One power cut in January, and everything falls in sequence

The scenario is entirely ordinary. An RCD tripping on water in an outdoor light fitting. A thunderstorm. A fault on a sump pump. Load shedding. Work by the network operator.

In an occupied house it is a ten-minute inconvenience. In an empty one it is the start of a sequence.

I. The sequence, hour by hour

H+0. The breaker opens. Complete silence. The internet router goes down: no connection, so no reporting. Cameras stop recording.

H+1 to H+8. The alarm panel runs on its backup battery — generally between four and twenty-four hours depending on the model. It should have sent a mains-failure signal. That assumes the signal left before the router died, and that it had an attentive recipient.

H+8 to H+24. The alarm battery runs down. The house is no longer monitored at all. The freezer has begun to warm; it will hold twenty-four to forty-eight hours depending on how full it is.

D+1. Frost protection has been off for twenty-four hours. In January the house now tracks the outside temperature with a lag of a few hours.

D+2 to D+4. Ventilation has stopped. Internal air loads with moisture, condensation begins on cold surfaces.

D+3 to D+7. If a freeze arrives, undrained pipework is exposed. The critical moment is not the freeze but the thaw: ice splits the pipe, water only emerges when it warms, often several days later.

D+5. The pool, filtration stopped, begins to deteriorate. Without frost protection, the plant room pipework is exposed in turn.

D+15 or later. Someone calls in and finds it. Or nobody calls in, and the owner finds it at Easter.

II. Why the failure does not announce itself

This is the vicious part. Almost every monitoring device depends on the very thing it is meant to monitor.

The router is mains-powered. So is the Wi-Fi camera. So is the home automation hub. So is the connected thermostat.

In other words, the event that should trigger the alert is precisely the one that destroys the alerting channel. It is a classic design fault, and it is present in most of the installations we take over.

III. The safeguards, by cost-effectiveness

1. Autonomous supervision. A battery-powered module communicating over a cellular or long-range network independent of the router, whose only job is to report loss of mains. This is the device to install first, before any other sensor. One to three hundred euros.

2. A UPS on critical equipment. A small uninterruptible supply on the router and alarm panel extends the window by several hours, enough to cover micro-cuts and let the alert leave.

3. An automatic reclosing contactor. A device that attempts to reset the RCD after a trip, useful for transient trips caused by moisture. To be fitted by an electrician, with the usual safeguards: you do not reclose indefinitely on a permanent fault.

4. Circuit separation. A well-designed consumer unit isolates the "survival" circuits — frost protection, ventilation, alarm, router, sensors — on dedicated protective devices. A fault on the outdoor lighting must not cut frost protection to the whole house. This costs a few hundred euros when a board is renewed, and it entirely changes how the house behaves in an incident.

5. Consumption tracking. Many smart meters allow the load curve to be viewed. Consumption falling to zero and staying there is a perfectly legible signal, available with no extra hardware.

IV. What to check after a cut

Once power is restored, several items do not restart on their own, or restart badly.

• The pool filtration pump: check the prime; a pump running dry destroys itself within hours.
• The sump pump: often the cause of the RCD trip in the first place, and a basement fills quickly.
• The hot water cylinder: on models with a day/night contactor, restart is not always automatic.
• The boiler or heat pump: frequently locked out, requiring a manual reset.
• Programming clocks: on equipment without backup, schedules revert to factory settings.
• The freezer: if the cut lasted more than twenty-four hours, the question is not whether it restarted but what is inside.

This is why recovery after a cut requires a physical visit, not just a green light on an app. The app will say the power is back. It will not say the filtration pump has been running dry for six hours.