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The override exception is where fan control capability
switches for nondedicated smoke control system fans
(i.e. HVAC) are located in electrical equipment or
mechanical rooms accessible only to authorized
personnel. In addition to authorized access, the
operation of one of these motor controller switches must
cause a trouble annunciation at the building's main
control center, in order that the FSCS need not override
or bypass these switches.
The FSCS must not override or bypass devices and
controls, designed to:
•
Protect against electrical overloads
•
Provide for personnel safety
•
Prevent major system damage
Controls not to be overridden include:
•
Overcurrent protection devices
•
Electrical disconnect switches
•
High-limit static pressure switches
•
Combination fire/smoke dampers beyond their
UL 555 degradation temperature classifications
The FSCS must display a building diagram that clearly
indicates the type and location of all smoke control
equipment. At a minimum, the FSCS should indicate the
following:
•
The actual status of the system components and
equipment which are activated or capable of
activation for smoke control are to be indicated at
the FSCS graphic annunciator.
•
Status indication for each fan having a capacity of
2,000 cfm (944 L/s) or more is to include on and off
conditions. The "ON" status should be sensed by
pressure difference at the design smoke control
airflow.
•
Damper position at smoke barriers and other critical
locations are to be confirmed by positive means.
VM-1 Smoke Management Application Guide
Chapter 2: Smoke control system hardware
VM-1 smoke control system
design considerations
Dedicated
Dedicated smoke control system mechanical
components such as fans and dampers are used only for
smoke control. Design and sizing of fans and other
components is focused upon static pressure control,
safety devices, and sizing to manage the required
smoke control air flows.
Dedicated smoke control systems include stairwell
pressurization, smoke shaft exhaust systems, elevator
shaft pressurization systems, and atrium smoke control
systems. Controls for dedicated smoke control systems
will be more straightforward since fans and dampers will
likely be under the sole control of the SCS.
Stairwell pressurization systems
Stairwell pressurization systems are designated as
either compensated or noncompensated.
Compensated systems have control provisions which
react to changes in airflow in order to maintain a specific
static pressure level. Depending upon the height of the
stairwell, sensors and exhaust dampers will adjust air
flows for pressure losses due to doors opening in the
stairwell. Current designs place sensors and exhaust
damper controls at every third floor in mid or high-rise
buildings.
An SCS design for compensated systems must provide
for control of fans and dampers at multiple points in a
compensated system. Fans are typically VAV type or
contain bypass ducts around the fan. Stairwells of
8 floors or less may be compensated with only fans at
the top or bottom of the stairwell and dampers on the
opposite end.
Noncompensated systems do not have static pressure
control provisions. Fans and dampers or vents are
designed and programmed to operate at a set pressure
for the stairwell.
Stairwell pressurization fan air intakes must be located in
a manner that helps to ensure that smoke from a
building fire is not drawn into the stairwell. The air
intakes will supply all of the air to the stairwell and
therefore requires a duct smoke detector which will shut
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