Consumer Unit (Fuse Box) Installation and Replacement in Porto and Greater Porto

Signs Your Consumer Unit Needs Replacing

If you open the fuse box and find porcelain fuses or cartridges rather than circuit breakers, you are looking at an installation that is more than thirty years old. It does nothing to protect people from electrocution, because there is no RCD, and it does not protect the cables properly either. This is the situation we come across most often in the older buildings of Porto, Gondomar and Rio Tinto.

The second common case is a board with no residual current device. The RCD is the safety switch that cuts the power when current leaks to earth, and it is what stops an electric shock from becoming fatal. Without one, a water heater with a perforated element or a cable with worn-out insulation can go unnoticed until someone touches a metal surface.

There are other warning signs too: breakers tripping more and more often, scorch marks or melted plastic inside the unit, a smell of burning, and boards where circuits have been bolted on over the years until there is neither space nor any logic left. If air conditioning, an induction hob, an EV charger or a heat pump has been added to an old installation, it is very likely running at its limit.

What a Consumer Unit Replacement Includes

A properly specified new consumer unit has a main switch, one or more 30 mA RCDs protecting the circuits, and a circuit breaker sized for each individual circuit: lighting, sockets, kitchen, water heater, washing machine and dishwasher, air conditioning. Circuits serving wet areas and outdoor sockets go on separate RCDs, so that a leak on the balcony does not plunge the whole flat into darkness.

We also label every breaker. It sounds like a small thing, but it is what lets you sort out half of your future problems on your own: knowing exactly which breaker feeds the kitchen saves you switching everything off blindly and hoping for the best.

Where the existing wiring has no earth conductor, we tell you before we quote. Fitting a modern consumer unit to an installation without an earth improves protection against overloads, but it does not give you full protection against electric shock, and that needs to be clear before you spend any money, not afterwards.

How Long It Takes and What It Costs

Replacing a domestic consumer unit is normally a single day's work, with the power off for a few hours. We agree the date in advance so you can plan around it, particularly if you work from home or have chest freezers to think about.

The price depends on the number of circuits and the condition of the installation. A typical domestic consumer unit usually comes to between 400 and 900 euros including materials; a board for a detached house with many circuits, or one that means redoing the supply cables, costs more than that.

When the job warrants it, we issue the documentation needed for certification purposes. If you need the installation certified for a new contract with your electricity supplier or for selling the property, tell us at the very start, because it changes what has to be documented. Contracts, forms and any correspondence are in Portuguese, so if that is a hurdle for you, we can take care of that side as part of the job.

Surge Protection and Earthing: What Everything Else Depends On

An RCD only protects you if there is a sound earth conductor. Without an earth, leakage current has nowhere to go, the RCD may never detect the imbalance it is meant to detect, and you end up with protection that exists on the board but not in real life. That is why, whenever we replace a consumer unit, we always measure the earth resistance rather than assume it.

The surge protection device is the second component that is almost always missing. It does not take a direct lightning strike: a strike a kilometre away induces a spike on the line that reaches your sockets and quietly burns out the power supplies in your router, television, induction hob and solar inverter. A surge protector costs a fraction of what it takes to replace that equipment.

In parts of Greater Porto served by overhead lines, and in detached houses, this matters more than in the city centre. And if you have solar panels, it always matters: the array on the roof is the highest point of the house and a surge's favourite way in.

How do I know whether my consumer unit has an RCD?

Open the little door on the fuse box and look for a switch that is wider than the others, usually with a small button marked T or TEST. If there isn't one, the board has no RCD and your installation is missing its main protection against electric shock.

Will I be without power for long while it is replaced?

Expect a few hours without electricity on the day itself. We agree the timing beforehand and, if you have equipment that cannot be switched off, we look at how to work around it during the visit.

Is it worth replacing just the RCD rather than the whole consumer unit?

If the rest of the board is in good condition and the circuits are correctly sized, yes, it is a small and perfectly valid job. If the board still uses fuses or is crammed with circuits added over the years, it is money badly spent.

Do I need a new consumer unit to install an induction hob or air conditioning?

Often, yes, because that kind of equipment needs its own circuit and dedicated protection. We check the capacity of your board first and tell you whether any work is needed.

Can I add breakers to the consumer unit I already have?

If there is spare space, the board is in good condition and it already has an RCD, yes. We do this regularly and it is considerably cheaper than a replacement. It is not possible when there are porcelain fuses, when there is no room, or when the enclosure is made of combustible material.

What is the circuit chart, and why do you insist on it?

It is the record of what each breaker supplies. It looks like a detail, but it is the difference between tracing a fault in five minutes and fumbling around in the dark by trial and error. We always leave the board labelled and give the customer a copy of the chart.

How long will I actually be without electricity during the replacement?

In an ordinary home, a few hours within one working day. We agree the schedule at the outset and, if something cannot be switched off, such as a full freezer, a home server or medical equipment, we assess during the visit how to get around it.