Lennox LHT Series Service Manual page 23

C-Blower Compartment
The blower compartment is located between the evapo-
rator coil and the compressor / control section on the op-
posite 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. 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 manufactured by various manu-
facturers, therefore electrical FLA and LRA 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 volt-
age phasing for incoming power. Supply Air Staged
Units and Units Equipped With Optional Voltage or
Phase Detection - The Unit Controller checks the incom-
ing power during start-up. If the voltage or phase is incor-
rect, 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 blow-
er. 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 applica-
tions 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.
Three Phase Scroll Compressor Voltage
Phasing
Three phase scroll compressors must be phased
sequentially 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 separately. Contact technical support if the
blower is rotating incorrectly.
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.
Page 23
IMPORTANT
WARNING