507961-01P
Page 42 of 58
Issue 1933
Electronic Air Cleaner
Terminals are provided on the integrated ignition/blower
control board for connection of a 120-volt electronic air
cleaner. The “EAC” terminal is energized whenever the
thermostat calls for heat, cooling, or continuous blower. See
furnace wiring diagram for specific connection information.
Variable Speed Features
This furnace is equipped with a variable speed circulation
air blower motor that will deliver a constant airflow within a
wide range of external static pressures. Other features of
this variable speed motor include:
Soft Start
The variable speed motor will slowly ramp up to normal
operating speed. This minimizes noise and increases
comfort by eliminating the initial blasts of air encountered
with standard motors.
Soft Stop
At the end of a cooling or heating cycle, the variable speed
motor will slowly ramp down after a short blower “off” delay.
If continuous blower operation has been selected, the
variable speed motor will slowly ramp down until it reaches
the airflow for that mode.
Passive and Active Dehumidification
Passive Dehumidification
For situations where humidity control is a problem, a
dehumidification feature has been built into the variable
speed motor. At the start of each cooling cycle, the variable
speed motor will run at 82% of the rated airflow for 7.5
minutes. After 7.5 minutes has elapsed, the motor will
increase to 100% of the rated airflow.
Active Dehumidification
To achieve additional dehumidification, clip the jumper
wire located below the DEHUM terminal on the integrated
ignition/blower control board and connect a humidity
control that opens on humidity rise to the DEHUM and
R terminals. The DEHUM terminal on the control board
must be connected to the normally closed contact of the
humidity control so that the board senses an open circuit
on high humidity. In this setup, the variable speed motor
will operate at a 30% reduction in the normal cooling airflow
rate when there is a call for dehumidification.
Both the passive and active dehumidification methods
described above can be utilized on the same furnace.
Circulating Airflow Adjustments
Cooling Mode
The units are factory set for the highest airflow for each
model. Adjustments can be made to the cooling airflow
by repositioning the jumper plug marked COOL – A, B, C,
D (see Figure 66). To determine what CFM the motor is
delivering at any time, count the number of times the amber
LED on the control board flashes. Each flash signifies 100
CFM; count the flashes and multiply by 100 to determine
the actual CFM delivered (for example: 10 flashes x 100 =
1000 CFM).
Heating Mode
These units are factory set to run at the middle of the
heating rise range as shown on the unit rating plate. If
higher or lower rise is desired, reposition the jumper plug
marked HEAT - A, B, C, C (see Figure 66) . To determine
what CFM the motor is delivering at any time, count the
number of times the amber LED on the control board
flashes. Each flash signifies 100 CFM; count the flashes
and multiply by 100 to determine the actual CFM delivered
(for example: 10 flashes x 100= 1000 CFM).
Adjust Tap
Airflow amounts may be increased or decreased by 10%
by moving the ADJUST jumper plug (see Figure 66) from
the NORM position to the (+) or (-) position. Changes to the
ADJUST tap will affect both cooling and heating airflows.
The TEST position on the ADJUST tap is not used.
Continuous Blower Operation
The comfort level of the living space can be enhanced
when using this feature by allowing continuous circulation
of air between calls for cooling or heating. The circulation
of air occurs at half the full cooling airflow rate.
To engage the continuous blower operation, place the
fan switch on the thermostat into the ON position. A call
for fan from the thermostat closes R to G on the ignition
control board. The control waits for a 1 second thermostat
debounce delay before responding to the call for fan by
ramping the circulating blower up to 50% of the cooling
speed. When the call for continuous fan is satisfied, the
control immediately ramps down the circulating blower.
Figure 66. ADJUST, HEAT, and COOL Taps on
Integrated Ignition/Blower Control Board
