Air con - which is better?

[Watwheels]

The other thing is that HOW COMFY you feel depends on TEMPERATURE AND HUMIDITY. I bet you that if I put you in a room at 28 deg and 20% humidity, you will swear it feels cooler than a room that is at 27 deg but 80% humidity

 

To put this in layman means moisture is 'transfered' to the outside so that even if u sweat, your sweat will be 'transfered' to the outside making u comfortable without feeling sticky and sweaty.

 

That's why u see outside the air-con system is always dripping with water even your underneath your car.

 

The removing of moisture is thru condensation. It's not your sweat or water 'leaking' from the air-con system. Ppl always get the wrong idea.

 

At the same time it'll also make your throat dry.

[Watwheels]

If there's no thermostat, how do u pre-set or adjust the temperature??

[Pskvin]

i alway though that 'auto' air con does not work as clever as people think, let compare with the indoor air conditioner some time u feel very cool with only 22 deg C setting but some time u feel not cool enough even with 18deg C. Maybe that prove that (like what u said) about the humidity issue.

 

OK here goes.

 

Air conditioners are at the most efficient (in terms of amount of cooling per unit power consumed) when the fan is at maximum as the increase in air flow over the cool condensor unit will improve heat transfer from the air to the coolant inside. Also you have greater air circulation and are less likely to have cold and hot spots in the cabin. However, there is a point beyond which any additional air throughput does not improve heat transfer and the increase in fan speed actually reduces efficiency as it starts to consume more power.

 

Temperature setting - Singaporeans have NO IDEA how thermostats work. Basically, car air con compressors have 2 settings - ON and OFF. When the desired temperature is reached, the compressor cuts off and then cuts in again when the temperature increases 1-2 deg above the set temperature. So, if it is 35 deg outside with a hot sun and it is 30 deg inside your car, turning the temp dial from 25 deg to 18 deg with have NOT turn the air con any colder.

 

So:

1. If your car is not hot (say in a MSCP), then turn on MED fan and then to MED or LOW when the car cools a bit.

 

2. If your car is HOT, turn on the FAN as HIGH as you can bear the noise until the car is cooler, then leave it at MED - if it is really hot outside, turning it to LOW should leave some parts of the car a bit warm.

 

3. Set the temperature at 24 or 25 degC. It is very highly unlikely that your car air con has enough capacity to cool it to 18 deg when it is 35 deg outside. At night, you might get to 18 deg as there is no sun to heat the car up, but then you end up burning a lot more fuel getting to that temp.

 

The other thing is that HOW COMFY you feel depends on TEMPERATURE AND HUMIDITY. I bet you that if I put you in a room at 28 deg and 20% humidity, you will swear it feels cooler than a room that is at 27 deg but 80% humidity - trust me, I have about 10 thermometers and a few hygrometers all over my apartment.

[Russ]

Thermostats are basically temperature regulators.

 

With ON/OFF compressor systems, it turns the compressor on and off depending on the set temp. e.g. set at 25 deg, it will turn on the compressor at say 26 deg and off when it gets to 24 deg.

 

With VARIABLE-SPEED compressor systems (home inverter systems have variable speed compressors), regulates the compressor speed to maintain the set temp, usually with much smaller tolerances e.g. set 24 degC, it will maintain sya 23.7 to 24.3.

 

With CAR variable volume compressors, I suppose something similar but not sure how exactly it works.

[Pskvin]

Do you mean

 

a. low temp + high fan

b. higher temp + low fan

 

instead?

 

bro, should be

 

a. low temp + low fan (since it is cooler temp u dont need high fan)

b. higher temp + high fan (since it is not very cool, u need high fan)

 

sory for create some confusion

[Russ]

That is because, in very hot weather, you set at 18 but the car air con can only manage to bring it down to say 27 degC. You can set at 22 or 18, makes no difference, the air con is doing its best and can only manage 27 deg.

 

Whereas, at night, you set at 22 and it does get to 22deg.

[Pskvin]

rally, i do not know why we need auto air con since it is really not difficult to adjust the air con fan & temp, the point is - why pay for something where we do not really need ?

 

another issue is - auto aircon does not work 100% auto, it need to preset. say u have set the aircon for a sunny day driving, but when rain come, the preset temp may become too cool, u need to reset. pls correct me if i'm wrong.

 

 

after so many year of driving, i still not sure on this:

which is the better way to switch on the air con for better car performance + better fc + better interior comfort(cooling)?

thanks.

 

It doesn't matter which ever way as long as you are satisfied that it's cold enough for you.

 

I think turning the fan higher will only cool the cabin faster and that's all. If you want colder air, you need to turn the temperature down.

 

Normally, I set my temp at 26 and when I auto on the air con, the fan speed can be between position 1 and 4 depending on the cabin's temperature. The fan speed will then auto drop to 1 when the desired temp is reached.

[Kklee]

If there's no thermostat, how do u pre-set or adjust the temperature??

 

Think still the same... fan speed and temperature control knob.

 

Variable displacement compressors are always "ON". When the temperature control knob is adjusted, it mixes with hot air from the engine.

 

Off the internet, it supposes to be more fuel efficient compared with fixed displacement compressors.

Edited January 8, 2007 by Kklee

[Russ]

rally, i do not know why we need auto air con since it is really not difficult to adjust the air con fan & temp, the point is - why pay for something where we do not really need ?

 

another issue is - auto aircon does not work 100% auto, it need to preset. say u have set the aircon for a sunny day driving, but when rain come, the preset temp may become too cool, u need to reset. pls correct me if i'm wrong.

 

 

REPLY

Try setting at 24 or 25 degrees. And just leave it at that 95% of the time regardless of weather out there. Once in a while, when the weather is very cool (like those rainy days around Christmas), you may need to LOWER, yes lower the temp to 23 degrees or so. Why? because, in that kind of weather, the aircon compressor may not kick in and then it gets humid and uncomfy inside and your windows start fogging up, so you need to lower the temp and bring the humidity down.

 

My auto setting never leaves the 23 to 26 deg range and I have no issues with the car becoming too cold.

[Kklee]

What I feel is that climate control good for those less technical folks... set once, can forget about it.