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Does high humidity affect the cooling or A/C systems? #5163260 07/17/19 08:58 AM
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atikovi Offline OP
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With miserable humidity and dew points in the upper 70's I was wondering if that affects the cooling and A/C systems in any way. Is it harder for the radiator to give off heat when the humidity is high? What about the condenser?

Re: Does high humidity affect the cooling or A/C systems? [Re: atikovi] #5163263 07/17/19 09:02 AM
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edyvw Offline
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Not sure about humidity, but at altitude, yes.


15' Toyota Sienna AWD (Mobil1 5W30 EP+OEM filter).
11' VW Tiguan 2.0T (Castrol 0W40+MANN filter)
Re: Does high humidity affect the cooling or A/C systems? [Re: atikovi] #5163269 07/17/19 09:08 AM
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Humidity probably not but other stuff like cabin filter, dirty condenser, and stuff like that it does.

Re: Does high humidity affect the cooling or A/C systems? [Re: atikovi] #5163273 07/17/19 09:12 AM
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Normally no, but with high humidity and high dew point temp, the evaporator may start to freeze, reducing cooling capacity. Keeping the air in recirculation mode helps tremendously in those situations.


2015 Grand Caravan 3.6L - 31k miles.
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Re: Does high humidity affect the cooling or A/C systems? [Re: atikovi] #5163275 07/17/19 09:14 AM
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mk378 Online Content
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It takes energy to condense water. High humidity significantly increases the demand on an A/C refrigeration system. Think of what it would take to boil the water as it comes out of the drain pipe.

Re: Does high humidity affect the cooling or A/C systems? [Re: mk378] #5163283 07/17/19 09:27 AM
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BMWTurboDzl Offline
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Originally Posted by mk378
It takes energy to condense water. High humidity significantly increases the demand on an A/C refrigeration system. Think of what it would take to boil the water as it comes out of the drain pipe.


I'm confused. The refrigerant converts from a liquid into a gas as it pulls heat (i.e. energy) out of the air passing through the evap coil. That heat is rejected by the outdoor condenser as the gaseous refrigerant returns to the outdoors. The only energy I can see in the system is that which runs the compressor converting gaseous refrigerant back into a liquid.

How does humidity increase the demands on the system?

Last edited by BMWTurboDzl; 07/17/19 09:28 AM.

“It took untold generations to get you where you are. A little gratitude might be in order. If you’re going to insist on bending the world to your way, you better have your reasons.”

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Re: Does high humidity affect the cooling or A/C systems? [Re: atikovi] #5163284 07/17/19 09:29 AM
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meep Offline
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YES.

Cabin air can't get cooler without moisture first being removed from the air. Especially when it's humid out, recirc is your friend. Also, lower fan speed allows deeper dehumdification, as the coils can stay colder and/or the air spends more time against the cold surface before moving on.

So, if you're running fresh air and it's humid out, the A/C will be limited in how cold it can blow, because it may not be able to pull enough moisture out in a single pass to cool the air enough. What blows will be sort of cool, and sort of wet. Moving to recirc gives the A/C multiple passes to dry the air and achieve colder temps.

2018 F150 must be run in recirc down here to get it cold, especially when it's our normal 95F and 85% humidity. Then it's quite comfortable, and the system does pull in a small mix of fresh air even in recirc to keep good air in the cab.


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Re: Does high humidity affect the cooling or A/C systems? [Re: atikovi] #5163294 07/17/19 09:42 AM
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KrisZ Offline
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The coil is cold and below the dew point, so when humid air hits it, the water condenses. It requires no extra energy from the AC system. It is also false that the AC will not start cooling until air is dehumidified. The air moves across the cold evaporator and exchanges heat with it regardless of the level of moisture in it.

Now, moist, cold air may feel less comfortable than dry, cold air, but it has no relation to air vent remperature.

Last edited by KrisZ; 07/17/19 09:42 AM.

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Re: Does high humidity affect the cooling or A/C systems? [Re: atikovi] #5163296 07/17/19 09:44 AM
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Not directly. Pulling moisture from the air is just an intended side effect. It does make it more comfortable to animals because their perspiration evaporates easier, but this is not an extra load on the system unless you set the A/C to a lower temperature in order to have comfort by pulling more moisture out of the air, instead of set to a specific temperature... so, yes and no, depends on how you look at it.

Re: Does high humidity affect the cooling or A/C systems? [Re: Dave9] #5163300 07/17/19 09:47 AM
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atikovi Offline OP
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Originally Posted by Dave9
Not directly. Pulling moisture from the air is just an intended side effect. It does make it more comfortable to animals because their perspiration evaporates easier, but this is not an extra load on the system unless you set the A/C to a lower temperature in order to have comfort by pulling more moisture out of the air, instead of set to a specific temperature... so, yes and no, depends on how you look at it.


Animals? Dogs and cats don't sweat,

Re: Does high humidity affect the cooling or A/C systems? [Re: atikovi] #5163305 07/17/19 09:53 AM
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BMWTurboDzl Offline
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Originally Posted by atikovi
Originally Posted by Dave9
Not directly. Pulling moisture from the air is just an intended side effect. It does make it more comfortable to animals because their perspiration evaporates easier, but this is not an extra load on the system unless you set the A/C to a lower temperature in order to have comfort by pulling more moisture out of the air, instead of set to a specific temperature... so, yes and no, depends on how you look at it.


Animals? Dogs and cats don't sweat,


Through the bottoms of their paws. wink


“It took untold generations to get you where you are. A little gratitude might be in order. If you’re going to insist on bending the world to your way, you better have your reasons.”

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Re: Does high humidity affect the cooling or A/C systems? [Re: Dave9] #5163307 07/17/19 09:57 AM
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Of course modern home systems let you set both desired humidity and temperature …

Re: Does high humidity affect the cooling or A/C systems? [Re: atikovi] #5163308 07/17/19 09:57 AM
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And a large part of cooling through panting is due to evaporative heat loss, so humidity does matter.


1994 BMW 530i, 246K
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Re: Does high humidity affect the cooling or A/C systems? [Re: BMWTurboDzl] #5163309 07/17/19 09:58 AM
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Nose and paws ?

Re: Does high humidity affect the cooling or A/C systems? [Re: atikovi] #5163315 07/17/19 10:01 AM
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Humidity removal produces latent heat at the evaporator as the dew point is crossed. It is the same as real heat in how the compressor and condenser must strain to deal with it. There is no change in temperature with latent heat but there is a release of energy. Another example (the reverse) is that you can put a lot of heat into a pot of boiling water without changing its temperature-- it will take a lot of gas for the stove to get rid of the water which wouldn't be necessary if the pot were dry in the first place. You doubters now know what to search for.

Last edited by mk378; 07/17/19 10:04 AM.
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