Engineering Manual

Method 3: Unconditioned Outdoor Air Ducted to Indoor Units
Untreated outdoor air is channeled through a duct system that is piped to the return air duct on Multi F ducted indoor units or to the frame of
Multi F four-way cassettes.
Advantages
• May require less ductwork if indoor units are
placed near outdoor walls or a roof deck.
• Controls must be interlocked to shut off the
outdoor air supply fan when the space is
unoccupied.
• Third-party demand-control ventilation
controls may be installed to regulate outdoor
intake based on the CO
2
levels of the
occupied space.
Disadvantages
• Fan(s) will be required to push outdoor air to the indoor unit to overcome the additional
static pressure.
• Filter required to be added to the outdoor air duct.
• Ducted and four-way cassette models are the only indoor units that accept the connection
of an outdoor air duct to the unit case.
• In most cases, in lieu of using the factory mounted return-air thermistor on indoor units, a
remote wall temperature sensor or zone controller will be needed to provide an accurate
reading of the conditioned area temperature.
• Unconditioned outdoor air may affect indoor unit performance, which may necessitate
oversizing the indoor unit.
Outside air may ow backward through the return air-lter grille when the indoor unit fan speed slows or stops in response to changes in the
space load. This may result in captured particulate on the lter media being blown back into the conditioned space.
OA Wall Cap
Damper
Inline Fan
with Filter
Figure 250: Unconditioned Outdoor Air Ducted to Indoor Units.
BUILDING VENTILATION DESIGN GUIDE
Due to our policy of continuous product innovation, some specications may change without notication.
©LG Electronics U.S.A., Inc., Englewood Cliffs, NJ. All rights reserved. “LG” is a registered trademark of LG Corp.
182 | APPLICATION GUIDELINES
Multi F and Multi F MAX Indoor Unit Engineering Manual
MULTI
F
MAX
MULTI
F