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A
B
D7
D6
R2
R1
D5
K1
D8
BLU
HI
AC
400
M-HI
HP
EFFY
M-LO
350
HP
315
CMFT
LO
COOL
COOL
AC
CFM
S
PER
HP
I
TON
Z
E
YEL
BLU
ORN
Fig. 20—Airflow Selector Control
pump heating best efficiency (HP EFFY) or enhanced
comfort (HP CMFT). HP EFFY provides the same heating
airflow as used for cooling. HP CMFT reduces the heating
airflow to 90 percent of the cooling airflow for a higher air
temperature rise and better comfort.
3. Continuous-fan
The GREEN jumper wire selects airflow CFM for continuous-fan.
LO provides 50 percent of airflow used for single-speed cooling or
2-speed cooling. MED provides 65 percent of cooling airflow. HI
provides 100 percent of cooling airflow for continuous-fan opera-
tion.
NOTE: If HI is selected with a 2-speed cooling or heat pump
system, the airflow will remain at 100 percent of high-
cooling/heating when the system is in low-cool and heat pump
low-heat mode. Continuous-fan selection has no effect on gas-
heating airflow.
4. As an alternative to selecting 315 CFM per ton for cooling
airflow, additional dehumidification on demand can be
achieved with use of a field-supplied humidistat. Remove the
factory-installed GREEN wire marked DEHUM from the
1/4-in. quick-connect at the G terminal on furnace control.
Connect a humidistat that opens-on-humidity-rise between the
green wire marked DEHUM and the G terminal on the furnace
control. When humidistat contacts open, airflow will be
reduced to 80 percent of selected airflow, but not less than 280
CFM per ton.
The humidistat may be located in the return air duct or the
conditioned space. Follow instructions included with humidistat.
NOTE: When a humidistat is calling for reduced airflow and the
thermostat is satisfied, blower will not operate on continuous-fan
LOW setting to prevent re-evaporation of condensate at the
evaporator coil. When continuous-fan MED or HI setting is
selected, normal airflow will be reduced to 80 percent.
Step 4—Start-up Procedures
1. Component test—The furnace features a component test
system to help diagnose a system problem in the case of a
C
D
P12
D1
D2
D10
D3
Q1
D4
R3
D11
D9
RED
GRN
HI
MID
M-HI
MED
LO
HI
GAS
CONTINUOUS FAN
HEAT
CFM
TEMP
RISE
RED
GRN
A96061
component failure. To initiate the component test procedure,
ensure that there are no thermostat inputs to the control and all
time delays have expired. Short the TWIN/TEST terminal to
ground or C
24v for 1 to 4 sec. (See Fig. 17.)
OM
NOTE: The component test feature will not operate if the control
is receiving any thermostat signals or until all time delays have
expired. The ICM2+ blower motor speed ramp-up will slightly
delay blower response times.
The component test sequence is as follows:
a. The furnace control checks itself, operates the inducer
motor on low speed for 7 sec and on high speed for 7 sec,
then stops.
b. The hot surface igniter is energized for 15 sec, then
de-energized.
c. The blower motor operates at continuous-fan airflow for 7
sec then stops.
d. The blower motor operates at high-gas heat airflow for 7
sec. The gas valve and humidifier terminal HUM are not
energized for safety reasons.
e. The blower motor operates at single-speed cooling/heat
pump heating airflow (or 2-speed heat pump high-
heat/high-cooling) for 7 sec, then stops.
NOTE: The EAC terminals are energized when the blower is
energized.
2. After all connections have been made, purge gas lines and
check for leaks.
Never purge a gas line into a combustion chamber. Never use
matches, candles, flame, or other sources of ignition for the
purpose of checking leakage. Use a soap-and-water solution
to check for leakage. A failure to follow this warning can
cause a fire, explosion, personal injury, or death.
3. To operate furnace, follow procedures on operating instruc-
tions label attached to furnace.
4. With furnace operating, set thermostat below room tempera-
ture and observe that furnace goes off. Set thermostat above
room temperature and observe that furnace restarts.
Step 5—Adjustments
1. Set gas input rate.
The gas input rate must be set for both high- and low-stage heat.
Each adjustment is made independently at the gas control regula-
tors. The gas valve regulator has been nominally set at 1.5-in. wc
for low-stage and 3.5-in. wc for high-stage for natural gas.
Furnace gas input rate on rating plate is for installations at altitudes
up to 2000 ft.
In the U.S.A., input rating for altitudes above 2000 ft must be
reduced by 4 percent for each 1000 ft above sea level.
In Canada, input rating must be derated by 10 percent for altitudes
of 2000 ft to 4500 ft above sea level.
Furnace input rate must be within ±2 percent of input on furnace
rating plate.
2. Determine natural gas orifice size and manifold pressure for
correct input.
a. Obtain yearly gas heat value average (at installed altitude)
from local gas supplier.
b. Obtain yearly gas specific gravity average from local gas
supplier.
18
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