Faults & diagnosis
Electrical fault finding and troubleshooting
A breaker that keeps tripping, lights that flicker, a run of sockets gone dead: each is a symptom, not a diagnosis. Fault finding is methodical testing to find the cause, such as a damaged cable, a loose connection, water in a fitting or a faulty appliance, so that it can be explained to you before any repair goes ahead.
- How it is found
- By testing: circuit by circuit, then point by point
- Before any repair
- The cause is explained and the work agreed with you
- After a repair
- The circuit is retested before it goes back into use
Select a numbered part to highlight it on the drawing.
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Here the RCD has tripped, so the fault is likely to be current leaking to earth on one of the circuits it protects or in something plugged into them. If a single circuit breaker had tripped, the search would start on that circuit.
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Each circuit on that RCD is isolated and tested on its own. Here the lighting and outside circuits, shown in grey, test clear, which leaves the sockets.
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Everything plugged into the suspect circuit is disconnected and checked separately, because a faulty appliance can trip an RCD too.
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With the circuit isolated, readings are taken at the board and at sockets along the run. Splitting the circuit at a socket and testing each part shows which side the fault is on.
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The fault lies between two test points: here, a fixing driven through the cable in the wall. Only that section needs to be opened up to repair it.
Sound familiar?
Symptoms worth tracing
Most faults are found by elimination. The device that tripped narrows the search to one circuit or the group it protects; testing those circuits one at a time picks out the faulty one; readings taken along it then place the fault in a single section. When nothing has tripped but sockets or lights are dead, the search is for a break in the circuit, often a connection that has worked loose or burnt out. Faults that come and go take longer, because they have to be caught when they happen or ruled out, which is why what you notice matters.
If a socket, switch or plug is hot, scorched or smells of burning, or water has reached a light or socket, keep away from it, do not touch it and call us. If there is smoke or fire, call 999 first. If a breaker trips again after one reset, leave it off. Urgent electrical problems.
- An RCD or circuit breaker that trips at random, or every time a particular appliance is switched on
- Tripping that happens after rain, overnight, or when the heating or outside lights come on
- Lights that flicker, dim or buzz, in one room or across the property
- A run of sockets or a group of lights that has stopped working, with nothing tripped at the consumer unit
- Sockets, switches or plugs that run hot, smell of burning or have discoloured
- Problems that started after building work, new shelving or fixings, a leak or a new appliance
- Tripping that began when more equipment was added to the same circuits
Who this helps
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Homeowners
A circuit that will not stay on, lights that flicker or sockets that have stopped working, and you want the cause found rather than reset again.
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Landlords and managing agents
A fault reported by a tenant that needs tracing, explaining and putting right. Tell us who arranges access: you, your agent or the tenant.
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Shops, offices and other businesses
Tripping that interrupts trading or equipment, where the cause could be the wiring or something connected to it.
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After an inspection report
The report records an observation coded FI (further investigation required without delay). For a rented home in England, landlords must have it investigated within 28 days, or any shorter period the report specifies.
Before we come
What to note before we come
A fault that comes and goes has often stopped by the time anyone arrives. Notes made when it happens narrow the search before any testing starts.
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1.Which device tripped
Which switch is down at the consumer unit and what its label says, if it has one. If more than one has gone off, note each of them.
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2.When it happens
The date and time of each trip, and any pattern: at night, at a particular time of day, or as soon as something is switched on.
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3.What was running
Appliances in use when it tripped, especially anything that heats water or air, and anything plugged in or wired outside.
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4.The weather
Whether it happens after rain, in damp or frosty spells, or whatever the weather. Water getting into outdoor fittings is a common cause of tripping that comes and goes.
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5.Recent work or changes
Building work, new shelves or fixings in walls, new flooring, a leak, a new appliance or electrical work by anyone around the time the fault began.
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6.Photos, taken safely
The front of the consumer unit, its labels and any scorched or damaged fitting, taken from a distance, without removing any cover or touching anything damaged.
Step by step
How the work is done
Before we quote
Start by telling us what happens, when it started and anything that changed around that time. That helps us judge whether it sounds like one circuit, one appliance or the whole installation, and whether it should be treated as urgent.
