What is the Dry setting on air conditioner?

Hi, I know this question's been up a while and I'm not sure if you care anymore but here goes anyway.

Most air conditioners are reverse cycle, so they can heat the air in your house or cool it down. What we are concerned with is the cooling side of things. So in this mode a working liquid is sprayed into the evaporator and cools its immediate surroundings. air is blown over the evaporator which cools the air. The local temperature around the evaporator is very cold, (how cold exactly I'm not sure) so the air in this region has a very poor ability to hold water and so (especially on a humid day) water condenses out of this air on the surface of the evaporator, is collected and drained away. The cooling function and dry function both use the "cooling" mechanism of the air conditioner. Both extract water from the air in this way but the primary purpose of the cooling function is to cool the air whereas the primary function of the dry setting is to dry the air... obvious I know.

Now in the dry setting the compressor will run with fan going at I imagine a relatively slow speed to chill and extract as much water from the air as possible and to minimise circulation. After a short time the compressor and fan will cut-out and then after a short interval start up again (I'm not really sure but I assume this is either controlled by a humidity sensor OR the temperature sensor monitors for a small change in temperature and shuts off the compressor and fan when it detects this). Now in cooling mode (depending on what temperature is set) the compressor will run for longer and more frequently and therefore remove more water. So why have a dry mode if cooling mode removes more water?... Well that really has the same answer as the question "when do I use dry mode?"

Well on a particular day where the temperature would normally be considered comfortable but on this day it is unusually humid, your body will find it difficult to radiate heat via sweat because of the already high RH (relative humidity) making you uncomfortable and feel "hot". Using dry mode will reduce this RH without adjusting the temperature by much, but you will perceive an ambient temperature drop due to your body being able to discard heat more easily... hence making you more "comfortable" in same way you would normally feel at that temperature.

On the contrary if you were to use cooling mode (which is regulated by temperature) you would have to set a temperature lower than ambient so that the compressor will "kick-in" rather than the air conditioner just running its fan...agree? So that means the air conditioner will reduce RH (which we want) giving you a perceived temp drop but it is also chasing the temperature which you set which will give a REAL temperature drop. So anyway the point is; if it was an unusually humid day on what would otherwise be a comfortable temperature, using cooling (remember the temp has to be set lower than ambient) instead of dry would result in you feeling cold very quickly due to the perceived AND real temperature drop.

So really the dry setting is for days which aren't too hot, but are humid.

I think my logic makes sense.

cheers Matt

Excellent reply! In short, if you live in a particularly humid climate -ie the tropics-, it is better, and cheaper to use the ´dry´ setting rather than the ´cool´ setting most of the time.

Thank you matty1313... had to kick on "dry" mode on my a/c due to it being 57% humidity outside and extreme stuffiness inside (allergies... stuffy nose, congested chest... general discomfort breathing the thickened air) and it has helped a lot. had been looking to get a dehumidifier but noticed this feature on the a/c helped a lot today alone, so i may hold off on the dehumidifier. i have to agree with what you said about using the "cooling" feature on a day such as today with the humidity b/c although it made it easier to breathe because it was cooler, it made us extremely COLD b/c the moisture is cooling as well... so, long story short: i never really noticed the "dry" feature (my manual didnt explain it as well) and have been using the "cooling" aspect at extreme lows (64 degrees) to make it easier to breathe on humid days, but after switching over to the "dry" feature @ the same temp... completely different feeling in here after about an hour (i live in a 500 sq ft apt and the a/c with the "dry" feature is a 220, but also have a 110 in the kitchen). hope this helps other ppl.

I have one of these, and this may help. All A/C\'s dehumidify. Period.

But, the dry mode cools the room SLOWER so that the A/C has more TIME to dehumidify it. (These answers assume you are in an area with high humidity)



So... if you have a BIG unit in a smaller area, the dry mode becomes terrific! Because if you just run it in COOL mode - your room reaches your desired TEMPERATURE really quick, and it\'s not enough time for it to remove the humidity properly, so you wind up with a real HUMID COOL room. Yuck. That\'s when you look at your thermostat and say to yourself "How can it be 73 degrees in here?! It still feels awful!"



If you have a tiny AC that is underclassed for the room size, the dry mode won\'t seem to make any difference - it may even seem to dehumidify LESS because it\'s running longer and more water evaporated than it collected. SO depending on your AC size and room size, the mode may or may not be useful to you.

I just spoke to an a/c expert as I have mini splits (4 internal units) of which two developed mold on the spinning turbo type fans. He explained all a/c units will remove moisture but in the dry mode the unit will continue to blow air after the cooling temperature has been reached and help dry the moisture that is on the coils and fan & tray so moisture or condensation pulled out but remains on the unit will evaporate and not permit mold to form as mold needs moisture to form and build. I now keep my units on the dry mode with some assistance from dehumidifiers to keep the units dry to avoid mold build-up!

Dry mode makes the a/c system work more as a dehumidifier than just an air conditioner.

I just purchased a new air conditioner and face the same question - what's the "dry" setting? No details noted on it's function or use in the user manual.