- System Operation
The main function of the system is to monitor any alarms, smoke detectors, beacons and emergency break glass units which may be activated. The sounder will trigger and depending on the zone in which the fire has broken out and the adjoining zones which may be affected a relevant tone will sound as further explained below.
The overall system operation is controlled via the Fire Alarm Control Panel (FACP) which receives information from input devices (smoke detectors, heat detectors etc), then processes the information and triggers an output device (audio or visual alarm) if there is the threat of a fire. All the information from each FACP can then be overseen from the control room BMS which acts as the master device which is constantly monitoring the system.
A conventional control panel is an alarm system that can only detect on/off signals and would be classed as an open-loop system. Conventional systems use separate wiring circuits called zones to relay information to the panel regarding the condition of the initiating devices. The panel monitors the condition of the detection devices throughout the whole system, with separate zones used to help pinpoint the location of the alarm. These systems allow the use of inexpensive detection devices and fire alarm control panels.
An addressable control panel is a system using a signalling technique, which allows a control unit to identify a specific initiating device or group of devices by location (in the case of Forth Valley Acute Hospital each zone is determined by each block, ranging from ‘Block A- Accident and Emergency’ to ‘Blocks T&U- Mental Health’).
Addressable fire alarm control panels (FACP), or intelligent fire alarm control panels, usually specify the number of detectors and modules that will be operated by the FACP. This is the same as the number of addressable devices. These are separate circuits or paths directly connected to the main control room as found at FVAH. This type of BMS can be determined as a closed-loop system. For example, the zone in which the alarm has been triggered will actuate as normal but it will also send a signal back to the FACP that the system is ‘IN ALARM’, which will send a signal to each alarm in the adjoining zones either in the next block or the floors directly above or below that there is a fire and set-off an intermittent alarm. All of this can be overseen from the control room and because of the addressable detector the exact location of the potential fire can be detected.
- Main component parts & their function
In this chapter I will explain the main components in which the L1 fire alarm system comprises off:-
3.1 Fire Alarm System
An automatic fire alarm system is designed to detect the unwanted presence of fire by monitoring environmental changes associated with combustion. In general, a fire alarm system is either classified as automatic, manually activated, or both. Automatic fire alarm systems can be used to notify people to evacuate in the event of a fire or other emergency, to summon emergency forces aid, and to prepare the structure and associated systems to control the spread of fire and smoke.
Fig 1.0- Typical example of an addressable L1 Fire Alarm System
- Fire Alarm Control Panel (FACP)
This component, the hub of the system monitors inputs and system integrity, control outputs and relays information which gets passed back to the control room.
Fig 1.1- Addressable Fire Alarm Control Panel
- Smoke Detector, Beacon & Sounder combined unit
This is a combined alarm unit which automatically detects the presence of smoke and within the one unit set’s of a beacon (also known as a strobe) for the hearing-impaired that there is an emergency and the sounder is triggered.
1.2- Typical intelligent Smoke detector, beacon & sounder
- Heat Detector, Beacon & Sounder combined unit
Again this is a combined alarm unit that responds to changes in . Typically, if the ambient temperature rises above a predetermined an alarm signal is triggered. Thus setting of the beacon and sounder as before.
1.3- Typical intelligent Heat detector, beacon & sounder
- Manual Break Glass Unit
This component is classed as an active fire protection device which is usually located next to emergency exits and stairwells, and can be activated by breaking a pane of glass to release an internal spring operated mechanism, which in turn initiates an alarm on the fire alarm system.
Fig 1.4- Typical British Standard Manual Call Point
- Operation (of main components)
This chapter will see the discussion of how the Consys BMS software controls various components in the L1 Fire Alarm System:
- Fire Alarm System
They provide system flexibility, intelligence, speed of identification and more importantly, a wide scope of control in the event of a fire or potential emergency.
This level of control is achieved because the system detectors are wired in a loop around the building with each detector or sensor having its own unique address. The system can contain a number of loops depending on the size of the system and design requirements, for FVAH an 8 loop system with the ability to network 125 addressable devices per loop has been used.
