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Discussion Starter · #1 ·
Hopefully, that is. Here goes. It's chilly outside. I give a voice command of "80 degrees." The air conditioner kicks on. When I go to the climate screen, I see that the "air conditioner" is on.

Why is this? I'm trying to heat the car. I can manually turn the air conditioner off, but why should I have to? Is there a reason of efficiency that it does this? If so, I'll be glad to leave it alone, but until then, it's bugging me.

I wish you could program it to turn on in a specific way (like have the blowers on "upper" setting only, etc.).

Thoughts, anyone?

Thanks!

marlowe
 

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"air conditioner" is just a generic term - it's a climate control system, so "air conditioner" means both a/c (in the traditional sense) and heat.

without the "air conditioner" on, you're going to be pretty cold all winter.

if you do a search or check out other sites like http://www.priuschat.org you'll probably be able to learn the tricks to change your default settings.
 

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"It's chilly outside. I give a voice command of "80 degrees." The air conditioner kicks on. When I go to the climate screen, I see that the "air conditioner" is on. "
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Most of the time the ambient air is close enough so I don't mess with the climate control much here in San Diego. But I thought I'd try your commands and see what happens.
1. Outside air = 60 degrees F. RH about 60%.
Car started. Climate display on. Voice command = "80 degrees" The temp "window" showed 80..The fan went to about 2/3 full, the inlet went to floor only and "Auto" was selected. NO a/c. Cool air now then Warm air started blowing in less than a minute. (I had driven the car about 2 hours before so it was carrying some stored heat)
2. I called "70 degrees": A/C on. Inlet bi-level. Fan stayed at medium setting. Cold air blowing in seconds.

As far as I can tell (and I surely don't fully understand the "Auto" system) it measures Humidity as well as Temp and picks whatever combination the computer thinks is right. If you don't like it for some reason, the manual settings are available.
One thing seems inevitable in Auto mode: When your "requested Temp" is a a long way from the ambient temp, you're going to get the fan full blast at first.
 

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The AC compressor may be used even when there is a heat demand in order to lower humidity.

So, yes, you will see the AC refrigeration system ENABLED. It is a continuously variable speed compressor, so for heat demand with dehumidification demand, it will run at its slowest speed. However, if it doesn't need to dehumidify, it may not be running at all, even though it shows it is enabled (on).
 

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mr.fadedglory said:
without the "air conditioner" on, you're going to be pretty cold all winter.
Are you saying the heater doesn't work unless the AC is enabled?

I run the heater all the time in manual mode (can't stand the AUTO setting, but that's another story), and I do not activate the AC. The heater works great. Of course, who knows what's actually going on behind the scenes, but I can tell you that the AC button is off.


DGStan
 

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No, I was saying not to be worried/annoyed/suprised that the AC is on when asking for heat. It won't run the AC compressor if the air is dry enough. Humans alone can excessively humidify the cabin, causing fog on the windows.

Might be good under some conditions :wink: but most of the time it can be annoying and even dangerous.
 

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marlowe7 said:
Hopefully, that is. Here goes. It's chilly outside. I give a voice command of "80 degrees." The air conditioner kicks on. When I go to the climate screen, I see that the "air conditioner" is on.

Why is this? I'm trying to heat the car. I can manually turn the air conditioner off, but why should I have to? Is there a reason of efficiency that it does this? If so, I'll be glad to leave it alone, but until then, it's bugging me.

I wish you could program it to turn on in a specific way (like have the blowers on "upper" setting only, etc.).
Just as an aside to your specific question. I have not owned previously, but have driven many vehicles with autoclimate (in the Toyota usage of it in the Prius, it also seems to mean A/C). The Prius is my first car with autoclimate and I find it convenient and intelligent. But I have discovered, that if a modern vehicle autoclimate system is set to full auto it will make decisions about air output, both vent sets and fan speed, based upon a number of environmental factors, but usually skewed toward temperature differential between your setpoint and the actual inside cabin temperature.

If you want the climate system to do something specific at startup I believe you have to go into the Air Conditioning screen and make those settings before you shut down so that they are in place when you go to start up the vehicle again. I don't believe the system will lock in the recirc button.

If somebody can refresh our collective memory regarding the Toyota tech sheet that has various settings that can be input by the THHT at a dealership regarding settings and such, that would be great. I vaguely remember some settings that might be able to be set by the THHT for the air conditioning system, however they might not apply to your desires.

I use a "set it and forget it" mentality with the system. I pick the temp I want and let the system figure out how it wants to get me to that point.
 

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Discussion Starter · #8 ·
air conditioner question

Jeromep,

As to your "set it and forget it" technique... Are you saying that you keep it on auto all the time? So that, even when it's temperate, the air kicks in on start-up?

I'm always of the mind to run the air (hot or cold) as little as possible. I can't see liking the air on all the time.

Unless I'm just totally wrong about how the thing works, which is always possible.

Any clarification would be appreciated.

Thanks to all for the input!

marlowe
 

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Except for setting it to "recirculate" constantly I also keep it on "auto" all the time and adjust the temp setting if the fan gets objectionable. That way I only need to use the steering wheel buttons and never have to fiddle with the "climate" menu. I sometimes let it bring in outside air during defrost.
 

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Our weather has been so cold here that I'm constantly changing the flow from my climate screen. (In summer the wheel buttons suffice). I need to start out with full defrost, both front and back, and then adjust the fan as the warmth arrives. Pressing the Auto button would be futile as the inside temp and outdoor conditions seem to vary quite a bit as does the body's comfort level. My mpg is really suffering as well.
 

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marlowe7 said:
Jeromep,

As to your "set it and forget it" technique... Are you saying that you keep it on auto all the time? So that, even when it's temperate, the air kicks in on start-up?

