Consumer Unit Installation and Replacement in Odemira and the Costa Vicentina

Fuses, Breakers and the RCD: What Each One Protects

There is a confusion here that costs money and sometimes more than that: the breaker protects the installation, the RCD protects people. They are different things and one does not substitute for the other.

The breaker — or the fuse, in older boards — cuts when too much current flows and the cable heats up. It prevents fires. The residual current device compares the current going out with the current coming back and cuts when some is missing, because that difference is passing somewhere else: through a person, through damp pipework, through a faulty machine. It operates in thousandths of a second and it is the only thing between a shock and an electrocution.

A board with only fuses, or with breakers but no RCD, is protecting the house and not the people in it. That is what we keep finding in houses built or rewired before the 1990s, which is a good part of the stock in Odemira and the Alentejo coast.

Type AC or Type A — Why It Matters Now

Not all residual current devices detect the same kind of fault, and this changed with modern appliances. Type AC, which is what sits in most older boards, only detects purely alternating leakage. Type A also detects leakage with a DC component.

The practical point: induction hobs, inverter air conditioning, heat pumps, machines with variable-speed drives and EV chargers generate exactly that kind of fault. In a board with a type AC device, the protection exists but may not see the fault that is now the most likely one — which is the worst of all outcomes, because it gives a sense of safety that does not match reality.

So the question is not only do I have an RCD? but what type do I have, and what do I have connected in the house. You can check it on the device itself, where the symbol is printed.

Surge Protection: the Local Problem

A good part of the grid in the Odemira municipality and along the Costa Vicentina is still overhead, and late-summer storms are frequent. A surge does not need a direct lightning strike: a strike a kilometre away induces a spike on the line that reaches the sockets and silently destroys the power supplies of everything connected — router, television, borehole pump, induction hob, solar inverter.

A surge protective device fitted in the consumer unit diverts that spike to earth before it reaches the appliances. It is a component you do not notice until the day you do, and it costs a small fraction of replacing a household's equipment.

To work, it needs a functioning earth, and that is the point that usually fails in older houses. Whenever we replace a consumer unit we measure the earth resistance — without that, neither the RCD nor the surge device delivers what it promises.

When the Unit Really Does Need Replacing

Not always. Very often an RCD and a couple of circuits are added to a board that still has space and is in good condition, and that solves it. Full replacement is justified when there are porcelain fuses, when there is no room to separate circuits, when the enclosure is of combustible material, or when the installation is about to be significantly extended — induction hob, air conditioning, heat pump, EV charger.

Circuit separation is the part most underestimated. A properly built unit has lighting, sockets, kitchen, heating and outdoors on separate circuits: when something fails, only that part of the house loses power, and the fault is located in minutes rather than by trial and error in the dark. In an isolated house, that is the difference between an inconvenience and losing the water pump on a Sunday.

If the replacement is for a new supply contract or because of a sale, a technical file and certification are required. We do the interior installation and the documentation it requires.

How do I know which type of RCD I have?

It is printed on the device itself, next to the test button: a sine wave means type AC; the same wave with an added line means type A. If you have an induction hob, inverter air conditioning or charge an electric car at home, it is worth confirming — and it takes seconds.

The RCD trips for no apparent reason. Is the device faulty?

Rarely. An RCD that trips is doing its job: there is leakage somewhere. The most common causes are a water heater whose element is starting to fail, damp in an outdoor box, or an ageing washing machine. It is found by elimination, circuit by circuit, and resolved on the visit in most cases.

Do I need surge protection even in a small house?

What decides it is not the size of the house but the type of grid and the value of what you have connected. With overhead supply — the situation across much of this municipality — and with a borehole pump, solar panels or electronics in the house, it almost always pays for itself. In an urban area with underground supply the risk is considerably lower.

Will I be without power all day?

No. Replacing a consumer unit in an ordinary house is a day's work, with the power off for a few hours of it. We agree the window in advance, and if there is equipment that cannot be switched off — a full freezer, a server, medical equipment — we assess at the visit how to work around it.