The signal words DANGER, WARNING,
CAUTION, and NOTE are used to identify levels of
hazard seriousness. The signal word DANGER is
only used on product labels to signify an immediate
hazard. The signal words WARNING, CAUTION,
and NOTE will be used on product labels and
throughout this manual and other manual that may
apply to the product.
DANGER− Immediate hazards which will result in
severe personal injury or death.
WARNING− Hazards or unsafe practices which
could result in severe personal injury or death.
CAUTION − Hazards or unsafe practices which
may result in minor personal injury or product or
property damage.
NOTE − Used to highlight suggestions which will
result in enhanced installation, reliability, or
operation.
Signal Words in Manuals
The signal word WARNING is used throughout
this manual in the following manner:
!
WARNING
The signal word CAUTION is used throughout
this manual in the following manner:
!
CAUTION
Signal Words on Product Labeling
Signal words are used in combination with
colors and/or pictures or product labels.
Safety−alert symbol
When you see this symbol on the unit and in
instructions or manuals, be alert to the
potential for personal injury.
TABLE OF CONTENTS
START−UP, ADJUSTMENT, AND SAFETY CHECK4...........
Use of the AHRI Certified TM Mark indicates a
manufacturer’s participation in the program.
For verification of certification for individual
products, go to www.ahridirectory.org .
Printed in U.S.A.440 04 4221 04 July 2012
SAFETY CONSIDERATIONS
Improper installation, adjustment, alteration, service,
maintenance, or use can cause explosion, fire, electrical shock,
or other conditions which may cause death, personal injury, or
property damage. Consult a qualified installer, service agency,
or your distributor or branch for information or assistance. The
qualified installer or agency must use factory−authorized kits or
accessories when modifying this product. Refer to the individual
instructions packaged with the kits or accessories when
installing.
Follow all safety codes. Wear safety glasses, protective clothing,
and work gloves. Use quenching cloth for brazing operations.
Have fire extinguisher available. Read these instructions
thoroughly and follow all warnings or cautions included in
literature and attached to the unit. Consult local building codes,
the current editions of the National Fuel Gas Code (NFCG)
NFPA 54/ANSI Z223.1, and the National Electrical Code (NEC)
NFPA 70.
In Canada refer to the current editions of the National standards
of Canada CAN/CSA−B149.1 and .2 Natural Gas and Propane
Installation Codes, and Canadian Electrical Code CSA C22.1.
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 these signal words; DANGER, WARNING, and
CAUTION. 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 hazards
which could result in personal injury or death. CAUTION is used
to identify unsafe practices which may 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.
!
WARNING
PERSONAL INJURY, AND/OR PROPERTY
DAMAGE HAZARD
Failure to carefully read and follow this warning could
result in equipment malfunction, property damage,
personal injury and/or death.
Installation or repairs made by unqualified persons could
result in equipment malfunction, property damage,
personal injury and/or death.
The information contained in this manual is intended for
use by a qualified service technician familiar with safety
procedures and equipped with proper tools and test
instruments.
Installation must conform with local building codes and
with the Natural Fuel Gas Code (NFCG) NFPA 54/ANSI
Z223.1, and National standards of Canada
CAN/CSA−B149.1 and .2 Natural Gas and Propane
Installation Codes.
!
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could cause personal
injury or death.
Before performing service or maintenance operations
on unit, always turn off main power switch to unit and
install lockout tag. Unit may have more than one power
switch.
!
WARNING
WARNING
CARBON MONOXIDE POISONING AND FIRE
HAZARD
Failure to follow safety warnings could result in personal
injury, death, and/or property damage.
This furnace is not designed for use in mobile homes,
trailers or recreational vehicles.
!
CAUTION
CUT HAZARD
Failure to follow this caution may result in damage
personal injury.
Sheet metal parts may have sharp edges or burrs. Use
care and wear appropriate protective clothing, safety
glasses and gloves when handling parts and servicing
furnaces.
2
Specifications are subject to change without notice.
440 04 4221 04
SERVICE AND TECHNICAL MANUALGas Furnace: (F/G)9MVT
START−UP CHECK SHEET
For Variable Speed Models (F/G)9MVT
(This sheet is optional. Keep for future reference.)
Date of Start−Up:
Dealer Name:
Address:
City, State(Province), Zip or Postal Code:
Phone:
Owner Name:
Address:
City, State(Province), Zip or Postal Code:
Model Number:
Serial Number:
Setup Checks
Check the box when task is complete.
