HVAC questions

[AndyH]

I think it may be that the cold weather package includes a different type of heater all together than the current water/air unit

on the Japan website the cold weather pack desc includes a 5kw PTC heater

that is an electric element to air, totally different than the current system

in addtion to the heated front seat, HEATED REAR SEAT, and heated steering wheel (nice feature)

Can you provide a link to the Japanese info you keep mentioning?

There is nothing yet in the US docs that show the cold weather package, yet the current Leaf already has a PTC heater. PTC only means 'positive temperature coefficient' and it's used for heaters, thermistors, thermal fuses, etc. etc.

 

[kmp647]

I think it may be that the cold weather package includes a different type of heater all together than the current water/air unit

on the Japan website the cold weather pack desc includes a 5kw PTC heater

that is an electric element to air, totally different than the current system

in addtion to the heated front seat, HEATED REAR SEAT, and heated steering wheel (nice feature)

Link? (I do trust Kevin, but I just want to see what else that site is saying now.)

http://ev.nissan.co.jp/LEAF/OPTION/

 

[kmp647]

i used google translator

the info is subject to some interpretation on meaning

is the PTC element inside the water tank like the current cars

or something new

shows heated steering wheel button ( I tried this feature on a Lexus, really nice!)

shows rear wiper ?

shows a heated seat button and says "rear seat cushion heated"

front heated seats too

 

[AndyH]

Thanks for the link. Unfortunately my German and Russian are letting me down in the translation department. :?

Note, though, that the options added for the cold weather package are highlighted. I would expect an additional cabin heater would be highlighted as well.

Also notice that current cars without the cold weather package have rear wipers, so this page isn't necessarily highlighting only cold weather package items.

It's possible that the 5kW heater mentioned is referring to the existing cabin heater on the 'non-cold-weather-package' car. It's also possible that it's mentioning an additional 5kW heater for the battery box (though my gut says a 5kW pack warmer might be a bit large).

 

[Sasparilla]

Thanks Kevin for putting up the details (as best as translation allows) and the link. Heated seats in the front and back are very good. As long as the heater they are talking about is seriously upgraded (and I wouldn't think they'd miss this since Japan has lots of cold weather in the winter - they've been working on this car for a long time), we're good.

Range will take a serious hit of course, but you've got to keep your occupants warm if the car is going to sell to normal folks in much of the U.S. that experience winter conditions. Now its more waiting to see how effective these additions are (and if the heater has been upgraded).

From this standpoint, I'll take the delay we're seeing (since I'm in Illinois and it was going to be late anyways) so I can see how effective this is before I take a Leaf home. Frankly I'm a little surprised that Nissan wasn't offering this as an option on the cars they were already selling here in the U.S. (OR, WA, and CA to a lesser extent, have areas that get seriously cold).

Anyone fluent in Japanese (or have a friend that is fluent) that can decode the Japanese Nissan page for us directly?

 

[Sasparilla]

Nissan, apparently, gave the good folks at Consumers Reports a Nissan Leaf to run in the Connecticut winter and they have a blog entry on it.

While Consumers Reports didn't detail the heating options on the car (probably don't know the difference between the one they have and the ones getting delivered in CA etc.), I'm guessing Nissan gave them a car with the "cold weather" package.

I'm guessing this because Nissan would be crazy to give Consumers Reports a vehicle in Connecticut in the middle of winter that doesn't get warm enough and also because of what they say about the heating in the 20 - 30 degree temps they are having:

"..Cabin heating and cooling can be a significant range-reducing factor in electric cars. At least the Leaf's heater provides ample heat."

This is a big change from what we are hearing about the cars arriving out west with regards to keeping the cabin warm, and great news. Range mentioned was as low as 65 miles (which isn't surprising). Ample Heat? I'll take it.

Here's the page:

http://blogs.consumerreports.org/cars/2011/01/second-drive-2011-nissan-leaf-going-out-on-a-limb.html?EXTKEY=I91CONL&CMP=OTC-ConsumeristRSS

 

[AndyH]

Nissan, apparently, gave the good folks at Consumers Reports a Nissan Leaf to run in the Connecticut winter and they have a blog entry on it.

