Ventilation problem

[larrys3255]

Nissan has decided that the Leaf driver cannot select "Air Recirculation" while the "Automatic Climate Control" is on but must use the "Fresh Air Intake" mode. This also occurs when you click on the "Front Defroster" button. I guess that some Nissan engineer in his wisdom has decided that it is more efficient to defrost the front windshield using fresh air intake and so has made that the only option for the driver. I don't know about you but I really dislike having to breath car fumes while driving and would gladly endure the somewhat lower efficiency while still benefiting from the Automatic Climate Control system. It seems to me that this is a software issue and could be easily corrected. Are there any other Leaf drivers who feel like I do?

Larry

 

[Volusiano]

Nissan has decided that the Leaf driver cannot select "Air Recirculation" while the "Automatic Climate Control" is on but must use the "Fresh Air Intake" mode.

Note entirely true. In AZ summer here, Auto climate control puts Leaf in air recirculation mode in very hot weather to conserve energy. In cooler weather, it may switch to fresh air.

This also occurs when you click on the "Front Defroster" button. I guess that some Nissan engineer in his wisdom has decided that it is more efficient to defrost the front windshield using fresh air intake and so has made that the only option for the driver. I don't know about you but I really dislike having to breath car fumes while driving and would gladly endure the somewhat lower efficiency while still benefiting from the Automatic Climate Control system. It seems to me that this is a software issue and could be easily corrected. Are there any other Leaf drivers who feel like I do?
Larry

If you don't agree with the Leaf auto climate control selection of which type of air, can't you just override the Auto Climate and select Recirculation or Fresh Air yourself? I don't know what the big deal is that the Auto has to perform the air control the way YOU want it. If you don't agree with its selection decision, then simply just push one button to force it to do what YOU want. That how the system is designed to give final control to the user.

To you, fresh air is bad because of auto fumes. To others, fresh air is desirable where they don't have auto fume problem.

 

[Levenkay]

To me the choice of outside-vs-cabin air source has more to do with humidity than fumes. But maybe I've always had misconceptions about how window de-fogging should work. I would think that the ideal operation would be to move humid air past the cooling elements of the A/C's heat pump, condensing out a bunch of the water. Via unspecified mechanical cleverness, the condensate is scraped/shaken/blasted/whatever off the cooling plates and ejected from the cabin in liquid form. Then the dehumidified air is ducted past the heating elements of the same heat pump, where it's warmed back up, probably (due to the heat given off by the condensing water vapor, plus inefficiencies in the system) warmer than it came in. Squirt the warm, dehumidified air at the inside surfaces of the windows to dry them off.

Is that how it works? If so, I would think that once you've gone to the trouble of dehumidifying the cabin interior, you'd prefer to avoid taking on any more water; hence, you'd want the operation to recirculate the cabin air. The few times I've tried to figure out how to enlist an auto's A/C in the futile (here in the Pac. NW) effort to combat the perpetual internal steam-bath that is the inside of any car I've driven here in wintertime, either the "defrost" air blown on the windows was *cold*, or the A/C functions semed to turn off. Do any auto A/C systems offer a "dehumidified warm air" service?

 

[highcountryrider]

I'm in the soggy PNW as well. I have always found the fresh air setting
on all my vehicles to be more effective at keeping the windows clear. Humidity builds
up in the cabin unless you flush it out with fresh air - from your body's normal
perspiration and moisture in exhaled breath, and from rain on your clothing. If you have
ever slept in a "two man" tent you have experienced this.

That is why most systems force outside air when you activate defrost. I would think you
could override it if you want, but I've never tried.

Another, sort of counter-intuitive, method is to keep the temperature low. The hotter
you get the car, the more you will perspire and the more the dampness in your clothes
will evaporate. Give it a try. If it's really bad, because my clothes are soaked, I often open
a window until things clear off.

 

[larrys3255]

Nissan has decided that the Leaf driver cannot select "Air Recirculation" while the "Automatic Climate Control" is on but must use the "Fresh Air Intake" mode.

