Understanding climate control

The auto air is magic, just set to auto and the temperature where you want it and drive. It just works in the most efficient manner possible for the results obtained. The compressor will only run if needed and only as fast as needed. Much better than running as fast as the engine like most cars. It is an inverter type air conditioner with hot liquid heating, magic.

 

In the manual it says that the AC defaults to using the floor vents because it uses recycled cabin air on the floor and fresh air on the vent or defrost. It does this to minimize energy used in creation of warm air.

The manual also says that it will automatically pump up the air flow when the air temperature is warm enough .. to save energy...

read the manual!

 

It's okay... my mom couldn't understand this concept either after we bought our first Lexus which had this feature(Toyota's A/C system). When she pressed auto on the climate controls in the winter, 1. no air was flowing for the first 10 minutes, and 2. all of it was coming out of the floor (your situation).

1. No air will circulate because nothing is warm yet (as said above). You can't just turn on the car and have heat blast out. If you do pump up the fan manually, you'll actually feel colder because cool air will be blowing out
2. Warm air rises; manually turning the climate to shoot out air from the dash, combined with number 1, will not be a pleasant experience at all.
3. Bottom line, in winter, be patient. Set temp to like 68, press "Auto A/C" on the steering wheel (look for the indicator on the dash), and wait. Good things (heat) will come to those who wait!

 

Has anyone tried setting their A/C at less than 65 F (18.33C)?
I tried, and the whole thing just switches to LO (temperature displayed is "LO") and jacks up the fans.
I didn't see anything bout that in the manual.
I'm going for minimal warmth (say 60F, 16-17C) - in the interest of fuel efficiency.

arbitrage
ps. strange to see this A/C thread in Audio and Electronics

 

Warmth does not have the same impact as cooling in terms of fuel efficiency. I am pretty sure - that besides keeping yourself cold - you are not doing anything to improve fuel efficiency.

The caveat to my statement is that your engine is generating excess waste heat as part of its operation.

In the case of warmth, you are using excess heat that the engine generates... and rather than having it go to the external radiator - you are using it in a small radiator located under the dashboard.

Now, I realize some of you live in very cold climates. However, once the engine and systems have come up to temperature; then the engine will create excess waste heat - which has to be disposed of anyway. Unless you know for a fact that your thermostat is always closed, I would find it hard to believe that there is no excess heat available to heat your interior cabin.

It's a completely different story for cooling. There, you have to run the AC compressor which does draw power from the system - and hence does affect fuel efficiency.

 

In principle, I agree with your assertion that heating does not consume energy like cooling does (as this heat would be "wasted"), except at startup in moderately cool environments.

If you have the Climate Control demanding heat and it is somewhat cool outside (say around 0C/32F), then the ICE will run when idle in order to generate the requested heat, when it otherwise would shut off if the climate control is turned off.

In this case, heating WOULD in fact impact your fuel economy...

 

This is what I am finding to be true. During my short trips to/from work, the engine keeps running at stop lights, coasting down hill, etc. if I have the heat on. Since I'm only in the car for 10 minutes, I leave everything turned off. I got a fleece throw that I put on my lap to help stay warm during those drives, plus I wear really warm gloves, and so far I've been comfortable.

On the other hand, during long highway drives I'm not seeing a difference in gas mileage with the heat on.

 

My situation is very similar to yours (15 min commute - to go less than 10 kms - sheesh) - anyway, i dont think the engine normally (normally being my winter commute @ <40F) generates enough waste heat to make 65F "free".
I do the opposite in the summers - slightly higher a/c temperature (77F / 25C) - which i still find comfortable.
All that being said, the best mpg isnt worth cold fingers or sweltering in heat.

Can someone try setting their a/c below 65F to see what happens? Though, I guess that's no fun in the winter

 

I fully agree with you... during the initial phase of operations (first 10 to 20 minutes), the car does not create waste heat... and as such, you should just keep warm in other ways during that time (My wife just hugs me and holds me... )

 

We would like to set our 2009 Prius for 60 F in winter because that is the temp that feels comfortable. 65 F is uncomfortably warm for us when ambient is around freezing. We find it bizarre that there is no way to set the heater to our preferred temp.

 

The battery likes to be kept warm, you might need to remove a layer of clothing.

 

I have a couple of newbie questions about climate control.

If I set the temperature (to 70 degress for example), will the CC try to maintain that temperature if I modify other settings (mode, fan speed, etc.). Specifically, I find that when it rains I have to change the mode to defroster up top and floor down below. Will the CC still try to maintain 70? What about if I increase the fan speed to increase the defogging?

I checked the manual, It's not too specific about this.

 

Yes, it will not change the temp setting. Try it and see!

 

But...when do we ever see COLD temperatures? I think the coldest I've seen out here in Fontana is MAYBE 44F.

Here in Southern California, we just get cool weather. None of this freezing nonsense.