Tightly integrated electrical and mechanical systems can perform many tasks over and above intelligent fire detection. Neil Woodward of Hochiki explains the advantages of this approach,
The ultimate objective of interdisciplinary research into ‘intelligent buildings’ is to combine electronics and civil engineering into the concept of IBMS (Integrated Building Management Systems). Central to this concept is a system which can control, monitor and optimise services such as fire and security alarms, lights, heating, access control and CCTV, ventilation and air-conditioning. It should, additionally, secure the networks and databanks of computer systems.
These systems save energy while increasing reliability, security and efficiency. A fully integrated system can detect and even overcome a malfunctioning part of the system or associated services, thus circumventing serious consequences, including a fire.
Such tightly integrated mechanical and electrical systems can perform every task, from controlling the building’s environment to maintaining high-speed data networks and emergency backup power generators. A sophisticated system can also monitor staff attendance and availability.
Distributed intelligence
An industry proven approach to fire safety in IBMS projects is the concept of ‘distributed intelligence’, because when system intelligence is spread over the complete fire system, its operation is more efficient as the signals are processed at the point of generation.
This selective distributed intelligence can yield increased reliability, speedier response times, and minimise false alarms and maintenance costs. There are significant benefits due to ‘on-sensor’ and ‘on-panel’ intelligence being prudently distributed across a fire detection system.
An intelligent addressable system can be defined as a system of devices, designed to interface with an intelligent control panel that has built-in intelligence to communicate with fire sensors at their individual addresses, and to interrogate them at a remote distance.
Intelligent fire detection systems now represent more than 50 per cent, by value, of all new systems installed worldwide. They can operate on two fundamentally different principles: either the sensor transmits the fire sensitivity information to the panel, where the alarm, fault and maintenance decisions are made; or the sensors determine whether a fire condition is present and transmit the decision to the panel. In both cases, within the devices, complex algorithms can be configured to process the incoming environmental data; hence, the choice of technique is dependent on the core system design. These are key criteria a designer should consider:
– Rapid verification. Smart sensors can rapidly evaluate the monitored environment, and make comparisons with the value set within the sensor from the control panel. This minimises the data on the system and allows a verification and a rapid response back to the control panel to indicate a fire condition.
– Diagnostics. Diagnostic capability is essential. Hochiki cites the specific example of its integral drift compensation to counteract possible smoke sensor contamination, which could affect a device’s performance. To prevent such degradation, the Hochiki ESP analogue addressable system automatically re-calibrates all smoke sensors once every 24 hours, supported by an built-in test facility that allows the fire alarm control panel to adjust the alarm threshold levels to compensate for contamination.
– Intelligence minimises maintenance. The main advantage of this technology is that maintenance of these sensors is pre-planned, taking account of the trend of accumulated build up of dust and dirt, to ensure sensor performance and system integrity is never compromised. A significant innovation has been the design of removable and replaceable chambers for photoelectric smoke sensors, thus extending their operational life. This permits rapid and low cost chamber replacement without involving any costly re-calibration.
– Programmable. The sensitivity of a smart sensor can be transmitted from the control panel to configure the sensor remotely. Intelligent sensors can thus be easily re-programmed to match changing operational conditions. This ensures that sensors are always programmed with the correct sensitivity at the correct location.
– Responsive. As the smart sensor originates the data from the fire location, the response times are excellent. For instance, at 1.5 second initiation, a signal transmitted by Hochiki’s ESP (Enhanced Systems Protocol) yields a response time that is over six times faster than requirements where statutory regulations apply.
– Alarm reduction management. A digital communications protocol, exemplified by ESP, employs numerous advanced techniques to minimise the potential for false or unwanted alarms. These techniques, in conjunction with the control panel, yield the far reaching benefits of a capability for alarm reduction management (defined by Hochiki as ARM).
– Alarm verification. An important system design element is programming individual sensors according to location conditions, such as hotel bedrooms and kitchens. Hochiki uses an alarm verification technique with a time delay integration algorithm that confirms the existence of smoke or heat over the programmed period, eliminating unwanted activations from transients.
Benefits of open protocol
Since maintenance costs are a continuing significant consideration in IBMS design, it is important to take into account the advantages of an open protocol, which permits interfacing with leading independent control panel manufacturers. An open protocol, like Hochiki’s ESP, provides an open choice on system design, installation and maintenance. Such flexibility provides freedom and security as it prevents any one supplier from locking in the user.
In the context of IBMS, signal interference in fire data communications can originate from many sources: mobile phone usage, industrial machinery or varieties of transmission corruption. Hazards of such transmitted ‘noise’ can cause unwanted alarms on some systems due to corruption of signals.
Accordingly, in today’s congested airwaves, exceptional immunity to false alarms requires high specification, ultra-intelligent, robust communications for the provision of high reliability and system integrity.
In terms of error detection, fire data protocols such as ESP now exist, where the communication between the fire detection devices and the panel are digital, and at the end of each transmission a Checksum protocol is transmitted. The ESP principle applies both Parity and Checksum error detection principles to every packet of data. This ensures that the data being transmitted between the control panel and the devices can be verified to ensure that no corruption has taken place, and eliminates unwanted activations from external noise. If corruption has occurred, the system perceives the data as not reliable and the information is discarded, requesting re-transmission of the data.
According to a major user of Hochiki’s technology, there are numerous methods by which building services can be controlled: ‘time-based’ to provide heating and lighting services, for instance; or ‘optimiser parameter-based’ by using a representative aspect of the service, such as temperature for space heating or lighting.
In addition, electrical and security system contractors routinely install low voltage communication network cables for a wide range of intelligent systems, incorporated at several levels. Services and equipment that use these networks include: security; multi-channel TV; telephones, door phones and intercoms; PC and Internet networks; surveillance cameras; parking vehicle sensors; communicating thermostats; motorised window blinds and curtains; entry systems; and even irrigation systems.
The latest concept in integrated building management systems is ‘interfacing occupancy information to building controls’. This means that, each service has an impact on others. For example, if there is a fire in the building, the whole process of fire-controlling mechanisms could be triggered without damaging the infrastructure and data.
The fire alarm initiates, along with the lift switches and, while other electrical devices shut off, electronically managed doors open automatically.
