What Does an Electrical Thermographic Survey Find?
Updated: Oct 9
A thermographic survey finds electrical faults that are giving off heat before they fail: loose or corroded connections, overloaded cables and breakers, and phases carrying unequal loads. An electrician uses a thermal imaging camera to scan distribution boards, switchgear and other equipment while it is running under normal load, then reports each hot spot with an image, a temperature and a priority. It is quick, it does not need the power turned off, and it sees problems that a visual check cannot.
What a thermal imaging survey finds
Heat is the symptom of most developing electrical faults. Wherever current meets more resistance than it should, some of the energy turns into heat, and the camera shows it.
Loose terminations. A screw terminal that has worked loose, or was never tightened properly, has a small contact area and high resistance. It shows as one bright point on an otherwise cool board.
Corroded or damaged connections. Damp, dust and age raise contact resistance in the same way.
Overloaded circuits. A cable or breaker carrying more than it was designed for runs warm along its length, not just at one joint.
Unbalanced phases. On a three phase supply, one phase noticeably warmer than the other two usually means too much load has been put on it as equipment has been added over the years.
Failing components. Breakers, fuses, contactors and busbar joints that are deteriorating internally often run hotter than identical parts next to them.
The comparison is the useful part. Three identical breakers carrying similar loads should look similar on camera. When one stands out, it needs investigating.
How a thermographic survey is carried out
The survey is done during normal working hours, because faults only heat up when current is flowing. Thermal camera manufacturers advise checking equipment once it is warmed up and carrying at least 40% of its typical load. A board scanned at 6am with the building empty can look perfectly healthy.
Agree the scope. Which boards, switchgear, motor control panels and busbars are included, and when they are carrying typical load.
Open up safely. To see the terminals, covers often have to come off while the equipment is live. That is work near live conductors, so it is done by a competent person with a risk assessment and suitable precautions.
Scan and record. Each panel is scanned, with thermal and normal photographs taken of anything abnormal, along with the load at the time.
Classify. Each finding is rated by how much hotter it is than comparable components and how serious the consequence would be.
Report. You get a report listing each finding, its location, images, readings and a recommended action and timescale.
Because the equipment stays live, there is no shutdown and no disruption to the business, which is one of the main reasons thermography is used on sites where downtime is expensive.
For commercial and industrial sites across the West Midlands, Shropshire and Staffordshire, thermal imaging fits best as part of planned electrical maintenance, scheduled alongside the periodic inspection so any issues can be put right in one programme.
Opening live panels safely
Removing covers from live distribution boards is not a job for a keen office manager with a borrowed camera. The Electricity at Work Regulations 1989 only allow work on or near live conductors where it is unreasonable for them to be dead, reasonable to work near them live, and suitable precautions are in place.
A thermographic survey can meet that test, because the whole point is to see the equipment under load. But it has to be planned: the right person, a clear working space, insulated barriers where needed, and nobody reaching into the board. Our guide to the Electricity at Work Regulations explains the live working rules in more detail.
Thermographic survey vs fixed wire testing
Thermography complements fixed wire testing; it does not replace it. The two look at different things.
An Electrical Installation Condition Report (EICR, often called fixed wire testing) inspects and tests the installation with the power isolated where needed. It measures earth continuity, insulation resistance, earth fault loop impedance and RCD operation, and checks the installation against BS 7671. None of that shows on a thermal camera.
A thermographic survey sees the installation working. It catches connections that test fine when dead but heat up under load, and overloads that only appear during busy periods. It is also faster and can be repeated more often, so it is a useful check between full inspections.
What thermography cannot do:
see inside cables buried in walls or behind closed enclosures
read accurately off shiny surfaces such as bare busbars without care, because they reflect heat rather than emit it
find faults on circuits that are carrying little or no load at the time
check earthing, insulation or RCD protection
Used together, the two give a much fuller picture than either alone, and both can form part of the evidence that you are meeting the duty in regulation 4(2) to maintain electrical systems to prevent danger. The same risk based thinking applies to portable equipment, which is covered by PAT testing rather than thermography.
If your insurer asks for a thermographic survey
If your insurer or a risk surveyor has asked for a thermographic survey, check the wording first: whether it names specific equipment, a frequency, or a form of report. Send the full report, not just a summary, and keep evidence that any urgent findings were put right.
If no one has asked, it is still worth considering where an unexpected electrical failure would stop the business, such as in manufacturing, cold storage, commercial kitchens or server rooms.
If you would like your distribution boards and switchgear looked at as part of a planned maintenance programme, contact us with a list of the boards and the kind of site, and we will suggest a sensible scope.
Thermographic survey questions, answered
How long does a thermographic survey take?
It depends on the number of boards and how easy they are to reach. A small commercial building with a handful of distribution boards is a far shorter job than a large industrial site with switchgear, motor control panels and busbars.
Is a thermographic survey worth it for a small office?
Sometimes. For a small office with one or two lightly loaded boards, the periodic EICR usually covers the main risks. It becomes more valuable as loads, equipment and the cost of downtime rise.
What happens after a hot spot is found?
Minor findings are usually fixed at the next planned shutdown. Serious ones, such as a terminal running far hotter than its neighbours, need isolating and repairing promptly, followed by a re-scan under load to confirm the fix.
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