Calculated Input (BTU) Rate: (See Checks and Adjustments
Section).
Heating Check
Measured Line Pressure During High Heat:
Measured Manifold Pressure: High Heat
Low Heat
Temperature of Supply Air: High Heat
Low Heat
Temperature of Return Air:
Temperature Rise (Supply − Return): High Heat
Low Heat
In Rise Range (see furnace rating plate)?
Static Pressure (Ducts) High Heat: Supply
Return
All Electrical Connections Tight?
Have hoses been relocated for furnace U/D/H application?
Condensate Drain Connected?
Condensate Drain Trapped?
Manual Gas Shut−off Upstream of Furnace/Drip Leg
Gas Valve turned ON?
Type of Gas: Natural: Propane:
Filter Type and Size:
Shade in Final Furnace Settings Below:
PL9
SW4
3 2 1
O
N
PL4
SW−1
8 7 6 5 4 3 2 1
SW2SW3
OAT
O
N
PL7
Optional Check: CO?
CO2?
Cooling Check
Temperature of Supply Air:
Temperature of Return Air:
Temperature Difference:
Static Pressure (Ducts) Cooling: Supply
Return
Dealer Comments:
O
3 2 1
N
440 01 4221 043
3 2 1
O
N
Specifications subject to change without notice.
SERVICE AND TECHNICAL SUPPORT MANUALGas Furnace: (F/G)9MVT
START−UP, ADJUSTMENT, AND SAFETY
CHECK
General
1. Furnace must have a 115-v power supply properly
connected and grounded.
NOTE: Proper polarity must be maintained for 115-v wiring.
Control status indicator light flashes code 10 and furnace does
not operate if polarity is incorrect or if the furnace is not
grounded.
2. Thermostat wire connections at terminals R, W/W1, G,
and Y/Y2 must be made at 24-v terminal block on
furnace control.
3. Natural gas service pressure must not exceed 0.5 psig
(14- in. w.c., 350 Pa), but must be no less than 0.16 psig
(4.5-in. w.c., 1125 Pa).
4. Blower door must be in place to complete 115-v electrical
circuit and supply power to furnace components.
!
CAUTION
UNIT OPERATION HAZARD
Failure to follow this caution may result in intermittent unit
operation or performance satisfaction.
These furnaces are equipped with a manual reset limit
switch in burner assembly. This switch opens and shuts
off power to the gas valve if an overheat condition (flame
rollout) occurs in burner assembly. Correct inadequate
combustion−air supply or improper venting condition
before resetting switch. DO NOT jumper this switch.
Before operating furnace, check flame rollout manual reset
switch for continuity. If necessary, press button to reset switch.
EAC-1 terminal is energized whenever blower operates. HUM
terminal is only energized when blower is energized in heating.
Setup Switches
There are four sets of setup switches on the furnace control
board. These switches configure the furnace for correct
application requirement. They also select the airflow settings for
Air Conditioning and Continuous Fan CFM.
The Setup Switch locations are shown and described on
Figure 4, Figure 5 and Table 5.The setup switches are also
shown on the unit wiring label.
Setup Switches (SW1)
The furnace control has 8 setup switches that may be set to
meet the application requirements. To set these setup switches
for the appropriate requirement:
1. Remove blower door.
2. Locate setup switches on furnace control.
3. Configure the set-up switches as necessary for the
application.
4. Replace blower door.
NOTE: If a bypass humidifier is used, setup switch SW1-3
(Low Heat Rise Adjust) should be in ON position. This
compensates for the increased temperature in return air
resulting from bypass.
Air Conditioning (A/C) Setup Switches (SW2)
The air conditioning setup switches are used to match furnace
airflow to required cooling airflow or high stage cooling airflow
when a two stage outdoor unit is used. Refer to the
Adjustments section for set up switch configurations.
To set the desired cooling airflow:
1. Remove blower door.
2. Locate A/C setup switches on furnace control.
4440 04 4221 04
Specifications subject to change without notice.
3. Determine air conditioning tonnage used.
4. Configure the switches for the required cooling airflow.
5. Replace blower door.
NOTE: Incorrect airflow caused by improper A/C switch setup
may cause condensate blow-off or frozen indoor coil in the
cooling mode.
