During an alarm, there is often a need to activate other systems or mechanisms in the building to help facilitate safe evacuation of the building’s inhabitants. System integration is when a fire alarm control panel (FACP) manages another system. Emergency control functions, like elevator recall, HVAC controls, and fire dampers, are types of system integrations. Accordingly, the mechanisms used to activate those controls are referred to as emergency control function interfaces (ECFI).
There are two ways to integrate emergency control functions into your fire safety system—by using relays or output modules. Relays are intuitive devices that may be used to activate emergency controls using the notification appliance circuit. On the other hand, addressable control modules are used in fire and security systems to apply more fine tuning in your ECFI setup, and they are connected to the FACP through the signaling line circuit. In the following sections, I will further elaborate on how these two modules work.
A relay is an electrically operated switch that establishes or interrupts an electrical connection between multiple circuit contacts. Activated by an electric pulse or control signal, it can switch ON or OFF, thanks to the presence of an electro-magnetic coil. Power from the NAC will energize the electro-magnetic coil, which will move the switch from the normally closed position into the normally open position. This action completes the circuit, which then allows power to run across an area known as the common terminal. As a result, the emergency control output receives power and is able to activate its alarm condition functionality.
Output modules are addressable, so they are located on the signaling line circuit and receive input signals from the FACP. Subsequently, when the module receives this input, it can control output devices, emergency controls and activate devices of higher voltages. The most typical use of an addressable output module is to engage a separate NAC circuit located elsewhere in the building. Thus, in essence, output modules can also be considered relays.
Read More: Addressable vs. Conventional Fire Alarm Systems >>
Relays and control modules may both be used as emergency control function interfaces, but they have several differences. One key difference is that multiple control modules may be managed independently by the same SLC, while a standard relay cannot. This means that you may have multiple output modules on the same SLC with different states.
Output modules can be a better option than using NAC circuit relays, since you will often want the emergency control functions to remain active even after the notification devices are silenced. If power is no longer being supplied to the NAC to silence your horns or strobes, all devices on that circuit will shut down. However, this can be a problem since you may also want to keep the door holders, dampers and other devices active if there is still smoke in the building. Output modules solve this problem because they respond to signaling from the FACP over the SLC circuit.
Examples of Emergency control functions include door controls, elevator controls, smoke control, pressurizing stairwells, opening up skylights or roof hatches, and more. The primary objective of these functions are to limit the spread of fire and smoke, while also assisting people with safely navigating away from danger. The possibilities for emergency controls continues to grow as builders innovate and modernize our facilities.
Magnetized door holders are used to hold doors open during normal activity. In an alarm state, these are released to help isolate smoke and fire to one location. In some instances, passageways in fire-resistant structures require protection with fire doors. To ensure your protection, these are usually fitted with automatic door closers.
During a fire emergency, elevators can be redirected to certain floors, or be shut down entirely. When the lift mechanism is required to have sprinklers, the elevator is typically shut down to protect any occupants. In some cases, the fire alarm control panel might be programmed to send the elevator to a designated floor. If smoke is detected on that floor, the elevator is redirected to another level to safeguard those evacuating the premises.
Smoke inhalation causes more fire-related deaths than do the fires themselves. As a result, it is important to control smoke by utilizing external systems, like HVAC. Following an alarm state in the FACP, fans and ventilation will be turned off to prevent the spread of toxic smoke.
In addition, stairway pressurization fans take in clean air from outside and push smoke back, away from the stairway. This process is essential because stairways are valuable escape routes, and the presence of smoke may cause injury to people trying to escape; smoke also deters people from using the escape route, causing them to seek another pathway of escape. In summary, stairway pressurization is an important facet of a complete high rise protection system.
Stairway pressurization fans will usually be equipped with a duct detector, which will detect if smoke is near the roof or the fan. Subsequently, the system will close a fire damper and prevent smoke from being spread into the stairwell. These devices are crucial in high-rises, where stairways are often the only means of escape, and may be required depending on the design and construction of the building.
We have a lineup of relays and modules, that are designed to be used as emergency control function interfaces. We also perform in-house systems design if you need more assistance with complex fire system layouts. Our professional team at firealarm.com is eager to meet your fire protection needs.
