Answer capsule
An air conditioner cools a room by moving heat, not by making cold. Refrigerant circulates through four parts in a loop: the compressor raises its pressure, the condenser releases heat outside, the expansion valve drops its pressure, and the evaporator absorbs heat from the room. The refrigerant changes between liquid and gas at each stage. That repeating cycle is what carries heat from inside your room to the air outside.
The one idea that makes it click
Nobody's air conditioner makes cold. It shifts heat around, lifting it out of the room you care about and letting it go somewhere you do not. Hold onto that and everything else here stops being mysterious.
Why refrigerant? Because it happens to change between liquid and gas at pressures that are easy to work with, and every time it hauls heat from one place to another, it does so in the middle of one of those changes. That is the whole trick, dressed up in four components.
The four stages, following the loop
Rather than list the parts, let me send you around the loop with a parcel of refrigerant and you can watch what happens to it.
It starts as a cool, low-pressure gas arriving at the compressor, which grabs it and squeezes hard. Squeeze any gas and it heats up, so by the time it leaves it is under high pressure and hotter than the air outdoors. From there it heads into the condenser, the coil sitting in your outdoor unit. Because our parcel is now hotter than the outside air, it loses heat to that air and settles back down into a liquid. That escaping heat is exactly what you feel as warm air blowing off the outdoor unit.
Still under high pressure, the liquid reaches the expansion valve, which is really just a deliberate bottleneck. Forcing it through that narrow gap makes its pressure collapse in an instant, and its temperature tumbles with it. What comes out the far side is a cold, low-pressure mix that is desperate to absorb heat. It gets its chance at the evaporator, the coil indoors. Room air blows across it, our parcel soaks up the warmth and boils back into a gas, and the air that carries on into the room is now noticeably cooler. The gas drifts back to the compressor, and the whole journey begins again. The compressor itself we cover in compressor brands.
The cycle at a glance
Stage | Part | Pressure | Refrigerant state | Heat action |
|---|---|---|---|---|
1 | Compressor | Rises | Gas | Energy added |
2 | Condenser | High | Gas to liquid | Releases heat outside |
3 | Expansion valve | Drops | Liquid to mix | Cools down |
4 | Evaporator | Low | Liquid to gas | Absorbs heat from room |
Why the coil materials matter
Notice that two of those four parts are coils, and coils are the places where heat actually crosses between the refrigerant and the air. How cleanly it crosses depends on what the coil is made of.
Coil material | Strength | Trade-off |
Copper tube | Excellent heat transfer, easy to repair | Higher cost |
Aluminium fin | Light, low cost, good surface area | Harder to repair |
Most quality units settle the argument by using both, copper tubes for the heat transfer and aluminium fins for cheap, light surface area. We weigh them up properly in copper coil vs aluminium fin.
What this means for buyers
You will never need to size a compressor yourself. But following the loop once does change the questions you ask a supplier.
Efficiency, for a start, is really just a measure of how well those four parts are matched to each other. Pair a strong compressor with weak coils and you have an unbalanced system that wastes what it could deliver, and that imbalance is precisely what the SEER and SEER2 ratings are trying to capture. The refrigerant matters too, since different ones run at different pressures and carry very different environmental rules, which is the whole subject of R32 vs R410A. And the charge has to be spot on, because a system running short or over on refrigerant limps along below its rating. That last point is exactly why charging by measured weight at the factory is worth insisting on.
At iClimaAir every split system is built as a matched set, with compressor, coils and valve engineered to work together and charged to a measured weight, so the cycle runs at its rated efficiency rather than somewhere in the neighbourhood of it. See the inverter split range.
Frequently asked questions
How does an air conditioner actually cool a room?
It moves heat rather than creating cold. Refrigerant absorbs heat from the room at the indoor coil, carries it outside, and releases it at the outdoor coil, then repeats the loop.
What are the four main parts of the refrigerant cycle?
The compressor, the condenser (outdoor coil), the expansion valve, and the evaporator (indoor coil). The refrigerant changes between liquid and gas as it passes through each.
Why does the outdoor unit blow hot air?
Because that is where the refrigerant releases the heat it collected from inside your room. The condenser coil dumps that heat into the outside air.
Why does the refrigerant charge matter?
The cycle only runs at its rated efficiency with the correct amount of refrigerant. Too little or too much reduces cooling and raises running cost, which is why quality factories charge each unit to a measured weight.