High Tower-Type Locksets. High tower-type locksets were developed and patented by Security Door Controls and have minimized the need for door modifications by providing power to the stairwell-side door frame instead of the door hardware. The occupied side of the door is unlocked to allow free egress from the floor into the stairwell. The stairwell-side door hardware is kept locked to prevent entry onto the floor. Upon activation of the building fire alarm panel, power is interrupted to the door power supply and the high tower-type electric strike is released to allow entry from the stairwell onto the floor while keeping the door latched. Pros: This approved design offsets the problem of using electric strikes, which are designed to release upon alarm, thus creating a breach of the fire barrier and smoke control. While providing controlled access and remote control capability, the door stays latched even when unlocked, maintaining fire door integrity. The high tower-type lockset consists of a mechanical door lock controlled by an electric actuator designed into the door frame. This actuator is powered by an external power supply connected to the fire alarm panel. Wiring runs inside the door frame instead of running from the power supply, through the door and to the door lock hardware. This method reduces the associated expenses related to electrified hinges, door modification and wiring. Cons: This design requires that existing locksets be sent back to manufacturers for minor modifications and retrofitting.
Steps of System Installation
During an alarm condition, the door must go from being fail secure to fail safe, instantly. Following the installation guidelines below will ensure it does just that.
Door Hardware Installation or Retrofit. To ensure the stairwell re-entry system activates appropriately during a life safety emergency, the owners should inspect the current stairwell doors and determine if modifications to the door hardware are needed.
Supply Power Sources to Each Stairwell Door. For a stairwell re-entry system to work properly, each stairwell door must be provided a power source that is connected to the fire alarm system. In most cases, engineers will design these power sources so they are connected to a main power panel at the lowest level of the stairwell. This main power panel is then connected through a dry contact relay to the fire alarm system. Upon activation of an alarm, the fire alarm system cuts power to the dry contact relay and the stairwell doors connected will lose power and unlock.
Provide a Fire Alarm Interface. A reputable fire alarm contractor should be brought into the design process to ensure the fire alarm interface and programming is done correctly. The dry contact relay must be programmed correctly to ensure that in the event of an alarm, power to the contact is interrupted, thus unlocking the stairwell doors. The interface to the fire alarm system must also include an interface that allows the local fire department to immediately and completely unlock all stairwell doors.
Provide Door Signage on Stairwell Doors. Upon installation of the new or modified stairwell locking hardware, each stairwell door should be provided with appropriate signage that alerts an individual of what floor they are on and where the next egress point is located.
Conduct a Test of the Stairwell Re-Entry System. The final installed system should be tested to ensure that when activated, all stairwell doors unlock properly and immediately. A test should also be conducted on the system to ensure the interface allows the local fire department to unlock all stairwell doors.
Stairwell re-entry systems can save lives. Scenarios in which the stairwells are either always locked or always open can create unsafe conditions both during life safety emergencies and in normal building occupancy. Professional engineering consulting firms can provide valuable direction and support when designing a stairwell re-entry system. Building owners should take a pro-active approach to ensure the safety and security of all occupants that reside or work inside their buildings.