Why Heat Is the Earliest Warning
A loose bolted connection, a worn contact, or a degraded busbar joint all share one symptom before they fail: increased electrical resistance, which converts current into heat at that specific point. That heat rise usually builds gradually over weeks or months, which means a periodic infrared inspection can find a developing problem while it is still a scheduled maintenance item rather than an emergency outage.
What a Thermal Survey Actually Looks For
- Bolted connections — busbar joints, cable lug terminations, and breaker primary contacts are the most common hot-spot locations.
- Phase-to-phase comparison — the three phases of a balanced load should run at similar temperatures under similar current; one phase noticeably hotter than its neighbours is often more meaningful than the absolute temperature reading.
- Comparison to ambient and to similar components — a connection running significantly hotter than an identical connection carrying the same load is a strong indicator of a resistance problem.
Doing It Safely and Getting Useful Results
A thermal camera only sees the surface it is pointed at, so panel covers generally need to be opened (or infrared inspection windows fitted) to see the actual connections, and that means the arc flash boundary and PPE requirements for that equipment apply during the survey — inspection windows exist specifically to reduce exposure by allowing a scan without opening the panel. The survey should also be done with the equipment under normal load: an idle or lightly loaded connection can look perfectly healthy and still fail under full load, since heat generated scales with the square of the current.
Acting on the Findings
Manufacturers and industry standards typically provide guidance on temperature-rise thresholds and how urgently to respond, and the safest practice is to follow those criteria rather than a single universal number. What matters most is repeating the survey on a regular schedule and comparing to previous results — a connection trending hotter each survey is telling you something even if it has not yet crossed any absolute limit.
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