What can't an electrical thermography survey detect?

Thermography only sees the surface temperature of what the camera has a clear line of sight to, under the load present at the time. It cannot see inside sealed components or through ordinary glass and most plastic covers, and it will not find faults on circuits that are off or lightly loaded. It complements electrical testing rather than replacing it.

It needs a line of sight

An infrared camera measures the heat coming off a surface. If a connection is behind a cover that cannot safely be removed, inside a moulded case, or at the back of a joint facing away from the camera, it cannot be imaged directly. Ordinary glass and most plastic shrouds block the wavelengths the camera uses, so a reading taken through them shows the cover, not the connection behind it. That is why panels are opened by the site’s authorised person during the survey, and why infrared windows are fitted where covers cannot be opened live.

It needs current flowing

A poor connection only heats up when current passes through it. Standby circuits, spare ways, a generator that is not running or a lightly loaded board can all look normal on the day and still have a problem. A useful report records the load at the time of each reading. See what load is needed for a survey.

It reads the surface, not the inside

The temperature inside a component can be higher than the surface the camera sees, especially inside enclosed parts such as fuses, breakers and insulated cable joints. A small rise on the outside can sit over a bigger one inside, so findings are judged against similar components under similar load rather than by the surface figure alone.

Shiny metal and reflections can mislead

Bare, shiny copper and aluminium give off little infrared and reflect heat from elsewhere, so they can read cooler than they really are or show a reflection as a hot spot. Experienced thermographers allow for this by measuring on painted or oxidised surfaces, insulation or labels where possible, and by changing the viewing angle to see whether a hot spot moves with it. Some parts run warm by design, such as heaters and reactors, and are not faults.

Some faults are not thermal

Thermography will not tell you insulation resistance, earth continuity, whether an RCD trips in time or whether a protective device is set correctly. Those need electrical testing, such as an EICR. See does a thermographic survey replace an EICR?

It is a snapshot

A survey shows conditions on the day. Comparing each survey with the last one shows what is changing. See comparing results year on year.

What it does well

Within those limits, it finds what is in view and carrying current, quickly and without a shutdown. On a London data centre build, commissioning thermography by our team found 16 busbar sections reading above 80 °C under test load, the highest 103.5 °C at a tap-off unit. Each one was located and imaged before handover. A good report also lists what could not be imaged and why, so a gap is never read as a pass.

Frequently asked questions

Can thermography find a loose connection that isn’t heating up yet?

Not if it is not producing heat at the time of the survey. That is why surveys are done under normal load and repeated on a regular cycle.

Can it see faults inside buried or ducted cables?

No. It can image cable terminations and exposed runs, but not cables inside walls, floors or ducts.

Does thermography replace electrical testing?

No. It finds heat at connections and components in view; testing checks the safety of the installation. Most sites need both.

What can’t an electrical thermography survey detect?