What a Thermal Scan Actually Finds in a Switchboard, and Why Insurers Ask For One
Most electrical failures announce themselves twice. The first announcement is heat, and it can run for months. The second is smoke, and by then you are having a very different conversation.
A thermal scan exists to catch the first one. Here is what the camera is actually measuring, what it genuinely finds, what it cannot find, and why a property insurer may ask whether you have had one done.
What the camera is actually measuring
A thermographic scan uses an infrared camera to record the temperature distribution across the surface of equipment. It is not an x-ray and it does not see inside anything. It sees the outside of things, in temperature rather than light.
What makes it useful is comparison. As QBE puts it in its own guidance for policyholders, hot spots are identified by comparing a component against surrounding components, similar equipment, or previous scans of the same equipment. One terminal running warmer than the three identical terminals beside it is the finding. An absolute number on its own means very little.
That last comparison point matters more than people expect. A scan taken today is a diagnosis. A scan taken today against a scan from two years ago is a trend, and a trend tells you whether something is deteriorating or has always run slightly warm.
What it finds
| What’s wrong | How it shows up | Where it ends if ignored |
|---|---|---|
| Loose or under-torqued termination | One terminal hotter than its neighbours on the same bar | Arcing, melted insulation, fire |
| Corroded connection | Localised heat with no obvious cause on the surface | Progressive failure, common near the coast |
| Overloaded circuit | Whole cable and breaker warm along their length | Nuisance tripping, cable damage, derating |
| Phase imbalance | One phase consistently hotter than the other two | Overloaded neutral, equipment stress |
| Failing breaker or contactor | Heat at the device rather than at its connections | Protection that no longer protects |
| Undersized or damaged cable | Heat concentrated at one section of a run | Insulation breakdown |
Notice the pattern. Almost every one of these is a connection problem rather than a component problem, and connection problems are exactly the kind that get worse on their own. Resistance makes heat, heat degrades the joint, the degraded joint has more resistance. It is the same mechanism behind a burning smell at a power point, just at a scale that can take a building with it.
The limitation nobody mentions: it has to be under load
This is the difference between a scan that manages risk and a scan that produces a certificate. Both cost you a morning. Only one of them tells you anything.
What a thermal scan does not find
Worth being straight about, because it gets sold as though it sees everything.
- Faults on circuits that are not energised or not loaded at the time
- Anything behind a closed metal panel, unless the panel has an infrared window fitted
- Insulation resistance problems, which need a meter rather than a camera
- Whether an RCD actually trips within its rated time, which is a separate test
- Wiring faults that generate no additional heat, including many earthing defects
So it belongs alongside conventional testing, not instead of it. A thermal scan plus a proper switchboard inspection and test covers what neither does on its own, and RCD testing answers the trip-time question the camera cannot.
Why insurers ask about it
Because faulty electrical equipment is one of the larger causes of commercial fire loss. QBE’s guidance for policyholders cites that 21% of industrial fires originated in electrical transformers, power supplies, wiring and related equipment.
They are also explicit about the ask. QBE states that it “may ask you to conduct regular thermographic scanning as part of your preventative maintenance regime and to demonstrate good management practices”. Read that carefully: the value to an insurer is not only the scan, it is the demonstration. A scan with a dated report is evidence that the building is being managed. An undocumented walk-around is not.
The Queensland duty runs in parallel. Under the Electrical Safety Act, a person conducting a business or undertaking has the primary duty to ensure the business is conducted in a way that is electrically safe, including that electrical equipment is electrically safe. WorkSafe Queensland’s code of practice on managing electrical risks lists what visual inspection looks for, and one of the items is “discolouration that may indicate exposure to excessive heat”.
In a body corporate building the duty lands on whoever is responsible for common property plant, which is a line worth being clear about before an incident rather than after one. That split is set out in body corporate versus unit owner electrical responsibilities, and the work itself sits under strata and body corporate electrical.
What to ask for, and what a real report contains
This is the part most buyers do not know to ask about, and it separates a genuine survey from someone waving a camera.
- Ask what certification the thermographer holds. QBE’s guidance points to Level I, II or III certification through AINDT or BINDT, aligned to ISO 18436-7. Ask the question before booking, whoever you use.
