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01892 531 728

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What is an RCD?

RCD’s (Residual Current Devices), are Electrical Safety Switches that stop / remove the electrical power supply to an electrical circuit, when the circuit is unsafe.  

Should a RCD “Trip” then it has tripped for a reason, this problem is rarely the RCD being Faulty

A lot of electrical problems where RCD’s may trip are literally momentary, just causing a trip in just a fraction of a Second.

The RCD is built in for safety, to protect yourself, your family, your staff from receiving electric shocks, and can also stop power getting to items which could catch fire.

Once this momentary Trip has occurred, and passed, it is possible to Reset the RCD, and restore power to the circuit or to your property.

There can be occasions that should a circuit be unsafe for more than that slight moment in time, then the RCD will trip again, needing a reset. 

There are some basic actions that customers can carry out to fix this problem.

Please follow our instructions below to guide you through.

Should the problem persist, then you should call out a Qualified Registered Electrician.

Continual resetting over several minutes can have an adverse effect with your RCD, and the RCD will not be effective, and may need a replacement.

 Finding your RCD

The RCD shown will be an RCD in a Domestic Consumer unit, and it will also have beside it around 10 Miniature Circuit Breakers (MCB’s)

Alternatively, some Domestic Distribution Boards have Combined RCD’s & MCB’s called RCBO’s see the difference in the photos.


The Domestic consumer unit will usually be in an “out of the way”, such as at the back of a Kitchen cupboard, in the cupboard under the stairs, in a cupboard close to the front of the house or even out in the garage.

An example of a Domestic Distribution board looks like this, (there are many different Variants. But the RCD will always have a “Test button” built into them somewhere on the front, and maybe in a different Colour.


The RCD is built into the consumer unit, and is around 2 inches (5cm) by 1 inch (2 ½ cm)



How to Reset an RCD

To reset an RCD move the main toggle switch to the other position (it depends on manufacturers, so, if it is down move it up, if it is sort of up, move it down (you may hear a click), and then move it up.  You may find that it is stiff, so will have to really push it up into position.

If you see the RCD main toggle switch is in a different position to the rest, then move it to the same position as the rest of the switches.   This is called “Resetting the RCD” 

If the RCD stays in it top Reset position, and the main toggle switch does not go back down to the other position, then the problem has been solved. 

However should the RCD goes back down to the other position, this is called a “constantly tripping RCD” see How to Investigate a Constantly Tripping (resetting) RCD.

Homeowners should be aware that dome Domestic Distribution boards have their own “Trip Switches”.  Some Distribution boards have their own Isolation switches (on/off switches).


How to Investigate a Constantly Tripping (Resetting) RCD

A RCD that trips again (and again) after resetting is a “constantly tripping RCD.

The problem is unlikely to be the RCD.

The problem is most likely an electrical appliance causing the RCD to Trip.

The RCD is doing its job, the RCD is removing the power supply to an unsafe electrical Circuit.

The approach to find what is causing the issue is a relatively simple one, but will mean running around your property.


The Electricians Proceedures for Checking Tripping RCD's  - Which you can do yourself.

Initially, as electricians, we switch off (clicked down) all the miniature circuit breakers (MCB’s) affected by the RCD.

The RCD is switch is then pushed back up, if it stays in place, then slowly push up one at a time the MCB’s.

At some point the RCD may trip back down again, look at the MCB’s and the circuit Distribution, this will identify the faulty circuit. (Could be Sockets / Cooker / Lights / Garage etc.)

At this point you can switch off the faulty circuit on your Distribution board, Reset the RCD, and push the remainder of your MCB’s up apart from the one that controls the faulty circuit.

You hopefully have identified the circuit, but don’t just assume it is just the name on the label, there could be other thing affected.

The MCB’s have numbers on them, so without a label you can identify roughly where you should be looking. 


50amp & 40amp will be for Cookers, Hobs, Electric Showers or a Sub main feed to a Garage or Shed.

32amp, will be for Sockets around your home or a Sub main feed to a Garage or Shed, but can also be for Cookers or Hobs,

20amp or 16amp, will be for just a few Sockets around your home possibly for a Sub main feed to a Garage or Shed, or water heaters or Electric Fires,

10amp or 6amp, will be for lighting

The Power circuit that has tripped has potentially a faulty electrical appliance, this is now where you must go around your house, and physically remove plugs (disconnect) as many electrical appliances from the circuit as possible. A faulty appliance will have caused the RCD to trip. 

Likely appliances are “White Goods” where there is heat and moisture involved, such as Kettles, Fridges, Freezers, Toasters, Dishwashers, Washing Machines, Tumble Dryers, Cookers, Hobs, Extension leads outside, Pond Pumps & Lights. 

