01 Home electrical fault guide
Why does my RCD
keep tripping?
Your RCD is not being dramatic. It has detected electricity taking a route it should not. Here is what that can mean, what you may safely observe and when the reset switch needs a rest.
Electrical safety disclaimer
This article is for educational purposes only. Electrical fault finding can expose you to lethal voltages, electric shock and fire. Do not remove covers, open electrical accessories, disconnect conductors or perform electrical tests unless you are suitably qualified and competent.Never repeatedly reset a protective device that continues to trip. If you are unsure, isolate the supply only if it is safe to do so and contact a qualified electrician.
01 / THE SHORT VERSION
An RCD trips when electricity leaks away
An RCD continuously compares the current leaving on the live conductor with the current returning on the neutral. If enough current is missing, it assumes some may be flowing to earth—possibly through damaged insulation, wet equipment or a person—and disconnects the supply quickly.
That does not automatically mean the RCD itself is faulty. Most of the time it is doing exactly the job it was installed to do. The useful question is not “How do I keep it on?” but “What made it turn off?”
02 / KNOW YOUR SWITCHES
RCD, MCB and RCBO: three letters, different jobs
Consumer units are fond of acronyms. They look like a row of similar switches, but they do not all watch for the same problem.
Watches for leakage
Protects one or more circuits by detecting an imbalance between live and neutral current.
Watches the current
Protects an individual circuit against overload and short-circuit current.
Does both jobs
Combines residual-current and overcurrent protection for one circuit.
If the main RCD trips while every MCB appears to remain on, that is not a contradiction. A leakage fault can operate the RCD without creating the overload needed to trip an MCB.
03 / THE SUSPECT LIST
Ten common reasons your RCD keeps tripping
These are possibilities, not a remote diagnosis. Electricity is invisible and rarely leaves a polite note explaining what happened.
- 01
A faulty portable appliance
Kettles, washing machines, tumble dryers, dishwashers and extension leads can develop insulation or earth-leakage faults. A trip that follows one appliance is a strong clue, but it still needs proper confirmation.
- 02
A heating element leaking to earth
Immersion heaters, ovens, dishwashers, washing machines and electric showers contain heating elements that can deteriorate. They may behave until the heating cycle starts, then trip the RCD.
- 03
Water or condensation
Moisture in outdoor lights, sockets, junctions, bathroom equipment or a shed supply can create an intermittent path to earth. Trips after rain are especially useful evidence.
- 04
Damaged cable or accessory
A crushed cable, screw through a conductor, deteriorated insulation, overheated socket or loose termination can produce leakage or a direct fault. This is not a “reset it and see” situation.
- 05
Outdoor equipment
Pond pumps, garden lighting, hot tubs, gates and garage equipment live a harder life than the average table lamp. Water, UV exposure, damaged flexes and poor joints make outdoor circuits frequent suspects.
- 06
Cumulative leakage
Modern appliances naturally produce small amounts of leakage. Several circuits sharing one RCD can sometimes add up to enough to trip it, even though no single appliance looks obviously guilty.
- 07
A neutral-to-earth fault
Neutral and earth touching downstream can cause confusing or intermittent operation, particularly as other loads switch on. Finding it normally requires circuits to be divided and tested systematically.
- 08
Mixed or borrowed neutrals
Incorrectly shared neutrals between circuits can upset the balance seen by an RCD or RCBO. This sometimes appears after alterations to lighting, fans or consumer units.
- 09
A circuit wiring fault
If the RCD trips with portable appliances unplugged, the fixed wiring or connected equipment may be involved. Unplugging items does not isolate boilers, immersion heaters, alarms or other fixed loads.
- 10
A deteriorated or unsuitable protective device
RCDs can fail or become unreliable, but replacing one before testing the installation is guesswork. The circuit leakage, device operation and board arrangement should all be checked first.
04 / SAFE OBSERVATIONS ONLY
What you can safely check without opening
The aim is to collect useful information, not to become an electrician during a stressful Tuesday evening. Do not remove the consumer-unit cover, socket fronts, switches or appliance panels.
Look and smell first
If there is smoke, heat, buzzing, water near electrical equipment, scorch damage or a burning smell, stop. Do not reset the RCD. Follow the urgent guidance below.
