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Ventilation without the heater in cooler weather?

Discussion in 'Model 3: Battery & Charging' started by Mr Toad, Jul 30, 2019.

  1. Mr Toad

    Mr Toad Member

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    Model 3 has a button to turn off the AC but unlike most other cars, it has nothing to prevent the heater from activating.
    Here on the Central Coast of California, it is quite cool in the mornings and evenings and unless I manually set the temperature way down until I hear the fan and heat go off, the heater comes on to warm up the car, using up significant battery and range. Turning it to manual fan with AC off does not prevent the heat from activating. Is there a way to prevent the heat from coming on while maintaining fresh air and, when necessary, AC to dehumidify and prevent fogging of the windshield? Thanks for your help and wisdom
     
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  2. Rocky_H

    Rocky_H Well-Known Member

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    I have a Model S instead, but I'm sure you can get the settings the same way. I wonder--have people had such fancy cars with digital fully AUTO climate control systems for so long that they don't ever remember how these things worked from back when it was three dials and a button? You can do the same things.

    Remember how you would do this on old cars from the 80's and 90's? You had the temperature dial, the vent direction dial, and the fan dial. Same thing to get just breezy air:

    1. A/C button off to make sure it's not running
    2. Temperature dial all the way to cold (so it's just outside air and not heating it)
    3. Vent direction to face or face/windshield, whatever
    4. Fan speed as you like.

    Done. That's exactly how you would do it on the old "three dials and a button" manual systems, and you can do those same settings with the touch screen controls in a Tesla or any other modern fancy touch screen car if you take it off the automatic mode.

    On my S, I keep the fan speed on my right scroll wheel on the steering wheel, but I'm not sure if you can do that in a 3 if you have all that autopilot stuff to control too.
     
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  3. Mr Toad

    Mr Toad Member

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    Thank you, Rocky, and I appreciate your response.
    I actually have done all that but obviously do not want to keep turning the temp down in the morning then up later in the day. Also, I still need the AC on to keep the windshield dehumidified, a frequent problem at least in the Model 3. If I turn off the Auto setting, and do not turn down the temp, the heater still kicks in unless I dial down the temp. I just want fresh or preferably dehumidified air with no chance that heat will turn on, draining the range. Is there some way of just turning off the heat like we turn off the AC?

    I do like your idea of having the steering wheel button assigned to fan speed, but I do not think you can do that in the Model 3.





     
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  4. Rocky_H

    Rocky_H Well-Known Member

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    Jeez. You want it to read your mind? You want to turn the heater off. That does require lifting a finger to do something.

    Oh. That's something I did forget to mention. The auto mode does like to keep recirculate mode on most of the time, which is directly what is causing your fogging up problems, because it's accumulating all of the moisture from your breath. Turn the recirculate mode off to make it use outside air, and it won't fog up the windows, and then you won't need the A/C to dehumidify anything.

    Yes--that's what it does. Turning down the temperature turns off the heater. I explained this.

    I already explained to you exactly how to do this. Why are you still complaining that you don't want to do it?
     
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  5. Big Earl

    Big Earl bnkwupt

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    You can’t get fresh, actively dehumidified air on a cool day without either freezing yourself or adding heat. To dehumidify requires the compressor to run, cooling the air. To not freeze requires you to add heat to get the cool, dehumidified air back up to the desired temperature (called “reheat” in the industry). Auto mode will balance dehumidification and energy savings based on the current conditions, but it will always prioritize comfort over raw efficiency, as one would expect.

    Tesla doesn’t have a heat button that you can toggle on and off. You either need to set the temperature to LO or turn the system off and roll the windows down. The latter is my preferred method of ventilation on cool days.
     
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  6. Eno Deb

    Eno Deb Active Member

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    I agree it would be nice to have a separate button for the heater, given how much energy it consumes. But note you can now tap and drag the temperature in the control bar at the bottom without even opening the A/C pop-up, which makes it a lot easier to change between "LO" in the morning and another temperature later.
     
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  7. KenC

    KenC Active Member

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    You're going to have to touch the control screen, until Elon's engineers allow voice control of the climate settings.

    Why not try, AC off, recirc off, and adjust temp to match outdoor temp. You'll get unheated, uncooled fresh air. Of course, as the day warms or cools, you will have to adjust the thermostat to match. When you need to defog, why not just hit the defog button?
     
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  8. darth_vad3r

    darth_vad3r Well-Known Sith

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    Sounds like OP wants a “dehumidify” button.

    “Fresh air” that’s not heated is easy. As already explained.
    To repeat, the quickest one-second, one-touch way to turn off heat is to slide the temperature setting number in the tray all the way left to “LO” in one quick motion. No tap then slide, just slide the number. You have to have A/C off of course otherwise this turns on cooling :)

    OP’s followup request of having “A/C” on to dehumidify but guarantee no heat, but not use LO because that’s too cold ... that’s not possible. You need to set the temp to your comfort level and live with how much A/C heat balance is used to achieve that.

    Are you THAT worried about a few extra Watts?
     
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  9. darth_vad3r

    darth_vad3r Well-Known Sith

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    Interesting. I’ve never owned a car that had a method to prevent the heater from “activating” other than the temperature dial (which the Tesla does have). What do other cars have, a heat button??

    BTW, ICE cars use the engine as the heater, so it’s always “active” when the car is on, even if there was a “heat off” button ... I guess you could say then shutting off the ignition can turn the heater off? :)

    Or are you talking about other EVs? Curious what method other cars use to turn the heat off that’s different than Tesla. Do other EVs have a separate “heat” button?
     
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  10. darth_vad3r

    darth_vad3r Well-Known Sith

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    To answer my own question, for at least one other EV, the Kona appears to have a “heat” button (why not, they have SO many buttons)...

