An RCD is the small switch in the distribution board that cuts off the power as soon as a leakage current occurs somewhere, for example when a hairdryer falls into a sink full of water or an old cable draws in moisture. It measures whether as much current returns as flows in, and if that difference becomes too large, it cuts the power within a fraction of a second. This is the most important protection against electric shock for people.
When renting a holiday home, one thing plays a major role here: an RCD usually protects not one circuit, but a whole block of circuits at once. If it trips, everything behind that block goes out, and that can also include the circuit with the refrigerator. That is precisely why it is worth knowing how your own distribution board is structured before you receive guests.
What a circuit actually does
A circuit is the other protection in the distribution board, and it is often confused with the RCD. A circuit protects against overload: too many appliances at once on one outlet circuit, which would cause the cable to get too hot. Think of the kitchen, where a kettle, microwave and air fryer together demand too much from one circuit. The circuit breaker then trips to prevent a fire.
The difference is therefore: a circuit looks at how much current flows through the cable, an RCD looks at whether that current flows properly. A house usually has several circuits, but often only one or two RCDs, each monitoring a number of circuits at the same time. How this distribution runs exactly varies from house to house and by building age, and this is something you can check when you consult the knowledge base about your distribution board.
Why this goes wrong slightly more often with guests
Guests use a holiday home differently than residents who know the house. They try out appliances, use their own chargers and hairdryers, and don't know which outlets belong to which circuit. An outdated charger, a damp bathroom or a cheap travel adapter can cause a small leakage current that causes the RCD to trip, even if nothing is broken. For the guest, that is inconvenient; for you as a landlord it is especially inconvenient if the refrigerator also goes out and the contents spoil over a weekend when you are not there.
This is precisely why a module like Staywatt's deliberately keeps the refrigerator circuit separate: if a guest's balance reaches zero, normal outlets and lighting go out, but the refrigerator circuit stays on. What a module cannot solve is an RCD that trips for a completely different reason, namely a fault somewhere in the wiring or in a guest's appliance. That remains a matter for the distribution board itself, not for the consumption system above it.
What an electrician actually checks here
In plain language: an electrician checks whether the refrigerator circuit is on a different RCD than the circuits that guests use frequently, so that a leakage current at the bedroom outlet does not automatically take the refrigerator with it. For those who want the exact specifications: in practice, for personal protection an RCD with a rated residual operating current of 30 mA is usually used, and in older installations it is possible that one RCD of this type covers the entire house. An electrician can advise whether it makes sense to put the refrigerator circuit under its own RCD, and which circuits in the existing wiring might be suitable for this. This is a technical assessment that varies from house to house and is best discussed with an authorised installer.
What this means for your situation
Whether your distribution board is already arranged so that the refrigerator is separately protected, you can only be certain after a look in the cabinet or a question to your installer. For most landlords this is not an urgent concern, but it is something to sort out properly once before the season starts. It saves a lot of hassle with spoiled stock and an angry guest who has to go to the local supermarket with a cool box.
Would you like to see how your situation looks before you call the electrician? Do the free quick-scan or browse through the topics in the knowledge base; those who prefer to first understand how the system itself works will find that via an overview of how measurement and billing work. If you are unsure whether your question has already been answered here, check the most frequently asked questions from other landlords, or go through in a few steps the selection guide that immediately gives an indication for your situation.