Domakihub How to Test Your RCD and Keep Your Home Safe
A plain-language guide to the monthly test button, what to do when it fails, and when to call an electrician.
Reviewed by Domakihub home & decor pros · 2026-06-23 · 5 min read
A residual current device (RCD) is the small switch inside your consumer unit that trips in milliseconds if it detects a dangerous earth-leakage current — the kind that can kill. The video above shows the basic test in action; this guide walks you through each step, explains what the result means, and tells you exactly when to stop and call a licensed electrician. Whether you own a villa, a holiday rental, or an apartment in Greece, verifying that your RCDs work is one of the few electrical checks any careful homeowner can and should do regularly.
What Is an RCD and Why Does It Matter?
An RCD continuously compares the current flowing out through the live wire against the current returning through the neutral. When those two values differ by as little as 30 milliamps — a sign that electricity is escaping through a person or a fault — the device trips the circuit in under 40 milliseconds, which is fast enough to prevent cardiac arrest.
In Greece, Type-A RCDs rated at 30 mA are required by ELOT HD 384 for sockets and bathroom circuits in all dwellings built or rewired since the 1990s. Holiday rental properties and hotels face stricter scrutiny because guests are unfamiliar with the local installation; a non-functioning RCD in a pool-house socket or a bathroom is a serious liability.
Understanding the Two Types of Tests
There are two fundamentally different ways to verify an RCD. The first is the built-in test button, which every RCD has and which any occupant can press safely — this is the only test covered in this guide. The second is an RCD tester (also called an ELCB tester or loop/RCD multifunction tester), which injects a calibrated fault current and measures the exact trip time in milliseconds. That second test is a professional instrument test and must be carried out by a qualified electrician using certified equipment — it is required as part of a full periodic inspection (Πιστοποιητικό Ηλεκτρολογικής Εγκατάστασης / ΥΔΕ) in Greece.
The test-button check described below tells you whether the mechanical trip mechanism is still working. It does not measure trip time or verify the 30 mA threshold — which is why it complements, rather than replaces, a professional periodic inspection.
How to Test Your RCD Using the Test Button
- 1
Locate your consumer unit and identify every RCD
Open the cover of your distribution board (πίνακας διανομής). RCDs look like ordinary circuit breakers but have a small button marked 'T' or 'TEST' — sometimes coloured red or blue. Modern boards often have one or two RCDs protecting groups of circuits. Note how many there are and which circuits each one covers, as shown on the board's legend.
- 2
Warn others and prepare your space
Let anyone else in the property know that power will cut briefly. Turn off or unplug sensitive equipment — computers, smart TVs, HVAC controllers, any device whose settings could be corrupted by a sudden power loss. You do not need to turn off the main switch; only the circuits protected by the RCD being tested will drop out.
- 3
Press and hold the TEST button firmly for one to two seconds
Press the button marked 'T' or 'TEST' on the RCD. The switch handle should snap to the OFF (or tripped) position immediately. If it does, the mechanical mechanism is functional. If the handle does not move, the RCD has failed and must be replaced by an electrician — do not attempt to open or repair it yourself.
- 4
Reset the RCD and restore power
Flip the RCD handle back to the ON position. It should click firmly into place. Power will return to the affected circuits. If the handle refuses to reset, or if it trips again within seconds without an obvious load connected, there may be a downstream fault or the device itself is faulty — call a licensed electrician before using those circuits.
- 5
Record the result and set a reminder
Write the date and result (passed / failed to trip / failed to reset) on a sticker inside the board cover or in a maintenance log. Greek regulations and IET guidance recommend testing RCDs at least every three months in domestic properties and monthly in rental or commercial premises. A failed test is not something to defer — an RCD that cannot be reset must be replaced before those circuits are used again.
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FAQ
- How often should I test the RCD in my holiday rental in Greece?
- Monthly is best practice for any property rented to guests. The higher turnover of occupants, the wider range of appliances they bring, and the increased liability exposure all justify the extra vigilance. Record every test date in a maintenance log — this also demonstrates due diligence if a safety incident is ever investigated.
- The TEST button tripped the RCD but it will not reset — what should I do?
- Do not use the affected circuits until an electrician has inspected them. A refusal to reset usually means there is a persistent earth-leakage fault on one of the downstream circuits — a damaged appliance, a wiring fault, or moisture in a socket. Disconnect all appliances on those circuits, then try resetting again. If it still trips, the fault is in the fixed wiring and requires a qualified electrician with a loop/RCD tester to locate it.
- Can I test an RCD with a multimeter or a DIY tester instead of the built-in button?
- Simple multimeters cannot test an RCD correctly — they do not inject a calibrated fault current. Proprietary plug-in RCD testers (sold at hardware stores) can perform a basic trip check, but they do not measure trip time and are not a substitute for a professional instrument test. The built-in TEST button is the safest and most reliable option for routine checks by a non-electrician. For a full verification of trip time and threshold, book a periodic inspection with a licensed Greek electrician (ηλεκτρολόγος) who carries a certified multifunction tester.