508134-01
Issue 2045
Page 45 of 53
Typical Operating Characteristics
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
subbase fan switch. With fan switch in ON position,
blower operates continuously. 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.
Temperature Rise (Figure 53)
Temperature rise for
GDD92C
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
“TEMP. RISE °F” listed on the unit rating plate.
Figure 53.
TEMPERATURE RISE
Supply Duct Temperature
Return Duct Temperature
_
Temperature Rise =
SUPPLY
AIR
Temperatures
RETURN AIR
External Static Pressure
1.
Tap locations shown in Figure 54.
2.
Punch a 1/4” diameter hole in supply and return air
plenums. Insert manometer hose flush with inside
edge of hole or insulation. Seal around the hose with
permagum. Connect the zero end of the manometer to
the discharge (supply) side of the system. On ducted
systems, connect the other end of manometer to the
return duct as above.
3.
With only the blower motor running and the evaporator
coil dry, observe the manometer reading. Adjust blower
motor speed to deliver the air desired according to the
job requirements. For heating speed external static
pressure drop must not be more than 0.5” W.C. For
cooling speed external static pressure drop must not
be more than 0.8” W.C.
4.
Seal the hole when the check is complete.
Figure 54.
EXTERNAL STATIC PRESSURE
Supply Duct Static
Return Duct Static +
Total Duct Static =
(dry coil)
Duct Static
or
Supply Air
Return Air
High “+”
Low “-”
+
−
Blower Speed Taps
Blower speed tap changes are made on the integrated
control. See Figure 3 or Figure 52. The heating tap is
connected to the “HEAT” terminal and the cooling tap
is connected to the “COOL” terminal. On all units the
continuous blower tap is connected to the “FAN” terminal.
Unused taps must be secured on two dummy terminals
labeled ”PARK. To change out existing speed tap, turn
off power and switch out speed tap with tap connected to
“PARK”. See blower speed tap table on unit diagram for
motor tap colors for each speed.
