The Electrical Panel: Breakers, RCDs and Circuits

How circuits are grouped in a home consumer unit, what breakers, RCDs and RCBOs do, and why clear labelling and panel location matter.

The electrical panel is the control centre of a home's wiring, yet in a renovation it often gets the least attention. In a panel where every circuit hangs off one or two breakers, a small fault plunges the whole flat into darkness, and finding the right breaker among unlabelled ones becomes guesswork. A well-built panel improves safety and makes everyday life simpler.

Why circuits are split into groups

Connecting every load in a flat to one cable is both dangerous and inconvenient. Splitting circuits serves several purposes: each cable is sized for its own load, a fault switches off only one area, and repairs or inspections do not require cutting power to the entire home.

A typical apartment layout looks like the list below, though the actual scheme is set by the designer or electrician according to the load:

• general lighting (sometimes split into two or three groups by room);
• socket circuits for the rooms;
• kitchen worktop sockets;
• a dedicated circuit for the electric oven or hob;
• separate circuits for the washing machine and dishwasher;
• air conditioners;
• the bathroom, underfloor heating and water heater.

Putting powerful appliances on their own circuits matters both to keep cables from overheating and to avoid tripping other devices.

What a circuit breaker protects

A circuit breaker protects the cable: when current exceeds the permitted level, through overload or short circuit, it opens the circuit. That is why its rating is chosen first of all by the cable cross-section of that circuit, not by the power of the appliance connected. Fitting a high-rated breaker to a thin cable is a common and dangerous mistake: the cable heats up, insulation deteriorates, and the breaker never trips.

The mistake is often made with good intentions. When a breaker keeps tripping, the owner or a passing handyman swaps the "weak" breaker for a stronger one, and the problem seems solved. In reality the circuit is now carrying more than it can handle and the protection has simply been switched off. Frequent tripping is a signal to move some load to another circuit or run a new one.

RCDs and RCBOs: protecting people

A breaker does not protect a person from electric shock, because leakage current may be far too small to overload the cable. That job belongs to the residual current device, or RCD. It compares the current going out along a circuit with the current coming back and trips when there is a difference, for example when current flows to earth through a human body or a damp wall. For personal protection an RCD with 30 mA sensitivity is normally used.

RCDs are especially important on circuits linked to wet areas: bathrooms, kitchens, washing machines, underfloor heating and balcony sockets. An RCBO combines a breaker and an RCD in one housing and saves space in the panel. Which to use depends on panel size and number of circuits; what matters is that both kinds of protection are provided.

RCDs have a test button. Manufacturers recommend pressing it periodically; if the device does not trip, call an electrician.

Labelling and a circuit diagram

Every breaker in the panel should carry a clear label: "Kitchen sockets", "Bedroom lighting", "Living room air conditioner". A simple diagram stuck inside the door saves time later for both the owner and any other electrician. When the renovation ends, keep the updated version together with the photographs of concealed work.

Panel location and spare capacity

The panel must be accessible. A unit installed deep inside a wardrobe, behind clothes or blocked by furniture becomes a problem in an emergency. A hallway or entrance area is the usual choice. Keep it away from damp places such as the bathroom and not directly next to water pipes.

When choosing the enclosure, it makes sense to leave spare module spaces. If you later need to add an air conditioner, an electric water heater or smart home equipment and there is no room left, a second panel will have to be mounted.

At handover, check that:

• breaker ratings match cable cross-sections;
• wet-area circuits are protected by an RCD or RCBO;
• neutral and earth conductors are correctly connected to separate bars;
• every breaker is labelled and the diagram is inside the door.

The electrical division of Zaferoğlu İnşaat carries out electrical work, including cable installation, in apartments, offices and public buildings. Send a photo of your current consumer unit and we can look at which circuits should be split during the renovation.