Tripping Circuits and RCDs: Safe Checks Before You Call an Electrician

A circuit that keeps tripping is annoying, but it is also the safety system doing its job. The breaker or RCD in your consumer unit is switching off the electricity because it has detected something it does not like. This guide explains what is likely to be happening, what you can check safely yourself and when you should stop and call an electrician. It applies to homes in England.

The advice here is limited to checks that do not involve opening anything or touching wiring. Electrical Safety First and NICEIC both advise against DIY electrical repairs. If you are in any doubt, leave it and call someone.

What the devices in your consumer unit do

Your consumer unit has several kinds of protective device, and they trip for different reasons.

• Circuit breakers (MCBs) switch off a circuit when it carries too much current, either because it is overloaded or because there is a short circuit.
• RCDs (residual current devices) switch off when they detect that current is leaking away from where it should be going, for example through a faulty appliance or damaged cable. Some are combined with a breaker, in a type called an RCBO.
• Fuses, in older units, melt when too much current flows. They have to be replaced rather than reset.

An RCD is an important protection against electric shock, so a trip is never something to ignore or to defeat. Do not tape down a switch or bypass a device so it cannot trip.

Common causes

• An overloaded circuit. Too many high-power appliances, such as a kettle, toaster and heater, on one circuit.
• A faulty appliance. Washing machines, tumble dryers, dishwashers, kettles, heaters and old power tools can develop faults that leak current, especially as they age or when water gets into them.
• Damp or water. Moisture in an outdoor socket, a light fitting, an extractor fan or an appliance can cause an RCD to trip, particularly in wet weather.
• Damaged cable or flex. A nail through a cable, a chewed flex, or a crushed extension lead.
• A worn component. Old fittings and old wiring can leak current as insulation degrades.
• A fault in the installation. Sometimes the problem is in the fixed wiring. This needs inspection and testing by an electrician.
• Nuisance tripping. An RCD can trip because of a lot of small leakages adding up across many appliances, or a surge such as a lightning strike. Your electrician can work out whether the device is at fault.

Safe checks you can do

Use your judgement. If there is a burning smell, scorching, smoke, noise or you can see damage, stop and skip to the next section.

1. Note what happened. What were you doing when it tripped? Which appliance was on? Did it happen after rain? Was it a bang, or quiet? This information is useful for the electrician.
2. Look at the consumer unit without opening it. See which switch has dropped down. A single circuit breaker points to that circuit. If the main RCD has dropped, more than one circuit is affected.
3. Unplug everything on the affected circuit. Switch off and unplug appliances and extension leads on that circuit, including those in the garden or garage.
4. Reset the device. With your hands dry, and standing on a dry floor, push the switch fully down and then firmly up. If it stays on, the problem may be something you unplugged.
5. Plug appliances back in one at a time. Switch each one on before you plug in the next. If the device trips when a particular item is connected, that item is the likely cause. Leave it unplugged and do not use it until it has been repaired or replaced.
6. Check for water. If it only trips in wet weather, look at outdoor sockets and lights for water, but do not touch anything damp. Leave the circuit off.
7. Test the RCD. Most RCDs have a test button. Pressing it should make the device trip. Electrical Safety First advises testing RCDs regularly, and the manufacturer's instructions will tell you how often. Pond pump supplies in particular are advised to be tested at least every three months. If the test button does not trip the RCD, call an electrician.

If the device resets and stays on and you can identify one faulty appliance, you may have solved the problem. If you cannot find the cause, the answer is not to keep resetting the switch.

What not to do

• Do not keep resetting a device that trips straight away. It is telling you something is wrong.
• Do not fit a bigger fuse or breaker, or replace a fuse wire with something thicker.
• Do not take the cover off the consumer unit, sockets or switches.
• Do not touch the unit or electrical items with wet hands or while standing in water.
• Do not use an appliance that smells of burning, is hot, or has damaged cabling.
• Do not use extension leads in a daisy chain. Electrical Safety First advises never plugging an extension lead into another extension lead.

When to stop and call an electrician

Call a registered electrician straight away if:

• there is a burning smell, smoke, sparks, scorch marks or a hot socket or consumer unit;
• an RCD or breaker will not stay on even with everything unplugged;
• the test button does not trip the RCD;
• someone has had a shock or a tingle;
• the trips are becoming more frequent;
• you cannot find a cause, or the problem comes back;
• water has got into the electrics.

If there is a fire, leave the building and call 999. Do not try to tackle an electrical fire with water.

In our area, you can use our emergency electrical repairs service or call 01253 364101. We cover Blackpool, the Fylde, Preston, Kirkham, Garstang, Over Wyre and Fleetwood.

What the electrician will do

An electrician investigating a tripping circuit will normally ask about the history, carry out tests with the supply isolated to find where the fault is and test the RCD itself to see whether it trips at the right level. They may disconnect parts of the circuit to narrow it down. Once they find the problem, they can explain the repair, which might be as simple as replacing a damaged fitting or as involved as repairing a section of cable.

If they find that the whole installation is deteriorating, they may recommend a more thorough inspection. See our EICR guide and our guide on signs your home needs rewiring.

Will a new consumer unit stop it?

Sometimes. If the existing unit has one RCD covering the whole house, a fault on one circuit can take out all the others, and a modern unit with separate protection for each circuit can make a problem easier to live with and to locate. However, a new unit does not cure a fault in the wiring or an appliance. The device is tripping because of a real fault that needs to be found. See our consumer unit guide.

Preventing future trips

• Spread high-power appliances across different sockets and circuits rather than running them together on one extension lead.
• Replace appliances that have started to trip the supply.
• Protect outdoor sockets and leads from rain, and use outdoor-rated equipment. Our garden electrics guide has more.
• Have your installation inspected at sensible intervals.