LG GEN2 Series Installation And Operation Manual page 35

Optional Component Operation
VFD Compressor
If the VFD compressor option is included, the
compressor VFD is mounted in the end of the
condensing section. Condensing section internal
components are accessible via the access panel on
the side of the condenser coil.
Envelope Control
The unit controller tracks the operating point of the VFD
compressor within the operating envelope at all times. If
the operating point is out of the envelope, the controller
will take action to bring it back in. If unsuccessful, the
controller will shut down the compressor. DO NOT
operate the compressor VFD in hand mode because
the envelope control safeties will not be in place. Refer
to the controls IOM for more information on envelope
control.
Electronic Expansion Valve
An electronic expansion valve is provided on the VFD
compressor circuit to ensure tight superheat control
throughout the compressor modulation band. The EXV
acts as a liquid line solenoid valve when the compressor
is off to prevent refrigerant migration.
Crankcase Heat
The VFD compressor will be heated by the compressor
stator. To ensure optimal performance and reliability, do
not disable stator heat. All other compressors will be
provided with a crankcase heater.
Oil Return Management
The compressor VFD has an oil return purge cycle such
that if the compressor has been operating below a set
RPM for a set period of time, the VFD will accelerate the
compressor to ensure sufficient lubrication.
DO NOT disable the oil return management function.
DO NOT operate the compressor VFD in hand mode
because the oil return management will not be
operational.
Ultraviolet Germicidal Irradiation (UVGI)
UV-C lights are mounted in the supply blower cabinet
and provide air disinfection. The lights are
factorypowered
and are on when the supply blower is running.
A kill switch on the supply blower access door turns the
lights off when that door is open.
Housing 352 Only
UV-C lights are mounted downstream of the cooling
coil, providing coil surface and drain pan disinfection.
The lights are factory-powered and are on when there
is power to the unit disconnect. A kill switch on the coil
access door turns the lights off when that door is
open.
Needlepoint Bipolar Ionization (NPBI®)
Needlepoint bipolar ionizers are mounted on the fan
inlet cone(s) and provide air disinfection. The ionizers
are factory-powered and are on when there is power to
the unit disconnect.
Frost Control
Extremely cold outdoor air temperatures can cause
moisture condensation and frosting on the energy
recovery wheel. Frost control is an optional feature that
will prevent/control wheel frosting. Three options are
available:
Polymer Energy Wheel
Available options are:
1. Timed exhaust frost control
2. Electric preheat frost control
3. Modulating wheel frost control
These options are provided with a thermodisc mounted
in the outdoor air intake compartment and a pressure
sensor to monitor pressure drop across the energy
wheel. An outdoor air temperature of below 5°F and
an increase in pressure drop indicate that frost is
occurring. Both the pressure sensor and the outdoor
air thermodisc must trigger to initiate frost control. The
two sensors together ensure that frost control is only
initiated during a real frost condition.
Timed exhaust frost control includes a timer in
addition to the thermodisc and wheel pressure sensor.
When frost control is initiated, the timer will turn the
supply blower off. The default timer setting will shut
down the supply fan for 5 minutes every 30 minutes,
allowing warm exhaust to defrost the energy wheel. Use
the test procedure in the Optional Start-Up Accessories
section for troubleshooting.
Electric preheat frost control includes an electric
heater (at outdoor air intake) in addition to the
thermodisc and wheel pressure sensor. When frost
control is initiated, the electric preheater will turn on and
warm the air entering the energy wheel. Use the test
procedure in the Optional Start-Up Accessories section
for troubleshooting.
Modulating wheel frost control includes a variable
frequency drive (VFD) in addition to the thermodisc
and wheel pressure sensor. When frost control is
initiated, the VFD will reduce the wheel speed, reducing
effectiveness and preventing condensation and frosting.
If the outdoor air temperature is greater than the frost
threshold temperature OR the pressure differential is
less than the set point, the wheel will run at full speed.
If the outdoor air temperature is less than 5°F AND
the pressure differential is greater than the set point,
the wheel will run at reduced speed until the pressure
differential falls below the set point. The VFD will be fully
programmed at the factory.