Why is half of my house without power?

Why half your house has no power: the possible causes

Losing power in half the house is more common than a total blackout. The good news is that it is usually quick to narrow down, because it tells you that electricity is reaching your home and the problem is in one part of the installation.

1. A switch in the fuse box has tripped

This is the first thing to check. A Spanish fuse box has a main switch, one or more RCDs (diferenciales) and an MCB (magnetotérmico) for each circuit: lighting, sockets, kitchen, bathroom. If your board has several RCDs, each one cuts its own group of circuits. If one is down, unplug the appliances in that area and reset it. If it trips again, there is a leak or an overload on that circuit.

2. A fault on a single circuit

If everything is up in the fuse box but the sockets in a bedroom or the lights in half the house do not work, there may be a burnt joint in a junction box, a loose cable behind a switch or socket, or a faulty breaker that looks as if it is on. It is typical of older installations, where many points hang off the same box.

3. A phase has dropped (three-phase supply)

In homes and premises with a three-phase supply, the installation is split across three phases. If one fails, at the service connection or on the grid, only the part connected to it goes dark. You will notice because some sockets and lights work and others do not, without anything having tripped.

4. A fault in the riser cable or on the grid

The individual riser cable (derivación individual) runs from the meter to your fuse box. A loose or burnt terminal can cause partial cuts, voltage dips and flickering lights. If the problem is before your meter, on the grid, it is a job for the distributor, which in Seville, Spain is e-distribución.

What to do in the meantime

• Check the fuse box and note what is down.
• Ask a neighbour whether they have the same problem.
• Do not keep resetting a switch that trips: every attempt stresses the installation.
• If you smell burning, switch off the main switch and touch nothing else.

When to call an electrician

Call if everything is up in the fuse box and part of the house is still dark, if a switch will not hold, or if your neighbours have power and that part of your home does not. In Seville, Spain, our 24-hour emergency electrician attends partial and total power cuts at any hour.