Analogue Addressable Fire Alarms
The second technology is far more advanced and is normally found in the larger premises. This is called Analogue Addressable and will pin point the exact location of a fire through zoning and also the detector in fire having it’s own number (address) and text allocated to it.
This system is wired in a loop and unlike the non addressable the zoning is done through programming, so the same cable can pass through the whole building. A typical loop can have up to 126 devices which are constantly tested by the control panel. On this system should a part of the loop wiring become damaged short circuit isolators ( SCI ) either side of the fault will shut down that particular section of wiring and continue to operate with the reminder of the wiring and devices. Again unlike the non addressable which would loose the zone in fault.
When a detector on the loop senses a fire, information is passed back to the control panel which is then processed and a decision is made by the panel not the detector whether it is a fire or not. Unlike the non addressable system each detector or MCP reports it analogue value back to the control panels front end processor ( FEP ). The device reports back whether it’s in a pre-alarm, alarm or fault state by differing analogue values. Under normal conditions the levels are low but if smoke enters the detector chamber the level will rise until it reaches a predetermined threshold and enters fire condition.
Individual detectors can have their threshold levels altered so for example can be less sensitive during the day and more at night if required. Another advantage it has over non addressable technology is that individual detectors can be isolated instead or an entire zone. This system can dramatically reduce unwanted alarms and unlike non addressable will let the user aware if a detector has become faulty.
In the event of a fire or fault the control panel offers text description of the condition, unlike the non addressable which will only illuminate relevant led’s. This make the location of fire and faults much quicker.
The panel operates on the same voltage as the non addressable and also has battery back up.
As with both non addressable and addressable all wiring must be in fire resistant cable.
There is also wire free radio based analogue addressable fire systems which have all the benefits of a hard wire system but with the obvious advantage of no cabling required to all the devices. This is an ideal option for listed buildings such as Churches, where cable runs would look unsightly. There is also no damage to the building or mess from drilling. Installation is far quicker and far less labour intensive but has the drawback of having to replace every battery in each device approximately every 5 years. The equipment is more expensive than hard wired but on the larger installations the reduction in labour costs can be balanced against the cost of hardwired.