SERVICE AND TECHNICAL SUPPORT MANUAL
Gas Furnace: (F/G)9MAE
Specifications subject to change without notice.
8
440 04 4700 00
Figure 3
Variable Speed Furnace Control for ECM Blower Motor (Modulating)
L11F091
24
ï
V THERMOSTAT
PL2
ć
HOT SURFACE
IGNITER & INDUCER
MOTOR CONNECTOR
115
ï
VAC (L2) NEUTRAL
CONNECTIONS
115
ï
VAC (L1) LINE
VOLTAGE CONNECTIONS
EAC
ï
1 TERMINAL
(115
ï
VAC 1.0 AMP MAX.)
PL1
ć
LOW VOLTAGE MAIN
HARNESS CONNECTOR
PL3
ć
ECM BLOWER
TERMINALS
HARNESS
TRANSFORMER 24
ï
VAC
CONNECTIONS
3
ï
AMP FUSE
STATUS AND COMM
LED LIGHTS
SW1 SETUP
SWITCHES AND
CONNECTOR
DELAY
MODEL PLUG
CONNECTOR
AIR CONDITIONING
(A/C) AIRFLOW
SETUP SWITCHES
COMMUNICATION
CONNECTOR
CONTINUOUS FAN
(CF) AIRFLOW
SETUP SWITCHES
OUTDOOR
BLOWER OFF
ï
IR TEMP
CONNECTOR
HUMIDIFIER
TERMINAL (24
A
VAC
0.5 AMP MAX.
FLASH
UPGRADE
CONNECTOR
(FACTORY
ONLY)
SW4 SETUP
SWITCHES
SOFTWARE
VERSION
PART NUMBER AND
DATE CODE WWYY
PL8
ï
MODULATING
ï
CONNECTOR
GAS VALVE
Adjust Temperature Rise
NOTE
: Blower door must be installed when taking temperature
rise reading. Leaving blower door off will result in incorrect
temperature measurements.
FURNACE DAMAGE HAZARD
Failure to follow this caution may result in:
S
Overheating the heat exchangers or condensing
flue gases in heat exchanger areas not designed
for condensate
S
Shortened furnace life
S
Component damage
Temperature rise must be within limits specified on furnace
rating plate. Recommended operation is at midpoint of rise
range or slightly above.
CAUTION
!
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 Minimum Heat,
Intermediate Heat and Maximum 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 and SW4-2 on
the furnace control board.
The 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 Minimum, Intermediate, and
Maximum 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 Min/Int Rise Adjust switch SW1
−
3 on furnace
control is in ON position when a bypass humidifier is
used. (See
Figure 3
for switch location.)
e. Check Troubleshooting Guide for Variable
−
Speed Step
Modulating Condensing Furnaces.
f. Verify correct model plug is installed.
To lock the furnace in Minimum Heat:
1. Turn SW1
−
2 ON at the furnace control. Set up switch
SW4
−
2 must be OFF.
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 Minimum
Heat:
1. Remove jumpers from R and W/W1.
