FIGURE 23
STATIC PRESSURE
TEST
MANOMETER
80UHG UNIT
Page 18
WARNING
Fire and explosion hazard.
These instructions MUST be followed exactly.
Can cause a fire or explosion resulting in property
damage, personal injury or loss of life.
V-TYPICAL OPERATING CHARACTERISTICS
A-Blower Operation and Adjustment
NOTE- The following is a generalized procedure and
does not apply to all thermostat controls.
1 - Blower operation is dependent on thermostat control
system.
2 - Generally, blower operation is set at thermostat subĆ
base fan switch. With fan switch in ON position, blower
operates continuously on heating speed. With fan
switch in AUTO position, blower cycles with demand or
runs continuously while heating or cooling circuit cycles.
3 - Depending on the type of indoor thermostat, blower
and entire unit will be off when the system switch is in
OFF position.
B-Temperature Rise
Temperature rise for 80UHG units depends on unit input,
blower speed, blower horsepower and static pressure as
marked on the unit rating plate. The blower speed must be
set for unit operation within the range of AIR TEMP. RISE
°
F" listed on the unit rating plate.
To Measure Temperature Rise:
1 - Place plenum thermometers in the supply and return
air plenums. Locate supply air thermometer in the first
horizontal run of the plenum where it will not pick up raĆ
diant heat from the heat exchanger.
2 - Set thermostat to highest setting.
3 - After plenum thermometers have reached their highĆ
est and steadiest readings, subtract the two readings.
The difference should be in the range listed on the unit
rating plate. If the temperature is too low, decrease
blower speed. If temperature is too high, first check
the firing rate. Provided the firing rate is acceptable, inĆ
crease blower speed to reduce temperature. To
change blower speed taps see the Blower Speed Taps
section in this manual.
C-External Static Pressure
1 - Tap locations shown in figure 23.
2 - Punch a 1/4" diameter hole
in supply and return air pleĆ
nums. Insert manometer
hose flush with inside edge
of hole or insulation. Seal
around the hose with perĆ
magum. Connect the zero
end of the manometer to the
discharge (supply) side of the system. On ducted sysĆ
tems, connect the other end of manometer to the reĆ
turn duct as above. For systems with non-ducted reĆ
turns, leave the other end of the manometer open to
the atmosphere.
3 - With only the blower motor running and the evaporator
coil dry, observe the manometer reading. Adjust blowĆ
er motor speed to deliver the air desired according to
the job requirements.
4 - External static pressure drop must not be more than
0.5" W.C.
5 - Seal around the hole when the check is complete.
D-Blower Speed Taps Leadless Motors
80UHG-1 Models
Blower speed tap selection is accomplished by changing the
taps at the blower motor harness connector. Disconnect harĆ
ness connector from motor to expose speed selectors.
Blower speed selections are listed in table 11.
To Change Blower Speed:
1 - Turn off electric power to furnace.
2 - Remove blower access door.
Disconnect blower motor harness from motor.
3 - Select desired speeds for heating and cooling. (Red =
heating, Black = cooling, White = common).
4 - Depress harness connector tab to release wire termiĆ
nal. Select connector location for new speed (refer to
unit wiring diagram). Insert wire terminal until it is seĆ
curely in place. See figure 24.
5 - Replace harness connector to motor.
TABLE 11