While Consumers Reports didn't detail the heating options on the car (probably don't know the difference between the one they have and the ones getting delivered in CA etc.), I'm guessing Nissan gave them a car with the "cold weather" package.

I'm guessing this because Nissan would be crazy to give Consumers Reports a vehicle in Connecticut in the middle of winter that doesn't get warm enough and also because of what they say about the heating in the 20 - 30 degree temps they are having:

"..Cabin heating and cooling can be a significant range-reducing factor in electric cars. At least the Leaf's heater provides ample heat."

This is a big change from what we are hearing about the cars arriving out west with regards to keeping the cabin warm, and great news. Range mentioned was as low as 65 miles (which isn't surprising). Ample Heat? I'll take it.

Here's the page:

http://blogs.consumerreports.org/cars/2011/01/second-drive-2011-nissan-leaf-going-out-on-a-limb.html?EXTKEY=I91CONL&CMP=OTC-ConsumeristRSS

At least the Leaf's heater provides ample heat, unlike the Chevrolet Volt we're now testing.

:lol:


Great find and great analysis of the situation! And since there aren't any 'cold weather package' cars known to be produced or in North America yet, the Leaf will just get better as time goes on...

 

[Sasparilla]

Thanks, you know that comment about the Volt was something they added to their blog after I referenced the page (it wasn't there initially).

Frankly I found that a little shocking, about the Volt (since I know it'll turn the engine on if it gets cold enough to heat things up), it'd be interesting to see what they say about the Volt's heating. I like both vehicles.

The fact that Consumer Reports is so positive on the Leaf's heater gives me total confidence on the only thing I had serious reservations about on the Leaf. Nissan did it right and made it to handle colder weather, yeah!

Can't wait to get mine - although since I'm in Illinois I'm guessing whether I'll be able to get it in 2011 or 2012.

 

[Nekota]

Google Translate got more than half the text translated. Just paste the url into the google translate for the whole page. Some of the info links did not get translated - probably bit maps or equivalent.

 

[Herm]

For that reason among others, I still can't see why they didn't just use reverse cycle on the AC for heat: Simple, almost instant, and more energy efficient...

How well does that work in below freezing temperatures?

There are new heat pump systems on the market, they work effectively down to -30° F. I believe they use CO2 as the refrigerant. Such a system would only use 1/2 the power of a simple resistance heater.

http://www.gotohallowell.com/Dealer-Resources/technical-information-35.html

 

[jkirkebo]

There are new heat pump systems on the market, they work effectively down to -30° F. I believe they use CO2 as the refrigerant. Such a system would only use 1/2 the power of a simple resistance heater.

http://www.gotohallowell.com/Dealer-Resources/technical-information-35.html

Even standard heatpumps with R410 works well in 0F weather.

 

[Smidge204]

There are new heat pump systems on the market, they work effectively down to -30° F. I believe they use CO2 as the refrigerant. Such a system would only use 1/2 the power of a simple resistance heater.

http://www.gotohallowell.com/Dealer-Resources/technical-information-35.html

Even standard heatpumps with R410 works well in 0F weather.

And as I've stated before, since the charger, inverter and traction motor all have liquid cooling, they have to throw off a decent amount of heat - too much to comfortably dissipate with air alone. So use the motor/inverter/charger loops as the source for your (water-water) heat pump. Put an aux immersion heater in the line for good measure and call it good I say.

Of course that would be somewhat more expensive to set up - the leading reason why they didn't do it IMHO. Not sure if a "car size" water-water heat pump even exists as an off-the-shelf part, let alone what it might cost compared to a standard car AC system.
=Smidge=

 

[LKK]

My home has a heat pump which has an efficiency factor of 3.7, meaning the electricity it consumes generates 3.7 times more heat than a simple resistive heater. The efficiency factor is measured at 50 degrees and drops as the outside temperature goes down, but I believe it is still greater than 2 at 32 degrees. The heat pump's air handler also employs resistive heat strips for very cold weather.

So it seems to me a heat pump would work very well in an application like the Leaf. The car already has an air conditioning system, so it wouldn't seem to be that much more difficult to go to a heat pump operation. For ordinary heating (say down to 5 or 10 degrees) it would generate significantly more heat than a resistive heater, and simple resistive heating could still be used at extreme temperatures to supplemental heat.

