Thinking of installing a domestic burglar alarm?
Firstly, what is it for? A strange question I know, but generally people install these things either to protect the house when they're not present, or so they can sleep easier at night without worrying that every audible knock and bang is someone wanting to get their hands on the family jewels (so to speak). Or both of course.
In the case of the former, you should have a trusted neighbour who has keys and the disarming code, otherwise there is a risk it will sound while you're getting drunk in Benidorm much to the annoyance of those left behind back in Blighty. To prevent it becoming a noise nuisance, the law states an alarm should be fitted with a 20 minute cutout, and if still sounding after an hour the local council can take steps to silence it even if that means entering your home (with a warrant) and landing you with a bill for their trouble.
For those who are more concerned simply with sleeping soundly when things go bump in the night, you should be prepared for the odd false alarm in the small hours. It shouldn't happen often but you should expect it. Usually there are seven reasons for a rude awakening:
1. Little Tiddles has accidentally been shut into a room where there's an active sensor.
2. A room has temporarily changed layout, e.g. rearranged during decorating or boxes from a delivery being stacked up allowing a cat/mouse to jump up and enter a sensor zone it wouldn't normally be able to stray into.
3. An insect has flown/crawled across the face of a sensor.
4. A door or window has not been secured properly and movement has tripped a magnetic sensor.
5. Inspection/maintenance is past due and parts have become worn/damaged over time or the battery backups are failing.
6. Movement of warm air from a vent, flue or other source is blowing across the face of a sensor.
7. None of the above.
Yes, number seven can happen; the alarm sounds and you have no idea why. The cause is likely to be number three, however said insect has then scuttled away before you've turned up in your longjohns armed with a big brass Cluedo-style candlestick for the clocking of any would-be blaggards.
To mitigate against these things happening, sensors can be placed where pets shouldn't ordinarily activate them, pet sensitive sensors can be employed and double-knock zones can be set where two positive hits are required within a certain time window before the alarm sounds to cut down on the likelihood of false hits.
The main control panel needs to be sited somewhere sensible. In the case of an alarm you want to set when entering/exiting the building, this is usually in a hallway near the front door. If you only use it at night, somewhere closer to the stairs or even on the landing may be more sensible or a secondary pad installed. Either way, entry, exit and walkthrough zones are set so you can get to the panel to shut it off before the bell-box outside starts warbling and annoys the neighbours. Any sensors outside these zones will sound the alarm immediately if tripped. The control panel itself should be within a PIR sensor range so nobody can stand in front of it without being detected.
How many sensors are required and of what type will depend on the premises to be protected. Each sensor needs to be wired back to the panel, so this either means unsightly wires clipped to walls or installed in trunking, or wires chased into walls, run under floors or above ceilings. Hidden wires look neater are less able to be tampered with. If you have a major redecorating project on, it’s wise to get an installation fitted before wallpapering or laying new laminate flooring/carpet so the walls can be chased and floorboards pulled up to conceal the cables. Because of the spaghetti of wiring involved, you don't want to install more sensors than you need. If I were doing the work, I'd have to perform a site survey to look at what areas should be covered in your house to ensure the effective placement of minimum sensors to keep costs and wiring down without compromising on the functionality.
Each zone can be configured differently to allow for normal movement through the house. If the alarm sounds, the panel will show which zone set it off so you know which room you should be checking. If desired, you can also have extra keypad(s) fitted to control the panel from another room and panic buttons to activate the alarm manually.
Anti-tamper comes as standard, so if any wires are cut or if the front panel is removed from a sensor or the main alarm panel, it will sound the alarm. The panel will require its own mains supply either on its own circuit from the consumer unit or a fused spur off the sockets. It will have a battery backup so it can continue working in the event of a power failure.
Wireless alarms are available, but I wouldn't fit one. They rely on the bell-box being charged by solar power and all components require their own battery supply to operate. This means lots of battery changes every so often, but more importantly it can't be relied upon in my opinion. Poor siting of the bell-box will mean it doesn't get the sunlight it needs to charge the battery, and batteries degrade over time. Any sensor with a poor battery or any wireless signals not received may mean the alarm fails to sound when you need it to. Swag-bag clad undesirables will recognise wireless installations and can overcome them more easily.
One last point to bear in mind - no alarm can provide an absolute assurance of protection. Whoever installs it will be unable to give you a guarantee in writing that it will be impossible for you to suffer losses through a burglary, and they’ll all have a small print disclaimer denying liability for loss or injury in the event of the alarm being disabled or malfunctioning. There isn't an alarm on the market that is guaranteed burglarproof, but having a well fitted installation is a deterrant and will give you peace of mind that you've taken the right steps to protect your family and property.
Update:
I pulled the plug on alarm and CCTV installations in 2018 as detailed here.
AFF4