Last updated 7 October 2026
A circuit breaker keeps tripping because it is detecting one of three things: too much current (an overload), a short circuit, or current leaking to earth. The fastest way to narrow it down is to notice when it trips: straight away, when one appliance runs, in wet weather, or at random. If it trips with nothing plugged in, the fault is in the wiring or a fixed appliance and needs an electrician.
This guide is about diagnosis: reading the pattern of the trips to work out the likely cause. For the step by step method of resetting a breaker and isolating appliances safely, see our guide on how to safely reset a breaker and fault find.
First clue: which device keeps tripping?
- MCB (miniature circuit breaker): trips on overload or short circuit. Think “too much current”.
- RCD (residual current device): trips when current leaks to earth, the kind of fault that can give someone a shock. Electrical Safety First says an RCD can disconnect in as little as 40 milliseconds.
- RCBO: both in one device, protecting a single circuit. It can trip for either reason.
Diagnose it by when it trips
Keep a note for a few days: the time, the weather, which device moved, and what was running. Then match it to the table.
| When it trips | Device | Most likely cause | What you can do |
|---|---|---|---|
| Instantly on reset, with nothing plugged in | MCB, RCD or RCBO | Fault in the fixed wiring, a fixed appliance (shower, cooker, immersion) or the device itself | Leave it off and book an electrician |
| Every time one appliance is switched on | Usually RCD or RCBO, sometimes MCB | A fault inside that appliance, often a heating element, motor or damaged flex | Stop using it and have it repaired or replaced |
| Only when several heavy loads run together | MCB or RCBO | Overload: kettle, heaters, dryer and cooker sharing one circuit | Spread the load; if it is routine, ask about an extra circuit |
| In rain, wind or overnight damp | RCD or RCBO | Water getting into an outdoor socket, garden light, outbuilding supply or a cable entry | Note which circuit; avoid outdoor fittings until checked |
| At set times, with no one using anything | RCD or RCBO | Something on a timer: immersion heater, storage or panel heaters, a freezer defrost cycle | Unplug or switch off timed items one at a time to find it |
| Randomly, more often as you have added electronics | RCD on a split load board | Small normal leakage from many devices adding up on one RCD, plus a minor fault tipping it over | An electrician can measure it and spread circuits, or fit RCBOs |
| When a light is switched on, or a bulb blows | Lighting MCB or RCBO | A failing lamp, a damaged fitting or a loose connection | Replace the lamp with the power off; if it continues, call an electrician |
| With a burning smell, buzzing or warm sockets | Any | Loose or overheating connection, possibly arcing | Leave it off and get it checked promptly; call 999 if there is smoke or fire |
The common causes in more detail
Overloaded circuits
Each circuit and its protective device are rated for a maximum current. Run a kettle, a fan heater and a tumble dryer on the same sockets circuit and you can exceed it. The MCB is doing its job. If the overload is part of normal life, the fix is a dedicated circuit, not a bigger breaker. Never fit a higher rated device yourself: the breaker is sized to protect the cable, not the appliance.
Faulty appliances
Appliances with heating elements or motors are the usual suspects: kettles, washing machines, dishwashers, ovens, immersion heaters and electric showers. Moisture in an element, worn motor brushes or a damaged flex can all leak to earth. If the trip follows one appliance whichever socket you use, you have found it.
Damp and outdoor electrics
Outdoor sockets, garden lighting, sheds and garages are exposed to rain and condensation. Water in a fitting or a joint gives current a path to earth, so the RCD trips, often in wet spells or overnight and then not again for days. That on and off pattern is a strong hint.
Cumulative leakage on a shared RCD
Computers, televisions, chargers and many modern appliances leak a small amount of current to earth in normal use. On an older split load board, a single RCD may cover half the house, so all those small currents add up on one device. A small extra leak somewhere can then trip it. BS 7671:2018+A4:2026 does not require every board to be all RCBO, and a dual RCD board can still be compliant, but giving each circuit its own RCBO means one fault switches off one circuit rather than half the house.
Damaged or ageing wiring
Cables nicked by a nail or screw, insulation that has deteriorated with age, rodent damage in a loft, or cables crushed under floors can all leak or short. These faults often trip with everything unplugged and need insulation resistance testing to find.
Loose connections
A loose terminal at a socket, switch, light fitting or in the consumer unit heats up under load. It may cause trips, flickering lights or a warm socket face. Only an electrician should open fittings to find and remake it.
A worn protective device
Occasionally the MCB, RCD or RCBO itself is at fault and trips below its rating. An electrician can test the device to confirm that before replacing it. Our pricing for an RCBO replacement is £25 to £30 + VAT per device, plus the time to fit it.
If you rent your home in Scotland
Report repeated tripping to your landlord or letting agent rather than living with it. Under section 13 of the Housing (Scotland) Act 2006, the repairing standard requires the installations for the supply of electricity, including residual current devices, to be in a reasonable state of repair and in proper working order. Your landlord also needs a current EICR for the property, normally renewed at least every five years.
What an electrician does to find the cause
- Talks through your trip log to narrow the circuit and the likely cause.
- Insulation resistance testing on the affected circuits to find leakage and damaged cable.
- RCD and RCBO testing to confirm the device trips when it should and not before.
- Load check on circuits that trip under heavy use.
- Visual inspection of fittings, outdoor equipment and the consumer unit for heat damage and loose connections.
This is what electrical fault finding in Aberdeenshire involves. Fault finding is £80 to £150 + VAT for the first hour, and our standard hourly rate is £55 to £75 per hour + VAT. If tripping is a symptom of an old board, a consumer unit upgrade in Aberdeenshire may be the lasting fix; if the wiring itself is failing, a house rewire in Aberdeen may be the honest answer. We cover the city from Peterhead; see our electricians in Aberdeen page for the areas we reach.
Frequently asked questions
Can a circuit breaker trip for no reason?
Not really. A trip means the device detected something, even if the cause has gone by the time you look. Intermittent causes include damp, timed appliances and loose connections. Less often, the breaker itself is faulty, which an electrician can confirm by testing it.
Why does my breaker trip when it rains?
Water is getting into something outdoors or at a cable entry, such as an outdoor socket, garden light, shed supply or external lamp, and creating a path to earth. The RCD trips to protect you. Have the outdoor circuit checked rather than leaving it off indefinitely.
Why does my breaker trip at night?
Look for anything that switches on by itself: immersion heaters, storage or panel heaters on timers, fridge and freezer defrost cycles, or outdoor lights on a sensor, plus overnight condensation. Switching those off one at a time over a few nights usually shows which it is.
Is a tripping breaker dangerous?
The trip itself is the safety system working. The danger is the fault behind it, and repeatedly resetting onto it. A trip with a burning smell, heat or scorching should be treated as urgent.
Should I replace my consumer unit if breakers keep tripping?
Not automatically. Most trips are caused by an appliance, damp or one circuit, and that should be found first. A new board makes sense when the old one is worn, has no RCD protection, or puts too many circuits on one RCD.
How much does it cost to find out why my breaker keeps tripping?
Our fault finding is £80 to £150 + VAT for the first hour. The repair cost depends on what is found, from replacing an appliance flex to replacing an RCBO.
Breaker still tripping?
Faithful Spark Electricians is a NICEIC Approved Contractor (620239) covering Aberdeen and Aberdeenshire from Peterhead. Call 07304 027013 (Mon to Fri 8am to 6pm, Sat 9am to 1pm) with your trip log, or get in touch through our contact page.
