⚡️ What is an RCD and Why Is It Important?

Explained by Anthony from AJOB Electrical Ltd – Trusted Electricians in Leeds & Wakefield

🔍 What is an RCD?

An RCD (Residual Current Device) is a life-saving safety device designed to prevent electric shocks and reduce the risk of electrical fires. It constantly monitors the flow of electricity in your circuits and disconnects the power within milliseconds if it detects even a small leakage of current — such as electricity flowing through a person or faulty appliance to earth.

🛠️ How Does an RCD Work?

In a healthy circuit, the current flowing in the live wire should match the current returning through the neutral wire. If there's a difference, the RCD senses it and trips the circuit immediately — often in under 30 milliseconds. This can prevent serious injury or death.

Standard fuses or circuit breakers don’t offer this level of protection.

🔄 RCD Types – Why Type A is Now Essential

Until recently, many consumer units used Type AC RCDs, which can only detect faults involving standard alternating current (AC). However, modern appliances — such as washing machines, dishwashers, LED lighting, and induction hobs — often create pulsed DC currents that Type AC devices cannot detect.

If your RCD can't recognise the type of fault, it simply won’t trip — which puts you and your home at risk.

🔁 Even Fairly New Consumer Units May Be Outdated

We frequently come across homes with consumer units installed in the last 5 to 10 years that still use Type AC RCDs.

But here’s the key point:

BS 7671 (18th Edition) Wiring Regulations were updated in 2018, with Amendment 2 in 2022, to require Type A RCDs for most circuits in domestic homes.

That means even fairly recent installations may now be non-compliant and not offering adequate protection for today’s appliances.

✅ Why Type A Is Safer

Here's a breakdown of how Type A compares to the older Type AC:

Detects AC faults
Type AC: ✅
Type A: ✅
Detects pulsed DC faults (common in modern appliances)
Type AC: ❌
Type A: ✅
Safe with modern electronics (like LED lights & smart devices)
Type AC: ❌
Type A: ✅
Compliant with latest wiring regulations (BS 7671:2018 + A2:2022)
Type AC: ❌
Type A: ✅

At AJOB Electrical, we only install Type A RCDs or RCBOs (which combine RCD and circuit breaker protection) in all new consumer units.

🧰 Do I Have the Right RCDs?

You can check your consumer unit by looking for labels marked “AC” or “A” near the test buttons.

If your RCDs are marked “AC”, or if your fuse box is over 10 years old, it’s worth having it inspected.

We can check this as part of a free visual assessment or an EICR (Electrical Installation Condition Report).

🏠 What We Do at AJOB Electrical Ltd

We’ve upgraded hundreds of homes across Leeds and Wakefield to safer RCD and RCBO protection. When we upgrade your system, we’ll:

Replace outdated devices with modern Type A RCDs or RCBOs
Test and certify your installation
Clearly label circuits for easy reference
Explain what’s been done and why — in plain English

🙋‍♂️ Frequently Asked Questions

What does the “AC” or “A” label on my fuse box mean?
“AC” means the RCD only detects standard AC faults.
“A” means it also detects pulsed DC faults from modern appliances. If you see “AC”, it’s time to consider upgrading.

Why are Type AC RCDs still being installed?
Unfortunately, some budget installations still use Type AC RCDs to save cost. But they no longer meet modern safety standards and are not compliant with current regulations.

What’s the difference between an RCD and an RCBO?
An RCD protects multiple circuits against earth faults.
An RCBO combines the functions of an RCD and a circuit breaker into a single device for each circuit. RCBOs are neater, more reliable, and safer — and are now our recommended standard.

📍 Serving Leeds & Wakefield Homeowners

We help customers across Leeds, Wakefield, Rothwell, Morley, Garforth and surrounding areas upgrade their home electrics to meet the latest safety standards.