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Chapter 2 Pre-installation considerations
24 BAS-APG001-EN
The smoke control system controls fans and positions dedicated and
nondedicated dampers, both in the smoke control zones and at the air-
handling systems. It may also position dampers or air modulation devices
such as variable-air-volume (VAV) boxes serving the smoke control zones.
Equipment associated with the smoke control system includes: dampers,
fans, verification of operation equipment, and the Tracer™ MP581
programmable controller.
For VAV-based systems, there must be some form of duct pressure relief
on each floor or in each smoke control zone. In smoke control mode, all
return and supply dampers will be set to 100% open. If the VAV dampers
are closed when this occurs, the duct pressure may be enough to damage
duct work. To avoid this possibility, duct pressure relief dampers, either
DDC or mechanically controlled, should be installed in the ductwork for
each smoke control zone.
It should be noted that careful sizing of smoke control supply air damper
and relief damper is necessary to use smoke purge and protect dampers.
In contrast to a VAV system, it is not necessary to provide separate duct
pressure relief in constant volume as this is a form of dedicated smoke
purge with supply and return/exhaust dampers already open. Supply
dampers should be sized such that any one damper can spill an adequate
amount of air.
Outdoor air, return air, relief, and exhaust dampers
A nondedicated comfort control system controls outdoor air, return air,
relief, and exhaust dampers. In normal operation, the return damper
operates in opposition to the outdoor air damper. However, during smoke
control system activation, all three dampers may be closed
simultaneously to isolate the air-handling system for smoke control
operations.
An elevator shaft damper, located at the top of a hoistway, relieves
pressure generated during elevator operation. Since elevator shaft
dampers are usually open, the natural stack effect of the building will
tend to distribute smoke through the building via the elevator shafts.
Some codes require a key-operated switch at the main floor lobby to close
the elevator shaft damper. With local approval, this switch can be located
at the FSCS.
Smoke dampers
A smoke damper is located in any duct that penetrates a smoke zone
perimeter. Smoke dampers that are listed by Underwriters Laboratories
(UL) are subject to more stringent leakage tests than are standard
control dampers. The listing usually includes the control actuator as part
of the smoke damper assembly, but does not include the end switches.
IMPORTANT
Smoke dampers must have a Underwriters Laboratories (UL) listing for
smoke control applications (UL 555S).