Multi F Outdoor Unit Engineering Manual

Table Of Contents

BUILDING VENTILATION DESIGN GUIDE

OA Wall

Louver

Damper

Roof Fan

Method 2: Unconditioned Outdoor Air (Non-Ducted, Fan Assisted Ventilation)

When approved by local codes, the fan assisted ventilation method uses exhaust fans to remove air from the building, and outdoor air is

drawn into occupied spaces through a wall louver or gravity roof intake hood. Supply fans can also be used to push the outdoor air into the

space and building positive pressure will vent the exhaust air through louvers or roof-mounted exhaust hoods. Outdoor air is neither cooled

nor heated before entering the building.

Advantages

•Outdoor air may be manually controlled by the occupant or auto-

matic controls may be installed to open/close outdoor air dampers

or to turn on/off ventilation fans.

•Useful for large open spaces like warehouses, garages, and

workshops.

•Outdoor air volume is a known quantity. Air loads may be easier to

calculate since fans will regulate the amount of outdoor air.

•May be used with the full lineup of Multi F indoor units.

This may result in loss of building pressurization control, increasing inltration loads with adverse effects.

Disadvantages

•In some locations of the country, it may be difficult to control

humidity levels.

•Indoor units may have to be oversized to account for the added

heating/cooling loads when louvers/hoods are open.

•Hot, cold, and/or humid areas may be present if the outdoor air is

not evenly distributed to the different spaces.

Figure 40: Unconditioned Outdoor Air (Non-Ducted, Fan Assisted Ventilation).

Due to our policy of continuous product innovation, some specications may change without notication.

ApplicAtion Guidelines | 187

Application Guidelines

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