Air handling systems must be balanced to establish correct flow in all floors and zones of a building. Fire and/or smoke dampers are required in barrier walls for safety. This requires two dampers in modern systems - the fire and smoke damper and the balancing damper.
The locations for the fire and smoke dampers and the floor balancing dampers are shown in the drawing above. Typically the dampers are above the ceilings or below the floors where space constraints exist.
Shafts are protected by fire and smoke rated walls and are required to have fire and/or smoke dampers by the International Building Code. A combination fire and smoke damper is required where the floor duct leaves the shaft and passes through a out of the area where a fire starts to other areas via shafts, elevator hoist ways, chases, stairwells, and unsealed holes in walls.
At one time, two separate dampers were required at the shaft exit - a fire damper and a smoke damper. An extra balancing damper was also required, typically located just outside the shaft. This is a standard control damper without an actuator.
The balancer sets the correct flow volume. The FSAF24-BAL (-S) allows one damper to do the job of three, and also meets UL555 (fire) and UL555S (smoke) requirements. The fire and smoke combination damper is controlled by an actuator which is 3-postion, the mid-position being an adjustable balancing position.
The FSAF24-BAL has a maximum potentiometer that sets the open balancing position. The maximum potentiometer is adjustable from 20% to 100% open for balancing.
In case of fire (sensed by the thermal temperature limit) or smoke (sensed by either a local smoke detector or an area smoke detector and alarm system relay), the damper actuator springs full closed.
A 100% full open mode is provided for smoke management systems. If a fire fighters’ smoke control panel switch is set to open, the damper actuator drives 100% open, overriding the maximum balanced position. The FSAF24-BAL and smoke damper becomes a fully adjustable balancing damper.
Summary
The goal is to protect people from the effects of toxic smoke that is generated in fires. Balancing all supply ducts is required to maintain proper air volume or inlet static pressure for VAV boxes. Rather than installing two dampers - a combination fire and smoke damper and a separate balancing damper - one damper can be installed for both purposes.