One of the easiest ways to find out if the circuit is alive or dead, is to switch your appliance on –

“Does it work?” YES or NO? 


To the “Dead Circuit” The home owner should remove (unplug) all electrical appliances and extension leads. 

If it is not possible to unplug, then turn the appliance off at the switch or appliance (this is the last possible option to consider). 

After unplugging all the appliances, or turning them off. Return to your distribution board, Test your “original faulty circuit, and then see if the RCD will reset.

If the RCD sets, then it is one of the appliances which is at Fault.

If the RCD fails to reset again, then the fault is with the Electrical Circuit. 

Call out a Qualified Registered Electrician.


If you have to Call out an Electrician for Help

To save time, and YOU to save money please explain what happened. When did it happen?     What were you doing?     What appliances did you have on?   Have you  had someone done some DIY – such as putting up shelves, or hung a picture?    Tell the electrician the time of day?   What the weather was like?     Which way (if at all)  was the rain falling against your home? 

Tell the electrician EVERYTHING however in-significant you think it could be.     Have our children over flowed a sink?     Have you heard mice around your floors or even in the attic?    Have you had other rodents around?     Is there a loose socket or plug on a wall?     Is there dampness on a wall?    Has a damp patch appeared on the ceiling which you may not have seen before?      Have you moved some heavy furniture?     Have you had some work done in your property in the last few weeks – ie new carpets?       Have loose floor boards been screwed down?

This will help the electrician to trace the fault quicker, it is far better to tell the electrician everything than you welcoming the electrician into you home – pointing at the Distribution board, and then promptly disappearing out of the way, and sitting hidden in your living room.  (believe me this does happen a lot)! 



That worked and the RCD is staying on

Should you be in the fortunate position of the RCD setting, and staying on – now is the task to start plugging things back in.

As electricians we have a “Cheats / easy way”        (let me explain …  Find a radio or a table lamp that can be plugged into the re-energized circuit, in a common part of the property say a hall or a landing plug it in, and turn it on  so it will be obvious that music is playing, or a light is on.

During the re-plugging the appliances back in, should the music stop, or the light goes out, then the last one or two items,  will have been the faulty appliance – this saves a lot of running around after plugging something in, then running down checking the Distribution board

At times the problem may come back – minutes or hours later, so it is best to unplug for a while items such as Fridges, as these will need to heat up, to cool down and spring into action, by doing this you will  see if the tripping has stopped. 

Plugging back in each appliance ONE at a time is not a 100% guarantee of finding the faulty appliance, it is the BEST way, but NOT a 100% guarantee.

Certain cause / effect situations, can suggest a faulty kettle, but the real problem is say a faulty Cooker.

Remember if you have a Garage or Shed connected to the house with electricity in it, unplug the equipment in there, - often we find an old Fridge (now a Beer Fridge) or Freezer which are very old that are the cause of the problem.

Once you have found the faulty appliance then it is a matter of choice,  for example a faulty Kettle, then replacing the this appliance, is cheaper than calling a Qualified Registered Electrician to look into the problem further.  

Should replacing the cheap appliance does not allow the RCD to be reset, then call a Qualified Registered Electrician.

If your faulty appliance is expensive, for instance a home cinema system, call a Qualified Registered Electrician..  The Electrician will look into the tripping RCD, to ensure the expensive appliance is causing the RCD to trip.

The electrician will also know what else can be done to stop the RCD tripping without replacing the expensive appliance, this will probably be cheaper than replacing the appliance.

In general likely appliances which are “White Goods” where there is heat and moisture involved, such as Kettles, Fridges, Freezers, Toasters, Dishwashers, Washing Machines, Tumble Dryers, Cookers, Hobs, Extension leads outside, Pond Pumps & Lights. 

Should one of these have tripped the circuit, and the appliance is over 5 – 6 years old then it is more cost effective to get it replaced.

But it was not a power Circuit – it was the lights that caused the tripping!

Again with the MCB - DOWN / OFF, go around the property, and switch all the light switches in the opposite position.

Reset your RCD, should the RCD work, then go around your property switching on all the lights, if the RCD trips, then it will be some of the light bulbs on that circuit which have died, and it is best to remove, and replace them.

Check your outside lights, are the light fittings with light bulbs inside swimming in water?  Is there an over flowing gutter where water is/has poured onto a light?

If it still  trips, then remove ALL the light bulbs – even the outside ones (sorry).  Reset the RCD – if it still Trips it is best to call out a Qualified Registered Electrician..

Should you have lots of lights in your property, or lights are in a difficult position to get to, then it is best to call out a Qualified Registered Electrician..

For more information, or immediate Help Give us a Call on 01892 531728 which is active 24/7. 

Alternatively fill out our web enquiry form, and we will respond quickly.

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