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HVAC Control - for those over 50

CWFLY

Member
May 9, 2018
70
66
San Diego
30 years ago, most houses had a thermostat with two settings:
  • How LOW the room temperature will go before the HEATER kicks on.
  • How HIGH the room temperature will go before the A/C kicks on.
Yes, you set a temperature range.

There were two slider adjustments to limit "how warm" and "how cool" the house would get before the A/C or Heater turns on to bring you back into the selected range.. These slider switches could not overlap.

EXAMPLE: Many people (especially in SoCal) were comfortable from 68-72 degrees. They felt no need to run an expensive A/C or Heater between this range.

Year 2021 - PROGRAMMING FOR AUTOMATION...
Today's automation is anything but automation. Sure, we can set a temperature, and the car will hold that value. But let's admit the truth... we set the temperature (auto) to 69º because it's hot, but then we start feeling chilled from the A/C blasting cold air around, so we move the setting to 70º and a few minutes later we notice that the heater has kicked on and its blowing hot air around making it uncomfortable, so we set it lower again and move the vents. This goes on all day. This is not automation! And it's wasting energy!

My Model-3 gives me only two options: AUTO vs MANUAL. You set a temperature, and you HEAT and COOL to exactly that temperature. In a one hour drive, you could be heating for 20 minutes and cooling for 20 minutes, with only minor changes in weather conditions. What a waste!

How about learning something from the engineers of the 60's and 70's. A Comfort range. A temperature range, that when you are within that range, you only get air circulation (absent of A/C and Heat). When outside of the range, your A/C or Heat turns on appropriately to bring you back the selected temperature range.

PS: Just kidding about the "over 50". Just suggesting that you might have to a bit older to remember how the old thermostats for houses and cars worked in the 70s and 80s. Kinda' like knowing where the term "dial the phone number" comes from - haha.
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
10,840
12,568
Riverside Co. CA
I only have to touch my AC control 1-2 times a year, with it being on AUTO, and at 70 degrees. In the wintertime (what passes for winter where we both are), I set it to 72. In the summer, I set it to 70. Thats it, and I am not that far from you.

I certainly do not experience "moving it down and up all the time" like you mention you experience. The car may be set to that temperature, but I am virtually certain it does not heat or cool within 1 degree of that temperature.


/shrug.
 

Big Earl

bnkwupt
Supporting Member
Jul 12, 2017
5,955
11,282
Springfield, VA
Automotive HVAC has more design challenges than your average home, most notably humidity control. For example, when the temp is cool but humid, you have to heat and cool simultaneously to dry out the air and prevent windshield fogging without also freezing the occupants. The car has a temp and humidity sensor in the rear view mirror housing that determines how much dehumidification is needed.

Yes, your proposed basic thermostat settings would save energy, but at the expense of occupant comfort and visibility in humid conditions.

Don’t get me wrong - Tesla’s programming isn’t perfect. Just cautioning against oversimplification.
 

FireflyGo

Member
Aug 25, 2021
10
0
USA
I only have to touch my AC control 1-2 times a year, with it being on AUTO, and at 70 degrees. In the wintertime (what passes for winter where we both are), I set it to 72. In the summer, I set it to 70. Thats it, and I am not that far from you.

I certainly do not experience "moving it down and up all the time" like you mention you experience. The car may be set to that temperature, but I am virtually certain it does not heat or cool within 1 degree of that temperature.


/shrug.
Yep, that's exactly what I do too, and we experience all 4 seasons where we live. There is very little need to fiddle with the climate, just set it to auto and forget it.
 

Big Earl

bnkwupt
Supporting Member
Jul 12, 2017
5,955
11,282
Springfield, VA
I’ve been looking for info on cabin sensor locations. Got any more info on this? How did you find it?

One sensor is located on the underside of the screen mount. The other is located in the rear view mirror. You can see the vents for both sensors.

Here are pics of the sensor in the mirror, which is primarily responsible for determining dehumidification needs to keep the windshield from fogging.

Mine needs to be replaced since it seems to have failed when I had the windshield replaced last week. With the sensor plugged in, it seems to be reading very high humidity, causing auto mode to do windshield vents, high fan speed, max compressor and some electric reheat.

Unplugging the sensor makes this behavior stop, but the system isn’t as responsive to cabin temperature changes and doesn’t dehumidify as well. It will probably require an entire new rear view mirror assembly… waiting on my service appointment to address it.

