- MozGlobal Engineering
- Inspection
- 5 min read
A loose connection heats up long before it fails. A thermal camera finds it while the installation is still running — if the survey is done properly.
Electrical connections fail slowly and then suddenly. A terminal that was not tightened correctly, or that has loosened through thermal cycling, develops resistance. Resistance generates heat. The heat accelerates the degradation, and the process continues quietly until the connection fails — often taking the equipment downstream with it.
The useful thing about that sequence is that it is visible long before the failure, if somebody looks with the right instrument.
What it finds
- Loose or corroded terminations, the most common finding by a wide margin
- Unbalanced loads across phases, visible as one conductor running hotter than its neighbours
- Overloaded circuits operating within their protection settings but above their comfortable rating
- Failing contactors and breakers, where the internal contact resistance has risen
- Undersized or damaged cable, running hotter than the installation design intended
It has to be done under load
This is the point most often missed. A thermal survey of a de-energised installation, or one running at a fraction of its normal load, finds almost nothing — because there is no current to generate the heat that reveals the defect. The survey has to happen while the installation is working, ideally at or near its normal operating load.
That has a scheduling consequence: thermography is done during production, not during the shutdown. Operations that plan it into the outage window are looking at exactly the wrong moment.
A thermal image of an unloaded panel is a photograph of nothing. The defect only shows when current is flowing through it.
Reading the image is not the same as taking it
A thermal camera produces an image that is easy to take and easy to misread. Reflective surfaces mislead. Different materials radiate differently at the same temperature. Ambient conditions shift the whole scale. A hot spot on a panel photographed in direct sun means something different from the same reading indoors.
What matters is the comparison: this phase against the other two, this connection against the identical one beside it, this reading against the same point three months ago. Absolute temperature alone is a weak indicator; difference is a strong one.
A finding is not a repair
Locating a hot connection is the easy half. Correcting it means de-energising the circuit, establishing why it overheated — a loose screw, a corroded lug, a conductor sized for a load that has since grown — and fixing that cause rather than simply retightening and moving on. A terminal that was tightened last year and is hot again this year is telling you something the torque wrench will not fix.
Frequency
Annual is a reasonable default for a stable installation. More often where the environment is dusty, humid or subject to vibration, where loads change frequently, or where a previous survey found several defects — because those conditions produce more of them. Each survey is worth more than the last, provided the readings are kept and compared.