Note what was operating
Write down what had just switched on: cooker, shower, heating, washing machine, garden lights or something automatic. Timing often narrows the search dramatically.
Switch off and unplug portable loads
Only use normal user controls and plugs that are dry, cool and undamaged. Do not disconnect fixed equipment or remove any cover.
Reset the RCD once
If it stays on, reconnect portable appliances one at a time using their normal plugs and controls. If a particular item causes another trip, leave it unplugged and stop using it.
If it trips again, stop resetting
Leave the affected circuit or appliance off and arrange testing. A second trip is the protective device repeating its warning, not asking for a more determined finger.
The boundary: normal switches and plugs are for users. Covers, conductors, test instruments and fixed-wiring disconnection are for suitably qualified and competent people.
05 / FOLLOW THE PATTERN
What the timing can tell your electrician
Patterns help decide where to begin, but they do not prove the cause. Two sockets in different rooms may still share the same circuit or RCD, which is why “it worked over there” is evidence—not a completed test.
06 / DO NOT WAIT
When RCD tripping is an urgent warning
Keep the supply or affected circuit off, if it is safe to operate the normal switch, and seek urgent help when you notice:
- Smoke, visible sparking or arcing
- A burning smell, buzzing or crackling
- A hot consumer unit, socket, switch or plug
- Water entering the consumer unit or electrical equipment
- An electric shock or tingling sensation from metalwork
- Scorch marks, melted plastic or damaged cables
- The RCD will not remain on with normal loads switched off
If there is smoke or fire, get everyone to safety and call 999. Do not touch wet or damaged electrical equipment. For a suspected supply-side problem around the meter or incoming service, contact the electricity network operator as well as an electrician.
07 / NO GUESSWORK
How an electrician finds the actual fault
Professional fault finding is a process of narrowing the installation safely. We start with the symptoms and timing, inspect for obvious damage, identify what the protective device controls, then test the relevant circuits and equipment.
Establish the pattern
What changed, what was running, when it trips and whether weather or heat affects it.
Divide the installation
Separate circuits and connected equipment methodically instead of replacing parts at random.
Measure and interpret
Use appropriate insulation, continuity, leakage and protective-device testing for the circumstances.
Repair and verify
Correct the cause, then retest the affected work and confirm that protection operates correctly.
Rudi Electrics’ North London fault-finding visit is currently £100 and includes up to one hour of diagnosis. Straightforward repairs can often be handled during the visit. Larger or concealed faults are explained and quoted before additional work begins.
RCD Tripping — Frequently Asked Questions
Clear answers about repeated trips, appliances, rain, overnight faults and when to stop resetting the protective device.
Why does my RCD keep tripping?
An RCD trips when it detects current flowing somewhere it should not, usually because of leakage to earth. Common causes include a faulty appliance, moisture, damaged wiring, outdoor equipment, heating elements, neutral-to-earth faults or the combined leakage from several appliances.
Can I keep resetting an RCD that trips?
No. One reset after switching off and unplugging portable appliances is a reasonable observation. If the RCD trips again, leave the affected circuit or appliance off. Repeated resetting can re-energise a dangerous fault and does not repair the cause.
Why does the RCD trip but none of the individual breakers trip?
The RCD and circuit breakers watch for different problems. An MCB normally responds to overload or short-circuit current, while an RCD responds to an imbalance caused by leakage to earth. A leakage fault can therefore trip the RCD without moving an individual MCB.
Why does my RCD trip overnight?
Equipment that operates automatically is often involved, including fridge-freezers, boilers, immersion heaters, outdoor lighting, timers and defrost cycles. Moisture and cumulative leakage can also make an intermittent fault appear overnight. The timing is a useful clue, but not a diagnosis.
Can rain make an RCD trip?
Yes. Water entering an outdoor socket, light, junction, pond pump, shed supply or damaged cable can create leakage to earth. Leave the outdoor circuit isolated and have it inspected rather than repeatedly resetting the RCD as the equipment dries.
How much does professional fault finding cost?
Rudi Electrics currently charges £100 for a North London fault-finding visit, including up to one hour of diagnosis. Straightforward repairs may be completed during the visit; larger work is explained and quoted before it begins.