3DCC8E11-A603-42B9-92DB-98DE926EACCD.jpeg


16B4C3FF-F4EC-4D21-9158-78727107E188.jpeg


Googling SHT31: https://store.ncd.io/product/sht31-humidity-and-temperature-sensor-±2rh-±0-3c-i2c-mini-module/
 
Last edited:

rjpjnk

Member
Mar 12, 2021
739
393
NJ
Thanks for that info. I had found the one under the lcd screen but not the other. I have a Model Y btw.

In my car, the one under the screen has a fan to draw in air, however this sensor appears to have no effect on HVAC that I can determine. Even with it unplugged the system seems to work and the reported cabin temp changes as well. Maybe it is not used in cooling mode?

I suspected there must be a sensor near the windshield because using a sun visor seems to keep the system calling for cool longer.
 

Big Earl

bnkwupt
Supporting Member
Jul 12, 2017
5,955
11,282
Springfield, VA
Thanks for that info. I had found the one under the lcd screen but not the other. I have a Model Y btw.

In my car, the one under the screen has a fan to draw in air, however this sensor appears to have no effect on HVAC that I can determine. Even with it unplugged the system seems to work and the reported cabin temp changes as well. Maybe it is not used in cooling mode?

I suspected there must be a sensor near the windshield because using a sun visor seems to keep the system calling for cool longer.

I think the system takes readings from both sensors to make decisions. My app still displays a cabin temp with the windshield sensor unplugged although it seems less accurate.
 
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rjpjnk

Member
Mar 12, 2021
739
393
NJ
Actually, it doesn't need to let in outside air. It can just stop running the compressor, which will stop chilling the recirculated inside air. The cabin will heat up from sunlight and occupants fast enough.

It is a shame to see such a marvelously complex system running so poorly. Needs an update for sure. It's embarrassing when people tell me they can't get enough air in my Tesla.
 

animorph

Active Member
Apr 1, 2016
2,152
1,580
Scottsdale, AZ
I'm fine with a constant 70 degrees.

For me, the major factor affecting my comfort is if the sun is shining directly on me. Then I'm a bit hot. Unless Tesla can check our skin temperature, all the standard cabin sensors won't help with that.
 

Marty3SR+

Member
Jan 16, 2021
28
10
Pleasant Hill, CA
It's strange that many people think of their situation and preference, and can't understand how someone can be different; or are they just Tesla apologists that think it's Tesla's design, so it must be right. I think the Tesla, like every other air-conditioned car I've owned, keeps it simple because it's not worth making it complicated like our home systems. At home, you may be far from the thermostat, and it would be a pain to need to adjust constantly, unless you have a wifi system. With a car, it's right there in front of you, so why make it complex?

If you are satisfied with a constant temperature, fine, be happy, but understand there are many reasons for people to desire changes. For example, I think it's best not to have too large a difference between inside and outside temps. If it's cold out, I may have a jacket on and don't want to get too warm, so I keep the heat a bit low - maybe 66 - 68. When it's hot, I don't want it to be too cold, so I set it a bit high, more like 70+. And where I live, it's 90s in the day, and 50s at night, plus I have a wife that likes it warmer. So, there's really no way for a thermostat to be smart enough.
 
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rjpjnk

Member
Mar 12, 2021
739
393
NJ
Mine is a Model Y so I realize this is the wrong forum but perhaps it is still useful to share. My problem is not that one temperature doesn't suit, but that the temperature is inconsistent.

One day I'll be turning the set temp down to 69 just to get enough cooling coming out, and the AC feels good at this setting. Then another day the car is freezing cold and I have to turn it up to 77-78 to make it comfortable. I am sure that if I measured the cabin temp it would not be swinging this much. I will eventually.

Every other car with climate control I've owner seemed to be able to maintain a comfortable setting that works for most Summer days. Even the Model 3 I received as a loaner car seemed to have excellent temperature control compared to my Model Y.
 

Gasaraki

Active Member
Oct 21, 2019
2,088
1,449
Syracuse, NY
It's strange that many people think of their situation and preference, and can't understand how someone can be different; or are they just Tesla apologists that think it's Tesla's design, so it must be right. I think the Tesla, like every other air-conditioned car I've owned, keeps it simple because it's not worth making it complicated like our home systems. At home, you may be far from the thermostat, and it would be a pain to need to adjust constantly, unless you have a wifi system. With a car, it's right there in front of you, so why make it complex?

