold
Pressure
Manifold
Pressure
Manifold
Pressure
Manifold
Pressure
Orifice
No.
Orifice
No.
Orifice
No.
Orifice
No.
Manifold
Pressure
Manifold
Pressure
Manifold
Pressure
Manifold
Pressure
—16—
TABLE 8—MODEL 373LAV ORIFICE SIZE† AND MANIFOLD PRESSURE FOR CORRECT INPUT (Continued)
(Tabulated Data Based on 23,000 BTUH Per Burner, Derated 4 Percent per 1000 Ft Above Sea Level)*
ALTITUDE
RANGE
(FT)
5001 800 43 2.8 43 2.9 43 3.0 43 3.1 43 3.2
to 850 43 2.5 43 2.6 43 2.7 43 2.8 43 2.8
U.S.A. Only
6000 900 43 2.2 43 2.3 43 2.4 43 2.5 43 2.5
ALTITUDE
RANGE
(FT)
6001 725 43 3.0 43 3.1 43 3.2 43 3.3 43 3.4
to 775 43 2.6 43 2.7 43 2.8 43 2.9 43 3.0
U.S.A. Only
7000 825 43 2.3 43 2.4 43 2.5 43 2.5 43 2.6
ALTITUDE
RANGE
(FT)
7001 700 43 2.7 43 2.8 43 2.9 43 3.0 43 3.1
to 750 43 2.4 43 2.5 43 2.6 43 2.6 43 2.7
U.S.A. Only
8000 800 43 2.1 43 2.2 43 2.2 43 2.3 43 2.4
ALTITUDE
RANGE
(FT)
8001 650 43 2.7 43 2.8 43 2.9 43 3.0 43 3.1
to 700 43 2.4 43 2.4 43 2.5 43 2.6 43 2.7
U.S.A. Only
9000 750 43 2.0 43 2.1 43 2.2 43 2.3 43 2.3
* For size 060135 only, input is 22,500 Btuh per burner. Deduct 0.1-in. wc from manifold pressure shown in table. Change orifice size if manifold pressure falls below 3.2-in.
wc on altitudes up to 2000 ft, otherwise change orifice size if manifold pressure falls below 2.0-in. wc.
† Orifice sizes shown in BOLD are factory installed.
AVG GAS
HEAT VALUE
AT ALTITUDE
(BTU/CU FT)
700 43 3.7 43 3.8 42 3.2 42 3.3 42 3.4
725 43 3.4 43 3.6 43 3.7 43 3.8 42 3.2
750 43 3.2 43 3.3 43 3.4 43 3.5 43 3.6
775 43 3.0 43 3.1 43 3.2 43 3.3 43 3.4
825 43 2.7 43 2.7 43 2.8 43 2.9 43 3.0
875 43 2.4 43 2.4 43 2.5 43 2.6 43 2.7
925 43 2.1 43 2.2 43 2.3 43 2.3 43 2.4
950 48 3.8 43 2.1 43 2.1 43 2.2 43 2.3
975 48 3.6 48 3.7 43 2.0 43 2.1 43 2.2
1000 48 3.4 48 3.5 48 3.6 48 3.7 43 2.1
AVG GAS
HEAT VALUE
AT ALTITUDE
(BTU/CU FT)
650 43 3.7 43 3.8 42 3.2 42 3.3 42 3.5
675 43 3.4 43 3.5 43 3.7 43 3.8 42 3.2
700 43 3.2 43 3.3 43 3.4 43 3.5 43 3.6
750 43 2.8 43 2.9 43 3.0 43 3.1 43 3.2
800 43 2.4 43 2.5 43 2.6 43 2.7 43 2.8
850 43 2.2 43 2.2 43 2.3 43 2.4 43 2.5
875 43 2.0 43 2.1 43 2.2 43 2.3 43 2.3
AVG GAS
HEAT VALUE
AT ALTITUDE
(BTU/CU FT)
625 43 3.4 43 3.6 43 3.7 43 3.8 42 3.2
650 43 3.2 43 3.3 43 3.4 43 3.5 43 3.6
675 43 3.0 43 3.1 43 3.2 43 3.3 43 3.4
725 43 2.6 43 2.6 43 2.7 43 2.8 43 2.9
775 43 2.2 43 2.3 43 2.4 43 2.5 43 2.5
825 48 3.7 43 2.0 43 2.1 43 2.2 43 2.2
850 48 3.5 48 3.6 48 3.7 43 2.1 43 2.1
AVG GAS
HEAT VALUE
AT ALTITUDE
(BTU/CU FT)
600 43 3.2 43 3.3 43 3.4 43 3.5 43 3.6
625 43 3.0 43 3.1 43 3.2 43 3.3 43 3.4
675 43 2.5 43 2.6 43 2.7 43 2.8 43 2.9
725 43 2.2 43 2.3 43 2.3 43 2.4 43 2.5
775 48 3.6 48 3.7 43 2.1 43 2.1 43 2.2
800 48 3.4 48 3.5 48 3.6 48 3.7 43 2.0
0.58 0.60 0.62 0.64 0.66
Orifice
No.
