redrab
Posts: 2
Joined: Tue Mar 06, 2018 5:35 am
Delivery Date: 06 Mar 2018

2015 Leaf S -- low output from heater

Tue Nov 13, 2018 8:14 am

Hi,
I have a 2015 Leaf S.

The heater does not seem to put out much heat. I have tried pre-heating at home on 240 charger but even then the interior of the car is very slow to heat up.

Are there some tricks I should know to keep the interior of the car warm in the Wisconsin winter?

Thanks,
Redrab

goldbrick
Posts: 270
Joined: Tue Aug 01, 2017 3:33 pm
Delivery Date: 01 Aug 2017
Leaf Number: 311806
Location: Colorado front range

Re: 2015 Leaf S -- low output from heater

Tue Nov 13, 2018 11:04 am

Are you in ECO mode? ECO mode will limit the heater power on a Leaf S since it only has a resistive heater.

Otherwise, the heater could be damaged or the air flaps could be stuck open, etc.

LeftieBiker
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Delivery Date: 30 Apr 2018
Location: Upstate New York, US

Re: 2015 Leaf S -- low output from heater

Tue Nov 13, 2018 12:19 pm

Use recirculate at first, then with the vents in floor only mode, press and hold the recirculate button until it starts to flash. Release it then, and it will flash twice and go into partial ("auto" in the manual) recirculate mode, bringing in 30% fresh air to stop the windows from fogging. Use the third fan speed until the car is warm, then the second speed.
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specialgreen
Posts: 150
Joined: Sun Mar 26, 2017 1:21 pm
Delivery Date: 26 Mar 2017
Location: Minnesota

Re: 2015 Leaf S -- low output from heater

Wed Dec 05, 2018 12:32 pm

Another Leaf-S owner here. To second what LeftieBiker said, use "full recirculate" when manually preheating.
  • If you are preheating using the scheduled preheater, then it will always heat a bit slowly (as if ECO was turned-on).
  • If you are heating the car while driving, then you can turn-off ECO to heat faster. You will use-up the energy sooner or later, so there's little benefit in heating the car slowly while you drive.
  • If you are preheating manually while charging, and your EVSE is smaller than 6kw, then turning-off ECO will cause the heater to draw more power than the EVSE can supply. This will use-up some energy from the battery.
  • If you are driving alone for less than 5 minutes, you can probably drive with "full recirculate" on without the windows fogging. That will heat the car faster. (I can do this taking a kid to school at 20F).
  • If I am driving alone for 5+ minutes, Recirculate will cause fogging. I find that I need to press-and-hold the Recirculate button until it flashes. This gives some fresh air (Arnis has estimated 30%) and 70% recirculate, which is enough fresh air to keep the windows from fogging.
  • If I have 2+ passengers, or it's cold out (<10F), then I find that I need to turn-off recirculate (use 100% fresh outside air) or else the windows will fog.
  • If I have a full car, or it's very cold, then I find that it is necessary to use Defrost (Heat+A/C) to keep the windshield clear.

The general strategy is to minimize intake of outside air, without fogging the windshield. The less outside air is brought in, the faster the car heats-up. However, since warm air can hold more moisture, if you park the car full of damp air, then you may return several hours later to find frost on the inside. To avoid that, I like to open the rear windows as I pull into the parking lot at my destination, then raise them again before shutting-off the car. This lets-out the humid air.

(I learned that trick when I once had to survive a winter of driving a VW without any heat at all, in Minnesota. Chipping ice on the inside is a royal pain: ice scrapers are curved the wrong way, a credit card is not strong enough for hard frost, and it's chilly here... should hit 2F/-17C tomorrow night).
Last edited by specialgreen on Wed Dec 05, 2018 2:14 pm, edited 5 times in total.

specialgreen
Posts: 150
Joined: Sun Mar 26, 2017 1:21 pm
Delivery Date: 26 Mar 2017
Location: Minnesota

Re: 2015 Leaf S -- low output from heater

Wed Dec 05, 2018 12:55 pm

specialgreen wrote:
  • If I have 2+ passengers, or it's cold out (<10F), then I find that I need to turn-off recirculate (use 100% fresh outside air) or else the windows will fog.
  • If I have a full car, or it's very cold, then I find that it is necessary to use Defrost (Heat+A/C) to keep the windshield clear.