Continuous Fan (CF) Setup Switches (SW3)
The CF setup switches are used to select desired airflow when
thermostat is in continuous fan mode or to select low-cooling
airflow for two-speed cooling units. Refer to the Adjustments
section for set up switch configurations.
To set the desired cooling airflow:
1. Remove blower door.
2. Locate CF setup switches on furnace control.
3. Determine air conditioning tonnage used for low cooling
(when used) or desired continuous fan airflow.
4. Configure the switches for the required airflow.
5. Replace blower door.
Additional Setup Switch (SW4)
The furnace control has three additional setup switches labels
SW4.
Setup switches SW4 are used for applications using a
communicating wall control and to adjust airflow. SW4−3 is
used to adjust airflow. Refer to the Adjustments section for set
up switch configurations. Refer to the communicating wall
control instructions for configuration of SW4 for
communications. Refer to Figure 5 for configuration of SW4
airflow options.
1. Remove blower door.
2. Locate setup switch SW4 on furnace control.
3. Configure the switches as necessary for the application.
4. Replace blower door.
Prime Condensate Trap with Water
!WARNING
CARBON MONOXIDE POISONING HAZARD
Failure to follow these warnings could result in personal injury
or death.
Failure to use a properly configured trap or NOT
water-priming trap before operating furnace may allow
positive pressure vent gases to enter the structure through
drain tube. Vent gases contain carbon monoxide which is
tasteless and odorless.
!
CAUTION
UNIT OPERATION HAZARD
Failure to follow this caution may result in intermittent unit
operation or performance satisfaction.
Condensate trap must be PRIMED or proper draining may
not occur. The condensate trap has two internal chambers
which can ONLY be primed by pouring water into the
inducer drain side of condensate trap.
1. Remove upper and middle collector box drain plugs
opposite of the condensate trap. (See Figure 1)
2. Connect field-supplied 5/8-in. (16 mm) ID tube with
attached funnel (see Figure 1) to upper collector box
drain connection.
3. Pour one quart (liter) of water into funnel/tube. Water
should run through collector box, overfill condensate
trap, and flow into open field drain.
SERVICE AND TECHNICAL SUPPORT MANUALGas Furnace: (F/G)9MVT
5. Connect field-supplied 5/8-in. (16 mm) ID tube to middle
collector box drain port.
6. Pour one quart (liter) of water into funnel/tube. Water
should run through collector box, overfill condensate
trap, and flow into open field drain.
7. Remove funnel and tube from collector box and replace
collector box drain plug.
Figure 1Priming Condensate Drain
FURNACE DAMAGE HAZARD
Failure to follow this caution may result in reduced furnace
life.
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 heat exchangers, causing failures. (See
Figure 2)
!
CAUTION
Figure 2Orifice Hole
Representative drawing only, some models may vary in appearance.
L11F065
Purge Gas Lines
If not previously done, purge the lines after all connections
have been made and check for leaks.
!
FIRE OR EXPLOSION HAZARD
Failure to follow this warning could result in personal injury,
death, and/or property damage.
Never purge a gas line into a combustion chamber. 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.
WARNING
Adjustments
!
FIRE HAZARD
Failure to follow this warning could result in personal injury,
death and/or property damage.
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.
WARNING
BURNER
ORIFICE
A93059
For proper operation and long term reliability the furnace input
rate must be within +/− 2 percent of input rate on furnace rating
plate, or as adjusted for altitude.
The gas input rate on rating plate is for installation at altitudes
up to 2000 ft. (610 M).
NOTICE
The NATURAL GAS manifold pressure adjustments in Table 3
compensate for BOTH altitude AND gas heating value. DO
NOT apply an additional de−rate factor to the pressures shown
in Table 3.
The heating content of natural gas at altitude may already
provide for a reduction in capacity or altitude. Refer to Table 3.
No adjustments to the furnace may be necessary at altitude for
certain gas heating values.
Refer to the instructions provided in the factory-specified
LP/Propane conversion kit for instructions for setting gas
manifold pressures for LP/Propane applications.
In the USA, the input rating for altitudes above 2000 ft. (610 M)
must be reduced by 2 percent for each 1000 ft. (305 M) above
sea level refer to Table 1. The natural gas manifold pressures
in Table 3 adjust for BOTH altitude and natural gas heating
value.
In Canada, the input rating must be reduced by 5 percent for
altitudes of 2000 ft. (610 M) to 4500 ft. (1372 M) above sea
440 04 4221 045
Specifications subject to change without notice.