Orifice
No.
Orifice
No.
Orifice
No.
Manifold
Pressure
0.58 0.60 0.62 0.64 0.66
Manifold
Pressure
0.58 0.60 0.62 0.64 0.66
Manifold
Pressure
0.58 0.60 0.62 0.64 0.66
Manifold
Pressure
Orifice
No.
Orifice
No.
Orifice
No.
Orifice
No.
SPECIFIC GRAVITY OF NATURAL GAS
Manifold
Pressure
SPECIFIC GRAVITY OF NATURAL GAS
Manifold
Pressure
SPECIFIC GRAVITY OF NATURAL GAS
Manifold
Pressure
SPECIFIC GRAVITY OF NATURAL GAS
Manifold
Pressure
Orifice
No.
Orifice
No.
Orifice
No.
Orifice
No.
Manifold
Pressure
Manifold
Pressure
Manifold
Pressure
Manifold
Pressure
Orifice
No.
Orifice
No.
Orifice
No.
Orifice
No.
Manifold
Pressure
Manifold
Pressure
Manifold
Pressure
Manifold
Pressure
Orifice
No.
Orifice
No.
Orifice
No.
Orifice
No.
Manifold
Pressure
Manifold
Pressure
Manifold
Pressure
Manifold
Pressure
—17—
TABLE 8—MODEL 373LAV ORIFICE SIZE† AND MANIFOLD PRESSURE FOR CORRECT INPUT (Continued)
(Tabulated Data Based on 23,000 BTUH Per Burner, Derated 4 Percent per 1000 Ft Above Sea Level)*
ALTITUDE
RANGE
(FT)
9001 625 43 2.5 43 2.6 43 2.7 43 2.8 43 2.8
to 675 43 2.1 43 2.2 43 2.3 43 2.4 43 2.4
U.S.A. Only
10,000 725 48 3.5 48 3.6 48 3.7 43 2.1 43 2.1
* For size 060135 only, input is 22,500 Btuh per burner. Deduct 0.1-in. wc from manifold pressure shown in table. Change orifice size if manifold pressure falls below 3.2-in.
wc on altitudes up to 2000 ft, otherwise change orifice size if manifold pressure falls below 2.0-in. wc.
† Orifice sizes shown in BOLD are factory installed.
BURNER FLAME
AVG GAS
HEAT VALUE
AT ALTITUDE
(BTU/CU FT)
575 43 3.0 43 3.1 43 3.2 43 3.3 43 3.4
600 43 2.7 43 2.8 43 2.9 43 3.0 43 3.1
650 43 2.3 43 2.4 43 2.5 43 2.6 43 2.6
700 48 3.8 43 2.1 43 2.1 43 2.2 43 2.3
750 49 3.8 48 3.4 48 3.5 48 3.6 48 3.7
775 49 3.6 49 3.7 49 3.8 48 3.4 48 3.5
0.58 0.60 0.62 0.64 0.66
Orifice
No.
Manifold
Pressure
BURNER
Orifice
No.
SPECIFIC GRAVITY OF NATURAL GAS
Manifold
Pressure
Orifice
No.
Manifold
Pressure
Orifice
No.
EXAMPLE: (0—2000 ft altitude)
Manifold
Pressure
Orifice
No.
Manifold
Pressure
Btu heating input = Btu/cu ft X cu ft/hr
Heating value of gas = 1050 Btu/cu ft
Time for 1 revolution of 2-cu ft dial = 82 sec
Gas rate = 88 cu ft/hr (from Table 9)
Btu heating input = 88 X 1050 = 92,400 Btuh
In this example, the orifice size and manifold pressure
adjustment is within ±2 percent of the furnace input rate.
MANIFOLD
A89020
Fig. 18—Burner Flame
EXAMPLE:
92,000 Btuh input furnace installed at 4300 ft.
