Overload your electrical system and the RCD (or MCB fuse) will do its job and trip cutting the power to the overloaded circuit and flicking the switch from on to the off position.
After the surprise of the sudden power cut, all that’s usually required is to flick the switch back to ‘on’ and the power’s restored.
There are times, however, when the RCD fuse will not reset. Turn the switch back on, remove your finger and the switch flicks back to ‘off ‘ (and the power with it).
There’s an issue somewhere that’s why the RCD won’t reset.
Here’s how to find the issue, remember always call a qualified electrician if you’re unsure or feel unsafe, electricity’s dangerous.
The Number One Cause
There are too many appliances plugged into a single circuit
The number one cause of an RCD that won’t reset is an overloaded circuit. If you’re using an extension lead with a number of appliances running off the same circuit unplug the extension lead.
Try resetting the fuse it’ll probably stay on now.
Run your appliances off of separate circuits, and it shouldn’t happen again, ideally use a single appliance to a single circuit.
If multiple appliances running off a single circuit are not the cause, then there’s probably another appliance in your home causing the RCD issue.
Switch off all appliances in your home one at a time and test the RCD each time.
By process of elimination, you’ll find out if a single appliance is stopping the RCD from resetting (you switch off an appliance test the RCD, and it stays on)
Keep the appliance unplugged and don’t use it (there’s a fault, and it could be dangerous) Get it checked out by an engineer most appliances come with a warranty, so you get an engineer sent out for free. Failing that check your home insurance.
Issues With The Electrical System
If the RCD won’t reset and it’s not an appliance, then there’s probably an issue with your electrical system.
Get your system looked at by a qualified electrician, don’t leave it an electrical fire is a real risk.
Issues can appear within the electrical system if you’ve fitted new switches, sockets or lights, drilled holes anywhere in the house, suffered any flood damage or suffered corrosion in the system.
A qualified electrician will fully test your system, identify and fix any issues that are preventing your RCD from resetting.
If an electrician finds no issue with the electrical system, then it might be the RCD fuse itself which is faulty.
The RCD Needs Replacing
RCD fuses last ten years (or more) a faulty RCD might not reset. While RCD’s can be bought cheaply from your local DIY store and can be replaced easily, you should always use a fully qualified electrician.
There are different types of RCD fuses with varying amp ratings, designed for different parts of the system. The right fuse must be fitted; otherwise, your electrical system could be dangerous.