I'm always of the mind to run the air (hot or cold) as little as possible. I can't see liking the air on all the time.

Unless I'm just totally wrong about how the thing works, which is always possible.

Any clarification would be appreciated.

Thanks to all for the input!

marlowe
Happy to respond and hopefully help. Let's see, how do I explain? Maybe a bit of a story.

I have a friend who purchased a house a few short years ago. The previous owners had installed a fairly sophisticated Florida Heat Pump. This heat pump was installed with a fully automated thermostat. With this system you set the temperature you want in your house for the lower range (heating) and the upper range (cooling) and the system will maintain your house inside that range. The first year he lived here he didn't use the automatic functionality at all. He set a temp for heating during the winter and then he set a temp for cooling during the summer and made frequent visits to the thermostat to adjust it up or down to turn the system on and off. During that year he complained that he felt the system was very expensive to run and the house wasn't that comfortable. So, I took a look at it, discovered that the system had a full automatic mode and asked why he wasn't using this. His answer, "because I think it will cost more than adjusting it manually." Wrong answer. So, I challenged him to let the system run itself at least through the end of the summer cooling season and then into the winter heating season. The result, his bill went down about 10% even though electric costs went up, and he was much more comfortable. The final word is that electronic control systems that are optimized for fully automatic operation run best when allowed to do their job.

I have found this to be true with the Prius. It is really quite intelligent with regard to heating and cooling the cabin. Some talk about high fan speeds at startup, and yes I have experienced that, but the typical fan cycle on automatic is as follows. Car is cold, cabin fan does not start immediately, but after the initial startup and self test and once coolant is flowing through the vehicle. The system will not start the cabin fan until there is some warm air to put out. If it ran the fan at startup it would just blow cold air. The fan kicks in at its lowest speed and as heat provided by ICE increases, the fan speed increases. Depending on the temperature differential between the set point and the cabin the fan may speed all the way up to HI or it might be a couple points below high. The fan will then run at a higher speed as it is working to achieve the cabin set point. As it gets closer to the set point the fan speed will drop and output vents might change to better reflect where heat is needed. The exception to this is if you hit the defrost button, when you do that the system places the fan on a higher setting and will engage the a/c compressor to provide dehumidification.

This certainly seems like intelligent design and reflects what high end home heating and cooling systems do. Carrier's Infinity series systems have variable speed fan motors and choose an optimal fan speed based on the temperature differential of the house compared to the thermostat set point.

So, to more directly answer your question; yes I keep my system on auto all the time because it makes proper decisions based upon the temperature differential between the set point and the actual cabin temperature. If I feel cold, I move the temp up a couple degrees. The system responds by putting more heat in the air flow and raising the volume of air flow a little and possibly changing the output destination. When that adjusted set point is reached the system will back down the fan speed to reduce airflow and it will reduce heat fed to the cabin.

I apologize if this has been hashed and rehashed before; as for the A/C button on the Air Conditioning screen, that is really nothing more than a compressor lockout button. Since the system only uses the compressor when it absolutely needs to and since it does provide dehumidification during the winter in some modes, there is no good reason to lockout the A/C during the winter.

Many years ago a very intelligent service manager, who actually knew about cars, and could give you a counter diagnosis based upon sounds or behaviors, said that A/C was a use it or loose it item in a vehicle. If you don't use it, you will not circulate enough oil through the system to keep the seals and tubing fresh and that will then lead to drying of the seals and refrigerant leakage. However, if you make a point of using your A/C, or rather in the case of the Prius, let the system use it when it needs to, you won't have nearly as much opportunity for seals to dry up or tubing to get brittle because refrigerant oil will have circulated in the system frequently keeping those items fresh.

But there is more. The HV battery basically requires a room temperature environment to operate most efficiently. Extreme cold and hot conditions prevent the battery from operating most efficiently, which will have an effect on your FE. As such, the auto climate system can help keep the battery at an optimal temperature by keeping the cabin at a temperature that is comfortable for the occupants. In other words, if the occupants are comfortable, not sweating and not freezing the battery is probably being provided with the correct ambient air temperature for efficient operation. That vent on upper edge of the rear seat on the passenger side is the air intake for the battery. There is a fan which will operate to circulate air from the cabin to the battery. The cabin is the source of cooler air in the summer and warmer air in the winter.

There you go. My reasons for operating the climate control on full auto year round.
 

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I largely agree with jeromep, but with one proviso. If you obsess about efficiency, then the automatic system tries too hard. If you just leave it at (say) 21C, then it'll do whatever it takes to reach that temperature, no matter how hot or cold it is outside, or how much energy it takes.

But to save energy, particularly on shorter trips, I'll nudge the temperature in the direction of outside ambient - eg 19C in the winter or 22C in summer. I'll accept those temperatures just to have it work less hard.

It would be nice to have some sort of "efficiency vs comfort" setting for the automatic system. For example, setting it to an "efficient" mode would deter the car from running ICE when stationary just for cabin heat.
 

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That's a pretty good idea, efficient mode and regular mode.

As for the overall efficiency of the vehicle when heating. Well, I do recognize your point. The climate control system does dominate the vehicle control system when heat output is desired. I have noticed many times that if you turn the entire climate control system off while at a stop light and the ICE is running, the ICE will turn off. That same behavior in cold weather could be achieved with an econ mode that would do just exactly that.

Well, I've never tried to be a hypermiler, so I've never really worried that much about the ICE running to provide heat. Especially when I'm cold and want to be warm.

Folks with long commutes can attest to the fact that the car isn't all that inefficient in the winter when doing a highway run because the ICE will usually run all the time on the highway and in that instance heat is generated so it should be used for something.
 
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