- Ask when they intend to scan. The answer should involve your operating pattern, not their run sheet.
- Ask what the report will contain. QBE’s stated expectations are thermal images, a summary of findings including the temperature differences detected, and recommended actions prioritised by repair urgency.
- Ask what happens to the findings. A prioritised list nobody actions is worse than no list, because it documents that you knew.
- Keep the reports. Comparison against previous scans is where the real diagnostic value builds up, and it is also what demonstrates a maintenance regime rather than a one-off.
On frequency, QBE’s published guidance ranges from every one to three years for regular office buildings, to at least annually for manufacturing sites, to as often as weekly on mining sites. Queensland’s code takes the same risk-based approach: the nature and frequency of inspections varies with the nature of the work carried out. Sensible reading for most Gold Coast commercial and strata buildings is annual to three-yearly, weighted by age of the board, load, and environment.
Where scanning is part of an ongoing arrangement rather than a one-off, it belongs in a preventative maintenance programme, which is also the easiest way to produce the documented history an insurer is asking to see. The service itself is commercial thermal imaging and reporting.
Does any of this apply to a house?
Less often, and I would rather say so than sell it to everyone.
Most homes do not need thermal imaging. The cases where it genuinely earns its place are older boards, boards that have had work added to them over decades, properties where something has already been warm or smelled hot, and anything close to the water. Salt-driven corrosion attacks connections rather than the cable between them, which is precisely what a camera is good at finding, and it is the same mechanism behind Gold Coast switchboards corroding faster than inland ones.
It is also worth considering before buying an older property, alongside a pre-purchase electrical inspection. For everything else, residential thermal imaging is available, but I would rather tell you it is unnecessary than take the booking.
Don’t wait for a scheduled scan if
- Anything at the board smells hot, or there is visible browning or scorching
- The board or a wall switch buzzes, hums or crackles
- Breakers trip under load and hold when the load comes off
- Any panel or cover is warm to touch
- Lights dim noticeably when large plant starts
Those are live faults, not maintenance items. A buzzing or humming board has its own diagnosis in why a switchboard buzzes, and anything urgent is a 24/7 emergency call rather than a booking for next month.
Frequently asked questions
What does a thermal scan actually detect in a switchboard?
Heat produced by resistance, which usually means loose or corroded terminations, overloaded circuits, phase imbalance or a failing protective device. Hot spots are identified by comparison against neighbouring components, identical equipment elsewhere, or previous scans of the same board. It finds developing faults months before they produce a smell or a trip.
Why do insurers ask about thermographic scanning?
Because faulty electrical equipment is a significant cause of commercial fire loss. QBE cites 21% of industrial fires as originating in electrical transformers, power supplies, wiring and related equipment, and states it may ask policyholders to conduct regular thermographic scanning as part of a preventative maintenance regime and to demonstrate good management practices. The documentation matters as much as the scan.
Does the building need to be running during the scan?
Yes, and this is the most common way a scan gets wasted. Heat comes from current flowing through resistance, so an unloaded board produces nothing for the camera to see. A scan taken in an empty building at 7am can return a clean report on a board carrying a real fault. The scan should be timed to representative load.
How often should a commercial switchboard be scanned?
QBE’s published guidance suggests every one to three years for regular office buildings, at least annually for manufacturing, and as frequently as weekly on mining sites. Queensland’s code of practice takes a risk-based approach, with frequency varying by the nature of the work. Board age, load and environment all shift the answer.
What should a thermal imaging report include?
QBE’s stated expectations are thermal images, a summary of findings including the temperature differences detected, and recommended actions prioritised by repair urgency. Ask what certification the thermographer holds as well: QBE’s guidance points to Level I, II or III through AINDT or BINDT, aligned to ISO 18436-7. Keep every report for comparison.
Can a thermal scan replace electrical testing?
No. It cannot see unloaded circuits, cannot see inside a closed panel without an infrared window, and cannot measure insulation resistance or confirm that a safety switch trips within its rated time. It finds heat, which conventional testing is poor at finding. The two are complementary, and neither substitutes for the other.
Insurer or committee asking for a scan and report? Give me a call and I’ll tell you what your building actually needs.
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