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How air conditioning works

What’s going on inside the units, in plain English.

8 guides · about 31 minutes of reading

  1. 01How air conditioning worksAir conditioning cools a room by moving heat out of it, not by making cold. In a typical split system, a refrigerant picks up heat from the room at the indoor unit and a compressor pumps it outside, where the outdoor unit releases it.4 min read
  2. 02What the indoor and outdoor units doThe indoor unit pulls room air through a filter and across a coil that cools or warms it. The outdoor unit holds the compressor that pumps the refrigerant, plus a second coil and fan that release heat outside when cooling and collect it when heating.4 min read
  3. 03The refrigeration cycle, step by stepRefrigerant boils in a cold coil, taking in heat; a compressor squeezes the vapour, making it hot; it condenses in a second coil, giving the heat away; and an expansion valve drops its pressure so it can boil again.4 min read
  4. 04What an inverter doesAn inverter lets the compressor change speed. Instead of switching on and off, the system runs hard to reach the setting, then slows down to match what the room needs, holding a steadier temperature with less noise.4 min read
  5. 05How air conditioning heats a roomTo heat, the system runs its refrigerant loop in reverse. The outdoor coil turns cold and collects heat from outside air, even below freezing, while the indoor coil turns hot and warms the air blown into the room.4 min read
  6. 06Air-to-air heat pumps explainedAn air-to-air heat pump collects heat from outdoor air and delivers it to your rooms as warm air, usually through wall-mounted units. It is the same equipment as air conditioning that can heat, so it also cools in summer, but it can't heat water.4 min read
  7. 07Why the outdoor unit defrosts in cold weatherIn heating mode the outdoor coil runs colder than outdoor air, so in damp weather near or below freezing, moisture freezes onto it. Every so often the system briefly reverses to send heat to the outdoor unit and melt the ice, which is normal.4 min read
  8. 08How air conditioning removes humidityAir conditioning removes humidity as it cools. Room air passes over a coil colder than its dew point, so water vapour condenses on the fins, drips into a tray and drains away through a hose.3 min read