SERVICE AND TECHNICAL SUPPORT MANUALGas Furnace: (F/G)9MVT
level. The natural gas manifold pressures in Table 3 adjust for
BOTH altitude and natural gas heating value.
NOTE: For Canadian altitudes of 2000 to 4500 ft. (610 to 1372
M) use USA altitudes of 2001 to 3000 ft. (611 to 914 M) in
Table 3.
Table 1Altitude Derate Multiplier for U.S.A.
ALTITUDE
FT. (M)
0–2000
(0−610)
2001–3000
(610−914)
3001–4000
(914−1219)
4001–5000
(1219−1524)
5001–6000
(1524−1829)
6001–7000
(1829−2134)
7001–8000
(2134−2438)
8001–9000
(2438−2743)
9001–10,000
(2743−3048)
* Derate multiplier factors are based on midpoint altitude for altitude range.
NOTE: For Canadian altitudes of 2000 to 4500 ft. (610 to
1372 M), use USA altitudes of 2001 to 3000 ft. (610 to 914
M)
To adjust manifold pressure to obtain the proper input rate, first,
determine if the furnace has the correct orifice installed. At
higher altitudes or different gas heat contents, it may be
necessary to change the factory orifice to a different orifice.
Tables have been provided in the furnace Service and
Technical Manual to match the required orifice to the manifold
pressure to the heat content and specific gravity of the gas. to
do this:
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. Find installation altitude in Table 3.
4. Find closest natural gas heat value and specific gravity in
Table 3. Follow heat value and specific gravity lines to
point of intersection to find orifice size and low−and
high−heat manifold pressure settings for proper
operation.
5. Check and verify burner orifice size in furnace. NEVER
ASSUME ORIFICE SIZE. ALWAYS CHECK AND
VERIFY.
PERCENT
OF DERATE
01.00
4−60.95
6−80.93
8−100.91
10−120.89
12−140.87
14−160.85
16−180.83
18−200.81
DERATE MULTIPLIER
FACTOR*
NOTICE
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.
6. Replace orifice with correct size, if required by Table 3.
Use only factory−supplied orifices. See EXAMPLE.
EXAMPLE 1:
0 - 2000 ft. (0 - 609.6M) altitude
Heating value = 1050 Btu/cu ft.
Specific gravity = 0.62
Therefore: Orifice No. 44
(Furnace is shipped with No. 44 orifices. In this example, all
main burner orifices are the correct size and do not need to be
changed to obtain proper input rate.)
Manifold pressure: 3.4-in. w.c. (847 Pa) for high heat, 1.4-in.
w.c. (349 Pa) for low heat
NOTE: To convert gas manifold Table pressures to Pascals,
multiply the in.w.c. value by 249.1 Pa/in. w.c. (1 in. wc. = 249.1
Pa).
Check Inlet Gas Pressure
The inlet gas pressure must be checked with the furnace
operating in maximum heat. This is necessary to make sure the
inlet gas pressure does not fall below the minimum pressure of
4.5 in. w.c. (1121 Pa).
1. Make sure the gas supply is turned off to the furnace and
at the electric switch on the gas valve.
2. Remove the 1/8 in. NPT plug from the inlet pressure tap
on the gas valve.
3. Connect a manometer to the inlet pressure tap on gas
valve.
4. Turn on furnace power supply.
5. Turn gas supply manual shutoff valve to ON position.
6. Turn furnace gas valve switch to ON position.
7. Jumper the R to W/W1 and W2 thermostat connections
at the furnace control board.
8. When main burners ignite, confirm inlet gas pressure is
between 4.5 in. w.c. (1125 Pa) and 13.6 in. w.c.(3388
Pa).
9. Remove jumper across thermostat connections to
terminate call for heat. Wait until the blower off delay is
completed.
10. Turn furnace gas valve electric switch to OFF position.
11. Turn gas supply manual shutoff valve to OFF position.
12. Turn off furnace power supply.
13. Remove manometer from the inlet pressure tap of the
gas valve.
!
WARNING
FIRE HAZARD
Failure to follow this warning could result in personal injury,
death, and/or property damage.
Re−install manifold pressure tap plug in gas valve to
prevent gas leak.
14. Apply pipe dope sparingly to end of inlet gas pipe plug
and re−install in the gas valve.
