Can outdoor electrical equipment be surveyed with thermography in UK weather?

Yes, but the weather decides how much you can trust the readings. Outdoor kiosks, feeder pillars, rooftop isolators and plant panels can be surveyed, ideally on a dry, still, overcast day or after dark. Rain, wind and direct sun all change what the camera sees, so a good survey records the conditions and opens enclosures where it is safe to.

What counts as outdoor electrical equipment

On most commercial and industrial sites, a fair amount of the electrical system lives outside: feeder pillars and kiosks, transformer LV terminations in a compound, rooftop plant panels and isolators, solar PV distribution boards, EV charger supplies, external lighting boards and generator sets with their own panels. These carry load like any indoor board, and they are often the items left off an indoor survey route.

How the weather affects the readings

Wind cools surfaces, so a connection in a breeze reads cooler than it would in still air. A reading taken on a windy day can understate the condition.
Rain and wet surfaces cool by evaporation and change how the surface emits and reflects. If equipment is wet, we don’t treat the readings as reliable.
Direct sun heats enclosures, especially dark ones, and polished metal reflects it straight into the camera. A sun-heated door or a reflection can look like a fault.
Cold air lowers the ambient, which changes the readings for the same load. That is why the report states the ambient temperature with each finding.

Getting a reliable outdoor survey

Plan for a dry day, with as little wind as you can get, and image when the sun is off the equipment: early morning, an overcast day, or after dusk. Where the equipment is in an enclosure, the site’s authorised person opens it so the connections are imaged directly rather than through a door that has been sitting in the weather. Anti-condensation heaters are common in outdoor panels and are designed to run warm; a good thermographer reads them for what they are. As with any electrical survey, the equipment needs to be carrying a typical load for the connections to show their condition.

What the report records

For each outdoor item we record the ambient temperature and the weather at the time, alongside the thermal and visual images, the measured temperature, exactly where it was taken and the difference in °C from a like-for-like reference. If conditions on the day meant an item could not be imaged reliably, the report says so and why, so it can be picked up on a better day. Ti inspects and reports; the site’s electrician investigates and carries out any work.

What we’ve found outside

On a commercial warehouse with rooftop solar PV, our ITC Level 3 thermographer recorded an apparent temperature of 195.0 °C at the main isolator supply connection in a roof-level PV distribution board, with ambient at 24.0 °C. That board sat outside the site’s usual survey route. Read the case.

Frequently asked questions

Can outdoor and indoor equipment be done in the same visit?

Yes. We usually plan the outdoor items for the part of the day when the sun is off them, and do the indoor boards around that.

Is there a best time of year for outdoor equipment?

Load matters more than season, but dry, still days are easier to find in some months than others. Our guide to the best time of year covers this.

Can you image through the enclosure door?

Sometimes, through an infrared window fitted for the purpose. A standard steel or plastic door blocks the camera’s view of the connections, so it needs to be opened by someone authorised to do so.