Design of the Automatic Fire Alarm System (AFAS)
As the contractor, we completed the design of the Automatic Fire Alarm System (AFAS) for the restoration work of the building annex.
AFAS Project Documentation
This section of the reconstruction project contains solutions for organizing the Automatic Fire Alarm, Notification and Evacuation Control System, and radio broadcasting for the restoration of an administrative building with an annex. This project is completed in accordance with current norms and rules.
The safety of maintenance personnel and the integrity of technical equipment is ensured by adhering to the measures and rules provided for in the design. The project uses serially produced equipment with valid safety certificates.
Purpose of the AFAS Section
Automatic Fire Alarm System
The automatic fire alarm is designed to protect material assets and premises from the occurrence and spread of fire. The automatic alarm system allows for rapid detection of fire sources in the premises and corridors of the building annex, simultaneously transmitting the alarm signal to the notification system.
The fire alarm system generates control signals for:
- Disabling supply and exhaust ventilation
- Closing fire dampers
- Opening smoke exhaust valves
- Activating smoke exhaust and air pressurization systems
- Disabling air conditioning
- Disabling air thermal curtains
- Lowering elevators to the evacuation floor and opening elevator doors
- Activating fire alarm and evacuation control
- Unlocking doors equipped with access control systems
The AFAS in the annex is implemented based on an integrated security and fire system. The installation of the automatic alarm is organized in conjunction with the security alarm system, access control system, and video surveillance system.
Fire Signals from the System
Technological and informational signals from the system software are displayed at the security workstation, providing system status information in graphical and textual form on the building's floor plans, with logging, long-term archiving, management, and report generation.
For backup control of AFAS devices when the personal computer is disconnected, a control panel is used. The panel, as part of the fire alarm, monitors and collects information from devices, logs events, indicates alarms, manages arming/disarming, and controls relay outputs. The personal computer and panel are located in the security room, which is staffed 24/7.
The control panel connects to the personal computer via an RS-232 interface. To eliminate galvanic coupling between the personal computer and the devices via the RS-232 interface, which could cause interference, an interface repeater with galvanic isolation is used.
Fire Alarm System Sections
For visual monitoring of the AFAS sections in the integrated network, the project uses an indication unit. In the annex, the fire alarm is implemented using addressable controllers connected to the RS-485 communication line of the control panel. The controller has one addressable two-wire communication line. Addressable fire detectors are included in the line.
In accordance with modern design requirements, at least two detectors are installed in each room of the building, except for rooms with wet processes and stairwells.
The following are used in the premises and corridors of the building annex to detect fire:
- Addressable analog smoke detectors
- Addressable analog thermal maximum-differential detectors
- Manual addressable call points
The network controller receives messages from the connected addressable analog detectors, as well as smoke density and temperature values at the installation point.
The AFAS of the administrative building annex includes the connection of executive relay blocks to the control panel's RS-485 line, the outputs of which connect to the notification system and access control – unlocking evacuation routes.
How AFAS Control Works
The design includes an RS-485 interface repeater with galvanic isolation, into which the interface with the system devices controlling the building automation is connected. Solutions for the RS-485 interface with the necessary automation control devices are provided in the project documentation.
In the server room and document storage rooms, a fire suppression system is provided. To activate suppression in the automatic fire alarm system, an RS-485 interface repeater with galvanic isolation is used. The transmission of the Fire signal to the centralized monitoring console is carried out via a dedicated telephone line using a telephone informer connected to the panel's RS-485 interface.
AFAS Delivery Set
From the AFAS of the building annex, an AFAS is organized in the building of the diesel power station located on the designed site. The design of the fire alarm for the power station building is included in the delivery set. Design solutions for laying the cable connecting the alarm of the administrative building and the fire alarm of the power station are provided in the section for on-site networks.
The RS-485 interface line between the alarm system devices is laid with a specific cable type. Since the devices in the network are powered from different sources, a third conductor in the cable is necessary to combine the 0V contacts of all devices in the network.
High System Reliability
To increase the reliability of the AFAS, this project uses a ring topology for the RS-485 interface. This scheme maintains full functionality in case of a single break and partial functionality with multiple breaks. Interface repeaters provide galvanic isolation of ring segments and protect the interface from short circuits by disconnecting the shorted segments.
The designed equipment is installed in cabinets in the dispatcher's room and in cross-connection cabinets on all floors.
Building the Notification and Evacuation Control System in the Annex
The Notification and Evacuation Control System is designed for automatic notification of people in the building about an emergency for their evacuation. The premises and corridors of the administrative building are equipped with a type 3 voice alarm and evacuation system. According to the code of practice, the number, placement, and power of the speakers must ensure the required sound level in all areas of permanent or temporary stay of people.
Zoning of the Notification System
The automated system for voice and emergency notification and music broadcasting is organized based on modern digital equipment, fully meeting safety standards.
The building features a multi-zone notification system which performs:
- Monitoring the fire safety situation of the facility
- Generating and transmitting fire alarm signals to all premises with permanent or temporary presence of people
- Automatic redundancy through additional control means
- Uninterrupted operation
This project provides for the installation of central notification equipment in the security room. Eleven notification zones are organized in the building. Zone selection and notification sequence are carried out automatically or manually from the operators' microphone consoles with a zone selector installed in the security and dispatch rooms.
