Thermographic inspection: what it finds and when to book one.

What thermal imaging actually detects

An infrared camera captures radiation in the 8–14 micrometre wavelength range and displays it as a temperature map. Electrical components running at elevated temperatures show up as hot spots against a cooler background. The challenge (and the skill) is interpreting what you're seeing and distinguishing a genuine fault from a normal temperature differential.

In commercial switchboards and distribution systems, thermographic inspection reliably finds:

Loose or corroded connections

A connection with elevated resistance (whether from a loose bolt, oxidation, or contamination) generates heat proportional to the current flowing through it. A connection that's 15°C above ambient under normal load will be 40°C above ambient under full load. Left unattended, the heat accelerates corrosion, which increases resistance, which generates more heat. It's a progressive failure mode that ends in an arc fault or fire.

The classic presentation in a thermographic image is a hot spot at a busbar connection, cable lug, or circuit breaker terminal. These are easy to miss visually during a normal inspection because the cables and components look intact. The only evidence is the temperature.

Overloaded conductors

A conductor carrying more current than it's rated for runs hot along its entire length, not just at a connection point. This shows up as a uniform temperature elevation on the cable rather than a localised hot spot. Common cause: circuit loading has crept up over time as additional equipment has been added, and the cable that was adequate five years ago is now marginal.

Failing contactors and circuit breakers

Contactors whose contacts are worn or pitted have elevated contact resistance, which generates heat under load. A contactor running significantly hotter than its peers in the same switchboard is telling you it's close to end of life. Catching this thermographically means replacing it on your schedule during planned maintenance, rather than during an emergency at 2am when it finally fails.

Circuit breakers can also show elevated temperature when their internal contacts are deteriorating or when they're carrying loads close to their rating. A breaker that's significantly hotter than others feeding similar loads warrants investigation.

Imbalanced three-phase loads

In a balanced three-phase system, all three phases should be carrying similar current and running at similar temperatures. Significant temperature differences between phases indicate load imbalance. One phase is working harder than the others, which reduces efficiency, stresses equipment, and can cause problems for motors and other three-phase loads connected downstream.

Thermographic inspection makes three-phase imbalance immediately visible in a way that a single-point current measurement doesn't.

Overheated neutral conductors

In circuits with significant harmonic distortion (common where variable speed drives, UPS systems or large switch-mode power supplies are connected) the neutral conductor can carry more current than the actives and run hot. This is a known issue in modern commercial buildings with high IT or VSD loading, and it's one thermal imaging picks up readily.

The standards and schemes behind a survey

There is no single dedicated Australian standard for electrical thermography. Surveys in Australia are run against international practice (ISO 18434 for condition-monitoring thermography procedures, with severity classifications typically drawn from the NETA or NFPA 70B schemes) inside an Australian safe-work framework. AS/NZS 4836 covers safe working on or near low-voltage equipment, which is what opening an energised switchboard amounts to.

The practical requirements that follow:

• Equipment must be operating under sufficient load (generally at least 40% of normal operating load) for meaningful temperature differentials to be visible. Thermal surveys conducted on lightly loaded equipment miss faults that would show under normal load.
• Ambient temperature and load at the time of the survey must be recorded and reported, as these affect the interpretation of temperature readings.
• The inspector must be trained. Thermographer certification follows the Level 1/2/3 hierarchy under ISO 18436-7 (administered locally through AINDT), and opening energised switchgear for the survey is electrical work that requires a licensed electrician.

When thermographic inspection is required

The most common trigger is insurance. A significant proportion of commercial property insurers now require annual thermographic inspection of switchboards for commercial clients above a certain sum insured, particularly in manufacturing, cold storage, food processing, and other industries with large continuous electrical loads. If your insurer requires it and you don't have a current report, you may have a gap in your cover that you're not aware of.

Beyond insurance requirements, thermographic inspection is worth scheduling:

• Before and after major changes to electrical loading: a new production line, a significant tenancy change, or a large HVAC installation can change the loading profile of a switchboard materially. A thermal survey before and after establishes a baseline and confirms the installation is coping.
• As part of a scheduled maintenance programme: for commercial and industrial clients, annual or biennial thermographic inspection as part of a maintenance contract is a reasonable and cost-effective way to catch developing faults before they become failures.
• When equipment age raises concern: switchboards that haven't been opened or inspected in a decade often have connection deterioration that's invisible until it's a problem. Thermal imaging is a good first pass before committing to a full maintenance schedule.
• Following an unexplained trip or fault: if a circuit breaker has tripped without obvious cause, thermal imaging of the affected circuit and switchboard can reveal a hot spot that explains the trip and hasn't yet progressed to failure.

Manufacturing and cold storage operations in Melbourne's eastern suburbs tend to have both the insurance requirement and the operational imperative. An unplanned electrical shutdown in a cold storage facility isn't just inconvenient. It's potentially a significant product loss event.

What a proper thermographic inspection involves

There's a meaningful difference between a thermographic survey conducted properly (under load, with a calibrated camera and findings classified against a recognised severity scheme) and someone pointing an IR camera at a switchboard and taking a few photos.

A proper inspection involves:

Pre-survey load check. The installation needs to be operating under at least 40% of normal load. For manufacturing clients, this usually means scheduling the survey during production. For office buildings, it typically means business hours on a normal working day. The load at the time of the survey is recorded.

Full coverage of distribution equipment. Main switchboard, sub-boards, motor control centres, distribution boards. All panels are opened and all equipment inspected under load. Connections behind covers and inside enclosures are checked, not just what's visible on the face.

Calibrated equipment. The camera must be calibrated and used by someone who understands emissivity correction, reflected apparent temperature, and the other variables that affect accurate temperature measurement. Without correct emissivity settings, temperature readings can be significantly off, leading to either missed faults or false positives.

Documented findings. Every anomaly is photographed in thermal and visual light, assigned a classification, and included in the report with temperature differentials, likely cause, and recommended action.

How findings are classified

The exact bands come from the severity scheme cited in the report (NETA MTS, NFPA 70B, or an insurer's scheme), but the practical framing is three levels:

Imminent: take out of service. A temperature differential significant enough to indicate imminent failure or fire risk. The component should be de-energised and repaired before being returned to service. In practice, this might be a loose main connection running 60°C above ambient.

Significant: repair within 30 days. A developing fault that isn't at immediate failure risk but is progressing. Schedule repair as a priority within the next maintenance window. Don't let this drift to the next annual survey.

Monitor: note and re-survey. A minor anomaly that warrants documentation but doesn't require immediate action. Confirm its status at the next inspection. If it's progressed at the next survey, escalate the priority.

This classification gives facility managers and maintenance teams a clear action framework rather than a report full of findings with no indication of urgency.

After the report: what happens next

When we find an imminent or significant defect, the next step is a repair quotation. Depending on what was found, that might be:

• Retorquing and re-terminating a loose connection (often a straightforward job)
• Replacing a failing contactor or circuit breaker
• Investigating an overloaded circuit and rectifying the cause
• Load-balancing three-phase distribution

In most cases, the faults found in a thermographic survey are not expensive to fix once they're identified. The cost is in not finding them.

If you operate a commercial or industrial premises and haven't had a thermographic inspection recently, get in touch about our thermographic inspection service.