What happens to your security system during a power cut?

There are few things in life more frustrating than a power cut. It always seems to happen at the most inopportune moments – when we’ve just settled in for a night of Netflix or when the baby has just dropped off to sleep. But aside from the inconvenience of having your night ruined, when the power shuts off due to an electrical fault or a problem with the grid, what happens to your security and fire alarms?

While most fire alarms are battery-powered anyway, one thing you’ve probably noticed if you own an intruder alarm is that, in the event of a power cut, it is likely to activate. The reason for this is simple – alarm systems typically use a backup battery power supply that kick in when the power shuts off. If that battery is dead when the mains power is cut, the control panel battery is unable to keep the system running. So the alarm isn’t informing you there’s an intruder, it’s informing you there’s a problem with the alarm.

How to stop an intruder alarm during a power cut

If you’re hearing a single tone rather than a continual beeping, you should be able to diffuse the situation (and the noise) by simply inputting your code. This tells your alarm you understand there has been a power cut. If the external alarm is beeping, however, you’ll need to either wait for around 20 minutes or replace the internal battery.

More advanced alarms can charge their own batteries through the mains’ power so are unlikely to ever run completely dry. So, if these alarms are ringing during a power cut there is probably a more serious fault that needs to be addressed by a security professional.

Replacing an intruder alarm battery

This should only ever be done by a trained security engineer. Note that if you have a maintenance contract with a security company you should always let them do the battery replacement.

The job involves isolating the supply to prevent electrical shocks and unscrewing the lid of the control box. This might sound simple but it’s very easy to make a mistake if you don’t know what you’re doing.

What if my alarm still doesn’t work after power is restored?

In the event your alarm is still not working when the power comes back on, you might need to reset it. If entering your master code doesn’t work then you might need to call out an engineer. If the power cut was caused by an electrical storm it can result in a blown fuse or something even more sinister. In this case, don’t try fixing the problem yourself, call out a trained security engineer.