Short answer: an insurer-ready electrical thermography survey is carried out by a certified thermographer, on equipment running at meaningful load, and every anomaly in the report is measured, compared, rated and given a clear action. If your electrician can’t go straight to the right terminal from the report, and your insurer can’t see how the risk is being managed, the job isn’t finished.
What insurers are actually asking for
When an insurer asks for an annual infrared survey of switchgear, distribution boards and MCCs, they aren’t asking for photographs. They want evidence that high-resistance connections, overloads and other heat-generating defects are being found before they become a fire. The report is that evidence, so the report is what gets judged.
Load: the most common reason faults are missed
Resistive heating scales with the square of current. Halve the load and you roughly quarter the heat from a poor connection. A termination sitting a few degrees above its neighbours at 25% load can be dramatically hotter at full demand.
General guidance is to survey at 40% of rated load or above, and ideally at normal peak. That means planning the survey around the site’s working pattern. The load at time of inspection should be recorded against each finding so the reader can judge how the defect will behave under full load.
Measurement: ΔT, emissivity and reflections
A temperature on its own means little. The useful number is the temperature rise (ΔT) against a similar component under similar load, for example the same terminal on the adjacent phase. Comparison against ambient is a secondary check.
Bare copper, aluminium and polished busbar have very low emissivity and reflect heat from their surroundings, so a competent thermographer measures on insulation, terminations or other high-emissivity surfaces and accounts for reflected apparent temperature. Readings taken off shiny metal without that correction are unreliable in both directions.
Interpretation: same colour, different problem
Hot spots that look identical on screen can mean very different things:
- High-resistance connection: heat concentrated at the termination, falling away along the conductor. Typically a loose, corroded or poorly made joint.
- Overload: the whole conductor evenly warm. A design or load issue rather than a maintenance defect.
- Warm neutral on a balanced supply: often harmonic currents from IT and LED loads, common in offices and data halls.
- Phase imbalance: one phase warmer along its full run rather than at a single point.
Getting this right is what separates thermography from taking thermal pictures, and it decides what the client should actually do.
Severity ratings and actions
Every finding should carry a priority based on ΔT, component type and the criticality of the circuit. Widely used ΔT bands for similar components run roughly from “possible deficiency, monitor” at a few degrees, through “probable deficiency, repair at next opportunity”, to “major discrepancy, repair immediately” above around 15°C. The rating should be paired with a recommended action, not left for the reader to interpret.
What the report must contain
- Thermal and visual image of each anomaly, with asset ID and precise location
- Measured temperatures, ΔT and the reference used
- Load at time of survey
- Emissivity and reflected temperature settings used
- Severity rating and recommended action for every finding
- An executive summary of findings by priority
- The thermographer’s name and certification level
Access and safety
Most electrical surveys require covers removed on live equipment. RAMS should be agreed in advance, cover removal carried out by an authorised person where site rules require it, and arc-flash risk assessed. On high-risk enclosures, infrared windows allow repeat surveys without opening panels.
After the survey
Send the report to your insurer, pass the remedial list to your electrical contractor, and book a re-scan of repaired items to confirm the fix. Keep every year’s report: trends between surveys are often more revealing than a single snapshot.
Why independence matters
Ti Thermal Imaging does not carry out electrical repairs. Our role is to find, measure, rate and report accurately; your electricians carry out the remedial work, and we re-scan to confirm it. That separation is something insurers and maintenance managers value.
About Ti Thermal Imaging
Ti Thermal Imaging is a Level 3 certified thermographic inspection company with over 14 years’ experience in electrical thermography across the UK and UAE, including data centres and BREEAM projects. To book an independent electrical survey, call 020 3885 7464.