How long a fault takes to find is rarely clear until testing starts. Ask us before you book how the visit is priced.
Photos of the consumer unit and any affected fitting help us prepare, but they do not replace testing: many faults are hidden inside walls, ceilings or the backs of fittings.
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Step 1:Hear the history
We go through what you have noticed: which device trips, how often, what was running and what changed recently. The pattern usually suggests where to start.
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Step 2:Check what can be seen
The consumer unit, accessories, visible cables and outdoor fittings are checked for signs of overheating, water getting in, loose or broken parts and damage from recent work.
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Step 3:Pin it to one circuit
Circuits are isolated and tested one at a time, and appliances on the suspect circuit are unplugged, until the fault is narrowed to a single circuit or a single appliance.
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Step 4:Find the section
Insulation resistance and continuity readings are taken at the board and at points along the circuit until the fault lies between two known points.
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Step 5:Explain and agree
We explain where the fault is and what putting it right involves. Nothing is repaired until you have agreed the work and its cost.
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Step 6:Repair and retest
After the repair, the circuit is tested again before it goes back into use, and the work is recorded on a certificate where one is required.
Methodical testing
Found by testing, not guesswork.
The device that tripped narrows the search to one circuit or group. Testing those circuits one at a time picks out the faulty one, and readings along it place the fault in a single section. The cause is explained to you before any repair goes ahead.
Scope
What is included
Included
- Going through the symptoms and their pattern with you
- A visual check of the consumer unit, accessories and visible wiring
- Testing to narrow the fault to one circuit, then to one section of it
- Checking connected appliances and equipment as a possible cause
- An explanation of what was found and what putting it right involves
Depends on what we find
- How long the search takes, particularly for a fault that comes and goes
- Whether the repair can be done on the same visit, or needs parts, more time or a return visit
- Whether floors, ceilings or plaster need opening to reach the damaged section, and who makes good afterwards
- Whether a damaged length of cable can be repaired or the run should be replaced
- Whether what we find suggests wider problems that an inspection of the whole installation should look at
Afterwards
- Keep any certificate issued for the repair, so that whoever next inspects the installation can see what was altered
- If a fault that came and went returns, note the date, time and what was running, and tell us
- If the fault pointed to wider problems, consider a full inspection, reported on an Electrical Installation Condition Report (EICR)
- Landlords: if the work followed an FI observation on an inspection report, get written confirmation that it has been done and send it, with the report, to your tenants and the local housing authority within 28 days of the work being completed
Not covered by this service: Repairing a faulty appliance itself, which is for the manufacturer, the retailer or an appliance repairer; Faults on the incoming supply, the main fuse (cut-out) or the meter, which are for your network operator (call 105) or your energy supplier; A full inspection of the whole installation, which is a separate report.
The paperwork you may receive
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Minor Electrical Installation Works Certificate
Small additions and alterations that do not add a new circuit, such as an extra socket on an existing circuit.
- A description of the work
- Test results for the circuit that was altered
- The signature of the person responsible
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Electrical Installation Certificate
New installations, rewires and new circuits.
- What was installed and the design details
- A schedule of test results for each circuit
- Signatures for design, installation and inspection
Simplified outline, not a real certificate (Illustration)
Standards and regulations
We are a NICEIC Approved Contractor, registration number 619998000, and fully insured. How to check our registration and insurance.
- REFRepairs carried out, inspected and tested to the current edition of BS 7671, the IET Wiring Regulations
- REFWhere a repair alters the installation, it is recorded on a Minor Electrical Installation Works Certificate, or on an Electrical Installation Certificate if a new circuit or consumer unit is installed
- REFPart P of the Building Regulations applies to electrical work in homes in England: installing a new circuit or replacing the consumer unit has to be notified to building control, but repairing a damaged cable or accessory usually does not
- REFIn workplaces, the Electricity at Work Regulations 1989 require electrical systems to be maintained, so far as is reasonably practicable, to prevent danger
Questions
Questions about fault finding
It tripped once and has been fine since. Should I still have it looked at?
A single trip with an obvious cause, such as an old filament bulb blowing or an appliance you have since unplugged and stopped using, may not need a visit. If there was no obvious cause, note when it happened and what was running, and get it looked at. If it trips again, leave it off and call us rather than resetting it.
