What a thermal scan shows
Electrical problems usually produce heat before they produce failures. A loose lug, a corroded connection, an overloaded conductor or a phase carrying more current than the others will run warmer than the parts around it. An infrared camera turns that heat into an image, so a trained thermographer can find the problem without touching anything.
Because thermography is non-contact and done while equipment is running, it is one of the most cost-effective tools in an electrical preventive maintenance program. One scan can cover a building's main switchgear, transformers, panels, motor control centres and disconnects in a few hours. The cost of a scan is small compared with a single unplanned outage.
How a scan is done
- The thermographer and a qualified electrician agree on the route and the equipment list.
- The electrician opens covers wearing the right PPE, or the scan is done through installed infrared windows.
- Each item is scanned under normal operating load, with a regular photo taken alongside each thermal image.
- Load readings are recorded so temperatures can be judged against how hard each circuit was working.
- Covers go back on, and findings are compiled into a report.
A scan on a quiet Sunday may show nothing. Book it during normal operating hours, or when production equipment is running, so connections are carrying real current.
Reading the report
A good report lists each anomaly with its location, the thermal and visible images, the temperature rise compared with similar parts under similar load, and a priority. Comparison is the key idea. Phase B running much hotter than A and C on the same breaker tells you more than a single temperature reading would.
| Priority | Typical meaning | Response |
|---|---|---|
| Low | Small rise, likely minor | Monitor at the next scan |
| Medium | Clear rise, developing problem | Repair at the next planned outage |
| High | Large rise or fast change | Schedule repair soon |
| Urgent | Severe heat or visible damage | Act now and reduce load if possible |
Exact temperature thresholds differ between standards and between thermographers, so look for a report that explains the criteria it used. Ask the electrician to walk you through the urgent and high items before they leave site. Urgent findings should never wait for the written report; a good thermographer tells you on the spot.
What it finds, and what it misses
Thermography is good at finding:
- Loose, corroded or poorly made connections
- Overloaded conductors and breakers
- Phase imbalance on three-phase equipment
- Failing breakers, contactors and fuse clips
- Overheating transformers and motor connection boxes
It has limits. A camera cannot see through closed metal enclosures. Shiny surfaces such as bare copper or polished bus can give misleading readings. A problem that only heats up under heavy load may hide during light load. Thermography also does not replace insulation testing, breaker testing or a careful visual inspection.
Making scans safer with infrared windows
Removing covers on energized switchgear exposes people to arc flash and shock hazards. That work needs a qualified electrician following CSA Z462 and your own safe work procedures. Our guide to arc flash basics explains why.
Infrared windows, fitted into covers during a planned shutdown, let future scans happen with the doors closed. They suit large switchgear and motor control centres that are scanned every year.
Never remove panel or switchgear covers to look for heat or to point a borrowed camera at the bus. Leave the scan to a thermographer working with a qualified electrician.
How often to scan
Many facilities scan main switchgear and critical equipment once a year, and more often where equipment is heavily loaded, critical to operations, or where a previous scan found problems. Insurers sometimes set their own expectations, so check your policy.
Repeat scans in the same season and at similar loads give the most useful comparison. In Edmonton, that often means scanning when heating or process loads are at their normal peak. See commercial maintenance and industrial maintenance.
Follow-up matters as much as the scan. Assign each finding an owner and a target date, and rescan repaired items to confirm the fix worked. A scan report that sits in a drawer finds problems but does not prevent failures.
Common questions
Does an infrared scan require a shutdown?
No. The scan is done while equipment runs under load. Any repairs it finds, such as re-terminating a hot connection, usually do need the circuit or equipment de-energized.
What does a hot spot usually mean?
Most often a loose or corroded connection. It can also point to an overloaded circuit, phase imbalance or a failing component. The report and the electrician's follow-up confirm the cause.
Can my maintenance staff do the scanning?
Thermal imaging interpretation takes training, and opening energized equipment takes a qualified electrician with the right PPE. Most facilities hire both together.
Will the scan tell us what needs replacing?
It tells you where heat is abnormal and how urgent it is. Deciding between a repair and a replacement takes a follow-up inspection with the equipment de-energized.
Codes and permit rules change and every building is different. For work on your system, talk to a licensed electrician and your local permit authority.