Get Your RCD tripping Sorted: Common RCD Issues With Fixes

My rcd tripping article is exactly what I would do If you hired me to resolve your tripping rcd. So read on, identify the problem and get your residual current device switched back on.

Switch the circuit breakers the rcd is protecting off (down). Now try to switch the rcd back on. If it stays on; try switching one circuit breaker on at a time. If the rcd trips when one breaker is on; something on that circuit is faulty. If the rcd trips with all the breakers off; do not try and hold it in the on position. Your RCD will get damaged and you would need help from your local Cardiff electrician to replace it . Your rcd will hopefully reset after each circuit is isolated. I’ll show you how in this article (about an eight minute read).

To start I’m going to show you a typical rcd consumer unit and point out what is what.

The photo below below contains two rcd units, six circuit breakers and a main switch – all housed inside a modern consumer unit. The rcds (devices with the yellow test buttons) power the three circuits to the left of them. So the rcd inside the yellow section will only trip if an fault exists on circuit 1 (cooker), 2 (sockets first floor) and 3 (first floor lights). Likewise, if the rcd tripped inside the green section it would be because of a earth fault on 4, 5 or 6. Reading more about what rcds do might help you understand earth faults.


Important: As a qualified electrician I should add there are occasions where you shouldn’t attempt to reset the rcd protection without further checks. Some scenarios I can think of include:

  • Someone has drilled a hole in the wall
  • Electrical work has been carried out recently
  • A light fitting or socket outlet has just been replaced.
  • Part of the electrical installation has become damaged – wiring or accessories
  • Heavy rain (and you have outside accessories)
  • An appliance no longer works or has been damaged

What should you do if your RCD keeps tripping?

Rcd trips often occur where sockets are involved. Unplug (not just switch off) all the appliances. Also check for things connected to them – such as bathroom heaters and outside lighting. You also need to check elsewhere (like the loft) aren’t connected to the circuit. Don’t be misled by labels, which can be wrong or incomplete. Check the accessories on the circuit you are testing are dead! So, if you switch off “upstairs sockets” and one is still working (like the loft or landing for example), it is being powered from another circuit.

For Kitchens: look in the cupboards. Yes, it can be a pain moving things, but you want that rcd switch back on right?! Some properties have no isolation other than directly behind the appliances. So, you might have to move a fridge or washing machine.

If your electric hob is being protected by the rcd; they can usually be isolated from the circuit. Big red switches (examples below). They break the live and neutral from the cooker in the same way unplugging something will do. Its common for rcds to trip after a hob or oven has been cleaned because water based cleaner has contaminated the control gear. Sometimes they dry out and cause no problem after a day or two (depending on how much it’s been contaminated). Single ovens are often plugged in; so look in the cupboards next to it. Sometimes there is a socket underneath the cabinet supplying the socket. You would need to take off the plinth to get access if this is the case in your kitchen.

If you suspect lights are the reason behind your rcd fault: Turn all switches and any dimmers to the off position and take the bulbs out (wherever possible). Put your hand near them first without touching to check they aren’t hot and going to burn you. Old halogen lamps get hot quick!

For suspected central heating system faults: there are often fused connection units (highlighted below) which will isolate the power supply for boilers and water heaters. Switch them off.

Fused connection units will remove the power supply from heating systems in the same way removing a plug would.

If you suspect the shower is the reason your rcd is tripping you should be able to isolate it. Look for a pull cord or big red switch in a nearby cupboard.

Do you have any outside items? They can sometimes become damaged and get contaminated with water. Wind can force rain in. Sometimes the tripping can be intermittent. If you think they are at fault: look for the isolation (often a fused spur in the bedroom)

Not sure what is causing your rcd to trip? Here’s how you can tell

Turn all appliances sensitive to having the power removed suddenly, off. Things like computers and televisions.

Press the test button, or switch the rcd off. Make sure the (mcbs) circuit breakers haven’t tripped are still in the on position.

Walk round your house and make a list of what no longer works. It’s worth spending some time making sure this is accurate; the list of things that do not work are being protected by the rcd and therefore at least one of them is the cause of your problem today.

If your consumer unit looks like the one below; the Residual Current Device is not powering all circuits. 1-6 (highlighted in red) are not protected. The circuits highlighted in green are.

The consumer unit photographed below has one residual device (always identifiable by a test button) powering the whole house. These are the hardest for people to troubleshoot because it could be any of the circuits or appliances within the home. Sometimes a combination of more than one fault. By following this guide; the customer turned the shower isolator off and the rcd trip switch went back on.