What is the difference between an RCD and a circuit breaker tripping?
An RCD switches off when it detects current leaking away, usually to earth, through damp, damaged insulation or a faulty appliance. One RCD often protects several circuits, so the fault could be on any of them. A circuit breaker (MCB) switches off when too much current flows in its own circuit, from an overload or a short circuit. An RCBO does both jobs for a single circuit. RCDs and RCBOs usually carry a small test button marked T or Test; plain circuit breakers do not. Knowing which one tripped tells us where to start.
Why do my lights flicker?
A single flickering light is often the lamp itself, or an LED lamp that does not suit the dimmer switch. Flickering in several rooms at once can point to a loose connection in the installation or, less often, a problem with the incoming supply. If flickering comes with buzzing, a burning smell, or a switch or fitting that is hot or discoloured, stop using that light and get it checked promptly. If the switch itself is hot, scorched or smells of burning, do not touch it.
Could one of my appliances be causing it?
Yes. Appliances with heating elements, such as kettles, washing machines, dishwashers and ovens, are common causes of RCD tripping, as are outdoor lights and anything plugged in outside. Computers and other electronic equipment each leak a small current to earth in normal use, and many of them on one RCD can add up to enough to trip it. We check connected equipment as part of the search. If an appliance turns out to be the cause, you will know which one, and it should not be used until it has been repaired or replaced.
How long does fault finding take?
It depends on the fault. One that is there all the time is usually quicker to trace than one that comes and goes. An intermittent fault may not show itself while we are there; testing can still rule circuits and appliances out, but finding the cause can take more than one visit. Notes made each time it happens shorten the search.
Will you need to cut into walls or lift floors?
Only where testing has placed the fault in that section, and only after we have discussed it with you. Narrowing the fault down between test points keeps the area opened up as small as possible, and sometimes running a new length of cable by another route is less disruptive than opening up the old one. Who makes good the plaster or flooring afterwards is agreed before that work starts.
What happens if the repair cannot be done on the same visit?
We explain what we found and what the repair involves, and quote for it in writing. If a circuit is not safe to use, it is normally left switched off until it has been repaired, and we tell you which sockets or lights that affects.
How do I know whether it is my wiring or the power supply?
If your neighbours have lost power too, or the main fuse or the cable coming into it looks damaged, call 105 to reach your network operator. The main fuse (cut-out) and the incoming cable belong to the network operator, and your energy supplier is responsible for the meter. Everything after the meter, including the consumer unit and your circuits, is your installation, and that is what we work on.
Often needed alongside
- Emergency electrical repairs Power loss, burning smells, damaged fittings or circuits that keep tripping — call us first.
- Electrical compliance and safety testing Inspection, testing, reports and remedial work so you know where your installation stands.
- Full electrical installations Rewiring, new circuits, extra sockets and complete installations for refurbishments and new spaces.
Read before you book
- How to choose an electrician Five practical checks that separate a competent, accountable electrician from the rest — and the paperwork you should expect at the end.
- Getting an accurate electrical quote: what to tell us A few details at the start save a second visit, avoid surprises in the quote and get the right person to your job sooner.
Next step
Tell us what the fault is doing
A description of what happens, when, and what changed is the best starting point. Send what you have, including photos taken safely, and we will talk it through with you before anything is booked.
What to send us
- What happens, when it started and how often
- Which switch goes off at the consumer unit, and its label if it has one
- What was running at the time, and whether the weather seems to matter
- Any recent building work, new fixings, leaks, new appliances or electrical work
- Photos of the consumer unit and any affected fitting, taken without removing covers
- The postcode, the type of property and who arranges access
An enquiry is not a booking: we contact you first, and you see a written quote before anything goes ahead.
We list towns in London and surrounding areas, Kent, Essex, East Sussex and West Sussex. Check your postcode.
Call or email us for a free quote
Tell us the postcode and a little about the job. We will contact you to discuss it, and you get a written quote before any work starts. Quotes are free. Some survey or diagnostic visits may be charged: ask when you book.
Our email address: support@dualcurrent.co.uk
Helpful to include
- The postcode of the property
- What the job is, or what is going wrong
- Photos, if you have them, taken without removing any covers