ComGas investigates electrical faults in homes across Farnham and the surrounding area — tripping circuits, intermittent problems and lighting or socket failures — using proper testing to isolate the actual cause rather than swapping parts and hoping. Findings and any repair are explained clearly before further work proceeds.
Finding the actual cause before anything gets replaced.
An electrical fault has a specific, findable cause — a damaged cable, a failed accessory, a loose connection, a fault at a specific point in a circuit — and the job of fault finding is to isolate exactly where and what that is before deciding what to do about it. Replacing a consumer unit or an appliance because it seems like the likely culprit, without confirming it, sometimes fixes the symptom and sometimes doesn't touch the actual cause at all.
We work through a circuit systematically: isolating sections, testing insulation resistance and earth fault loop impedance, and narrowing down to the specific point of failure, rather than starting with the most convenient explanation. It takes longer than a guess, but it means the repair addresses what's actually wrong.
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How we diagnose electrical faults
RCDs, MCBs, intermittent faults and the testing behind a proper diagnosis.
Different symptoms point to different kinds of fault, and each needs a different diagnostic approach — from a straightforward overload to an intermittent fault that only shows itself occasionally.
Tripping RCDs & MCBs
An RCD and an MCB trip for different reasons, and telling the two apart correctly is the first step in diagnosing why a circuit keeps going off.
An RCD trips on earth leakage — current escaping to earth rather than returning through the correct path
An MCB trips on overload or a short circuit — too much current, or a direct fault between conductors
A device that trips only with a specific appliance plugged in points toward that appliance rather than the fixed wiring
A device that trips with nothing obvious plugged in points toward the fixed circuit itself and needs proper testing
Faults that come and go — with temperature, with a door closing, with a particular appliance running — are usually more time-consuming to isolate than a fault that's present continuously, because the circuit has to be caught in the state where the fault actually shows.
Connections that loosen with heat or vibration can produce a fault that only appears under load
A borrowed neutral — where a neutral conductor is shared incorrectly between two circuits — can cause faults that only appear when both circuits are used together, and is a genuine safety issue when found
Faults linked to movement, such as a damaged cable flexed by a door or drawer, are traced by testing under the conditions that trigger them
We explain what's been ruled out and what's still being investigated rather than leaving an intermittent fault as an open question
Proper diagnosis relies on the same testing used for certification — measuring the electrical values a circuit should have, and finding where they depart from what's expected.
Insulation resistance testing checks for current leaking between conductors through damaged or degraded insulation
Earth fault loop impedance testing confirms a fault would clear quickly and safely if one occurred
Sections of a circuit isolated in turn to narrow a fault down to a specific run of cable or a specific accessory
Test results compared against what the circuit should read, not just whether it currently 'works'
Lighting and socket faults range from a single failed accessory to a wiring problem affecting an entire circuit, and the fix depends entirely on which one it turns out to be.
Failed switches, damaged accessories and loose terminations are common, straightforward causes
A whole lighting circuit going out can point to a failed connection at a junction box or ceiling rose rather than any individual fitting
Socket faults are checked for loose terminations, damaged cable and, where relevant, incorrect wiring from previous work
Faulty accessories are replaced as part of the same visit where the cause is confirmed and a suitable replacement is available
Systematic testing takes longer than a guess — that's what makes it reliable.
A fault-finding visit generally starts with understanding exactly when and how the fault occurs — constantly, under a specific load, at a particular time of day — before any testing begins, because that information narrows down where to start looking. From there, the circuit is tested and isolated in sections: checking insulation resistance, earth fault loop impedance and continuity at each stage, rather than testing the whole circuit as one block and hoping the result points somewhere useful.
How the work is charged reflects that process. Diagnostic time is assessed on the complexity of the fault and how long it genuinely takes to isolate, and we agree the scope with you before any more intrusive investigation — lifting flooring, opening up walls — goes ahead. We won't recommend bypassing or disabling a protective device to make a symptom go away; if something is tripping for a real reason, the answer is finding that reason, not removing the protection that's correctly responding to it.
Diagnosis starts with understanding exactly when and how the fault occurs
Circuits are tested and isolated in sections rather than as one block
Insulation resistance, earth fault loop impedance and continuity all inform the diagnosis
We won't bypass or disable a protective device to mask a genuine fault
Reviews from real ComGas customers, shown as submitted through Google.