Furnace Input
Rate at
Sea Level
92,000 0.82 75,440
X
Derate
Multiplier
Factor
Furnace Input Rate
=
at Installation
Altitude
CANADA
At installation altitudes from 2000 to 4500 ft, this furnace must be
derated 10 percent by an authorized Gas Conversion Station. To
determine correct input rate for altitude, see example above and
use 0.90 as derate multiplier factor.
a. Turn off all other gas appliances and pilots.
b. Start furnace and let operate for 3 minutes.
c. Measure time (in sec) for gas meter test dial to complete
1 revolution.
d. Refer to Table 9 for cu ft of gas per hr.
e. Multiply gas rate (cu ft/hr) X heating value (Btu/cu ft)
using natural gas heating value from local gas
utility/supplier.
2. Set temperature rise.
Furnace must operate within range of temperature rise
specified on the unit rating plate. Determine the air temperature rise as follows.
a. Place duct thermometers in return and supply ducts as
near furnace as possible. Be sure thermometers do not
"see" heat exchangers so that radiant heat does not affect
thermometer readings. This is particularly important
with straight-run ducts.
b. When thermometer readings stabilize, subtract return-air
temperature from supply-air temperature to determine
temperature rise.
c. Adjust air temperature rise by adjusting blower speed.
Increase blower speed to reduce temperature rise. Decrease blower speed to increase temperature rise.
WARNING: Disconnect the electrical power before
changing the speed tap. Failure to follow this warning
could result in personal injury.
d. To change blower motor speed selections for heating
mode, remove blower motor lead from control HEAT
terminal. (See Fig. 14.) Select desired blower motor
speed lead from 1 of the other terminals and relocate it
to HEAT terminal. See Table 10 for lead color identification. Reconnect original lead on SPARE terminal.
Follow this same procedure for proper selection of COOL
speed selection.
CAUTION: Recheck temperature rise. It must be within
limits specified on unit rating plate. Recommended operation is at midpoint of rise or above.
—18—
TABLE 9—GAS RATE (CU FT/HR)
SECONDS
FOR 1
REVOLUTION
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
SIZE OF TEST DIAL
1
cu ft2cu ft5cu ft
360
720
327
655
300
600
277
555
257
514
240
480
225
450
212
424
200
400
189
379
180
360
171
343
164
327
157
313
150
300
144
288
138
277
133
267
129
257
124
248
120
240
116
232
113
225
109
218
106
212
103
206
100
200
97
195
95
189
92
185
90
180
88
176
86
172
84
167
82
164
80
160
78
157
76
153
75
150
73
147
1800
1636
1500
1385
1286
1200
1125
1059
1000
947
900
857
818
783
750
720
692
667
643
621
600
581
563
545
529
514
500
486
474
462
450
439
429
419
409
400
391
383
375
367
SECONDS
FOR 1
REVOLUTION
50
51
52
53
54
55
56
57
58
59
60
62
64
66
68
70
72
74
76
78
80
82
84
86
88
90
92
94
96
98
100
102
104
106
108
110
112
116
120
SIZE OF TEST DIAL
1
cu ft2cu ft5cu ft
72
144
141
138
136
133
131
129
126
124
122
120
116
112
109
106
103
100
97
95
92
90
88
86
84
82
80
78
76
75
74
72
71
69
68
67
65
64
62
60
360
355
346
340
333
327
321
316
310
305
300
290
281
273
265
257
250
243
237
231
225
220
214
209
205
200
196
192
188
184
180
178
173
170
167
164
161
155
150
71
69
68
67
65
64
63
62
61
60
58
56
54
53
51
50
48
47
46
45
44
43
42
41
40
39
38
38
37
36
35
35
34
33
33
32
31
30
→TABLE 10—SPEED SELECTOR
COLOR SPEED
Black High COOL
Yellow
(When present)
Medium-High SPARE
Blue Medium-Low HEAT
Red Low SPARE
White Common L2/COM
FACTORY-
ATTACHED TO
3. Set thermostat heat anticipator.
The thermostat heat anticipator must be set to match the
amp draw of the electrical components in the R-W circuit.
Accurate amp draw readings can be obtained at thermostat
subbase terminals R and W. Fig. 19 illustrates an easy
method of obtaining the actual amp draw. The amp reading
should be taken after the blower motor has started. See the
thermostat manufacturer’s instructions for adjusting the
heat anticipator and for varying the heating cycle length.
NOTE: When using an electronic thermostat, set cycle rate for 3
cycles per hr.
E. Check Safety Controls
The flame sensor, gas valve, and pressure switch were all checked
in the Start-Up Procedures section as part of normal operation.
