The Fundementals of Smoke Control
Andover Controls Corporation 1-13
TOC
dampers when it is heated to a certain temperature. Once the fusible link
releases, the dampers close by the force of gravity. So, fire dampers
operate even if the electricity has failed. The specifications for fire
dampers appear in the document UL555, Standard for Fire Dampers.
If you want a damper to function as both a smoke damper and a fire
damper, it must meet the requirements for both devices. These dampers
can be operated by electric motors or pneumatics. But it must, however,
also have a fusible link or other means of closing automatically, like a
regular fire damper. The control system can override the closure due to
temperature. The damper needs the fusible link in case the automatic
control of the damper by the control system is interrupted.
Choosing Fans and Duct Work
The fans and duct work used in the smoke control system must be
capable of providing the amount of pressure you calculated earlier. In a
nondedicated system, this may mean that you need to install fans that
have a higher capacity than the HVAC system calls for. The ducts must
be capable of taking the pressurization (or the depressurization, for the
fire zone’s return duct) that the smoke control system will exert.
Both the fans and the ducts should meet the requirements stated in
NFPA 90A, Standard for the Installation of Air Conditioning and
Ventilating Systems.
Fans for a smoke control system normally do not have to meet any
special heat resistance rating. In a smoke control system, fans must be
able to reach the required setting in 60 seconds. Each fan must have a
pressure monitor mounted so that the smoke control system can receive
feedback on the status of the fan to determine whether it is actually
operating or not.
In some climates, the outside air can be so cold that drawing it directly
inside the building can damage the building’s interior (freeze pipes or
damage temperature-sensitive equipment, for example). In these cases,
some sort of preheater needs to be installed on the air inlet. The smoke
control system does not have to control the heater as closely as one in an
HVAC system, since maintaining comfort levels is not an issue. It
simply has to make sure the air sent into an area is not going to damage
the building’s interior.
Technical Manuals Online! - http://www.tech-man.com
To Next Page
Loading...
