How to Read Thermal Images for HVAC: Spot Airflow Issues, Electrical Faults & More

If you're just getting started with thermal imaging in HVAC, those colorful blobs on screen might look a bit confusing. But once you know what to look for, thermal images can help you spot HVAC issues in seconds—saving time, money, and headaches for both you and your clients.

In this guide, we’ll break it down simply so any Aussie tradie can understand how to read heat signatures like a pro.

🧰 Why Thermal Imaging Matters for HVAC Techs

Thermal cameras don’t just look cool—they help you “see” temperature differences that the naked eye can’t. That means you can:

• Pinpoint airflow issues inside ductwork

• Detect low refrigerant levels

• Spot overheating electrical connections

• Identify insulation gaps

• Catch failing compressors before they break down

By catching these problems early, you can avoid expensive call-backs and give your clients peace of mind.

How to Read a Thermal Image (Without the Guesswork)
Here are some common heat patterns HVAC techs should watch for:

1. Airflow Problems

Look for cooler (blue or purple) spots near ceiling vents or ducts. These often signal collapsed or blocked ductwork. After fixing, the temperature pattern should even out.

2. Low Refrigerant Lines

One refrigerant line should be cold (suction line), and the other warm (liquid line). If one is much colder than usual, it might indicate low refrigerant levels.

3. Electrical Issues

Hot spots (shown in white, yellow, or red) on electrical panels or connections mean potential overheating. After repair, the image should show a cooler, even tone.

4. Poor Insulation

Warm areas near return ducts or attic spaces could signal missing insulation. After sealing, heat should no longer leak into those areas.

Top Tips for Using Thermal Imaging on HVAC Jobs

• Let the system run: Before scanning, make sure the HVAC system has been running for at least 10–15 minutes for accurate readings.

• Compare sides: Always compare similar systems (e.g., multiple duct runs or compressors) to spot irregularities.

• Use a reference point: Check outdoor ambient temperature to get a better idea of what “normal” should look like.

• Take before-and-after shots: Great for showing clients the difference and proving your work.

Best Thermal Cameras for Aussie HVAC Pros

At HVAC Trade Supply, we stock some of the best-value thermal cameras designed for real HVAC work. Whether you're a solo tradie or running a team, there's a model for you.

🔗 Explore the full Thermal Imaging Camera Collection

Real Story from the Field

Mick, a tech from Melbourne, scanned a ceiling after a client complained of poor airflow. The thermal image showed a dark blue patch—one duct had collapsed. After fixing it, the airflow returned, and the follow-up scan showed a perfectly even temp. The client was stoked. No guesswork, no fuss.

Know What You're Looking At

Reading a thermal image isn't hard once you understand the patterns. With the right thermal camera and a bit of practice, you'll catch HVAC issues faster and look like a legend doing it.

👉 Ready to up your game? Check out our full range of thermal imaging cameras here: