Interactive cutaway
An air conditioner does not make cold. It moves heat — out of your room and into the street — by boiling a liquid indoors and squeezing it back into a liquid outdoors. Everything below runs live: change the weather or the thermostat and watch the loop, the room and the numbers react.
Coil below freezing. Too little air over the evaporator, or a setpoint the room has already passed — condensate is turning to ice instead of draining. A real unit loses airflow and then stops cooling. Raise the fan speed.
Short cycling. The compressor is reaching the setpoint faster than it can wring water out of the air, so it stops and starts. The room is cool but still clammy — this is why an oversized air conditioner feels worse, not better. Try the inverter, or a warmer setpoint with a slower fan.
Too gentle to dry the air. The inverter has throttled right back, which is efficient — but a slow compressor means a warm coil, and a coil above the room’s dew point condenses almost nothing. The room is at temperature and still humid. This is the trade real inverter units make, and the reason they ship with a “dry” mode that deliberately runs the compressor harder and the fan slower.
What you ask the room to be.
The hotter it is out there, the harder the condenser has to push.
Humid air costs cooling capacity — it goes into wringing out water.
People, screens, lamps, sunlight through the window.
Less air means a colder coil, less capacity, and eventually ice.
Fixed speed cycles on and off. An inverter throttles instead — and uses noticeably less energy for it.
The room is simulated 120× faster than real life so you can watch it cool. The refrigerant loop itself always animates at a watchable pace — it is showing you the path, not the clock.
One closed loop of refrigerant, four changes of state. Pick one to highlight it in the cutaway. The numbers are live, straight from the cycle being simulated above.
Engineers draw this loop as a pressure–enthalpy diagram. Pressure runs up the side, and enthalpy — the heat energy each kilogram of refrigerant is carrying — runs across. The dome is the boundary between liquid (left), boiling mixture (inside) and gas (right). The four corners are the same four points as the cards above, and the rectangle redraws itself as you change the controls.
R-410A · the wider the loop, the more work the compressor is doing
There is no tank of cold in the box. The only trick an air conditioner knows is making a liquid boil somewhere you want cooled, and condense somewhere you do not care about. Boiling absorbs heat; condensing releases it. The compressor's job is to make sure those two things happen in the right two places.
A liquid's boiling point depends on its pressure. Water boils at 100 °C in your kitchen and around 70 °C on Everest. The refrigerant is the same: at the low pressure indoors it boils at about 7 °C, which is cold enough to chill a room; at the high pressure outdoors it condenses at around 50 °C, which is hot enough to shed heat into a 35 °C afternoon. Two pressures, one substance, two useful temperatures.
The coil indoors runs below the dew point of your room air, so water condenses on it exactly the way it beads on a cold glass. That water is the reason the room feels drier, not just cooler — and it is why an air conditioner that is too big for its room can leave you cold and clammy. It hits the setpoint and shuts off before it has had time to wring the air out.
Watch the efficiency figure: a good unit moves three or four joules of heat for every joule of electricity. That is not a violation of anything. The electricity is not becoming the cooling — it is only paying for the pumping. A heater can never beat 1.0; a heat pump routinely beats 3.
Reverse the direction of the refrigerant and the indoor coil becomes the condenser and the outdoor coil becomes the evaporator. Now it boils refrigerant using the heat in cold outdoor air and dumps it into your living room. Same four parts, one extra valve. That is a heat pump, and it is why the same box on your wall can both cool in August and heat in January.
Push the outdoor temperature slider up and watch two things fall at once: the capacity drops, because the condenser has a harder time shedding heat into hot air, and the efficiency drops, because the compressor is pumping across a bigger pressure gap. You get less cooling and you pay more per unit of it — on precisely the day you need it most.