The consumer unit below is full of rcds, called rcbo’s. Whatever rcbo trips; just locate what no longer works and you know what is causing the problem. In the scenario photographed below; the rcbo for the cooker tripped so the customer knew there was an issue with the cooker, or its circuit. The wiring to the cooker tested OK. It was the cooker at fault. It was replaced and the rcbo went back on.


Still can’t reset your rcd switch?

If you are still having problems resetting your rcd then I need to explain a few technical things to help you get it back on:

Remember I mentioned in Step 1 you needed to unplug everything, not just switch it off? This is because rcds trip when the live and neutral conductors are imbalanced. Some socket outlets only remove the live when turned off – leaving the neutral still connected. John Ward explains why rcds can trip when the circuit has been switched off. A ramp test shown in the video below confirms how much current causes the rcd to trip. 24 milliamps in this instance.

Look for Fused connection units which remove the live and neutral from accessories like bathroom heating, central heating and outside accessories.

Sometimes there is no isolation for electrical items. You will probably have fused connection units for under floor heating and outside security lights inside new build houses in The Mill, St Fagans and Creigau. But ask any Cardiff electrician working in Pontcanna, Cathays or Cyncoed and that might not be the case! As electrical installation requirements have altered throughout the Welsh Capital over the years; so have the techniques. As a consumer all you can do is isolate the supply to as many devices as you can, safely (by using the dedicated switch supplied). I would advise against removing parts which are intentionally live.

RCDs trip when they see an imbalance of appropriately 30 milliamps of current. The more items one protects; the more current is likely to be leaking. With this in mind, it can be a red herring for people when troubleshooting tripping problems without the test gear electricians carry. If you turned the kettle on and the rcd trips; you would understandably believe there is a fault with the kettle. But, it could be you have two faults; you could have a leak on the oven and a leak on the kettle. When both in use it is enough to trip the rcd but not when used by themselves.

How to troubleshoot intermittent rcd tripping issues (the most difficult)

Intermittent tripping is the most difficult to diagnose. Sometimes electricians cannot find a fault whilst on site. Even thou the rcd has tripped that day. I’ve made a list of common things you can hopefully isolate if your rcd switches off randomly:

  • Extractor fans. Most models run on after the light is turned off so look for the isolator and turn it off. It’s common for wind to blow water in through the vent and cause tripping issues.
  • Floodlamps. Maybe it hasn’t worked for a long time, but if it’s still got power going to it; it could well cause rcd problems when the winter comes.
  • Hobs and ovens. Sometimes cleaning products can get in to elements and the control gear. I’ve seen an rcd flip off because a pan boiled over causing a short in the igniter.
  • Rarely used appliances. Does your tripping have any type of pattern? Could it be whenever you use a certain appliance only used for parties or at Christmas for example?
  • Immersion heater. If you wake up in the morning with the Residual Current Device in the off position – could it be your water heater?
  • Outdoor equipment. Electrical accessories outside can get damp and break down over time. If you don’t use them all year round; perhaps they could be causing an issue? Some items I can think of include pond pumps, patio heaters and summer house heating.

RCD trip headache still going on? Here are some things to think about

When did the tripping first happen? What happened around that time – if anything? Have a good think as it may lead you / your electrician to the problem. Here’s some common causes of tripping:

  • Shelves being mounted on the wall.
  • Fixing your TV to the wall.
  • New skirting boards.
  • New kitchen cupboards
  • An item that stopped working

How will a professional electrician get your rcd switched back on?

All electrician’s in Cardiff have fault finding techniques of their own. The first thing I do is check earth leakage. I have a clamp meter which measures very small amounts of current. When clamped on the meter tails it measures the imbalance exactly the same way your rcd does.

I then remove the power to each circuit in exactly the same way you did following this guide. Sometimes the amount of leakage does not change when the circuit breakers are turned off. When this happens it’s because there is a neutral to earth fault. This is the very reason I asked you at the the start of this guide to unplug everything. Switching socket outlets off sometimes only removes the live, not the neutral. Electricians call this single pole switching. So, if your washing machine has a neutral to earth fault causing the rcd to trip you might have missed that if you didn’t unplug it.

With the cover now off the fuse board I would remove the neutrals from the terminal whilst keeping an eye on the reading. When the reading drops; the fault has been cleared and the troubleshooting can begin.

Hopefully my rcd tripping troubleshooting guide has helped you get your rcd switched back on. If it hasn’t, maybe it’s helped you at least pinpoint the problematic circuit so your time hasn’t been wasted. If you live in Cardiff and need help, then please get in touch.