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

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.

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OA Wall Cap

Damper

Inline Fan

with Filter

Figure 42: Unconditioned Outdoor Air Ducted to Indoor Units.

BUILDING VENTILATION DESIGN GUIDE

Methodology illustrations are for examples only and do not depict actual

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trations to show ventilation design only.

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54 | APPLICATION GUIDELINES

Multi F and Multi F MAX Indoor Unit Engineering Manual

MULTI

MAX

MULTI