LG GEN2 Series Installation And Operation Manual page 34

Optional Component Operation
Electronically Commutated (EC)
Condenser Fans with Standard Scroll or
Digital Scroll Compressors
The EC condenser fan(s) will modulate up and down
to maintain the optimal liquid line pressure using built
in control sequences within the factory controller. One
pressure transducer is provided with each refrigeration
circuit for monitoring and the factory controller will ramp
condenser fan(s) up or down based on the condenser
set point.
Economizer Fault Detection Diagnostics
Provides the status and faults of the air economizer
to indicate proper economizer sequence operation.
This assures the benefits of free cooling when outdoor
conditions are suitable for economizer functions. The
fault detection diagnostics system will indicate when
free cooling is available and if the outside air damper
and recirculation damper are reacting properly. If the
dampers are not functioning correctly an alarm will be
generated.
Air-Source Heat Pump
Operating Conditions and Limitations
To operate in Cooling mode, the following conditions
must be true:
1. Supply air temperature above minimum low supply
temperature limit (35°F)
2. Outside air temperature above the cooling ambient
lockout (55°F, adj.)
To operate in Heating mode, the following conditions
must be true:
1. Supply air temperature below maximum high
supply temperature limit (120°F)
2. Supply air temperature above 35°F
3. Outside air temperature above the low ambient
lockout (10°F, adj.)
For more information on air-source heat pump
operation, reference the supplemental Reference Guide
for Microprocessor Controller.
IMPORTANT
Air-source heat pumps are equipped with a defrost
cycle to remove ice from the outdoor coil. During
defrost cycles, melted water may drip from the
bottom of the refrigeration section under the outdoor
coil. In cold climates, proper drainage/heat tape must
be installed under the outdoor coil to prevent the
buildup of ice on the roof.
IMPORTANT
Melted water from snow accumulation on the unit
roof can be sucked into outdoor fans, resulting in ice
formation on fan blades under certain conditions.
Remove snow accumulation from the unit roof and
outdoor coil section after snow storms.
Airflow Monitor
A factory-wired, mounted, and powered airflow
monitoring system is provided in the outdoor,
supply and/or exhaust air streams. The airflow
control system displays outdoor, supply, and/or
exhaust air in actual cubic feet per minute (CFM)
at factory controller or can be read by a building
management system if communication is
established.
Operation
Outdoor and/or exhaust airflow monitoring is
accomplished using two thermal dispersion
sensors that accurately measure airflow velocity
down to zero feet per minute (fpm). The airflow
controller takes the average measurement for
two sensor configurations, and determines the
outdoor airflow rate based on the effective
intake area. For additional information on how to
navigate through the airflow controller menus,
refer to technical manuals from GreenTrol®
Automation Inc. at www.greentrol.com.
Supply and/or exhaust airflow monitoring is
accomplished by measuring the pressure drop
across the fan inlet venture. The airflow is then
calculated by the factory controller based on the
measured pressure drop and a K-Factor specific
for each fan size.
Hot Gas Reheat Valve
Units equipped with a reheat coil use a
three-way valve with actuator to control
the supply air discharge temperature of
the unit during dehumidification mode.
The unit controller provides a 0-10 VDC
signal to control the amount of reheat to
meet the supply temperature set point.
Control by Others
The reheat coil needs to be purged to ensure adequate
oil return. It is recommended that every six hours of
reheat compressor run time should initiate a six minute
purge cycle. During the purge cycle, the reheat valve
should be modulated to 100% open to the reheat coil.