Why is it a good idea to come out of "recirculation" (just after a few minutes) when you have your car A/C on?

Question

Recirculation shuts off air from the ouside and cools air inside the passenger compartment. Does it increase compresor load? I know air outside will be fresh, but what does that really mean in terms of thermodynamic benefit?

Answer 1

recirculation will make your system work less, because its cooling the air it has already cooled. bringing in the air from outside will make it work harder, but as you have said, it will bring fresh air in and give you less headaches from stale air.

Answer 2

The recirculation-mode of your AC system pulls air from inside the car and re-cools it.
A couple little-known facts about that mode-
1)When your AC system is operating as designed, it will normally pull about 40 degrees of temperature off the air that it sucks in. Not too bad, if you have been running the AC and the inside of the car is around 70 degrees, right?Nice, cold air.
But how about the air in the car after its been sitting in an unshaded parking lot?
If , for example, the AC drops the air it sucks inby 40 degrees, and its 90 degrees outside, yet the car, sitting in the sun, has an inside air temperature of 140 degrees, do you get better cooling on "recirc' or "max" ?
Absolulely not-the inside air, being 140 degress, drops that same 40 degrees, so 100 degree air leaves the vents. However, the outside air, being only 90 degrees, and being dropped 40 degrees , means that 'way cooler air will be coming out of the vents. Best thing to do upon entering the car? Open the windows and take the system off of MAX or RECIRC for a few minutes-the air discharging from the vents will be cooler, and the car will cool down inside faster.
2)Leaving the system on MAX or RECIRC , especially in humid climates, can allow the build up of smelly, harmfull bacteria on the evaporator core(the piece under the dash thatcools theair down) The evaporator core condenses moisture on it (that's the wateryou see dripping out from under the car) much like a cold drink condenses water on it sitting on the table. Moving the system off of recirc for a time can actually help dry the evaporator, and keep the fungi in check. If you live in a relatively humid climate, such as down here in Florida, its a good idea to have a professional annually clean the core with a product designed to kill molds and mildews, and keep the core fresh-smelling. Those molds can also trap moisture, causing premature corrosion of the evap core.

Answer 3

If its hotter inside the car than outside, you don't want to have "recirculation" on at the onset. Its more efficient to cool the cooler outside air than the hot air in the car.

After the car cools down, if you want it colder still, then use the "recirculate" mode.

Compressor load is the same under either condition. Its just a matter of whether to cool outside air or inside air. So if you want a car to cool down faster, you have to judge whether outside air or inside air is cooler.

Answer 4

I rarely use the recirc feature. I normally open the window or the sun roof long enough to get the hot air out of the car and then I close the windows after it has cooled down and the AC is putting out cold air.

If there are objectionable odors outside, then the recirc is a good feature. good luck.

Answer 5

Go the internet. Look for a forum on this question.

Answer 6

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