# How a Split AC Works

How a split air conditioner moves heat out of a room, from the indoor coil and refrigerant loop to the compressor and outdoor fan\.

By Blessen Abraham

Topic: Machines

[Open the interactive Jig](https://ask.jig.com/j/7J6cVsI4M4Sf)

## Transcript

### 1. Two boxes, one job

A split air conditioner comes in two parts: one high on the wall inside, one out in the open air\. Pipes join them through a small hole in the wall\. Together they carry heat out of your room\.

An air conditioner does not make cold\. It moves heat from inside to outside\.

### 2. The indoor unit

The long white box near the ceiling is the indoor unit\. When it starts, the flap at the bottom swings open and a fan inside begins to turn\. Press the button to switch it on with the remote\.

### 3. Warm air in, cool air out

Behind the front cover, a long fan pulls warm room air in through the top\. The air passes a dust filter, then a cold metal coil full of thin fins\. It leaves through the flap at the bottom, cooler than it came in\.

The fins are only about 1\.2 mm apart, so the air touches lots of cold metal\.

### 4. The coil soaks up heat

Inside the coil flows a special fluid called refrigerant\. It boils at a very low temperature, so the warmth of room air is enough to turn it from liquid into gas\. Boiling soaks up heat, just like a puddle drying in the sun\.

A common refrigerant, R\-32, boils at about −52 °C at normal air pressure\.

### 5. Water from thin air

Room air holds invisible water vapour\. When it touches the cold coil, it turns into drops, like mist on a cold glass\. The drops fall into a tray and run outside through a drain hose\.

So the drip outside is just water from your room air, not a leak\.

### 6. Two pipes through the wall

Two copper pipes carry the refrigerant between the units\. The thicker one takes the warm gas outside; the thinner one brings cold liquid back\. Foam wraps them so they don’t pick up or lose heat on the way\.

On a small unit, the pipes are only about 10 mm and 6 mm across\.

### 7. The compressor squeezes

In the outdoor unit, a pump called the compressor squeezes the gas into a much smaller space\. Squeezing a gas makes it hot\. Now it is hotter than the outside air, even on a summer day\.

The compressor is the part that uses most of the electricity\.

### 8. Heat out, cold again

A big fan blows garden air across the outdoor coil\. The hot refrigerant gives its heat to that air and turns back into a liquid\. Then it squeezes through a tiny valve, where the pressure drops and it turns icy cold, ready to go back inside\.

### 9. Round and round

The same refrigerant goes round this sealed loop again and again; it is never used up\. Many split units can also run the loop backwards to warm a room in winter\. Try both ways\.

A small unit can move about 2\.6 kW of heat while using only about 0\.73 kW of electricity\.