AC *and* Heater simutaneously reducing efficiency?

[EVDRIVER]

disabling the heater element will render the auto temp control inoperative as the system will not be able to maintain a set temp by mixing a/c and heater core air together

a 10 year old could have designed a better HVAC system for an EV

how about a heatpump with a toaster coil backup for starters !

that would be my choice

The new Prius will use a heat pump and supplemental electric heater with no water, they way the LEAF should have been.

 

[TomT]

No argument here but that the Leaf heating system is a price of crap and that Nissan should be embarrassed by it...

However, having disconnected my heater element for the summer to try it, I can say that the AC auto temperature control works just fine that way. It has no problem maintaining the temperature I set just as it did before I disconnected the heating element. It's nice to be able to use the fan, AC, and temperature control in any combination I like without having to worry about engaging the heating element...

disabling the heater element will render the auto temp control inoperative as the system will not be able to maintain a set temp by mixing a/c and heater core air together

 

[EVDRIVER]

Has anyone tried to cross-reference components from the Leaf's HVAC system with other vehicles they make? I'm very skeptical they did it the way they did just to save money on standard parts. Best I can figure, trying with limited success to parse the service manual's descriptions, is the water system provides an advantage of control over air temperature - especially if you pre-condition the vehicle before unplugging.

By having ~2 liters of good thermal mass you can provide very consistent air temperatures across varying air inlet temperatures. A bare heating element would have short but noticeable heat up and cool down times, but the coolant loop is a good buffer that will hold temp until the heating element can adjust. Of course, you sacrifice efficiency in the form of "standby losses" for a heating system you may never use.

I suspect the heater core is always at a temperature appropriate for whatever the desired cabin temp is, regardless of heating/cooling mode. Immediate air heating is controlled by the mixing dampers (5 & 6) while the water temp is adjusted on setpoint and other conditions. Even if you set the temp all the way down and turn the A/C off, best I can tell from the manual all that does is keep damper 5 open and 6 shut... the heater is probably still working.

Seems like a good mod to try and disable the heating element via switch to save a few watts.


=Smidge=

The heater is only on when there is a call for heat. The Leaf heat system is from the Versa or one of their other ICE cars, the difference is they bolt on the
tank-based water heater into the system and circulate it to the coil in the dash, these are sold to use on EV conversions but they are very inefficient since they must heat much water (slowly) and travel to the coil in the dash. Most EV converters don't even use this system. In time people are going to see how Nissan cut many corners to get this car rushed out and how the car is more like a conversion then ground up which is why they bottled things on quickly rather then designing them for the car. Besides the poor heater choice the controls were poorly designed so that the heat can't be shut of manually and if you have just the fan on to bring in cool air rather than use AC, the heat will come on if the temp setting is not set low enough, this is completely stupid in an EV. If you want to see a mass produced ground-up EV then look at pictures of the EV-1, I can't think of another example and the LEAF is more of a conversion then the EV-1 which had a more advanced heater as does the very old RAV4. Nissan needs to back off that marketing BS and start using more modern and efficient technology.

Here is a similar EV conversion heater for lazy converters and Nissan that is used in the LEAF:

http://www.metricmind.com/" onclick="window.open(this.href);return false;

Look at ev fluid heater link on left, few people use these but they are handy if you can't get behind the dash to replace the heater core.

 

[Herm]

The new Prius will use a heat pump and supplemental electric heater with no water, they way the LEAF should have been.

That sounds like a perfect solution for cold places. How about factory tinted windows?, I believe they have a UV tint now.

 

[TomT]

I'm not a big fan of Toyota, considering the crap that they pulled the last few years, but clearly their engineering on the latest Priuses is far more elegant and sophisticated than the relatively crude routes that Nissan took with the Leaf. Should Toyota ever decide to build a mass market BEV, I suspect that it will be engineered just as well.

The new Prius will use a heat pump and supplemental electric heater with no water, they way the LEAF should have been.

 

[kmp647]

Tom , how did you disconect the heater element, is it hard?

 

[Herm]

I dont think you want to use bare heater coils in a car, every autumn it would smell up your car when you turned the heat on for the first time that year. Lots of whining would be heard afterwards. Perhaps they could market that as a feature and not a bug, example: "The advanced Leaf AC systems periodically sterilizes its filter with clean electric heat.. no more cat dander, fungus spores and pollen trapped in your car!".. a light would flash on the panel "Self cleaning cycle active".

The Volt uses a similar system to the Leaf, with a loop for liquid cooling/heating the batteries.. and GM did not spare any expense in its development. The Volt forums also wondered why GM did not use an inexpensive heat pump system, all it takes is a reversing valve, about $15 worth of hardware.

 

[highcountryrider]

Tom , how did you disconect the heater element, is it hard?

+1 I've been trying to find time to work this out, but if you already have.

 

[mxp]

No argument here but that the Leaf heating system is a price of crap and that Nissan should be embarrassed by it...

