271043-UIM-B-0707
Unitary Products Group
23
ADJUSTMENT OF TEMPERATURE RISE
The temperature rise, or temperature difference between the return air
and the heated supply air from the furnace, must be within the range
shown on the furnace rating plate and within the application limitations
as shown in Table 7.
After about 20 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 (1.83 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.
VARIABLE SPEED MOTORS
The variable speed motor must be configured so the blower will provide
a sufficient airflow so that the furnace operates with in the temperature
rise range on the rating plate and within the application limitations
shown in Table 7 in these Instructions.
ADJUSTMENT OF FAN CONTROL SETTINGS
Heating Indoor Fan Off Delay
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 sec-
onds. 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 23.
WITH BURNER BOX COVER IN PLACE
WITH BURNER BOX COVER REMOVED
FIGURE 22:
Reading Gas Pressure
6
5
4
3
2
1
0
1
2
3
4
5
6
BURNER BOX
WITH COVER
OUTLET
PRESSURE
TAP
GAS VALVE
U-TUBE
MANOMETER
TEE
FITTING
BURNER BOX
PRESSURE
REFERENCE
HOSE
3.5 IN
WATER
COLUMN
GAS PRESSURE
SHOWN
6
5
4
3
2
1
0
1
2
3
4
5
6
U-TUBE
MANOMETER
3.5 IN
WATER
COLUMN
GAS PRESSURE
SHOWN
BURNER BOX
WITH COVER
REMOVED
OUTLET
PRESSURE
TAP
GAS VALVE
BURNER BOX
PRESSURE
REFERENCE
HOSE
(not used)
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 7 “ELECTRICAL AND PERFORMANCE
DATA”.
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.
FIGURE 23:
Furnace Control Board
CONTINUOUS
FAN SPEED
JUMPER
BLOWER
OFF DELAY
JUMPER
HI HEAT
DELAY
JUMPER
HEAT
DELAY
JUMPER
DEHUMIDISTAT
JUMPER
LOW
VOLTAGE
TERMINALS
BLOWER
SPEED
JUMPERS
COOLING
PROFILE
JUMPER
