grbadave
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Joined: Sat Mar 03, 2018 4:41 pm
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Leaf Number: 409068

most efficient HVAC setting

Sat Mar 03, 2018 4:51 pm

Hi. In my 2013 I recently started checking the instantaneous energy consumption for climate control during winter driving; trying to maximize range. Intuitively I would've expected activating both HEAT and A/C would consume more, but my display seems to generally show more consumption when using HEAT alone. Does this make sense? Also- has anyone compared the AUTO setting to manual? I normally drive with fan on lowest setting and 68 deg but given the results described in the experiment above I an beginning to wonder if I should trust AUTO to do it more efficiently than I can. Have not found this question in forum; sorry if I missed it.

LeftieBiker
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Re: most efficient HVAC setting

Sat Mar 03, 2018 5:51 pm

The most efficient setting is with the blower on the lowest speed, the vents set to either Floor only or High, or High - Low, and the recirculate set to partial/auto. You do that by turning recirculate on, then pressing the button again and holding it for exactly two seconds. The recirculate light will flash twice and then go out, leaving you in the otherwise unidentified partial mode. This brings in about 30% fresh air, and with the vent set to Floor only, will also allow the windshield to stay clear in most weather. In damp weather you will need to run the fan speed a little higher. The Auto setting is designed to achieve the desired temperature as quickly as possible, not as efficiently as possible.

If the energy meter is showing no more power used with both heat and A/C running, then it is either programmed incorrectly or you have a non-functioning HVAC component - probably the PTC heater. Do you get plenty of heat, or is the heater weak?
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Nubo
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Re: most efficient HVAC setting

Sat Mar 03, 2018 6:14 pm

The most efficient setting is "OFF" :lol:

I'll see myself out.
I noticed you're still working with polymers.

LeftieBiker
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Re: most efficient HVAC setting

Sat Mar 03, 2018 7:01 pm

Not performing a task at all is different from performing it with maximum efficiency. Arguably the most efficient cooling setting can be fan only, though.
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alozzy
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Re: most efficient HVAC setting

Sat Mar 03, 2018 7:19 pm

Sounds like the OP has an SV or SL with the hybrid heating system. It's always been a pet peeve of mine that, to engage the more efficient hybrid heating, you have to enable both heat and AC - it's counter-intuitive. I finally convinced my wife that turning on the AC isn't going to cool down the cabin, but it took me showing her the efficiency screen a few times before she believed me.

With AC turned off, energy efficiency goes down because only the conventional heater is enabled, not the heat pump. [edit] At least, that's what I've guessed as it makes no sense to me that sometimes as much as 6 kW of energy usage occurs on really cold days in heat only mode.

Nissan should have a dedicated "Hybrid heater" button, much less confusing...
Last edited by alozzy on Sun Mar 04, 2018 12:06 am, edited 1 time in total.
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LeftieBiker
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Re: most efficient HVAC setting

Sat Mar 03, 2018 10:48 pm

alozzy wrote:Sounds like the OP jhas an SV or SL with the hybrid heating system. It's always been a pet peeve of mine that, to engage the more efficient hybrid heating, you have to enable both heat and AC - it's counter-intuitive. I finally convinced my wife that turning on the AC isn't going to cool down the cabin, but it took me showing her the efficiency screen a few times before she believed me.

With AC turned off, energy efficiency goes down because only the conventional heater is enabled, not the heat pump.

Nissan should have a dedicated "Hybrid heater" button, much less confusing...


I'm not following this. I don't have to have A/C on to get full heat! It's true that the same unit provides both A/C and heat-pump-derived heat, but you aren't running the A/C when in heat mode unless both buttons are on. I'm guessing the energy screen just (mis)identifies all heatpump activity as A/C...
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PLEASE don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

alozzy
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Re: most efficient HVAC setting

Sun Mar 04, 2018 12:00 am

@LeftieBiker According to the owner's manual:

Cooling and/or dehumidified heating: The dehumidified heating mode can be used to keep the windows from fogging. In this mode, the heat pump compressor is used in A/C mode for dehumidifying the air instead of heating it. The PTC heater is also used in conjunction to heat the air. This mode will increase energy consumption and therefore reduce range.


However, based on the energy consumption shown on the "Energy Info" screen's "Climate Control" graph, using this mode is more energy efficient, not less. So, I typically use this mode since dry air reduces condensation on the windshield. It's true that it doesn't heat the cabin as quickly as heat only mode, but heat only mode typically uses 3 kW or more, at least on my LEAF. With both A/C and heat on, I typically see energy usage in the 1-2 kW range on the "Climate Control" graph.

I assumed that the stated usage included both PTC and heat pump (including compressor) energy usage. Is that not the case?

The owner's manual isn't clear as to whether heat only mode turns on the heat pump as well as the PTC. When I first got my SV, I assumed that to be true. However, the "Climate Control" graph confused me as it made no sense to me that energy usage would be >3kW if both the PTC and heat pump were heating incoming air - seemed too high to me.

For those with an SV/SL, how does your energy usage compare in "heat only" mode vs with AC also enabled?

As long as the "Climate Control" graph is reflecting actual energy usage for both the PTC and heat pump (including the compressor), then I'll continue to leave the AC on to save energy. I don't really care about the cabin temp much, I just want the most efficient method of keeping the windshield defogged.
Vancouver, CA owner of a 2013 Ocean Blue SV + QC, purchased 01/2017 in WA
Zencar 12/20/24/30A L1/L2 portable EVSE
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LeftieBiker
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Re: most efficient HVAC setting

Sun Mar 04, 2018 12:21 am

The Heat button turns on both heaters, and the PTC boosts the energy consumption at first. After a bit, the PTC reduces power or turns off if the outgoing air temp is close to the desired setting. The meter shows 3kw or more at first with both heaters on, then it drops to 1.5kw or less when the PTC shuts down. Using both heat and A/C to heat the cabin uses more power, but I now understand what is confusing you. The first minute or two, when both heaters are running, is essentially using the same power as using heat and A/C, because the same two units are both running in both scenarios. But in Heat/A/C mode they both stay running, because the PTC is the only source of heat, while in heat mode the PTC will usually shut off, dropping consumption a lot. The exception is when outside temps are frigid. The energy meter is apparently using "A/C" for "Heat Pump." This may be because it predates the heat pump and was never changed to reflect it - we all know how Nissan loves to save a buck by keeping things the same! It may also be effectively impossible for the system to distinguish power drawn by the heatpump for heat from power drawn for A/C.

Anyway, to put it another way, running the heat and A/C together is effectively the same as running the heat in temps below 10F. And we know what that does to energy consumption... (The system won't provide A/C in frigid temps, AFAIK.)
Scarlet Ember 2018 Leaf SL W/ Pro Pilot
2009 Vectrix VX-1 W/18 Leaf modules, & 3 EZIP E-bicycles.
PLEASE don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

grbadave
Posts: 2
Joined: Sat Mar 03, 2018 4:41 pm
Delivery Date: 03 Mar 2018
Leaf Number: 409068

Re: most efficient HVAC setting

Fri Mar 09, 2018 9:53 pm

Thanks for the posts.

Yes, it is an SL. And I was thinking it had something to do with the hybrid/ heat pump heater.

I'll keep experimenting. But it's not so cold anymore so I might have to wait until next winter. In the milder but still wintry weather lately I've noticed in HEAT + AUTO mode the graph sometimes drops to 0 which is never does in other modes. Interestingly, he A/C light does not illuminate and if I press it, the AUTO turns off.

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