1. Check primary limit control.
This control shuts off the combustion control system and
energizes the circulating-air blower motor if the furnace
overheats.
The preferred method of checking the limit control is to
gradually block off the return air after the furnace has been
operating for a period of at least 5 minutes. As soon as the
THERMOSTAT SUBBASE
TERMINALS WITH
THERMOSTAT REMOVED
(ANITICIPATOR, CLOCK, ETC.,
MUST BE OUT OF CIRCUIT.)
R Y W G
10 TURNS
FROM UNIT 24-V
CONTROL TERMINALS
EXAMPLE:
5.0 AMPS ON AMMETER
10 TURNS AROUND JAWS
Fig. 19—Amp Draw Check With Ammeter
limit has shut off the burners, the return-air opening should
be unblocked. By using this method to check the limit
control, it can be established that the limit is functioning
properly and operates if there is a motor failure.
2. Check blocked vent safeguard switch.
The purpose of this control is to permit the safe shutdown
of the furnace during certain blocked vent conditions.
a. Disconnect power to furnace and remove vent connector
from furnace outlet collar. Be sure to allow time for vent
pipe to cool down before removing.
b. Restore power to furnace and set room thermostat above
room temperature.
c. After normal start-up, allow furnace to operate for 2
minutes, then block flue outlet 100 percent. Furnace
should cycle off within 2 minutes.
d. Remove blockage and reconnect vent pipe to furnace
outlet collar.
e. Wait 5 minutes and then reset blocked vent safeguard
switch.
3. Check pressure switch.
This control proves operation of draft inducer blower.
a. Turn off 115-v power to furnace.
b. Remove control door and disconnect inducer motor lead
wires from wire harness.
c. Turn on 115-v power to furnace.
→
d. Set thermostat to "call for heat" and wait 1 minute. When
pressure switch is functioning properly, hot surface
igniter should NOT glow and control diagnostic light
flashes a status code 31. If hot surface igniter glows
when inducer motor is disconnected, shut down furnace
immediately. Determine reason pressure switch did not
function properly and correct condition.
e. Turn off 115-v power to furnace.
f. Reconnect inducer motor wires, replace control door, and
turn on 115-v power to furnace.
4. Check auxiliary limits (when used).
HOOK-AROUND
AMMETER
0.5 AMPS FOR THERMOSTAT
=
ANTICIPATOR SETTING
A96316
—19—
a. Turn off 115-v power to furnace.
b. Remove blower access door.
c. Disconnect red motor lead at blower speed selector.
Mark terminal for proper re-connection.
d. Replace blower access door.
e. Turn on 115-v power to furnace. Be sure room thermo-
stat is calling for heat.
f. Allow furnace to operate until auxiliary limit activates,
but DO NOT operate furnace longer than 4 minutes.
g. If furnace operates for 4 minutes, check/replace limit
switch(es).
h. Turn off 115-v power to furnace.
i. Remove blower access door.
j. Reconnect red motor lead, reset switch, and replace door.
k. Turn on 115-v power to furnace.
F. Checklist
1. Put away tools, instruments, and clean up debris.
2. Verify manual reset switches have continuity.
3. Ensure blower and control access doors are properly installed.
CHECKLIST—INSTALLATION
LOAD CALCULATION
____________ Heating Load (Btuh)
____________ Cooling Load (Btuh)
____________ Furnace Model Selection
AIR FOR COMBUSTION AND VENTILATION
____________ Unconfined Space
____________ Confined Space
VENTING
____________ NFGC (United States)
____________ NSCNGPIC (Canada)
____________ Local Codes
____________ 1/4-in. Upward Slope
____________ Joints Secure
____________ See Attached Vent Table Instructions
CHECKLIST—START-UP
4. Cycle test furnace with room thermostat.
5. Check operation of accessories per manufacturer’s instructions.
6. Review User’s Manual with owner.
7. Leave literature packet near furnace.
____________
____________ Temperature Rise Adjusted
____________ Thermostat Anticipator Setting Adjusted or
____________ Thermostat Cycle Rate (3 cycles per Hr)
CHECK SAFETY CONTROLS OPERATION
____________ Primary Limit
____________ Pressure Switches
____________ Draft Safeguard Switch
____________ Auxiliary Limit Switch(es)
Gas Input Rate
(Set Within 2 percent of Rating Plate)
© 1999 Bryant Heating & Cooling Systems 7310 W. Morris St. Indianapolis, IN 46231
—20—
Printed in U.S.A. 373l3521 Catalog No. 5337-305
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