Eli5 how dry mode works in air conditioner in difference to cool mode?


Eli5 how dry mode works in air conditioner in difference to cool mode?

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I am not quite sure as I have not seen this on any of the air conditioners I have had. But I would imagine it works similar to an air dryer. Air conditioners are able to operate in two primary modes, cooling and heating. They do this be setting some valves to change the flow of the cooling loop. When cooling they use an evaporator on the inside and when they heat they use a condenser on the inside.

My air conditioners all had one heat exchangers that could work as both but for drying you need two heat exchangers, one evaporator and one condenser. Instead of taking the cooling loop outside to the exterior evaporator heat exchanger you pump the fluid between the two inside heat exchangers. So on would become cold and cause humidity in the air to condense into water and one would become warm to heat the air back up to temperature. By using the inside evaporator where it is cold you get a lot better efficiency then using the outside evaporator where it is warm.

I could be wrong about the two inside heat exchangers and they could be using some timer or even electric heaters in the dry mode. It could also be simple thermostat settings where the air conditioner will turn on based on humidity rather then on temperature.

Dry mode focuses on removing the moisture from the air, but it does not cool the air. The air coming out in dry mode feels cooler because dry air feels cooler than humid air.

In cool mode, the air conditioner will also drop the temperature of the dried air so it comes out significantly cooler.

Let’s say you have an ambient temperature in the room of 75 degrees – dry mode will pull moisture out of the air and maybe drop the temp to 73 or 74. Cool mode, however, will be able to drop the temp down to 68.

If an ac offers “dry mode”, most likely it is to function as a dehumidifier rather than to cool the air. However, there are 2 distinct possibilities that distinguish AC units from actual dehumidifiers:

(1) A dehumidifier has a *humidistat* rather than a thermostat. So it runs based on the measured humidity of the air, rather than the temperature. An AC in “dry mode” may or may not have a humidistat.

(2) A dehumidifier prevents the air from becoming too cold, by having the air flow against both the evaporator and condenser parts of the loop. An AC is not normally designed to do this, it’s designed to have the evaporator in the indoor part and the condenser in the outdoor part. So it might not be possible to route the air over the condenser to warm it back up after cooling it.