5715184-BIM-A-0519
28
Johnson Controls Ducted Systems
AIRFLOW SETTINGS
Cooling Airflow Settings
This unit is equipped with a five-speed blower motor. The required cool-
ing airflow can be selected by connecting the required motor speed tap
wire to the HI COOL terminal on the control board. The speed must be
selected to deliver approximately 350–400 CFM per ton of A/C cooling
capacity. Use of airflow outside of this range may result in diminished
air conditioning performance, lower overall energy efficiency, and
higher electric utility bills. See Table 17 for default cooling blower set-
tings.
Continuous Fan Airflow Default Setting
The default blower speed for continuous fan operation is LOW speed.
The continuous fan speed is set at the factory to the default continuous
fan blower speed.
In certain circumstances, it may be necessary to move the continuous
fan speed to a different speed tap. However, doing so results in higher
than normal electrical energy usage and electric utility bills.
Continuous Fan Jumpers
This furnace can be operated in continuous fan mode by setting the wall
thermostat FAN switch to ON. To select the required continuous fan air-
flow, place the FAN SPEED jumper on the control board on the pins
adjacent to the required speed. There are four options:
•
With the FAN SPEED jumper in the G position, the blower runs
during continuous fan operation at the motor speed connected to
the G terminal on the control board.
•
With the FAN SPEED jumper in the HI COOL position, the blower
runs during continuous fan operation at the motor speed con-
nected to the HI COOL terminal on the control board.
•
With the FAN SPEED jumper in the LO COOL position, the
blower runs during continuous fan operation at the motor speed
connected to the LO COOL terminal on the control board.
•
With the FAN SPEED jumper in the HEAT position, the blower
runs during continuous fan operation at the motor speed con-
nected to the HEAT terminal on the control board.
The default position is with the jumper in the G position and the LOW
speed motor wire on the G terminal. In certain circumstances, it may be
necessary to move the continuous fan speed to a different speed tap.
However, doing so is not recommended because it results in higher
than normal electrical energy usage and electric utility bills.
Gas Heating Airflow Default Setting
This unit is equipped with a five-speed blower motor. The heating
blower speed is set at the factory to the default blower speed, which is
the blower speed that delivers the correct airflow for proper heating
operation in most applications. The default heating blower speed for
each model is shown in Table 17. Use of a heating speed other than the
default heating blower speed may result in reduced energy efficiency
and higher electric utility bills.
In certain circumstances, it may be necessary to move the heating
blower speed to a different motor speed tap. Not all five motor speeds
are appropriate for gas heating operation. The use of heating airflow on
a speed other than the default speed results in diminished heating per-
formance and may cause the furnace temperature limit controls to shut
down the furnace.
Measurement of Temperature Rise
After about 5 minutes of operation, determine the furnace temperature
rise. Measure the temperature of both the return air and the heated air
in the ducts approximately 6 ft (1.83 m) from the furnace, where they
are not affected by radiant heat. Increase the blower speed to decrease
the temperature rise. Decrease the blower speed to increase the tem-
perature rise.
The blower speed taps are located on the furnace control board in the
blower compartment. Refer to Figure 33 and the unit-wiring label to
change the blower speed. To use the same speed tap for heating and
cooling, the heat terminal and cool terminal must be connected using a
jumper wire and connected to the required motor lead. Place all unused
motor leads on park terminals. Two park terminals are provided.
ADJUSTMENT OF FAN CONTROL SETTINGS
This furnace is equipped with a time-on/time-off heating fan control. The
fan-on delay is fixed at 30 seconds. The fan-off delay has 4 settings
(60, 90, 120, and 180 seconds). The fan-off delay is factory set to 120
seconds. The fan-off setting must be long enough to adequately cool
the furnace, but not so long that cold air is blown into the heated space.
The fan-off timing may be adjusted by positioning the jumper on two of
the four pins as shown in Figure 33.
Table 17:
Default Blower Speeds
Model Number
Default Blower Speeds
Heat
Cool
Continuous
Fan
MM9E060B12
Medium Low (4)
High (1)
Low (5)
MM9E080B12
Medium (3)
High (1)
Low (5)
MM9E080C16
Medium (3)
High (1)
Low (5)
MM9E080C20
Low (5)
High (1)
Low (5)
MM9E100C16
Medium High (2)
High (1)
Low (5)
DANGER
The temperature rise, or temperature difference between the return
air and the supply (heated) air from the furnace, must be within the
range shown on the furnace rating plate and within the application
limitations shown in Table 5.
The supply air temperature cannot exceed the “Maximum Supply
Air Temperature” specified in these instructions and on the fur-
nace rating plate. Under NO circumstances can the furnace be
allowed to operate above the Maximum Supply Air Temperature.
Operating the furnace above the Maximum Supply Air Temperature
will cause premature heat exchanger failure, high levels of Carbon
Monoxide, a fire hazard, personal injury, property damage, and/or
death.
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