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JOHNSON CONTROLS
FORM 100.50-EG12 (918)
FIGURE 3 -
JOHNSON CONTROLS FLEXSYS UNDERFLOOR AIR DELIVERY
SYSTEM
With the Johnson Controls FlexSys Underfloor Air System, conditioned air is ducted to the
underfloor plenum. As shown in
Figure 3 on page 17
, this conditioned air flows freely
throughout the plenum to individual supply discharge outlets. Unlike the larger single sup-
ply duct outlets typical of overhead systems, underfloor systems are configured to have a
large number of smaller supply outlets, in close proximity to the building occupants. These
adjustable outlets provide an opportunity for nearby occupants to have some amount of
control over thermal comfort conditions in their local environment. Air is returned from the
room at ceiling level (unducted plenum return is shown). The resulting overall floor-to-
ceiling airflow pattern takes advantage of the natural buoyancy produced by heat sources
in the space and more efficiently removes heat loads and contaminants from the space,
particularly for cooling applications. In fact, some of the most important advantages of
underfloor systems over ceiling-based systems occur during cooling conditions, which
are required year-round in the vast majority of interior office space in many parts of the
United States.
HARSH ENVIRONMENTS – CONDENSER AND EVAPORATOR COIL PROTECTION
For harsh environmental conditions such as seashore applications, Johnson Controls of-
fers two types of coil protection: copper fin evaporator coils and post coated condenser
coils. Johnson Controls recommends that for corrosive environments that copper fins be
used to protect the evaporator coils. In areas where chemicals that can corrode copper
are present, such as ammonia, Johnson Controls recommends that post coated con-
denser coild be used for maximum protection.
BUILDING PRESSURE CONTROL SYSTEMS
Building pressure control systems are often necessary when economizers are used to
bring in outdoor air. Without proper building exhaust, the building may become over pres-
surized. The pressure control system maintains the proper building pressure by expelling
the appropriate amount of air from the building.
Return fans
– For high return static applications, such as buildings with ducted return
systems, a powered return fan may be necessary to maintain building pressure control.
Johnson Controls offers a powered return fan that is located in the return plenum. This fan
operates coincidentally with the supply fan and draws return air back through the return
ductwork and into a pressurized plenum. A control damper modulates to exhaust air out
of the building and maintain the building pressure. A second control damper modulates to
provide return air from the ductwork to the unit air mixing section.