If you are satisfied with a constant temperature, fine, be happy, but understand there are many reasons for people to desire changes. For example, I think it's best not to have too large a difference between inside and outside temps. If it's cold out, I may have a jacket on and don't want to get too warm, so I keep the heat a bit low - maybe 66 - 68. When it's hot, I don't want it to be too cold, so I set it a bit high, more like 70+. And where I live, it's 90s in the day, and 50s at night, plus I have a wife that likes it warmer. So, there's really no way for a thermostat to be smart enough.
Exactly. They won't be able to make everyone happy. If it's too hot, lower the temp, if it too cold raise the temp or open the vents. The buttons are 1 foot away all the time. Controlling stuff manually is OK.
 

Candleflame

Active Member
Mar 9, 2015
3,319
1,792
QLD, Australia
30 years ago, most houses had a thermostat with two settings:
  • How LOW the room temperature will go before the HEATER kicks on.
  • How HIGH the room temperature will go before the A/C kicks on.
Yes, you set a temperature range.

There were two slider adjustments to limit "how warm" and "how cool" the house would get before the A/C or Heater turns on to bring you back into the selected range.. These slider switches could not overlap.

EXAMPLE: Many people (especially in SoCal) were comfortable from 68-72 degrees. They felt no need to run an expensive A/C or Heater between this range.

Year 2021 - PROGRAMMING FOR AUTOMATION...
Today's automation is anything but automation. Sure, we can set a temperature, and the car will hold that value. But let's admit the truth... we set the temperature (auto) to 69º because it's hot, but then we start feeling chilled from the A/C blasting cold air around, so we move the setting to 70º and a few minutes later we notice that the heater has kicked on and its blowing hot air around making it uncomfortable, so we set it lower again and move the vents. This goes on all day. This is not automation! And it's wasting energy!

My Model-3 gives me only two options: AUTO vs MANUAL. You set a temperature, and you HEAT and COOL to exactly that temperature. In a one hour drive, you could be heating for 20 minutes and cooling for 20 minutes, with only minor changes in weather conditions. What a waste!

How about learning something from the engineers of the 60's and 70's. A Comfort range. A temperature range, that when you are within that range, you only get air circulation (absent of A/C and Heat). When outside of the range, your A/C or Heat turns on appropriately to bring you back the selected temperature range.

PS: Just kidding about the "over 50". Just suggesting that you might have to a bit older to remember how the old thermostats for houses and cars worked in the 70s and 80s. Kinda' like knowing where the term "dial the phone number" comes from - haha.

this is not how air conditioning works. the AC only has 1 level and that is COLD. you then use warm air to warm it up.
 
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rjpjnk

Member
Mar 12, 2021
739
393
NJ
Strictly speaking, addition of warm air is only needed if you want to change the humidity level. The heat load (in this case sunshine, thermal conduction, and occupants) will increase the temperature if the AC is off. So although the AC has only one setting, (cold), the system can be turned on for just a short time until the cabin is cold enough and then turned off until it heats back up again -- essentially, matching the heat load using duty cycle of the compressor. This is the way old automotive AC worked and pretty much all home central AC systems, and I think this is what CWFLY was referring to.

Now one problem with that simple system is that you have no control over humidity, and a system therefore has to be perfectly matched (sized) to the heat load expected or it may feel either too dry or too clammy. Adding a heating element (or condenser in the case of Tesla Octovalve) allows for the system to produce air at the exact temperature and humidity required. Unfortunately, for many of us, it is not working right and ends up putting out heated air on hot days. I am hopeful it can be corrected with a software update or some better sensors.
 

oreobbq

Member
Jan 8, 2021
257
329
Houston
This must be a cali problem. If the heat came on in 100 degree weather here I'd put my fist through the iPad.

The car is intelligent enough to only switch on vents where the seat is occupied so that helps maintain the selected temp.
 

rjpjnk

Member
Mar 12, 2021
739
393
NJ
My car definitely does not maintain a set temperature. Yes it is highly intelligent but I’m starting to think it’s just book smart☹️
No experienced hvac system would turn the heater on in summer.
 
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Rtmpaul

Member
Jul 3, 2021
27
43
Hudson Valley, NY
Here is a thought, don't know if it is right... Perhaps the heat is turned on to keep things as dry as possible. Moisture left on the AC coils is how one gets a 'smelly' ventilation system and there have been plenty of threads here about that.
 

Big Earl

bnkwupt
Supporting Member
Jul 12, 2017
5,955
11,282
Springfield, VA
My car definitely does not maintain a set temperature. Yes it is highly intelligent but I’m starting to think it’s just book smart☹️
No experienced hvac system would turn the heater on in summer.

Please describe the circumstances under which your car turns on the heat (blows hot air) in the summer.
 

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