In our last post we walked through how the refrigeration cycle works – compression, condensation, expansion, evaporation, repeat. If you haven’t read it, worth a look before this one.
But reading about heat transfer and seeing it are two different things. That’s where infrared imaging comes in. The video below puts a thermal camera on a domestic fridge and shows exactly where heat is moving, where it’s being released, and what the cycle looks like in the real world.
What Is an Infrared Camera?
An infrared camera – also called a thermal imaging camera – is a non-contact device that detects infrared energy (heat) radiating from a surface and converts it into an electronic signal. That signal is processed into a thermal image on screen, with different temperatures displayed as different colours. Hotter surfaces appear in warmer tones (reds, oranges, whites) and cooler surfaces in cooler tones (blues, purples, black).
Importantly, thermal cameras don’t see through objects – they read surface temperatures. What they’re exceptionally good at is making invisible heat patterns visible at a glance.
What You’re Seeing in the Video
The Back of the Fridge Glows Hot
The first thing that stands out in infrared is the condenser. On most domestic fridges, the condenser coils run across the back panel or underneath the unit – and in thermal imaging, they light up. This is exactly what should be happening.
The condenser’s job is to dump heat. The refrigerant arrives there as a hot, high-pressure gas after being compressed, and it releases that heat into the surrounding room air before condensing into a liquid. In infrared, you can see that heat radiating clearly from the coil area.
This is also why your fridge needs ventilation space around it. If you box it in tight against a wall or into a cupboard without airflow, the condenser can’t reject heat efficiently, the system has to work harder, and your energy bills go up.
The Cabinet Stays Cool
Inside and around the cabinet itself, the thermal image stays in the cool colour range. The insulation is doing its job – keeping the heat out and the cold in. What you’re looking at is the evaporator doing its work on the inside: absorbing heat from the air in the cabinet, cooling it down, and sending the refrigerant back around the loop.
Hot Spots Around Door Seals
One thing infrared makes obvious is door seal performance. If a seal is worn, cracked, or not sitting flush, warm air leaks in around the edges. In a thermal image that shows up as a warmer band running along the door frame – a clear sign the cabinet is working harder than it needs to.
This is one of the most common and easily fixed causes of a fridge running constantly or struggling to hold temperature.
Why Thermal Imaging Is Useful for Refrigeration Diagnostics
A thermal camera turns an invisible problem into an obvious one. For domestic fridges it’s a handy diagnostic tool. For commercial refrigeration – cool rooms, display cabinets, blast chillers – it’s genuinely valuable.
Here’s what a thermal inspection can reveal that a standard visual check can’t:
Condenser issues – dirty or blocked condenser coils can’t reject heat properly. In infrared, you’ll see uneven or restricted heat distribution across the coil surface, or a coil running hotter than it should because airflow around it is compromised.
Insulation failures – in cool rooms and refrigerated cabinets, insulation panel joints that aren’t properly sealed create heat bridges: warm spots visible in infrared where outside heat is leaking in. This drives up running costs and puts product temperature at risk.
Evaporator problems – ice build-up on the evaporator (often caused by a faulty defrost system or a door seal issue letting in humid air) changes how the evaporator looks in thermal imaging and affects its ability to absorb heat from the cabinet.
Compressor heat – a compressor running hotter than expected can indicate it’s under stress, possibly from a refrigerant charge issue, a blocked filter drier, or a struggling expansion valve.
Door seal leaks – immediately obvious in thermal imaging. Warm patches along door edges show exactly where the seal is failing.
The Bigger Picture
What the infrared camera makes viscerally clear is the point we made in the last post: a fridge isn’t creating cold. It’s moving heat. The cold side of the system is cold because the hot side is doing its job of rejecting heat to the outside.
When you see the condenser glowing in the thermal image and the cabinet sitting cool, you’re watching thermodynamics in action. Heat flows from hot to cold. The refrigeration cycle exploits that principle in reverse – using mechanical work to push heat from a cool space to a warmer one.
It’s the same principle whether you’re looking at a domestic fridge in a kitchen or a 50-pallet cool room in a meatworks.