1083287-UIM-A-0114
34
Johnson Controls Unitary Products
ADJUSTMENT OF TEMPERATURE RISE
After about 5 minutes of operation, determine the furnace temperature
rise. Take readings of both the return air and the heated air in the ducts,
about six feet (1.8 m) from the furnace where they will not be affected
by radiant heat. Increase the blower speed to decrease the temperature
rise; decrease the blower speed to increase the rise.
All direct-drive blowers have multi-speed motors. The blower motor
speed taps are located on the furnace control board in the blower com-
partment. Refer to Figure 42, 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 desired 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
blower-fan on delay is fixed at 30 seconds. The “Blower Off Delay
Timer” has 4 settings (60, 90, 120 and 180 seconds). The blower off
delay is factory set to 120 seconds. The blower-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 “Blower Off Delay Timer” may be
adjusted by positioning the jumper on two of the four pins as shown in
Figure 42.
MANIFOLD PRESSURE “U” TUBE CONNECTION
FIGURE 41:
Reading Gas Pressure
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 6.
The supply air temperature cannot exceed the “Maximum Supply
Air Temperature” specified in these instructions and on the furnace
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 pre-
mature heat exchanger failure, high levels of Carbon Monoxide, a fire
hazard, personal injury, property damage, and/or death.
U-TUBE
MANOMETER
3.5 IN
WATER
COLUMN
GAS
PRESSURE
SHOWN
GAS
BURNERS
OUTLET
PRESSURE TAP
GAS VALVE
FLAME
SENSOR
1/4” TUBING
MAINIFOLD
PIPE
DANGER
Do not energize more than one motor speed at a time or damage to
the motor will result.
FIGURE 42:
Furnace Control Board
PARK PARK
HI COOL
HEAT
EAC-H
L1
XFMR
NEUTRALS
HUM
TWIN
60
90
120
180
BLOWER
OFF
DELA
Y
Y/Y2
W
R
G
C
Blower Off Delay Timer
Adjustment Jumper
(in seconds)