However, having disconnected my heater element for the summer to try it, I can say that the AC auto temperature control works just fine that way. It has no problem maintaining the temperature I set just as it did before I disconnected the heating element. It's nice to be able to use the fan, AC, and temperature control in any combination I like without having to worry about engaging the heating element...

disabling the heater element will render the auto temp control inoperative as the system will not be able to maintain a set temp by mixing a/c and heater core air together

Doesnt leaving the heater element disconnected cause an Error condition on the system resulting in some type of indicator on the dash?

 

[palmermd]

no errors. works just fine.

 

[TonyWilliams]

no errors. works just fine.

Great. Where is the fuse that you're pulling?

 

[TomT]

Basically, all you do is disconnect the connector that plugs in to the heating element. It can be reached from under the car. Disconnecting it causes no errors to be set. You should protect the connectors from the elements when you do this by either taping over them, sealing them in some fashion, or inserting dummy connectors in to them (which is what I did). Be advised that the cable connector has high voltage on it so you want to use proper safety precautions and protect the cable end of the connector accordingly! If you don't know what you are doing, I highly suggest that you don't do this!

Tom , how did you disconect the heater element, is it hard?

 

[kmp647]

Tom have you needed to re connect the heater yet? and if so can you report on the consumption difference?
I guess my question is , is it worth it to disconnect each summer?

you do need heat there right?

 

[palmermd]

Basically, all you do is disconnect the connector that plugs in to the heating element. It can be reached from under the car. You should protect the connectors from the elements when you do this by either taping over them, sealing them in some fashion, or inserting dummy connectors in to them. Be advised that the cable connector has high voltage on it so you want to use proper safety precautions and protect the cable end of the connector accordingly! If you don't know what you are doing, I highly suggest that you don't do this!

Tom , how did you disconect the heater element, is it hard?

+1

Use the manual to figure it out. If you don't know how to use the manual and don't know what you are doing, don't attempt it. HAC-25 remove connector with 1,3,4. This connector does not contain high voltage, but is very near a high voltage connector, so care must be taken when working in this area. I plan on installing a relay/switch on the wire on pin 4 so I can turn off the heater via a switch on the dash.

 

[LEAFfan]

It's a poorly thought out system for an EV, if you want to use fan only with no AC it will often turn the heat on when you don't want it and are unaware. I constantly find the heat coming on and it's really annoying.

When it turns the heat on with just the fan, what energy reading do you usually get on the energy screen if you don't turn down the temp? I haven't tried this yet because it hasn't been cool enough here to use fresh air until this week.

 

[EVDRIVER]

It's a poorly thought out system for an EV, if you want to use fan only with no AC it will often turn the heat on when you don't want it and are unaware. I constantly find the heat coming on and it's really annoying.

When it turns the heat on with just the fan, what energy reading do you usually get on the energy screen if you don't turn down the temp? I haven't tried this yet because it hasn't been cool enough here to use fresh air until this week.

It's 1500-2k or more. It only happens when I have the temp set about 71 or so which is where I leave it when I use AC, If the AC is off and the car is say 68 and I have the fan on to bring in the 58 degree outside air to cool without AC the heater thinks I want it warm and the heat comes on without me knowing it because of the long heater lag. Thus I must always be messing with the temp control to bring it much lower. Then when I want to use the AC I have to turn it back up because it is too low and the car will be too cold. This is not an issue on an ICE as many have the heat "dial" that is off or if it works the same as above it is only engine heat used. On an EV one may not be aware the heater is on when they want it off. I found it is better to leave the AC on all the time under these conditions.

 

[TomT]

I've had the car since March 1st and needed the heater exactly once so far. What I use much more often is AC, briefly, to demist the windows...

I disconnected it more as an experiment than anything. It certainly makes it easier to get only ventilation when you want it without having to turn down the temperature, etc., to insure the heater doesn't come on... However, it is not that big a deal to turn the temp all the way down, turn off the A/C, select outside air, and then modulate the fan speed to get whatever level of ventilation and temp I want, so I'll likely hook it back up at some point and not worry about it.

Tom have you needed to re connect the heater yet? and if so can you report on the consumption difference?
I guess my question is , is it worth it to disconnect each summer?

you do need heat there right?

 

[TomT]

Yes, since there is high voltage in that area, I was trying to instil the fear of God in people so they wouldn't go blindly forward! I assumed that those who did know what they were doing and how to do it would understand the subtleties...

I had thought about hooking up a switch but have pretty much decided that it is not worth it to me and thus will likely just hook it back up at some point and not worry about it...

Use the manual to figure it out. If you don't know how to use the manual and don't know what you are doing, don't attempt it. HAC-25 remove connector with 1,3,4. This connector does not contain high voltage, but is very near a high voltage connector, so care must be taken when working in this area. I plan on installing a relay/switch on the wire on pin 4 so I can turn off the heater via a switch on the dash.

 

[gbarry42]

In my case, having seen this car in Nov of 2009, I am glad I got it as soon as May 2011, and did not have to wait until Dec of 2013 to get my hands on the first ownable EV. Which is what would have happened if I'd said, "Don't bother talking to me until you get that heater thing designed properly...and the parking brakes...and that Guess-O-Meter..."

As for the Prius, it has a lot of nice enhancements to the system that sure as heck weren't there when they first started making them. The first model couldn't even shut the engine off if the A/C was on!