Adjust Manifold Pressure
1. Adjust manifold pressure to obtain low fire input rate.
(See Figure 3)
a. Turn gas valve ON/OFF switch to OFF.
b. Remove manifold pressure tap plug from gas valve.
c. Connect a water column manometer or similar device
to manifold pressure tap.
d. Turn gas valve ON/OFF switch to ON.
e. Move setup SW1—2 on furnace control to ON
position to lock furnace in low−heat operation. (See
Figure 4 and Figure 5)
f. Manually close blower door switch.
g. Jumper R and W/W1 thermostat connections on
control to start furnace. (See Figure 4)
h. Remove regulator adjustment cap from low heat gas
valve pressure regulator (See Figure 3) and turn
low−heat adjusting screw (3/16 or smaller flat−tipped
screwdriver) counterclockwise (out) to decrease input
rate or clockwise (in) to increase input rate.
6440 04 4221 04
Specifications subject to change without notice.
SERVICE AND TECHNICAL SUPPORT MANUALGas Furnace: (F/G)9MVT
c. When correct input is obtained, replace caps that
NOTICE
DO NOT set low−heat manifold pressure less than 1.3−in. w.c.
(324 Pa) or more than 1.7−in. w.c. (423 Pa) for natural gas. If
manifold pressure is outside this range, change main burner
orifices.
i. Install low−heat regulator adjustment cap.
j. Re−install manifold pressure tap plug from gas valve.
k. Move setup switch SW1−2 to OFF position after
completing low−heat adjustment.
l. Leave manometer or similar device connected and
proceed to Step 2.
2. Adjust manifold pressure to obtain high fire input rate.
(See Figure 3)
a. Jumper R to W/W1 and W2 thermostat connections
on furnace control. This keeps furnace locked in
high−heat operation.
b. Remove regulator adjustment cap from high−heat
gas valve pressure regulator (See Figure 3) and turn
high heat adjusting screw (3/16−in. or smaller
flat−tipped screwdriver) counterclockwise (out) to
decrease input rate or clockwise (in) to increase input
rate.
Figure 3
1/2” NPT Inlet
1/8” NPT Inlet
Pressure Tap
Redundant Automatic Gas Control
Valve (2−Stage)
ON/OFF Switch
Regulator Seal Cap
Regulator Adjustment
Regulator Seal Cap under Cap
1/8” NPT Manifold
Pressure Tap
1/2” NPT Outlet
A11152
NOTICE
DO NOT set high−heat manifold pressure less than 3.2−in. w.c.
(797 Pa) or more than 3.8 in. w.c. (947 Pa) for natural gas. If
required manifold pressure is outside this range, change main
burner orifices to obtain manifold pressure in this range.
NOTE: Contact your HVAC distributor or gas supplier for metric
gas meter Tables, if required.
conceal gas valve regulator adjustment screws. Main
burner flame should be clear blue, almost
transparent. (See Figure 14)
d. Re−install manifold pressure tap plug to gas valve.
e. Remove jumpers R to W/W1 and R to W2.
!
WARNING
FIRE HAZARD
Failure to follow this warning could result in personal injury,
death, and/or property damage.
Re−install manifold pressure tap plug in gas valve to
prevent gas leak.
3. Verify natural gas input rate by clocking meter.
a. Turn off all other gas appliances and pilots served by
the meter.
b. Move setup switch SW1−2 to ON position. This
keeps furnace locked in low−heat operation when
only W/W1 is energized.
c. Jumper R to W/W1.
d. Run furnace for 3 minutes in low−heat operation.
e. Measure time (in sec) for gas meter to complete 1
revolution and note reading. The 2 or 5 cubic feet dial
provides a more accurate measurement of gas flow.
f. Refer to Table 2 for cubic ft. of gas per hr.
g. Multiply gas rate cu ft./hr by heating value (Btuh/cu
ft.) to obtain input.
h. If clocked rate does not match required input from
Step 1, increase manifold pressure to increase input
or decrease manifold pressure to decrease input.
Repeat steps b through e until correct low−heat input
is achieved. Re−install low heat regulator seal cap on
gas valve.
i. Jumper R to W/W1, and W2. This keeps furnace
locked in high−heat operation when both W/W1 and
W2 are energized.
j. Repeat items (d) through (h) for high−heat operation,
repeating Step 2 and adjusting the high−heat regular
screw, as required.