Note entirely true. In AZ summer here, Auto climate control puts Leaf in air recirculation mode in very hot weather to conserve energy. In cooler weather, it may switch to fresh air.

This also occurs when you click on the "Front Defroster" button. I guess that some Nissan engineer in his wisdom has decided that it is more efficient to defrost the front windshield using fresh air intake and so has made that the only option for the driver. I don't know about you but I really dislike having to breath car fumes while driving and would gladly endure the somewhat lower efficiency while still benefiting from the Automatic Climate Control system. It seems to me that this is a software issue and could be easily corrected. Are there any other Leaf drivers who feel like I do?
Larry

If you don't agree with the Leaf auto climate control selection of which type of air, can't you just override the Auto Climate and select Recirculation or Fresh Air yourself? I don't know what the big deal is that the Auto has to perform the air control the way YOU want it. If you don't agree with its selection decision, then simply just push one button to force it to do what YOU want. That how the system is designed to give final control to the user.

To you, fresh air is bad because of auto fumes. To others, fresh air is desirable where they don't have auto fume problem.

In Los Angeles where I live, you really don't want to breath the air on a Freeway or behind a truck or SUV. And we don't have to worry about excess humidity since it is usually very dry. The reason that I wanted to use the Automatic Climate Control is that the Manual says that the Automatic system provides the best driving efficiency. However, if Automatic is on, when you manually change the circulation to internal, it shuts off the Automatic system. No big deal, but it is annoying.

 

[Volusiano]

The reason that I wanted to use the Automatic Climate Control is that the Manual says that the Automatic system provides the best driving efficiency. However, if Automatic is on, when you manually change the circulation to internal, it shuts off the Automatic system. No big deal, but it is annoying.

Thanks for the clarification. I think the reason Auto is more efficient is because it will turn down the fan speed when the desired temperature set and the actual inside temperature as read by the sensors converge.

It may also cycle the compressor off or to a lower rate when the 2 temperatures converge. But I'm not sure about this later part because some people are inclined to think that the compressor stays on all the times and the system actually kicks on the heater if the inside temperature starts getting colder than the desired temperature. If this is the case, in no way the Auto mode is behaving efficiently as the manual claims.

Finally, Auto does help with efficiency through the selection of Air intake. For very hot weather like in AZ, it's more efficient to select Recirculated cooled air because it's more efficient to continue cooling the already cooled air more and more, as opposed to keep drawing in very hot outside air which has not been pre-cooled already like the circulated air. Probably same logic in very cold weather.

But when the outside and inside temperature difference is small, in more moderate climate such as LA, there's little difference for efficiency whether the air comes from inside or outside. I would guess that in such case, outside air would trump over inside air because outside air is automatically assumed to be fresher. But of course this logic about outside air being fresher air is not always true, so that's why they give you the override buttons to select which air you want.

However, I don't think that your manual selection of air intake will completely disengage the Auto mode. I think the system will still continue to regulate the fan speed automatically for best efficiency. Unless, again, you use the fan speed override buttons.

It will also still continue to regulate the compressor (maybe in conjunction with the heater) to best match the inside temperature with the desired temperature. However, as mentioned above, this may become anti-efficient if the heater is used in conjunction with the AC compressor to reach the desire temperature.

 

[highcountryrider]

This stuff is very climate dependent for sure. While keeping the windows
defogged is a major problem here in the Seattle area, many of us get along
with just the blower much of the time for cooling, and not much heat is required
most of the time.

Now, if I was in Phoenix in August

, I'd have the system on recirc with the A/C on
for sure. Likewise if I was in St. Paul in February

, I'd be using recirc and have the
heat cranked. Not much worry about humidity in either place.

 

[planet4ever]

What I hate most about the climate control system is that it has a few predefined modes which are not well documented, and I seem to spend a lot of time punching buttons to see if I can outguess what the system's computer is going to do. Rather than the silly "Mode" button that you have to cycle through sequentially to find what you want, they should have a button that brings up a climate screen. There you should be able to set what temperature you want, where you want the air to go, and whether auto is on or off. If on, it should show you what choices it has made, and if off you should be able to set everything exactly as you want it.