Just my 2 cents.

 

[Nubo]

The 5Kw draw of the heater just seems high to me. I've got a small ceramic space heater, about an 7" cube, which heats up a small room quite nicely. It only draws about 500 watts on low, up to 1000 watts on high. I can't imagine needing the output of more than 3 of these things to keep a small cabin reasonably warm! But maybe I am underestimating the heat loss. If 5Kw isn't enough for cold climates then what is the solution? Better insulation would seem to be in order.

 

[Smidge204]

The 5Kw draw of the heater just seems high to me. I've got a small ceramic space heater, about an 7" cube, which heats up a small room quite nicely. It only draws about 500 watts on low, up to 1000 watts on high. I can't imagine needing the output of more than 3 of these things to keep a small cabin reasonably warm! But maybe I am underestimating the heat loss. If 5Kw isn't enough for cold climates then what is the solution? Better insulation would seem to be in order.

Two things:

1) How long does it take for that 7" cube to heat the space?

As long as the heat put into a room exceeds the heat escaping that room, the room will warm up. It's just a matter of how patient you are. When someone flicks the heater on in their car there is a reasonable expectation they will get copious volumes of warm air in fairly short order.


2) Is that a radiant or convective heater? Big difference. The Leaf uses a convective heater.


Edit: Actually, does a 5kW heater make sense?

Simply: You got 5,000 watts (17MBH) max heat available. Assuming 250 CFM of air pushed through the blower (and humidity is low enough that we can ignore it), you've only got a temperature rise of ~60 degrees. So if your cabin is 10 deg. F like mine was this morning, the air vents are kicking out 70 deg F air at full power.

This is why pre-heating is important. Not only does it get the heating system fluid up to temp (and thus buffer that energy), it also takes the strain off the system trying to get everything up to temp so it only needs to maintain losses after that. Remember that most of the cabin envelope is single-pane glass!
=Smidge=

 

[AndyH]

The 5Kw draw of the heater just seems high to me.

It's spot-on, considering that the Leaf uses a 5kW heater.

 

[EVDRIVER]

The 5Kw draw of the heater just seems high to me.

It's spot-on, considering that the Leaf uses a 5kW heater.

This is why the new plug in Prius will use a heat pump and a resistance heater, it's already in the service manuals.

 

[DaveEV]

Of course that would be somewhat more expensive to set up - the leading reason why they didn't do it IMHO. Not sure if a "car size" water-water heat pump even exists as an off-the-shelf part, let alone what it might cost compared to a standard car AC system.

Guess what - you've already got 98% of the parts of a heat pump in your car - it's called air conditioning.

Seriously - a heat pump uses basically all the same bits that an air conditioning uses, except that it has a few additional valves so it can run backwards and instead of moving heat outside the car (air conditioning) it can run the other direction and move heat into the car (heating mode).

The main drawback of the heat pump is that it can't dehumidify the air - what a regular car will do is run both the air conditioner and heater at the same time - the air conditioner freezes the water out of the air, then engine heat (or in the case of the Leaf resistance heating) heats it back up.

Now heating up air naturally "dehumidifies" the air since warm air can hold more water, but since the windows remain cold you still need to be able to dehumidify.

A successful heat-pump in a car will need a humidity sensor along with backup resistance heating so that it can run in AC mode + backup heat to dehumidify the car when it's needed to defog the windows.

(FWIW, I believe the Tesla Roadster has 15 kW of resistance heating AND a 3 kW heat pump)

 

[Sasparilla]

This is a great discussion of Heat Pumps, I had no idea that they could work well to such low temps (with the right refridgerant).

It'll be interesting to see what Nissan has gone with (guess we'll have to wait till they roll out the Leaf to the cold weather states - the forgotten 36? to see).

It did my heart serious good to see the Consumer Reports blog report the heater's ability for them.

 

[kolmstead]

But, since the LEAF doesn't have a heat pump other than the air conditioner, it might be useful to mention that the heating system will put out a lot more than the normal 1.5 kW if you ask it to. Turning the fan up to high and heat to max, I saw almost 5 kW energy consumption. It seems to stay around 1.5 kW if you leave it on automatic. Range suffers, of course!

-Karl