Engineering Manual

MULTI
F
MAX
MULTI
F
Mechanical Specications and Features
DUCT (HIGH STATIC) INDOOR UNITS
Ceiling-Concealed Duct (High Static)
Indoor Unit
General
All LG indoor units are factory assembled, wired, piped, and provided
with a control circuit board, fan, and motor. Ceiling-Concealed Duct
(High Static) units are designed for high-speed air volume against an
external static pressure up to 0.78″WG for the 24,000 Btu/h model;
up to 0.55″WG for the 36,000 Btu/h model.
Coil
Indoor unit coils are factory built and are comprised of aluminum fins
mechanically bonded to copper tubing. Each unit has two rows of
coils, which are pressure tested at the factory. Each unit is provided
with a factory installed condensate drain pan below the coil.
Refrigerant System
System is designed for use with R410A refrigerant. The refrigeration
circuit is pressure-tested at the factory and shipped with a holding
charge of helium gas. Refrigerant pipe connections are 45° flare,
and all refrigerant lines from the outdoor unit to the indoor units must
be field insulated.
Electrical
Each indoor unit is designed to operate using 208–230/60/1 power
with voltage variances of ±10%.
Casing
The casing is designed to mount fully concealed above a finished
ceiling. Casing is manufactured of galvanized steel plate. Cold sur-
faces of the unit are covered internally with a coated polystyrene in-
sulating material, and covered externally with sheet insulation made
of ethylene propylene diene monomer (M-Class) (EPDM). External
insulation is plenum rated and conforms to ASTM Standard D-1418.
Hanger brackets are included on the casing to support the weight on
four corners. Unit has a front horizontal supply air discharge outlet,
and one dedicated rear horizontal return air inlet.
Fan Assembly and Control
The units have two direct-drive, Sirocco fans made of high strength
ABS GP-2200 polymeric resin that are statically and dynamically
balanced. The fans are mounted on a common brushless digitally
controlled (BLDC) motor with permanently lubricated and sealed
ball bearings. The fan / motor assembly is mounted on vibration-at-
tenuating rubber grommets. Fan speed is controlled using a micro-
processor-based direct digital control algorithm. The indoor fan has
Low, Med, High, and Auto settings for Cooling mode; and has Low,
Med, High, and Auto settings for Heating mode. Each of the settings
can be field-adjusted from the factory setting (RPM / ESP). The Auto
setting adjusts the fan speed based on the difference between the
controller setpoint and space temperature.
Air Filter
Return air is filtered with a factory-supplied, removable, washable
filter accessible from the rear of the indoor unit. High efficiency air
filter options include a return filter box and an LG / Dynamic supplied
air cleaner (both sold separately).
Microprocessor Control
The unit is provided with an integrated control panel to communicate
with the outdoor unit. All unit operation parameters are stored in non-
volatile memory resident on the unit microprocessor. The micropro-
cessor controls space temperature through using the value provided
by the temperature sensor within the indoor unit. The microprocessor
control will activate indoor unit operation when the indoor room tem-
perature falls below or rises above a setpoint temperature, at which
point, a signal is sent to the outdoor unit to begin the appropriate
mode. The microprocessor will also provide self-diagnostics and auto
restart functions. A field-supplied four-wire power / communications
cable must be installed to connect the indoor unit(s) to the outdoor
unit.
Controls
The indoor unit is supplied with an LG wired controller. Communica-
tion between the indoor units and the outdoor unit is accomplished
through 18 AWG, four-core, stranded and shielded power / communi-
cation cable.
Condensate Lift/Pump
The indoor unit is provided with a factory installed and wired internal
condensate lift/pump capable of providing a minimum 27.5 inch lift
from the bottom surface of the unit. Drain pump has a safety switch
to shut off the indoor unit if the condensate rises too high in the drain
pan.
• Inverter (Variable speed fan)
• Internal drain pump
• Control lock function
• Auto operation
• Auto restart operation
• Dehumidifying function
• Two thermistor control
• External static pressure control
• Group control
• Self-diagnostics function
• Wired thermostat included
Features
Figure 155: Ceiling-Concealed Duct (High Static) Indoor Unit.
Due to our policy of continuous product innovation, some specications may change without notication.
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112 | DUCT (HIGH STATIC)
Multi F and Multi F MAX Indoor Unit Engineering Manual