    59339C7D-61A1-4D3E-9FD0-6BDBB3CBA893.jpeg

    Heres a better shot:
    AF78B14B-D9C8-4353-B679-B12635C040AD.png

    So many buttons :)
    Think 22 here.

    So now I wonder if you turn the temp knob up towards “hot” do drivers complain nothing happens unless you press the “heat” button, or does it just turn on automatically if you do that and you turn it back off if you want.
     
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  11. darth_vad3r

    darth_vad3r Well-Known Sith

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    Hey, the shift “order” here is R, P/N, D ... this came up in the “my car made me go the wrong way thread” ... If Tesla showed it this way in the display people might not sometimes look at “PRND” and incorrectly think “down” to get from P to R.
     
  12. Mr Toad

    Mr Toad Member

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    I would like to thank you all for your thoughtful replies.
    I am sure the confusion is due to my explanation. I would have hoped this would all have been simpler but that was my fault.

    I am not, as some posters mentioned, asking for a miracle that is not available in other cars as is evident in in the EV Kona pictures above. I am also not asking to never touch the screen or controls. I thought that was obvious.

    darth_vad3r actually hit on it by simply showing in his post what every other car I have ever owned has, and that is a way to have fresh air without turning on the heat but still keeping the AC on to decrease the humidification (because in our foggy climate, fresh air does (obviously this means without recirculation) mean windows do not fog up...they absolutely do). This would mean, here is coastal California, leaving the temperature set on say, 68, so it will not get cooler than that, but on our cool summer mornings the temp outside is 62 until it warms up later. I simply do not want the heat to come on, and yes, it uses significant energy, vastly more than the AC.

    So you have all answered me that no, there is no heat setting to toggle on and off , but there certainly should be like is present in any ICE car I have ever owned.

    Thank you all again for contributing.
     
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  13. Rocky_H

    Rocky_H Well-Known Member

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    Can you name an ICE car that has that?
     
  14. Big Earl

    Big Earl bnkwupt

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    My ICE cars with automatic climate control did not have heat on/off buttons. I didn’t see a heat on/off button in any car until the Kia Soul EV came along. Or maybe the LEAF was first.

    Anyway, I wouldn’t mind a heat toggle just like the A/C toggle. Gives us more options for managing energy consumption.
     
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  15. nayr14

    nayr14 Member

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    I agree, even in the summer my garage is partially below grade so it's cool, sometimes below my set temp of 72-74. When I leave it will start the heat if left on auto and severely affect my wh/mi ratings on shorter trips. In a ICE car this wouldn't matter. Having all digital controls in a sub menu makes it a pain to change, and you have to do it very quickly or the heater is already fired up.
     
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  16. bay74

    bay74 Member

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    I've never had a (ICE) car with a "heater" button, but on a combustion vehicle it's also irrelevant because the heat source is always available and costs nothing extra. In an EV, using heat does (usually) cost extra, and hence should be controllable (in my view).

    Question about the air conditioning system: the enthalpy removed when the air conditioner is cooling the air, is this (mostly, or partially) returned to the air if the temperature setting is higher than the cooled air?

    What I'm getting at is this: when running, the air conditioner evaporator cools the air to or below the incoming air-stream's dew point; this condenses some of the moisture. But what about when the temperature control is set 'higher' than this cooled air? Does the cooled, partially-"dried" air pass by the condensor before going to the cabin, or does it only go through the electrical heater (which would, in my view, be dumb as the condensor has enthalpy it needs to be rid of anyway).

    Further, if anyone knows: how much does the air conditioner cool the incoming air when the cabin temperature setting is higher than the exterior ambient (and the air conditioning is on just for de-humidification purposes)? Maximum power (i.e. electrical power to the compressor)? Not sure how it would decide how cold to aim for (and hence how much moisture to remove).

    Back to the non-existent heat button: would be nice to be able to set the cabin temperature to "warm" but still have the electrical heater turned off, so that any available drive-train waste heat would go to the cabin but no extra electrical energy.

    Cheers,
    A.
     
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  17. darth_vad3r

    darth_vad3r Well-Known Sith

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    If you get in the habit of turning auto off and A/C off before you end your trip, then heat or A/C won’t turn on next time you get in. It’s a good habit for A/C to avoid mildew from latent moisture anyways. You’ll save some energy at end of trip and start of next one!
     
  18. Big Earl

    Big Earl bnkwupt

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    On a Tesla, it will have to get reheated by the electrical heater since there is no condenser in the dash board. Some EVs with heat pumps have a second condenser in the dash so they can do dehumidification without using the electric heat, but Tesla does not.

    I've only noticed significant reheat when temps are mild and humid, usually when it's raining. Most of the time it will just slow the compressor and fan speed down to maintain cabin temp and humidity without overcooling and needing to use reheat.

    If the setpoint is above the current temperature, it won't run the compressor at all unless it's very humid.

    Drivetrain waste heat cannot be used to heat the cabin because there is no liquid heater exchanger in the cabin. The only way to heat the cabin is with electric heat.
     
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  19. beachmiles

    beachmiles Member

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    Yet another thread about the need for more HVAC controls. We need 2 temp setpoints like the Nest. My personal low setpoint would be 60F and my high would be 72F. In this range no heater or AC will come on, only the vent if I desire. Below or above these setpoints the heater or AC will come on automatically. Saving tons of energy and frustration in the process.
    Trying sum up all the links here but may need to make a separate thread that lumps all the threads from all the tesla forums over the years for this feature request.
    Don't want heater on damn it!
     
  20. Mr Toad

    Mr Toad Member

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    EXACTLY!!!! Well said
     
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