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SERVICE AND TECHNICAL SUPPORT MANUAL
CAUTION
!
FURNACE OVERHEATING HAZARD
Failure to follow this caution may result in shortened
furnace life.
Set air temperature rise within limits specified on the
rating plate to prevent reduced life of furnace
components. Operation is within a few degrees of the
mid−point of rise range when setup switch SW1−4 is
OFF.
Figure 3
Variable Speed Furnace Control for ECM Blower Motor (Modulating)
MODEL PLUG
CONNECTOR
SW1 SETUP
SWITCHES AND
BLOWER OFF-
DELAY
AIR CONDITIONING
(A/C) AIRFLOW
SETUP SWITCHES
24-V THERMOSTAT
TERMINALS
STATUS AND COMM
LED LIGHTS
3-AMP FUSE
TRANSFORMER 24-VAC
CONNECTIONS
115-VAC (L2) NEUTRAL
CONNECTIONS
PL1 – LOW VOLTAGE MAIN
HARNESS CONNECTOR
Adjust Temperature Rise
When setup switch SW1-4 is ON, operation will be near the
high end of the rise range for improved comfort.
Furnace must operate within ranges of temperature rise
specified on the furnace rating plate. 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
440 04 4201 01
COMMUNICATION
CONTINUOUS FAN
CONNECTOR
(CF) AIRFLOW
SETUP SWITCHES
PART NUMBER AND
DATE CODE WWYY
EAC-1 TERMINAL
SOFTWARE
(115-VAC 1.0 AMP MAX.)
VERSION
Specifications subject to change without notice.
CAUTION
!
FURNACE DAMAGE HAZARD
Failure to follow this caution may result in overheating
the heat exchangers or condensing flue gases in heat
exchanger areas not designed for condensate.
Temperature rise must be within limits specified on
unit rating plate. Operation is within a few degrees of
midpoint of rise range when setup switch SW1−4 is
OFF.
OUTDOOR
SW4 SETUP
AIR TEMP
SWITCHES
CONNECTOR
PL8 - MODULATING
GAS VALVE
CONNECTOR
PL2 – HOT SURFACE
IGNITER & INDUCER
115-VAC (L1) LINE
MOTOR CONNECTOR
VOLTAGE CONNECTIONS
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 Heat 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.
Gas Furnace: (F/G)9MAC
HUMIDIFIER
TERMINAL (24-VAC
0.5 AMP MAX.
FLASH
UPGRADE
CONNECTOR
(FACTORY
ONLY)
PL3 – ECM BLOWER
HARNESS
CONNECTOR
L11F061
7
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