The Notification System for the entire building and for individual dedicated zones provides:
- Broadcasting voice messages about a fire, both automatically and manually from operators' microphone consoles
- Broadcasting programs and emergency radio broadcast messages
- Automatic broadcast of special texts about the need for evacuation, evacuation routes, directions of movement, and other actions necessary for people's safety upon receiving a Fire alarm from the system
Functions for Emergency Situations
To enable the transmission of very important emergency government messages, weather forecasts, and broadcast of radio programs from the city radio broadcast network, an input from the city radio broadcast network is provided at the input of the preamplifier-mixer of the notification system. A digital tuner for receiving and reproducing AM and FM radio programs is also included.
The designed notification system can be used simultaneously in music broadcast mode and emergency notification mode. Upon receiving a signal from the AFAS, music broadcast will be stopped and an emergency notification will be made to the corresponding zones.
Indicating Evacuation Direction
Notification of evacuation routes and directions is carried out using light direction indicators and Exit signs provided in the project's electrical lighting section. The central equipment of the Notification System is housed in a 19" cabinet in the security room.
The following are to be installed in the annex:
- In corridors and rooms with suspended ceilings – ceiling speakers of various wattages
- In rooms without suspended ceilings and on the floor – wall-mounted speakers of various wattages
The notification speakers do not have volume controls and are connected to the notification network without connectors.
Project Part: Radio Broadcast Network
The organization of radio broadcasting in the building is carried out from the city radio broadcast network. Connection to the city radio broadcast network is performed under a separate contractor's project after obtaining technical conditions.
According to the design results, a radio mast is to be installed on the building roof, to which the main line of the city radio broadcast network is connected. The mast's attachment on the roof is provided in the structural solutions section of this project. A subscriber transformer is installed in a cabinet on the technical floor. From the subscriber transformer, the radio broadcast feeder cable is routed through a limiting box to a radio broadcast outlet in the security room.
A subscriber three-program loudspeaker is installed in the security room. A connecting cable is laid from the loudspeaker to the notification system rack for the possibility of transmitting emergency government messages and broadcasting radio programs from the city radio broadcast network through the notification system in the administrative building.
Best Practices for AFAS Cable Installation
Installation should be performed after lighting fixtures are mounted. The distance between system elements and power cables must be at least 0.5 meters. Addressable loop circuits are executed with specific cable types.
Smoke detectors are installed in rooms without suspended ceilings directly on the ceiling surface. In rooms with suspended ceilings, smoke detectors are mounted using a mounting kit. Manual call points are placed on the wall at a height of 1.5m from the floor level.
Detector installation must be carried out in accordance with the relevant fire safety codes. Notification system lines throughout the building are executed with fire-resistant cables. Speakers are connected with specific cable types from junction boxes in corridors and rooms.
Designed AFAS cables are laid:
- Along building corridors – in the space above the suspended ceiling in a corrugated conduit on wire cable trays
- In building rooms with suspended ceilings – in the space above the suspended ceiling in a corrugated conduit attached to walls and suspended ceiling structures
- In the security room, dispatch room – in an electrical duct
- In building rooms without suspended ceilings – openly along walls in mini-skirtings
Between floors, the designed cables are laid in the low-current riser – on the wall on wire cable trays, in the floor slab – in steel pipes. For cable passages through walls, sleeves made of steel pipes are provided.
Cable routes for the fire alarm and notification network throughout the building must be executed according to equipment layout plans and considering the placement of the lighting network and other utilities. Equipment installation must be performed in accordance with this documentation, the manufacturer's technical documentation, and the equipment operating instructions.
AFAS Power Supply and Grounding Specifics
According to the Electrical Installation Rules, the installation of the automatic fire alarm and voice notification system are classified as first-category reliability consumers, which is ensured by power supply from two independent inputs via an Automatic Transfer Switch and from an uninterruptible power supply.
Power supply for the designed fire alarm devices is provided by 12V DC voltage from redundant power supply units. The batteries of the redundant power supplies ensure device operation in standby mode for 24 hours and in Alarm mode for at least 3 hours. The power sources are supplied with 220V AC voltage from power panels provided in the electrical equipment documentation.
Power supply for the notification system equipment units is provided by a power source producing 24V DC and 220V AC. When the main power is disconnected, the notification system automatically switches to independent power sources - batteries, ensuring continuous operation in standby mode for 24 hours and in alarm mode for 1 hour. The design includes a charger that automatically turns on when battery charging is needed.
The power source is supplied with 220V AC voltage from the power panel located in the security room, as provided in the electrical documentation of this project. Grounding of the power supply units is performed via the 3rd wire of the power cables.
Grounding of metal cabinets for the AFAS and the 19" cabinet for the notification system is done with specific wire types from the protective earth bars provided in the electrical documentation. Lightning protection for the radio mast installed on the building roof is provided from the lightning protection mesh on the roof as per the structural documentation of this project.
Labor Protection and Safety
This working documentation for the AFAS is developed in accordance with health and sanitary standards. The noise produced by the equipment does not exceed permissible levels. The installed equipment does not emit harmful substances into the environment. Construction and installation work for cable laying, equipment installation, and mounting must be performed in compliance with labor safety and health measures.
During the installation and configuration of the fire alarm, notification, and radio broadcast equipment, the handling rules and safety measures specified in the operational documentation, installation instructions for the equipment and components, as well as the Electrical Installation Rules, must be observed. To protect personnel servicing the technological equipment, the project provides for grounding of the designed equipment, selection of appropriate cables, and their marking.
Equipment grounding must be performed in accordance with the Electrical Installation Rules and building codes for electrical devices, as well as the requirements of relevant safety standards and the technical documentation of the manufacturers of the designed equipment. The resistance of the protective grounding must be no more than 4.0 Ohms.