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Lucie Victoria
15 May 2025
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Excellent service, highly recommend
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James Mowat
30 April 2025
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Incredible service — problems fixed perfectly once again.
Lee, Paul and the team at COMGAS are fantastic. They arrived on time and got straight to work, quickly identifying the root cause of the plumbing and heating issues I was experiencing.
The problems were diagnosed swiftly, I was kept fully informed throughout, and both issues were fixed with impressive speed and precision.
Having worked in the industry for nearly 20 years, I know how rare it is to find reliable, trustworthy, and genuinely skilled professionals — let alone a team this good.
I joked about it at the time, but it’s true: I had the best shower I’ve ever had in this house after they finished the job — and I’ve lived here for 10 years!
I honestly couldn’t ask for more and can’t recommend COMGAS highly enough.
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Faz
31 March 2025
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ComGas replaced my boiler and water tank at short notice. So glad i used them. Thank you
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Laura Andrews
26 March 2025
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Lee came out to the school I work in to look at a problem with our heating, he diagnosed the issue and was able to fix it on the spot in a neat and tidy manor. Would highly recommend
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Chloe
26 March 2025
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I recently used Comgas for a gas and heating service, and I couldn't be more impressed! From start to finish, their team was professional, friendly, and highly knowledgeable. They quickly identified the issue with my heating system and explained everything in detail, offering both short- and long-term solutions.
The technician was punctual and took extra care to ensure everything was running smoothly. I really appreciated their attention to detail and how they made sure to clean up after the work was completed. My home is now warm and cozy, all thanks to their expert service. I highly recommend Comgas for anyone looking for reliable, efficient, and trustworthy gas and heating professionals!
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Bec Newey
8 July 2024
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Messaged Lee on a Sunday evening with request. Instant reply that evening and engineer came next day. Polite, professional and helpful. Thorough investigation and speedy resolution to a leak with sink in wc. Happy customer.
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P Duffy
2 April 2024
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Scott and the team have served me well over several years. Skilled craftsmen. Dependable careful and very cosy-effective. I highly recommend them.
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Cilla Trout
22 March 2024
Trustindex verifies that the original source of the review is Google.
Definitely recommend friendly reliable service
Scott was helpful and reassuring regarding our boiler answered our concerns and explained the problem and best course of action thank you for your advice
Fault finding questions
Frequently asked questions.
If a circuit keeps tripping or something in the house has an intermittent fault you can't pin down, get in touch and we'll work through it properly.
An RCD trips on earth leakage, so the cause is usually a fault on one of the circuits it protects, a faulty appliance plugged into one of those circuits, or occasionally moisture affecting an outdoor circuit. Isolating which circuit and which cause requires testing rather than guessing.
Why does my MCB trip only when I use a specific appliance?
That points toward an overload on that circuit or a fault within the appliance itself, rather than the fixed wiring generally. We test the circuit's capacity and, where appropriate, advise on the appliance separately.
What is a borrowed neutral and why does it matter?
It's where the neutral conductor for one circuit is incorrectly shared with another, usually from earlier wiring work. It can cause faults that only appear when both circuits are used together, and it's a genuine safety issue that needs correcting properly, not just working around.
How do you find a fault that only happens occasionally?
By understanding the conditions under which it occurs — heat, movement, a specific appliance — and testing the circuit under those conditions rather than only when it's behaving normally. It typically takes longer than diagnosing a constant fault.
What is insulation resistance testing?
A test that checks for current leaking between conductors through damaged or degraded cable insulation, measured in megohms. A low reading points to a specific section of cable or an accessory needing further investigation.
How is fault-finding work charged?
Diagnostic time is assessed on the complexity of the fault and how long it takes to isolate, and we agree the scope with you before any more intrusive investigation, such as opening up walls or lifting flooring, goes ahead.
Can a tripping circuit just be left switched off until it's fixed?
That's a reasonable temporary measure for an isolated affected circuit, but we won't recommend bypassing or disabling the protective device itself — it's doing its job correctly by tripping, and the answer is finding the fault, not removing the protection.
Do you replace the faulty part as part of the same visit?
Where the cause is confirmed and a suitable replacement part is available, yes. Where the fault is more involved — a cable needing replacement, for example — we'll explain what's required and scope that separately.