The Fire Detection and Alarm Control Panel ‘communicates’ with each detector or sensor individually and receives a status report as to whether it is healthy, or approaching alarm or fault conditions. Therefore, should an incident occur, the fire alarm control panel is able to display the nature of the incident and precise location of the device in question. This feature speeds up the ‘response’ process and enables fast and measured control procedures to be brought into force to minimize the effects of the incident.
- Fire Alarm Control Panel (FACP)
In an addressable FACP as used at FVAH, detectors are wired in a loop around the building with each detector having its own unique ‘address’. The system contains 8 loops which ‘communicates’ with each detector individually and receives a status report, i.e.:- ‘HEALTHY’, ‘IN ALARM’, or ‘IN FAULT’. As each detector has an individual address the FACP is able to display/indicate the precise location of the device in question, which obviously helps speed the location of an incident.
- Smoke/Heat Detector, Beacon & Sounder combined unit
Addressable detectors are in themselves, intelligent devices which are capable of reporting far more than just fire or fault conditions. For example, most detectors are able to signal if contamination within the device (dust etc) reaches a pre-set level enabling maintenance to take place prior to problems being experienced. Addressable detectors are also able to provide pre-alarm warnings when smoke/heat levels reach a pre-set level, enabling investigation of the fire to take place prior to a full evacuation alarm and fire brigade signalling taking place.
- Manual Break Glass Unit
In terms of control, the manual break glass units will all be visible on the graphics and as all other equipment will each have an individual address. If for example there was a potential fire which was spotted and manually triggered by a member of staff or the public it would show up on the control room fire alarm system as being ‘IN FAULT’. The system would pinpoint the exact location of where the threat may be and the address which would in turn set off the sounders in that zone and trigger the intermittent alarm in the adjoining zones.
- System performance
First and foremost the full Fire Alarm System performance at Forth Valley Acute Hospital must be in accordance with the requirements of the Chief Fire Officer. In the specification the requirements are ‘the need for fire safety personnel to instantly understand the status of a panel in an emergency situation’. Additional requirements which have been met are: - ‘the compliance with regulatory requirements, multiple protocols (ie: - FACP’s), simple and robust design, intuitive to use, easy to maintain, low running costs, easy to expand, easy to install and easy to configure’.
Overall the system performance is far superior to that of a standard (non-addressable) L1 fire alarm system as the BMS is constantly sending, receiving and monitoring ever component of the fire alarm system and in the event of a fire can pinpoint the exact location. Furthermore they can control the spread of fire via additional components not talked about, such as smoke fire dampers closing, automatic fire doors closing giving a one hour fire barrier.
- Suggestions/ Modifications/ Improvements
This chapter will discuss how the system could me modified/ improved.
With a BMS L1 Fire Alarm Systems they are constantly evolving and bringing new technologies to the market, so what may seem advanced to day may become common place tomorrow.
Through working with ADT at FVAH it can be said that the system as a whole isn’t 100% user friendly. I would suggest to make the system more understandable the addresses each component is given be relevant to the zone, block and floor level they are on. For example if a heat detector is on the first floor, ward block ‘G’ (zone 21) that the reference be ‘HD/L1/G/021’, Rather than at present where the address bears no relation for an untrained operative to understand where the heat detector is, such as ‘08/021/A26’. This refers to the FACP which it is supplied from (panel number 8), the zone 021, and the number of the component supplied from the FACP (A26).
- Bibliography
7.1-
7.2-
7.3-
7.4-
7.5-
7.6-
7.7-
7.8- Quotations from 5.0 System Performance extracted from: ‘(NHS) Forth Valley Acute Hospital- Building Specification (Revision 7, 2009)’
Images
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- Proved by ADT – Drawing Reference:- ADT-G(67)X-X-001
Appendix 1- System Schematic
Fig. 2.0- FVAH Networked Fire Alarm System Schematic
