How to wire a residual current device (RCD) — step by step

A Residual Current Device (RCD) is an essential component in every modern electrical installation. It protects people from electric shock in the event of faulty appliances or cables. In this article, we will look at how to correctly connect a two-pole RCD.

What is an RCD and why is it important

An RCD monitors the difference between the current entering and leaving the conductors. If a leakage current occurs – for example, by touching a live wire or an appliance fault – the protection switches off the circuit in less than 0.04 seconds. Models with 30mA sensitivity are designed for human protection and are mandatory in bathrooms, kitchens, and outdoors.

What you will need

- Two-pole RCD (2P) — for example, Schneider Electric Easy9 40A 30mA or 63A 30mA
- Screwdriver with insulated handle
- Wire strippers
- Stranded or solid core copper cable

RCD terminals

The standard terminal designations for a two-pole RCD are:
- 1 — phase input (L)
- 2 — phase output (L)
- N input — neutral input
- N output — neutral output

Inputs are at the top, outputs at the bottom. Always check the diagram for the specific model.

Step-by-step connection

Step 1 — Turn off the power
Before any work on the electrical panel, switch off the main circuit breaker. Check with a tester that there is no voltage.

Step 2 — Mount the RCD on a DIN rail
The RCD is clipped onto a DIN rail in the electrical panel. Press the bottom tab and tilt it slightly until it clicks into place.

Step 3 — Connect the input (top)
From the main circuit breaker or busbar, bring the phase to terminal 1 and the neutral to terminal N input. Strip the cable by about 12-15mm, insert it into the terminal, and tighten the screw.

Step 4 — Connect the output (bottom)
From terminal 2 and N output, the wires run to the circuit you are protecting – sockets, lighting, etc.

Step 5 — Test
After turning on the power, press the TEST button on the RCD. It should trip immediately. If it does not trip, there is a problem with the connection.

Choosing the right model

- 40A — suitable for protecting domestic circuits with moderate loads (lighting, sockets)
- 63A — suitable for circuits with higher loads (boiler, cooker, air conditioning)

Both models have 30mA AC sensitivity — the standard for human protection.

See available models in our store:

- Residual Current Device 2P 40A 30mA AC:

- Residual Current Device 2P 63A 30mA AC:

Important: Electrical installations must be carried out by a qualified electrician. The information in this article is for educational purposes only.