Same Hotspot on Every Thermal Survey? Here's Why a Recurring Thermal Hotspot Won't Go Away

TL;DR

• A hotspot that reappears on consecutive thermal imaging surveys almost always means the previous repair fixed the symptom, not the underlying cause.

• Common root causes include loose connections that were re-tightened rather than replaced, unresolved load imbalance, and components that were already degrading.

• A recurring thermal hotspot can be a genuine fire risk assessment finding, not just a facilities snagging item.

• The right response is a proper root-cause investigation, not a repeat of the same repair.

• If the same reading keeps flagging red, it is worth asking exactly what the previous contractor checked and why the fault returned.

A recurring thermal hotspot almost always means one thing: the last repair addressed the symptom, not the cause. If your latest thermal imaging survey has flagged the same reading for a second or third time running, that is not bad luck and it is not simply the system still settling down after a repair. It is a clear signal that whatever was done last time did not actually fix the underlying fault.

For property and asset managers responsible for commercial buildings, this pattern is worth taking seriously. A hotspot that will not stay fixed points to a connection, component or load issue that was never properly resolved. Left unaddressed, it raises the risk of an unplanned power outage, equipment damage, or in more serious cases, an arc flash event.

What a Recurring Thermal Hotspot Actually Means

A recurring thermal hotspot is a point on a distribution board, switchboard or cable run that shows an abnormal temperature rise on more than one survey in a row, even though remedial work was carried out in between. It is different from a one-off hotspot picked up for the first time. A single reading might reflect a genuine new fault. A repeat reading, in the same place, after a repair, tells you the repair did not hold.

Thermographic surveys measure temperature difference against a reference point, known as delta-T. A connection running a few degrees warm is worth monitoring. A connection running significantly hotter than a comparable load-bearing point, especially if that reading has shown up before, is the kind of finding a competent thermographer will flag as urgent. A full thermal imaging survey records these readings against a baseline so recurrence is easy to spot from one visit to the next.

Why Does the Same Hotspot Keep Showing Up?

In nearly every case, a recurring thermal hotspot comes down to one of three underlying issues.

Loose Connections That Were Re-Tightened, Not Replaced

The most common cause is a connection that was simply re-torqued rather than properly remade. Re-tightening a terminal can bring the temperature down for a few months, but if the contact surface, cable end or lug was already damaged by the original heat, the connection will loosen again under normal thermal cycling. The fix needs to include remaking the joint properly, not just tightening what is already there.

Load Imbalance That Was Never Investigated

A hotspot on one phase of a three-phase system is often blamed on the connection alone, when the real driver is an imbalance in the load carried across the phases. If nobody checks actual current readings across all three phases at the time of the repair, the connection can be remade correctly and the hotspot will still return, because the underlying overload was never addressed.

A Component That Was Already Failing

Breakers, fuses and switchgear components degrade internally in ways that are not always visible from the outside. If the original repair replaced a cable or tightened a joint but the component itself, such as a circuit breaker contact or fuse holder, was already past its working life, the hotspot will reappear as that component continues to fail. This pattern is similar to switchgear that keeps tripping repeatedly, where a repeat symptom points to an unresolved root cause rather than a one-off event.

Is a Recurring Thermal Hotspot a Compliance Failure?

Yes, in most cases it should be treated as one. A hotspot that keeps returning is evidence that a known electrical defect has not been properly remediated, which sits squarely within the kind of finding covered under common electrical defects that require EICR remedial works. Under BS 7671 and the Electricity at Work Regulations 1989, duty holders have an ongoing obligation to keep electrical installations safe, not just to have carried out a repair at some point in the past.

The same principle applies whether the recurring reading is on a distribution board or elsewhere in the system. Reviewing findings from distribution board thermal imaging surveys alongside the repair history is a useful way to see whether a fault is genuinely new or has quietly recurred.

What Should You Do Next?

1. Request the full thermographic report, including delta-T readings and photographs, from both the original survey and the most recent one, so you can compare exactly what changed.

2. Ask the contractor carrying out remedial work to confirm what specifically was done, not just that a connection was tightened, but which component was inspected, replaced or tested.

3. Check load readings across all phases at the time of any repair, not just at the point of the hotspot itself.

4. Commission a proper electrical remedial repair rather than a like-for-like reapplication of the previous fix.

5. Re-survey under comparable load conditions after the repair, ideally with similar equipment running, to confirm the fault has actually gone rather than just cooled temporarily.

If a burning smell has ever accompanied the hotspot, treat this as urgent and do not wait for the next scheduled survey.

Why Ignoring a Recurring Thermal Hotspot Raises Liability Questions

If a recurring hotspot is documented across multiple survey reports and nothing changes, that paper trail works against the duty holder, not for them. In the event of an incident, an insurer or investigator will ask why a known, repeated finding was not properly resolved. Commissioning a full survey that gets to the root cause, rather than accepting a repeat of the same repair, is the more defensible and genuinely safer path.

Frequently Asked Questions

Why does my thermal imaging survey keep flagging the same hotspot?

It almost always means the previous repair addressed the visible heat rather than the underlying cause. Common culprits are a connection that was re-tightened instead of remade, an unresolved load imbalance, or a component that was already degrading. A proper root-cause investigation, rather than a repeat of the same fix, is the only way to stop it recurring.

Is a recurring hotspot on a thermal imaging survey a fire risk assessment finding?

Yes. A hotspot that keeps returning is evidence of an unresolved electrical defect, which is exactly the kind of issue a fire risk assessment should capture and duty holders are obliged to act on. Treating it as a routine maintenance note rather than a compliance finding leaves the responsible person exposed if an incident follows.

How many degrees above ambient counts as a hotspot on a thermal survey?

There is no single fixed number, but most thermographers treat a temperature rise of around 10 to 15 degrees Celsius above a comparable reference point as worth investigating, with anything above roughly 40 degrees Celsius rise treated as urgent. Context matters as much as the figure: a smaller rise on a critical circuit, or one that keeps recurring, should be taken just as seriously as a larger one-off reading.

Can a hotspot go away on its own without repair?

No. A genuine thermal hotspot is caused by a physical fault, such as a loose connection, overload or failing component, that will not resolve itself. Any apparent improvement without remedial work usually reflects a change in load at the time of the survey rather than the fault actually clearing.

Who is liable if a hotspot recurs after remedial work has been carried out?

Liability depends on what the original contract covered and what was actually done, but the duty holder retains the underlying legal responsibility for the safety of the installation regardless of who carried out the repair. This is why requesting a clear record of what the previous contractor checked and fixed matters, both for accountability and for planning the next repair properly.

How often should a thermal imaging survey be repeated after a repair?

Best practice is to re-survey shortly after remedial work, under comparable load conditions, to confirm the fault has genuinely cleared rather than simply cooled temporarily. Beyond that, most commercial buildings benefit from annual thermal imaging surveys as part of a routine electrical maintenance programme, with more frequent checks on any circuit that has previously shown a fault.

What should a proper root-cause repair for a recurring hotspot include?

It should include remaking the connection properly rather than simply re-tightening it, checking load balance across all phases, and inspecting the condition of the component itself, such as a breaker or fuse holder, rather than just the cable or joint. The repair should be followed by a re-survey under similar operating conditions to confirm the hotspot has actually gone.