On AC units, why is 20°C on cold mode colder than 20°C on warm mode? Why isn’t it the same temperature?
In: Technology
Humans don’t actually experience heat itself. We experience heat energy as temperature. Temperature is relative. If you’re setting your AC to 20C on “warm”, it’s probably to heat up the colder air around you, hence feeling warmer, and vice versa.
There are a few reasons this could be the case. One is that thermostats don’t actually switch at exactly the temperature you set them at. They usually switch at a couple of degrees above/below the temperature. If your AC/Heating is good at quickly cooling/heating and your house is well insulated, then your house will remain a bit warmer than 20C when set to warm mode and a bit cooler when set to cold for longer than when the thermostat turns on in the other direction.
I’ve been wondering exactly the same for years. In your car you only set your desired temperature and the car does the rest.
At home you can switch between hot or cold and then the temperature. I still don’t get why.
Typical AC units reduce humidity when cooling. They also create a draft. The combination of those two makes sweat evaporate much more quickly which “steals” heat from your body. This is why 25°C in an air conditioned room can feel very cold when you enter it dripping with sweat.
Another factor is that the thermostat is usually not placed directly under the AC. To cool a room down to 20°C at the thermostat the output of the AC has to be much colder. When warming it’s exactly the opposite.
AC units don’t temperature adjust.
They blow Hot air, or Cold air.
They have a thermometer in them to let them know the room has achieved the set temperature and to then stop/slow flow until the temperature changes again then to restart.
You can test it by setting it to as High or as Low as it can go (rather than the 20 you want), the temperature of the air coming out won’t change, just how long the machine stays on will.
The thermostat is a destination not a throttle
If its currently 25C in your room and you set it to 20C the AC will blow out air that is the same temperature as if you set it to 18C or any other number below 25, and it’ll keep blowing that cool air until it reaches 20C and then it will stop.
If you set it to warm instead it will blow out warm/hot air until it reaches the target temperature and then it’ll stop
If your AC unit blew air that was 20C when the room is 25C it’ll take *forever* to cool the room down, and it’ll never get to the 20C you requested so its generally cooling the air down towards 10-15C and blowing that out.
You are setting the temperature you’d like it to be in *the room* and the AC unit will adjust its output until the room gets to that temperature, you are *not* setting the temperature of the *AC unit*
Latest Answers