Ray

 

[highcountryrider]

+1

 

[aqn]

Nissan has decided that the Leaf driver cannot select "Air Recirculation" while the "Automatic Climate Control" is on but must use the "Fresh Air Intake" mode.
[...]
Larry

The LEAF has "Automatic Climate Control"?! Oh yeah, so it does. I forgot 'cause I stopped using it long ago on grounds that it's even dumber than our 43rd President.

I would think that the ideal operation would be to move humid air past the cooling elements of the A/C's heat pump, ...condensing

Just to make sure we have things straight: the LEAF does not have a heat pump. It has a separate A/C system (like normal cars) and a resistive heater with a liquid-to-air heat exchanger, which heat exchanger is known as the "heater core" in normal cars, where it's heated by engine coolant.

condensing out a bunch of the water. Via unspecified mechanical cleverness, the condensate is scraped/shaken/blasted/whatever off the cooling plates and ejected from the cabin in liquid form. Then the dehumidified air is ducted past the heating elements of the same heat pump, where it's warmed back up, probably (due to the heat given off by the condensing water vapor, plus inefficiencies in the system) warmer than it came in.

AFAIK, that's the air flow path for every car: the A/C's evaporator is always upstream of the heater core just for that purpose, to condense moisture out of the air, drying it before heating it up, if it's ever necessary to do both, as in when de-fogging the windshield.

Do any auto A/C systems offer a "dehumidified warm air" service?

In the two cars that come to mind (my previous car, a GTI, and my wife's car, a BMW 528), pushing the windshield defroster switch also turns on the A/C as well as switches to fresh outside air intake. If one doesn't want outside air during defrosting, one can switch back to recirculation.

 

[highcountryrider]

<snip>I forgot 'cause I stopped using it long ago on grounds that it's even dumber than our 43rd President.<snip>

Oh, that's not fair! Nothing is THAT dumb.

 

[Levenkay]

Just to make sure we have things straight: the LEAF does not have a heat pump. It has a separate A/C system (like normal cars).

An Air Conditioning system IS (or is that "HAS"?) a heat pump. But I guess you're saying that the heat-rejection side of the pump is permanently configured to dump into the radiator or some other heat sink, and typically doesn't offer the option of being used a heater. But, ya know.... in a car like the Leaf, where there *isn't* a raging fire under the hood to tap into for cabin heat, wouldn't it make better sense (seeing that an A/C system has, I believe, all the pieces necessary to become a heat pump), to allow the A/C to be configured for heating? So the efficiency might not be the greatest; it's got to beat a resistive electric heater...

It would take some clever air ducting, and better-than-average quality air valves, and a little extra space, but ought to be possible.

 

[highcountryrider]

<snip>It would take some clever air ducting, and better-than-average quality air valves, and a little extra space, but ought to be possible.

It would take all that for sure. It would be an interesting project. You'd have to be able to move outside air over
either the evaporator or the condenser, move inside air over either/both, and you'd have to have a way to add heat
during heat & defrost in order to warm the cabin. It should be more efficient than resistive heat, but very complicated.

I still wonder why Nissan didn't use the waste heat from the drive system to supplement the heater; seems like it would
have been easy to transfer some of it to the hot water system. Safety concerns maybe?

 

[BLUEH20]

Do you as a democrat really want to get into a discussion about dumb presidents and who eleted them?

Lets get back to the smartest thing I have seen in a very long time--The LEAF!

 

[LEAFfan]

In AZ summer here, Auto climate control puts Leaf in air recirculation mode in very hot weather to conserve energy. In cooler weather, it may switch to fresh air.

It depends on where you set your TS. In very hot weather, it will still switch to 'outside air' if you set the temp above 80 or so. It will mix in the outside air to keep the higher temp. I know the heater does not come on or the meter would show that. When it goes to 'outside air', the mileage loss is very low -1/-2).

