If continuous temperature sensors are fitted, is an annual electrical thermography survey still needed?

Usually, yes. Fixed sensors watch the points they are fitted to, all the time. An annual electrical thermography survey images every accessible board, panel and connection across the installation, including the ones no sensor covers. The two do different jobs: sensors track known critical points between surveys, and the survey finds the problems nobody knew to watch.

What a sensor measures

A wireless or contact temperature sensor reads one point: the busbar joint, cable lug or breaker terminal it is fixed to. It does that well, around the clock, and can alarm when the reading changes. But it only sees that point. A poor connection on the next joint along, the neutral on the same board or a terminal in the panel next door will not show up unless a sensor happens to be fitted there. Sensor positions are chosen in advance, based on where people expect trouble.

What a survey covers

On a survey, an ITC Level 3 thermographer images every board and panel the site can safely open, under normal load, and looks at the whole picture: phases compared side by side, similar components compared with each other, and anything warmer than it should be. That is how unexpected findings turn up. 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. A sensor programme would only have caught those if sensors had been fitted at those exact points.

Where continuous monitoring earns its place

Continuous monitoring is worth having on a small number of critical points: a single point of failure feeding a whole hall or building, equipment whose load changes a lot through the day, or connections that sit behind covers that cannot be opened live. It gives you a trend between surveys and an early warning if something changes. Fixed thermal cameras do the same for a wider view of a critical asset. None of these replace a look at the rest of the installation.

Use the survey to decide where sensors go

The most useful order is survey first, sensors second. The survey shows which connections run warmest under real load and which assets matter most, so sensors go where they add the most. Keep the annual survey afterwards: it checks the sensors are reading the right thing, picks up anything new since the last visit and covers boards added after the sensors were fitted. Comparing each survey with the last one shows what is changing. See comparing results year on year.

A sensor log is not a survey report

A sensor log shows temperatures at fitted points over time. A survey report shows every item imaged, the load at the time, located findings with thermal and visual images, and what could not be reached and why. If an insurer, auditor or client asks for thermography evidence, check which one they mean. See do insurers require an electrical thermographic survey?

Frequently asked questions

Can wireless temperature sensors replace the annual thermography survey?

Not on their own. They cover the points they are fitted to; the survey covers every accessible connection, including ones nobody expected to be a problem.

Where are temperature sensors most useful?

On a few critical connections, especially single points of failure, equipment with changing load, and connections behind covers that cannot be opened live.

How often should a site with continuous monitoring be surveyed?

Most sites keep their normal survey cycle, usually annual. Criticality, load changes and insurer requirements decide it. See how often a live data centre should be surveyed.