I’ve read every single manual on the Internet and I still don’t understand what the difference is. I’ve also used both settings and don’t see much difference. When I use dry, the room cools off, but the machine will shut down and turn back on which I find very annoying. When I use cool the room, the room will cool but the machine stays on.
It’s currently nighttime with the 70° temperature outside in the 71% humidity. WWYD right now, for example?
In: Technology
The dry setting is going to act as a dehumidifier for inside. It doesn’t matter how humid it is OUTSIDE – it will dry out the INSIDE of your home.
I always avoid it for the most part because it tends to dry out the home rather quickly and causes me to cough or irritates my skin. Cool works great! It doesn’t shut off as often because it’s not trying to manage the humidity inside in addition to cooling – it’s only worried about the temperature.
Edit: you can always get a super cheap digital thermometer to see how humid it is inside your home and the actual temperature inside each room if you’re worried about either.
Dry generally uses less power than cooling, so if the actual temperature isn’t too bad, but uncomfortably humid the dry function usually works pretty well.
If it’s just hot, the dry function won’t do anything.
I’d try to keep humidity below 65%. More than that results in formation of black mould and spores, and also higher humidity indoor air is harder to heat.
Dry and Cool mode do the exact same thing, as far as the AC itself is concerned.
When warm air enters the AC condenser (in the big fan unit) and hits the very, very cold condenser unit. The warm air gives up its heat to the condenser as they attempt to reach the same temperature. The now-cold air goes into your house, and the now-warm refrigerant heads back to the outside unit.
That’s just one part, though. When that warm air hits those fins, the temperature of the air immediately dives *way* below the dew point, and that causes all of the moisture in it to immediately drop out of the air and… well, *condense* onto those fins. This is why every AC unit has a drain line coming out of the house somewhere, because the nature of AC is that it produces water that has to be dealt with.
Incidentally, the original reason this whole setup was invented was to dehumidify. The whole “air cooling” part didn’t actually come until a few years later. Originally, the condenser (inside set of fins) and the evaporator (outside set of fins) were both in the same air flow path (modern dehumidifiers are still built this exact same way). After dumping a bunch of water onto the condenser fins, the now-cold air would hit the evaporator coil, which was generally a good 50 degrees (or more) hotter than the air, and this would cause any remaining moisture to quickly *evaporate* as it passed through the evaporator coil.
Now obviously your house AC isn’t going to be able to change the air path to turn itself into a true dehumidifier, but just running the air through the cold condenser coil is enough. The difference in the two modes is whether it is prioritizing temperature, or humidity. If you set it to “cool”, it’s going to turn off when the target temperature is reached, be it 72 or 68 or whatever. If you set it to “dehumidify”, it’s going to keep cooling, beyond the temp set point if necessary, to take the humidity down to whatever its goal is. 40-70% is generally the “comfortable” range for humidity.
Dry function is taking the humidity out of the air… and it has to go somewhere. If it’s a floor unit with a window bracket, your ac is probably full of water and in need of draining. Should have come with a pan, but you can also put it a tub and open the drain. Check the manual for location or other instructions for draining.
Very humid conditions can make this necessary even when running in cool mode. Some models are made to pump it back out with the outgoing hot air, but mixed results. Floor units almost always have a reservoir.
The difference between the two is that the “Cool” function will run the AC unit until a temperature is reached (to the limit of its capacity), while the “Dry” function will run it intermittently to pull moisture out of the air regardless of temperature.
Unless you find yourself in a position where you do not want to reduce the temperature of the room, but you do want to reduce the humidity, you should run it in “Cool”, which will incidentally dry the air as well.
If it helps, think of the functions as “Cool and Dry” and “Dry only”.
The “dry”-setting makes your A/C function like a dehumidifier. Dehumidifiers work by cooling air down, which causes moisture in the air to condense (i.e. turn into liquid, which can be collected or disposed), and then heating the air back up to (approximately) its original temperature (ideally by running the air past the part of the A/C that gets hot anyway as part of the heat exchange mechanism). Thereby removing moisture from the air and lowering the humidity.
The “cool”-setting does just that: it cools the air, while omitting the step of heating it back up. This ends up dehumidifying it as well. This might come as a surprise to you, if you know that normally, when you lower the temperature of air, its (relative) humidity increases. The reason an A/C does dry the air as it cools is that, locally, inside the machine, the air gets much cooler than the target room temperature, in order to cool the room quickly. This (again, same as in the “dry” setting) causes the moisture in the air to condense into liquid water, and that liquid water is either collected or disposed outside (e.g. via a tube). And then the greatly cooled air mixes with the room air and warms back up some. So this way, water still gets removed from the air, and the humidity is lowered.
If the A/C also ends up cooling your room while on the “dry” setting, this may be because the amount of cooling and heating that go into the dehumidifying process aren’t perfectly balanced. Perhaps the manufacturer even deliberately erred on the side of cooling (a little) rather than heating (a little), given how they know A/Cs are typically used.
As for WIWD in that scenario: you haven’t told us what it’s like *inside* the room, which is more relevant. You want to keep the humidity indoors below 60%, as much as possible, and ideally (for your own comfort) a bit lower than that (30-50% or 40-60% are optimal, depending on who you ask). If it were 71% humidity *inside*, I’d say definitely do something about it. And then what you do depends on whether you are okay with the temperature. If it’s 70°F inside as well, then personally I wouldn’t necessarily set the A/C to cool.
I live in a relatively high humidity area, the walls inside sweat a lot (pools of water on the floor on bad days) I find the dry setting doesn’t do much, I use the cool setting at 21deg C and it dries the rooms well.
Dry mode runs the fan slower and cools less to try to keep capturing moisture on its radiator without lowering the room’s temperature as much. So it tries to run like a dehumidifier, useful if it’s cold and humid because you don’t want to make the room even colder.
The “dry” setting on your air conditioner is ideal when humidity is high, like at night with 71% humidity
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