Lennox LHT/LDT024 Installation Instructions Manual page 24

Start-Up
IMPORTANT
If unit is equipped with a crankcase heater. Make
sure heater is energized 24 hours before unit start-
up to prevent compressor damage as a result of
slugging.
A-Start-Up
Heating - LHT/LDT024 Unit Only
1- In heat pump heating, 024 units will automatically
stage-up for outdoor temperatures below 40_F (for
increased performance and efficiency). No external
demand is required, this operation is completely
automatic. At temperatures above 40_F, compressor
will automatically stage-down to maintain operational
efficiency.
Heating - LDT Units
Note - L1 reversing valve is de-energized in the
heating mode.
1- Set thermostat or temperature control device to
initiate a first-stage heating demand.
2- Outdoor Temperature ABOVE Balance Point
Setpoint (35_F default):
A first-stage heating demand (W1) will energize
compressor heat pump heating, the outdoor fan, and
the blower.
A second-stage heating demand (W2) will
de-energize compressor heat pump heating
through K27. High gas heat will be energized.
3- Outdoor Temperature BELOW Balance Point
Setpoint (35_F default):
A first-stage heating demand (W1) will energize low
gas heat and the blower motor.
A second-stage heating demand (W2) will energize
high gas heat.
Heating - LHT Units
1- Set thermostat or temperature control device to
initiate a first-stage heating demand.
2- A first-stage heating demand (W1) will energize
compressors 1 and outdoor fan.
Note - L1 Reversing Valve is de-energized in the heating
mode.
LH Units With Optional Electric Heat -
An increased heating demand (W2) will energize electric
heat. Electric heat is also energized during the defrost
cycle to maintain discharge air temperature.
Cooling
Note - 024 units are single-speed cooling operation only.
1- Initiate full load cooling operation using the following
mobile service app menu path:
RTU MENU > COMPONENT TEST > COOLING >
COOLING STAGE 2
2- Units contain one refrigerant circuit.
Note - Units are equipped with two-stage compressors.
3- Unit is charged with R-410A refrigerant. See unit
rating plate for correct amount of charge.
4- Refer to Refrigerant Charge and Check section for
proper method to check refrigerant charge.
B-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 K1 contactor. Do not reverse wires at
blower contactor.
Make sure the connections are tight.
Discharge and suction pressures should operate at
their normal start‐up ranges.
C-Refrigerant Charge and Check - Fin/Tube Coil
WARNING-Do not exceed nameplate charge under
any condition.
This unit is factory charged and should require no further
adjustment. If the system requires additional refrigerant,
reclaim the charge, evacuate the system, and add
required nameplate charge.
NOTE - System charging is not recommended below
60°F (15°C). In temperatures below 60°F (15°C) , the
charge must be weighed into the system.
If weighing facilities are not available, or to check the
charge, use the following procedure:
1- Attach gauge manifolds and operate unit in cooling
mode on HIGH SPEED with economizer disabled
until system stabilizes (approximately five minutes).
Make sure outdoor air dampers are closed.
Note - Use mobile service app menu path RTU MENU >
COMPONENT TEST > COOLING > COOLING STAGE 2
Page 24
LHT/LDT024, 036, 048, 060