Why Does My Electric Keep Tripping? How to Find the Cause
Updated: Oct 9
Your electric keeps tripping because a protective device in the consumer unit has detected a problem: too much current on a circuit, a short circuit, or current leaking to earth. The most common causes, roughly in order, are a faulty appliance, an overloaded circuit, earth leakage from damp or water, and a fault in the fixed wiring. The quickest way to narrow it down is to look at which switch has tripped.
Which trip switch has gone off?
Open the cover of your fuse box (consumer unit) and look for the switch that is down. It tells you what kind of fault you are dealing with.
A single MCB (circuit breaker): these small switches protect one circuit each, such as upstairs sockets or kitchen lights. An MCB trips on overcurrent, meaning an overload or a short circuit on that circuit only.
An RCD: a wider switch, usually with a "T" test button, covering several circuits at once. An RCD compares the current going out on the line conductor with the current coming back on the neutral. If some is leaking to earth, through damp, a damaged cable or a person, it switches off. RCDs protecting household sockets are rated at 30 mA.
An RCBO: looks like an MCB with a test button and does both jobs for one circuit.
The whole house is dead and nothing has tripped: check whether your neighbours have power. If not, it is a supply fault, and 105 is the number for your electricity network operator.
On most boards the main switch is just an on-off isolator, so it does not trip for a fault.
A faulty appliance
If the trip happens the moment you switch something on, suspect that appliance first. Kettles, washing machines, dishwashers, tumble dryers, ovens and immersion heaters all have heating elements, and a failing element is one of the most common causes of an RCD trip. A short inside an appliance or its flex usually trips the MCB instantly instead.
Extension leads and adaptors count as appliances here too. A crushed or water-damaged lead can trip the circuit it is plugged into.
An overloaded circuit
An overload trip usually comes after a delay rather than instantly, because the MCB's thermal element responds to heat building up over time. The classic pattern is several high-power items running together on one circuit: a kettle, a fan heater and a tumble dryer on the same kitchen ring, for example.
If it only trips when you use a particular combination of appliances, spread them across different circuits. If a circuit trips under normal everyday use, it may be undersized for how the room is now used. Our electrical fault finding and maintenance visits check circuit loading as well as faults, and adding a circuit is notifiable work under Part P, so it must be done by a registered electrician who can self-certify it or notified to building control before work starts.
Earth leakage, damp and nuisance tripping
When an RCD keeps tripping, water is a frequent culprit. Outside sockets, garden lighting, junction boxes in lofts or outbuildings, and fittings under a leaking bathroom can all let current leak to earth, especially after heavy rain.
Leakage also adds up. Computers, televisions and washing machines leak a tiny amount of current by design, and with many of them on one RCD the total can approach the trip level. That is why a board where one RCD covers half the house can seem to trip "at random". A neutral-to-earth fault, often caused by a nail or screw through a cable, can do the same, tripping the RCD when a load on a different circuit is switched on. Both need test equipment to find, and we cover RCD-specific causes in more depth in why an RCD keeps tripping.
An occasional trip during a thunderstorm can be caused by a voltage surge rather than a fault, provided the switch resets and stays on afterwards.
When the lights keep tripping
A lighting circuit that trips often points to a blown bulb (older filament lamps can short briefly as they fail), water coming through a ceiling rose or downlight from a bathroom or roof, or a loose connection in a fitting. If the lights trip with every switch off, the fault is in the wiring rather than a lamp.
What you can safely check yourself
These steps use only the switches on the front of the board. Do not remove any covers.
Note which device has tripped and which circuits it covers.
Unplug everything on the affected circuit, or on every circuit under a tripped RCD, and switch off wired-in appliances such as an immersion heater or cooker at their own switches.
Reset the switch once.
If it stays on, plug appliances back in one at a time, waiting a minute between each. When it trips, stop using the last item and have it checked.
For an RCD, you can switch off all the MCBs beneath it, reset the RCD, then turn the MCBs back on one by one to find the circuit that trips it. If the RCD will not reset even with all its MCBs off, stop there: that points to a neutral-to-earth fault or a faulty RCD.
If it trips again with nothing plugged in, the fault is in the fixed wiring. Leave that circuit off.
When to stop and call an electrician
Stop resetting and get help if the switch will not stay on with everything unplugged, if you can smell burning, see scorch marks or hear buzzing, or if water is involved. Never tape or hold an RCD on, and never fit a higher-rated breaker to stop the trips, because those are the situations where a tripping breaker becomes dangerous rather than just a nuisance.
Electrical Safety First says that if the RCD in your fusebox keeps tripping, there is likely to be a fault that needs investigating, either with an appliance or the wiring itself. Our fault finding starts where the checks above stop, with insulation resistance testing to locate leakage and faults on each circuit. For a burning smell, sparking or a total loss of power, call our emergency electrician team instead of waiting.
Tripping questions, answered
Why does my electric trip at night?
Look for anything on a timer: immersion heaters, storage heaters, dishwashers set on delay, or a fridge freezer's defrost cycle. A heating element failing on one of those is a common cause of night-time RCD trips.
Can the trip switch itself be faulty?
Yes, though it is less common than people hope. RCDs and MCBs can wear out. Electrical Safety First suggests checking an RCD with its test button; if it does not trip when pressed, get a registered electrician to investigate.
Does an old fuse box make tripping worse?
An old board with a single RCD covering most circuits is more likely to suffer nuisance trips from cumulative leakage, and one fault takes out half the house. Boards with rewireable fuses do not trip at all: the fuse wire blows instead. Either can be a reason to consider a consumer unit upgrade.
Getting a tripping fault traced
We are based in Shifnal, fully insured and registered with a Competent Person Scheme, with over 20 years of experience tracing faults in homes and businesses across Wolverhampton, Telford, Shropshire and Staffordshire. If your electric keeps tripping and the steps above have not found it, contact us and we will test the circuits and find the cause.
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