Cooling Start-Up - Lennox LGT092H Installation Instructions Manual

Cooling Start-Up

IMPORTANT-The crankcase heater must be energized
for 24 hours before attempting to start compressor. Set
thermostat so there is no demand to prevent
compressors from cycling. Apply power to unit.
A-Start-Up
1- Initiate full load cooling operation using the following
mobile service app menu path:
RTU MENU > SERVICE > COMPONENT TEST > COOLING
> COOLING STAGE
2- Refer to Cooling Operation section for cooling
start-up.
3- Units have two refrigerant circuits. See figure 22.
4- Each refrigerant circuit is charged with R410A
refrigerant. See unit rating plate for correct
amount of charge.
5- Refer to Refrigerant Check and Charge section for
proper method to check refrigerant charge.
REFRIGERANT STAGES
TRADITIONAL FIN/TUBE COIL
CONDENSER COIL
STAGE 1
CONDENSER COIL
STAGE 2
EVAPORATOR
COIL STAGE 2
2
1
FIGURE 22
(BOTH FANS ARE ENERGIZED
WITH A Y1 DEMAND)
B4
B5
EVAPORATOR
COIL STAGE 1
B-R410A Refrigerant
Units charged with R410A refrigerant operate at much
higher pressures than R22. The expansion valve and
liquid line drier provided with the unit are approved for use
with R410A. Do not replace them with components
designed for use with R22.
R410A refrigerant is stored in a pink cylinder.
Manifold gauge sets used with systems charged with
R410A refrigerant must be capable of handling the higher
system operating pressures. The gauges should be rated
for use with pressures of 0-800 on the high side and a low
side of 30" vacuum to 250 psi with dampened speed to
500 psi. Gauge hoses must be rated for use at up to 800
psi of pressure with a 4000 psi burst rating.
Mineral oils are not compatible with R410A. If oil
must be added, it must be a polyol ester oil.
C-Compressor Controls
See unit wiring diagram to determine which controls are
used on each unit.
1- High Pressure Switch (S4, S7)
The compressor circuit is protected by a high
pressure switch which opens at 640 psig + 10 psig
(4413 kPa + 70 kPa) and automatically resets at 475
psig + 20 psig (3275kPa + 138 kPa).
2- Low Pressure Switch (S87, S88)
The compressor circuit is protected by a loss of
charge switch. Switch opens at 40 psig + 5 psig (276
+ 34 kPa) and automatically resets at 90 psig + 5 psig
(621 kPa + 34 kPa).
3- Crankcase Heater (HR1, HR2)
Compressors have belly band compressor oil
heaters which must be on 24 hours before running
compressors. Energize by setting thermostat so that
there is no cooling demand, to prevent compressor
from cycling, and apply power to unit..
4- Diagnostic Sensors (RT46-RT49)
Four thermistors are located on specific points in the
refrigeration circuit. The thermistors provide constant
temperature feedback to the Unit Controller to protect
the compressor. Thermistors take the place of the
freezestat and low ambient pressure switch.
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IMPORTANT