One thing I have wondered is: where is the cross-over point, where you spend less energy doing Defrost with Recirculate, versus Heat with 100% fresh air. In the former, you are cooling the air enough to condense, then re-heating. In the latter case, you are just heating dry air, but by a lot (80F!).

Trying to estimate energy use, I'm going to ignore condensation: each resting adult should exhale between 15g/hr water vapor at room temp, and 20g/hr at -10C. A rough guess is that it takes only about 12 watts per adult to condense that water. Even with four adults, that's less than 2% of the 3000+ watts used in heating.

If the car has temperature set-point of 20C with 60% relative humidity (high-end for "comfort" humidity), then each cubic meter of air through the A/C system holds about 10 grams of water. If the HVAC system is cooling that from 20C to 12C (dew point), then condensing a bit of it, then heating it up to 20C again; and if the Leaf's heat-pump is 200% efficient vs inductive heat, then you'd spend about 120 calories per cubic meter of air through the HVAC system (plus a small bit for condensation, plus lots of fan motor load).

On the other hand, if you're drawing-in outside air at -5C, 90% RH, then there's only about 3 grams of water per cubic meter of air. You're heating it to 20C, which is a full 25C rise, but because there is so much less water, it should take only 75 cal per cubic meter, which is 37.5% less energy consumption (plus fan motor load).

Going back to Defrost, if the HVAC system is dehumidifying all the way down to 30% RH at 20C (2C dew point, below low-end for "comfort"), then there'd only be 5 grams of water per cubic meter, or 60 calories spent cooling+heating, which is 20% less energy than heating dry outside air.

Unfortunately, there are too many unknowns: What dew point does Defrost achieve, at what ambient temp? Does the defrost cycle run the same CFM? (the blower sure sounds louder on Defrost). You'd probably set the fan to "1" or "2" on the "outside air" case, but for Defrost, cooling is very inefficient at low airflow.

I think the only way to guess would be to test. With outside temps at (say) -5C, you could charge the car to 100%; then turn it ON and set it to Defrost+Recirc at 20C; and put an electric kettle inside (on extension cord) with 24cc of water and boil it off (to load-up humidity above dew point) then unplug the kettle. Then let the car run like that for 8 hours, then check how many watt-hours remain (then add 10 to 50 watt-hours per hour to account for condensation). Then do a similar the test using plain Heat with no Recirc.
Last edited by specialgreen on Wed Dec 05, 2018 3:14 pm, edited 8 times in total.

BrockWI
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Re: 2015 Leaf S -- low output from heater

Wed Dec 05, 2018 1:42 pm

What everyone has said I 3rd, 4th and 5th. Not in eco mode for full heat, fan speed 3 to feel the warmth.

I usually switch between partial and full re-circ set to floor, speed 2, when alone depending on window fogging, I try to avoid "defrost" as much as I can trying to use the floor / defrost mode if I can.

Also if you have passengers in the back on re-circ they won't feel the heat as it is sucked in the front and vent back out in the front. Even on partial re-circ they will feel more heat in the back, but usually you can't run re-circ if you have people in the back anyway due to window fogging.
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jjeff
Posts: 1732
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Re: 2015 Leaf S -- low output from heater

Wed Dec 05, 2018 2:54 pm

specialgreen wrote:[*]If you are preheating manually while charging, and your EVSE is smaller than 6kw, then turning-off ECO will cause the heater to draw more power than the EVSE can supply. This will use-up some energy from the battery.

I have a '13S with upgraded charger and have found that ~18a is the minimum EVSE charge that won't lose charge, of course at 240v. Doing that math it comes out to ~4.3kw. Now for me ECO is on all the time, driving or preheating, not sure if that makes a difference. Setting my EVSE to 19a will give me a slight charge even during a full 1/2hr preheat. I know the heater is supposed to be something like 6kw but I've never seen a full 6kw constant draw, even in biter cold. Now on my '12SL which has the instantaneous power draw meter I see a 6kw draw but unfortunatly the '12 only has a max 3.8kw charger so no matter what EVSE I use I lose charge when preheating in the bitter cold :(
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