An RCD (residual current device) and an RCBO (residual current breaker with overcurrent protection) look alike, sit on the same shelf at the store, and both react to current leakage. That leads people to treat them as interchangeable, but they're actually devices with different functions, and inside a panel they solve slightly different problems.
Here's what actually separates them, what each one protects against, and how to pick the right option for a given circuit.
What an RCD does
An RCD only monitors current leakage — for example, when part of the current escapes through damaged insulation or through a person who accidentally touches a live wire. When it detects an imbalance between the live and neutral conductors, it trips the circuit quickly. What an RCD does not do is protect against overload or short circuit — a separate breaker is always required alongside it for that.
What an RCBO does
An RCBO is essentially an ordinary circuit breaker and an RCD combined into one housing. It trips the circuit for overload, short circuit, and current leakage all at once. That's convenient in terms of panel space and simplifies the wiring diagram, but if one function fails, the entire device has to be replaced.
RCD vs RCBO: a comparison
Here's a condensed comparison of the key parameters that makes the practical difference clear.
| Parameter | RCD | RCBO |
|---|---|---|
| Leakage current protection | yes | yes |
| Overload / short circuit protection | no, needs a separate breaker | yes, built in |
| Panel space | RCD + breaker — two modules | one module |
| Cost | cheaper individually, but plus a breaker | pricier per unit, saves space |
| Replacing after a fault | RCD and breaker can be replaced separately | replaced as a whole unit |
Situations where leakage protection is essential
- Bathrooms — high humidity and contact with water.
- Kitchens — washing machines, dishwashers, water heaters, and other appliances with metal casings.
- Socket circuits on a balcony, in a garage, or outdoors.
- Children's rooms — as extra protection against accidental contact with wiring.
In all these cases the circuit needs either an RCD paired with a separate breaker, or an RCBO — which specific option depends on the panel layout and budget.
What to choose for an apartment panel
A common setup is one RCD on the incoming supply or on a group of wet-area circuits, followed by separate breakers for each line: it's cheaper and needs fewer RCD modules overall. RCBOs are handy where a specific circuit needs independent protection without affecting neighboring groups — for example, a dedicated one for a water heater or washing machine, so a leakage fault doesn't cut power to the whole apartment's lighting.
Either way, it's worth working out the final layout with an electrician: what matters isn't just module count, but also the RCD type (AC, A), the trip sensitivity, and the overall load on the circuit.
When to call an electrician
If an older panel has neither an RCD nor an RCBO anywhere, that's worth a consultation, especially for wet areas. An electrician will pick the right devices for specific circuits, check compatibility with the existing wiring, and lay out the panel so that one device tripping doesn't cut power to the whole apartment. ELECTRIC ASTANA handles this kind of work 24/7, around the clock; the cost of installing RCDs or breakers is quoted after inspecting the panel.