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TRANSITION
BLOWER
DIVIDER PANEL
ADJUST PULLEY
TO CHANGE SPEED
MOTOR
MOTOR
BASE
REMOVE SCREWS (4) TO
REMOVE BLOWER
FIGURE 8
Three-phase and Single-phase Belt drive motors
Belt-drive blower motors used in LGA/LCA units are single or
three-phase. Three-phase motors do not use run capacitors.
Single phase motor run capacitors are integral to the motor.
All motors are single-speed ball-bearing type which use an ad-
justable pulley for adjusting blower speed.
5- Motor Fuses F27
Blower motors in 575V direct-drive units are protected by line
voltage fuses located in the upper portion of the blower
compartment.
6- Blower Motor Capacitor C4
All single-phase blower motors are PSC type which require a
run capacitor. Capacitor ratings may be different for each mo-
tor, but the rating and repair part number will be printed on the
side of the capacitor.
7-Transformer T4
575 (J) voltage direct-drive voltage units use a line voltage to
460V auto-transformer to power the indoor blower and out-
door fan. This autotransformer is also connected directly to
line voltage and is powered at all times. It has a maximum
rating of 3.4A.
D-BLOWER OPERATION / ADJUSTMENT
1-Blower Operation
NOTE-The following is a generalized procedure and does not apply to all
thermostat control systems.
LGA/LCA SUPPLY
AIR BLOWER
BELT DRIVE SHOWN
REMOVE SCREWS (4) TO
REMOVE BLOWER
BLOWER
BELT
TENSIONER
Page 20
1- Blower operation is dependent on the thermostat control
system option that has been installed in the LGA/LCA
units. Refer to operation sequence of the control system
installed for detailed descriptions of blower operation.
2- Generally, blower operation is set at the thermostat fan
switch. With the fan switch in "ON" position and the OCP
input is "ON", the blower operates continuously. With
the fan switch in "AUTO" position, the blower cycles
with demand.
3- In most cases, the blower and entire unit will be off when
the system switch is in the "OFF" position. The only ex-
ception is immediately after a heating demand when the
blower control keeps the blower on until all heat is ex-
tracted from the heat exchanger.
2-Temperature Rise
Temperature rise for LGA/LCA 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 horizontal
run of the plenum, close to unit, yet far enough away it
will not pick up radiant heat from the heat exchanger.
2- Set thermostat to highest setting.
3- After plenum thermometers have reached their highest
and steadiest readings, subtract the return temperature
from the supply temperature. The difference should be
in the range listed on the unit rating plate. If the tempera-
ture is too low, decrease blower speed. If temperature is
too high, first check the firing rate. Provided the firing rate
is acceptable, increase blower speed to reduce tempera-
ture.
3-External Static Pressure
1- Measure tap locations as shown in figure 9.
2- Punch a 1/4" diameter hole
in supply and return air ple-
nums. Insert manometer
hose flush with inside edge
of hole or insulation. Seal
around the hose with perma-
gum. Connect the zero end
of the manometer to the dis-
charge (supply) side of the system. On ducted sys-
tems, connect the other end of manometer to the return
duct as above.
3- With only the blower running and the evaporator coil
dry, observe the manometer reading. Adjust blower
motor speed to deliver the air desired according to the
job requirements.
4- Seal around the hole when the check is complete.
STATIC PRESSURE
TEST
MANOMETER
LGA/
LCAUNIT
FIGURE 9
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