 

[kovalb]

Nissan has decided that the Leaf driver cannot select "Air Recirculation" while the "Automatic Climate Control" is on but must use the "Fresh Air Intake" mode. This also occurs when you click on the "Front Defroster" button.

Just because the "AUTO" indicator light goes out when selecting recirculation mode does not mean it is not in AUTO, just that the fresh/recirc is being handled manually. The other components, such as fan speed are still being handling automatically.

The reason fresh is selected automatically when in defrost mode is to prevent fogging. The windows will fog up very quickly when there is any humidity in the air if left in recirc.

 

[LEAFfan]

Just because the "AUTO" indicator light goes out when selecting recirculation mode does not mean it is not in AUTO, just that the fresh/recirc is being handled manually. The other components, such as fan speed are still being handling automatically.
The reason fresh is selected automatically when in defrost mode is to prevent fogging. The windows will fog up very quickly when there is any humidity in the air if left in recirc.

+1!

 

[aqn]

Nissan has decided that the Leaf driver cannot select "Air Recirculation" while the "Automatic Climate Control" is on but must use the "Fresh Air Intake" mode.

I went out to the LEAF and started pushing buttons and I thought I saw this behavior, but then was not able to reproduced it. If the "AUTO" light is on, I can change ventilation mode (fresh air-to-recirc and vice versa), which has the side effect of turning off "AUTO".

Just because the "AUTO" indicator light goes out when selecting recirculation mode does not mean it is not in AUTO, just that the fresh/recirc is being handled manually. The other components, such as fan speed are still being handling automatically.

How does one turn off "AUTO" mode if "AUTO" mode is on but the "AUTO" light is not on? How did you figure out that "other components [...] are still being handling [sic] automatically" when the "AUTO" light is off?

Not that the Owner's Manual is The Bible when it comes to the LEAF's operation (to wit, first paragraph on page 4-5, regarding setting the "automatic control mode"), but this needs some further research/verification/substantiation: Owner's Manual, page 4-4:
"When pushing any operating buttons while the
climate control is activating in the AUTO mode,
the climate control turns to the manual mode."

I just verified this much on my LEAF:
If "AUTO" is lit, using any switch (windshield defroster, "mode", climate control on/off, A/C, ventilation control, fan speed) other than the temperature setting or the rear defroster switch will turn off the "AUTO" light. (Note I'm slavishly avoiding saying "turning off 'AUTO' mode, since that's currently in question.)

AFAICT, AUTO mode is not on at all if the AUTO light is not lit.

This also occurs when you click on the "Front Defroster" button.

The reason fresh is selected automatically when in defrost mode is to prevent fogging. The windows will fog up very quickly when there is any humidity in the air if left in recirc.

I have also just verified this much on my LEAF:
If "AUTO" is lit, pressing windshield defroster would turn it off; upon turning off the windshield defroster, "AUTO" comes back on.
If "AUTO" is not lit, pressing windshield defroster would not change it; upon turning off the windshield defroster, "AUTO" remains unlit.

 

[davewill]

... How did you figure out that "other components [...] are still being handling [sic] automatically" when the "AUTO" light is off? ...

If you start playing with the temp buttons it becomes obvious fairly quickly. The fan changes speeds and the AC gets colder if you turn the temp down.

The part that chaps my hide is the I can hit the "OFF" button to completely kill auto, then use mode, fresh air, and the fan speed buttons to set things the way I like, but the heater will STILL kick in if the temp isn't turned down.

 

[highcountryrider]

Couldn't agree more. I love the car, but Nissan needs to add a VENT button, no heat, no cool, just
vent. I am thinking of adding a switch & relay to disable the heat.

<snip>The part that chaps my hide is the I can hit the "OFF" button to completely kill auto, then use mode, fresh air, and the fan speed buttons to set things the way I like, but the heater will STILL kick in if the temp isn't turned down.