What Causes an RCD to Trip?

A Residual Current Device (RCD) is designed to protect people from electric shock by disconnecting the power supply when it detects an imbalance in electrical current. While an RCD tripping can be frustrating, it usually indicates a genuine safety issue that should not be ignored.

Understanding what causes an RCD to trip can help homeowners, facilities managers and electrical professionals diagnose problems more quickly and restore power safely.

How an RCD Works

An RCD monitors the current flowing through the live and neutral conductors. In normal operation, the current in both conductors is equal. If some current leaks to earth—commonly referred to as an earth fault—the RCD trips, cutting off the supply in milliseconds.

Unlike an MCB (Miniature Circuit Breaker), which responds to overloads or short circuits, an RCD specifically protects against electric shock caused by leakage current.

Common Causes of RCD Tripping

1. Faulty Electrical Appliances

Damaged or ageing appliances such as washing machines, kettles or immersion heaters can allow current to leak to earth.

What users can do:
Unplug all appliances, reset the RCD, then reconnect items one at a time to identify the faulty device.

2. Moisture and Water Ingress

RCDs frequently trip in wet areas such as kitchens, bathrooms, garages and outdoor circuits. Moisture reduces insulation resistance and increases leakage current.

What users can do:
Check for damp fittings, dry the affected equipment, and ensure outdoor sockets and lighting have appropriate IP-rated protection.

3.Electrical Wiring or Installation Issues

Damaged cables, poor connections or ageing insulation within the distribution board can cause persistent earth faults.

What users can do:
If the RCD trips with all appliances disconnected, a qualified electrician should carry out insulation resistance testing.

4. Cumulative Earth Leakage

Modern installations often contain multiple electronic devices—LED lighting, IT equipment, EV chargers—each producing small leakage currents. Together, these can exceed the RCD’s rated sensitivity.

What users can do:
Split circuits across multiple RCDs or install RCBOs to reduce nuisance tripping and improve circuit discrimination.

5. Power Surges and Transient Events

Voltage spikes caused by lightning or switching operations can occasionally trip an RCD, particularly where surge protection is absent.

What users can do:
Fit surge protection devices (SPDs) to improve overall system stability.

Typical RCD Tripping Causes and Solutions

Choosing a Reliable RCD Protection with MK Circuit Protection

Reducing unwanted RCD tripping starts with using high-quality circuit protection devices. MK Circuit Protection offers a comprehensive range of RCDs and RCBOs designed to meet current UK wiring regulations, providing reliable performance and consistent sensitivity.

Engineered for durability and ease of installation, MK devices help minimise nuisance tripping while maintaining essential protection against earth faults and electric shock. For installers and end users alike, selecting proven circuit protection from a trusted UK brand can make a significant difference to long-term safety and reliability.

When to Seek Professional Advice

Occasional RCD tripping may be unavoidable, but frequent or unexplained trips should always be investigated. Ignoring the issue can put people and property at risk.

By understanding the common causes of RCD tripping—and by choosing dependable solutions such as those from MK Circuit Protection—users can ensure their electrical installations remain safe, compliant and reliable.

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