Lennox LDT Series Information page 22

C-Blower Compartment
The blower compartment is located between the
evaporator coil and the compressor / control section on the
opposite side of the condenser coil. The blower assembly is
accessed by disconnecting the blower motor wiring (and all
other plugs) and removing the screws on either side of the
sliding base. The base pulls out as shown in figure 12.
1-Blower Wheels
All units have two 15 in. x 15 in. (381 mm x 381 mm) blower
wheels. Both wheels are driven by one motor.
2-Indoor Blower Motor B3
All units use three‐phase single‐speed blower motors.
CFM adjustments are made by adjusting the motor pulley
(sheave). Motors are equipped with sealed ball bearings.
All motor specifications are listed in the SPECIFICATIONS
(table of contents) in the front of this manual. Units may be
equipped with motors
manufacturers, therefore
specifications will vary. See unit rating plate for information
specific to your unit.
OPERATION / ADJUSTMENT
Supply Air Staged Units - The blower rotation will always
be correct on units equipped with an inverter. Checking
blower rotation is not a valid method of determining voltage
phasing for incoming power.
Supply Air Staged Units and Units Equipped With
Optional Voltage or Phase Detection - The Unit
Controller checks the incoming power during start-up. If the
voltage or phase is incorrect, the Unit Controller will display
an alarm and the unit will not start.
A-Blower Operation
Refer to the Unit Controller Setup Guide to energize blower.
Use this mobile service app (the QR is located in the control
area) menu:
SERVICE > TEST > BLOWER
Instructions provided with the thermostat may also be used
to initiate blower only (G) demand. Unit will cycle on
thermostat demand. The following steps apply to
applications using a typical electro-mechanical thermostat.
1- Blower operation is manually set at the thermostat
subbase fan switch. With fan switch in ON position,
blowers will operate continuously.
2- With fan switch in AUTO position, the blowers will cycle
with demand. Blowers and entire unit will be off when
system switch is in OFF position.
manufactured by various
electrical FLA and LRA
Page 22
IMPORTANT
Three Phase Scroll Compressor Voltage Phas­
ing
Three phase scroll compressors must be phased se­
quentially to ensure correct compressor and blower*
rotation and operation. Compressor and blower are wired
in phase at the factory. Power wires are color-coded as
follows: line 1-red, line 2-yellow, line 3-blue.
1-Observe suction and discharge pressures and blower*
rotation on unit start-up.
2-Suction pressure must drop, discharge pressure must
rise and blower* rotation must match rotation marking.
If pressure differential is not observed or blower* rotation
is not correct:
3-Disconnect all remote electrical power supplies.
4-Reverse any two field-installed wires connected to the
line side of S48 disconnect or TB13 terminal strip. Do not
reverse wires at blower contactor.
5-Make sure the connections are tight.
Discharge and suction pressures should operate at their
normal start‐up ranges.
*Supply air inverter blower motors should rotate in the
correct direction; verify scroll compressor rotation sepa­
rately. Contact technical support if the blower is rotating
incorrectly.
WARNING
1-Make sure that unit is installed in accordance with the
installation instructions and applicable codes.
2-Inspect all electrical wiring, both field‐ and factory‐
installed, for loose connections. Tighten as required.
3-Check to ensure that refrigerant lines do not rub against
the cabinet or against other refrigerant lines.
4-Check voltage at disconnect switch. Voltage must be
within range listed on nameplate. If not, consult power
company and have voltage condition corrected before
starting unit.
5-Make sure filters are new and in place before start‐up.
B-Blower Access
1- Disconnect jack/plug connector to blower motor. Also
disconnect jack/plug connector heating limit switches
on gas units.
2- Remove screws on either side of blower assembly
sliding base. See figure 12.
3- Pull base toward outside of unit.
C-Determining Unit CFM
IMPORTANT - Multi-staged supply air units are factory-set
to run the blower at full speed when there is a blower (G)
demand without a heating or cooling demand. Refer to the
field-provided, design specified CFM for all modes of
operation. Use the following procedure to adjust motor
pulley to deliver the highest CFM called for in the design
spec. See Inverter Start-Up section to set blower CFM for
all modes once the motor pulley is set.