4. Restore furnace to normal operating condition.
a. Turn gas valve On/Off switch to OFF.
b. Remove water column manometer or similar device
from manifold pressure tap.
c. Replace manifold pressure tap plug to gas valve.
d. Turn gas valve On/Off switch to ON.
e. Move setup SW1−2 on furnace control to position
required for attached thermostat (OFF for
single−stage thermostats, ON for two−stage
thermostats).
f. Check for gas leaks and verify furnace operation.
440 04 4221 047
Specifications subject to change without notice.
SERVICE AND TECHNICAL SUPPORT MANUALGas Furnace: (F/G)9MVT
Figure 4Example of Variable Speed Furnace Control for ECM Blower Motor
MODEL PLUG
CONNECTOR
SW1 SETUP
SWITCHES AND
BLOWER OFFï
DELAY
AIR CONDITIONING
(A/C) AIRFLOW
SETUP SWITCHES
24ïV THERMOSTAT
TERMINALS
STATUS AND COMM
LED LIGHTS
COMMUNICATION
CONNECTOR
CONTINUOUS FAN
F) AIRFLOW
(C
SETUP SWITCHES
OUTDOOR
IR TEMP
A
CONNECTOR
SW4 SETUP
SWITCHES
HUMIDIFIER
TERMINAL (24
0.5 AMP MAX.
FLASH
UPGRADE
CONNECTOR
(FACTORY
ONLY)
VAC
ï
3ïAMP FUSE
TRANSFORMER 24ïVAC
CONNECTIONS
115ïVAC (L2) NEUTRAL
CONNECTIONS
PL1 ï LOW VOLTAGE MAIN
HARNESS CONNECTOR
AND ECM BLOWER
HARNESS CONNECTOR
SOFTWARE
VERSION
PART NUMBER AND
DATE CODE WWYY
EACï1 TERMINAL
(115ïVAC 1.0 AMP MAX.)
115ïVAC (L1) LINE
VOLTAGE CONNECTIONS
PL2 ï HOT SURFACE
IGNITER & INDUCER
MOTOR CONNECTOR
L11F081
8440 04 4221 04
Specifications subject to change without notice.
SERVICE AND TECHNICAL SUPPORT MANUALGas Furnace: (F/G)9MVT
NOTE: Blower door must be installed when taking temperature
rise reading. Leaving blower door off will result in incorrect
temperature measurements, due to possible changes in duct
static pressure and airflow.
!
CAUTION
FURNACE DAMAGE HAZARD
Failure to follow this caution may result in:
SOverheating the heat exchangers or condensing
flue gases in heat exchanger areas not designed
for condensate.
SShortened furnace life.
SComponent damage.
Temperature rise must be within limits specified on furnace
rating plate. Recommended operation is at midpoint of rise
range or slightly above.
Furnace must operate within ranges of temperature rise
specified on the furnace rating plate.
When setup switch SW1−4 is ON, operation will be near the
high end of the rise range for improved comfort.
Determine air temperature rise as follows:
1. Place thermometers in return and supply ducts as near
furnace as possible. Be sure thermometers do not see
heat exchanger so that radiant heat does not affect
readings. This practice is particularly important with
straight−run ducts.
2. When thermometer readings stabilize, subtract return−air
temperature from supply−air temperature to determine air
temperature rise.
NOTE: Temperature rise can be determined for low−heat
operation by locking the furnace in each mode of operation.
The mode of operation is based on the position of set up switch
SW1−2 on the furnace control board.
This furnace is capable of automatically providing proper
airflow to maintain the temperature rise within the range
specified on furnace rating plate. If temperature rise is outside
this range, proceed as follows:
a. Check gas input for low− and high−heat operation.
b. Check derate for altitude if applicable.
c. Check all return and supply ducts for excessive
restrictions causing static pressure greater than
0.5−in. w.c.
d. Ensure Low Heat Rise Adjust switch SW1−3 on
furnace control is in ON position when a bypass
humidifier is used. (See Figure 4 for switch location.)
e. Check Troubleshooting Guide for Variable−Speed
Condensing Furnaces.
To lock the furnace in Low Heat:
1. Turn SW1--2 ON at the furnace control. Set up switch
2. Connect a jumper across R and W/W1 at the thermostat
terminals at the furnace control.
3. Allow the burners to ignite and the blower to turn on.
4. Allow the supply temperature to stabilize and verify the
proper rise range.
If the temperature rise is too high or too low in Low Heat:
440 04 4221 0411
Specifications subject to change without notice.
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