By Kent Traders · Updated 23 October 2026 · 8 min read · UK

An RCD plug adaptor is cheap, small and easy to fit, which is why people treat it as a shortcut. It is not a replacement for the RCD in the consumer unit. It is a second option for a single socket, and knowing the difference decides which one you buy.

Does an RCD plug adaptor replace a fixed RCD?

No. A fixed RCD sits in your consumer unit and protects the circuits it covers. Electrical Safety First says it protects you from electric shocks if a product is faulty. A plug-in RCD adaptor sits in one socket and protects only what is plugged into it.

The charity's advice has two parts. If your fusebox has no RCD protection, use a plug-in RCD on the socket the product uses. And use an RCD with all outdoor electrical equipment. Read the full Electrical Safety First garden safety advice. If you are unsure what your fusebox has, ask a registered electrician to check.

Fixed, plug-in or inline: what each covers

Three formats cover most jobs. They differ in where they sit and what they protect.

Both Masterplug units are double pole and list a maximum load of 3,120W. That is 13A at 240V, so check the wattage of your equipment before you plug in.

Non-latching RCDs: why they trip on a power cut

Both units are non-latching. The ARCDKG page explains it: every time the supply to the RCD is interrupted, it trips and needs resetting. After a power cut, nothing restarts until you press reset.

That is useful for a hedge trimmer, because it will not spring back to life unattended. It is a problem for a freezer, because a trip you do not notice can spoil the contents.

Outdoor checks that matter more than the adaptor

Electrical Safety First lists the checks that decide whether outdoor power is safe. They matter as much as the RCD.

• Use only leads rated for outdoor use, weather-resistant with moulded connections.
• Fully unwind cable reels, and look for a thermal cut-out.
• Never plug an extension lead into another one.
• Check cables, plugs and connections for damage before every use.
• Switch off and unplug before cleaning, adjusting or checking equipment.
• Keep outdoor tools dry, and do not use them until they are dry.

Our guide to cable reel overheating explains the thermal cut-out in detail. For lead choice, see the extension leads collection. For a fixed outdoor point, see the weatherproof accessories.

Worked example: a hedge trimmer on a 15m reel

Take a 600W hedge trimmer, which is our assumed figure. At 240V it draws about 2.5A, well inside the 13A limit of either unit. Prices below were checked on 22 October 2026.

The plug-in route is the cheapest and the simplest. The inline route costs £5.46 more and gives you an IP65-rated unit in the lead, but it is rewireable, so have a competent person fit it. Either way, the reel is fully unwound before use.

Spotting an unsafe plug-in RCD

Electrical Safety First lists a recall of the OANON Safety RCD Plug Adapter Portable Circuit Breaker. The notice says live parts may be accessible, the plug does not meet BS 1363 dimensions, it lacks the fuse link required by BS 1362, and it carries no conformity marking. Users are told to stop using it immediately. Read the Electrical Safety First recall notice.

The lesson is simple. Buy a known brand, look for a fused plug and proper markings, and treat an unbranded adaptor from a marketplace listing with suspicion.

Where RCD adaptor choices go wrong

Five mistakes come up again and again.

• Treating an adaptor as a replacement for the fixed RCD in the fusebox.
• Using a non-latching adaptor on a freezer.
• Daisy-chaining one extension lead into another.
• Running an indoor lead outdoors.
• Buying an unbranded adaptor with no fused plug or markings.

What to buy: Masterplug RCD options

Three Masterplug items cover the garden jobs above. All were in stock on 22 October 2026. Browse the full Masterplug range for more.

Check before you order:

• Whether your fusebox already has RCD protection.
• The equipment's wattage against the 3,120W limit.
• A thermal cut-out and outdoor rating on any reel, confirmed on the datasheet.
• Whether the equipment can safely sit on a non-latching adaptor.

FAQs

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