2020 Leaf ... adjust air temp?

SBCLeaf said:

Nubo said:

Perhaps there's a problem with your car, because my experience with the LEAF electric AC is the exact opposite. If I monitor the energy consumption I can clearly see it decline from a high level initially when starting in a hot car, and gradually dropping as the internal temperature reaches the set point.

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I'm not as concerned with the energy consumption as I am with the temperature. The air coming out of the vents is 40 - 42°F whether the temperature control is set to 60 or 90. No adjustment of the knob has any effect on the temperature of the output. Even with the cabin at 65° in the morning, the A/C will still output 40° with the temperature set to 90.

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Something seems obviously wrong if the AC is blasting when you've selected 90 degree cabin temperature when it's already cold.

Nubo said:

Something seems obviously wrong if the AC is blasting when you've selected 90 degree cabin temperature when it's already cold.

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I'll try and have the dealer look at it. Every car I've ever had would just blow air the same as fan-only if the set temperature was set higher than ambient. This car just blows 40 degrees no matter what all the time.

SBCLeaf said:

Nubo said:

Perhaps there's a problem with your car, because my experience with the LEAF electric AC is the exact opposite. If I monitor the energy consumption I can clearly see it decline from a high level initially when starting in a hot car, and gradually dropping as the internal temperature reaches the set point.

Click to expand...

I'm not as concerned with the energy consumption as I am with the temperature. The air coming out of the vents is 40 - 42°F whether the temperature control is set to 60 or 90. No adjustment of the knob has any effect on the temperature of the output. Even with the cabin at 65° in the morning, the A/C will still output 40° with the temperature set to 90.

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yeah, its an ON OFF situation... no "on" option.

A/C and heat run independently of each other and your suspicion is correct; they will fight each other.

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Hey, I told him this, early on. Whoever mentioned the fact that ICE vehicles blend in heat as needed was right, although probably not the cheaper ones. With the Leaf, doing that has a big cost in power consumption. Still, if that is what is desired, it should work to run heat and A/C at once. It's also possible that the Leaf in question has a bad interior temp sensor.

DaveinOlyWA said:

yeah, its an ON OFF situation... no "on" option.

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The manual says otherwise. Seems like even Nissan expects it to work the way I do.

Nubo said:

SBCLeaf said:

Nubo said:

Perhaps there's a problem with your car, because my experience with the LEAF electric AC is the exact opposite. If I monitor the energy consumption I can clearly see it decline from a high level initially when starting in a hot car, and gradually dropping as the internal temperature reaches the set point.

Click to expand...

I'm not as concerned with the energy consumption as I am with the temperature. The air coming out of the vents is 40 - 42°F whether the temperature control is set to 60 or 90. No adjustment of the knob has any effect on the temperature of the output. Even with the cabin at 65° in the morning, the A/C will still output 40° with the temperature set to 90.

Click to expand...

Something seems obviously wrong if the AC is blasting when you've selected 90 degree cabin temperature when it's already cold.

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For insight to the problem; review the location of the temperature sensor. That is 90% of the problem. The remaining 10% is the sensitivity setting of the thermostat. Delta is simply too large.

DaveinOlyWA said:

For insight to the problem; review the location of the temperature sensor. That is 90% of the problem. The remaining 10% is the sensitivity setting of the thermostat. Delta is simply too large.

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This shouldn't involve the temperature sensor. When the system isn't in AUTO mode it should behave just the same as a car from the 1970's. They didn't have temperature sensors. You just turned on the A/C and dialed the knob (or slider) to whatever made the air coming out of the vents the temperature you wanted. End of story. The only thing needed to gauge whether it's working is a thermometer stuck in one of the vents.

SBCLeaf said:

DaveinOlyWA said:

yeah, its an ON OFF situation... no "on" option.

Click to expand...

The manual says otherwise. Seems like even Nissan expects it to work the way I do.

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The initial power levels seen would imply that the cold is adjustable but is it? Because I see no evidence of that and neither do you.

We jump in car, turn on A/C and feel...warm air. Luckily the system is quite efficient and that air becomes cool quickly (at least for me but I tend to avoid areas that bake. Hot is good enough for me) and that coolness is partially due to the immediate effect of lower moisture content.

During this time, the condenser has not reached its operating goal so the power stays high. As the operating point gets nearer, the power starts to drop down. Eventually the operating point is obtained and power is low and in some cases, toggles on and off bouncing between zero power up to 200 to 500 watts or so. Now this power is controlled by the feedback loop. IOW, the difference in the temperature of the coolant returning to be recooled, NOT the thermostat.

So what does the thermostat do? Its an on off switch. So effectiveness is based on two things;

Location of the switch
parameters required to turn switch on and off or the delta of the thermostat.

Now this is a basic AC system. Obviously there are several options that can be applied like multiple sensors, etc. We can assume that Nissan exercised minimal options. If you can get yours to work better by visiting the dealership, most definitely report back here.

As for me; I nixed the dealership option favoring workarounds. I have had cars with better A/C systems and wish I knew more about them but it was simply not interesting to me at the time.

DaveinOlyWA said:

Now this is a basic AC system. Obviously there are several options that can be applied like multiple sensors, etc. We can assume that Nissan exercised minimal options. If you can get yours to work better by visiting the dealership, most definitely report back here.

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The plan is to dump the car as soon as it doesn't hurt me too much financially. It's my first experience with a Nissan and I don't intend to repeat it. I'm just hoping to cope in the meantime. Just looking for a way to keep the fan speed constant and be able to exercise control over the cabin temperature.

Nubo said:

It seems to me LEAF varies the compressor RPM as opposed to ICE vehicles with mechanical compressors that are either ON or OFF. The service manual confirms this (range is 0-9000 rpm). It's one of the advantages of an electric compressor.

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Some ICE cars use variable displacement compressors (ie the number of pistons being used varies) but even then the aim is just to keep the low and high pressures in the AC system at the right operating point. The amount of evaporation will vary based on the amount of heat being absorbed in the condensor so a closed loop system is required. I agree that an electrical compressor system is far better though, even to the point of wondering why ICE cars don't use them more. Of course I'm sure the answer is 1) cost and 2) 'we've always done it this way'

Edit to correct info. AFAIK, all variable ICE compressors are variable displacement.

goldbrick said:

Some ICE cars use variable speed compressors and I think I've even heard of some that use variable volume compressors (ie the number of pistons being used varies) but even then the aim is just to keep the low and high pressures in the AC system at the right operating point. The amount of evaporation will vary based on the amount of heat being absorbed in the condensor so a closed loop system is required. I agree that an electrical compressor system is far better though, even to the point of wondering why ICE cars don't use them more. Of course I'm sure the answer is 1) cost and 2) 'we've always done it this way'

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The only comparable cars in terms of being electric I've had are the Prius Plug-in and the Prius Prime. The Prius Plug-in worked the way I describe and did not use the heater to modulate the temperature. You would know because it would have to start the ICE motor to engage the heat, and it never did such a thing while using the A/C no matter what temperature was set. The Prime uses a heat pump for heat and A/C, so it would be more difficult to assess what was happening. However, I know I could set the fan on HIGH and the A/C on 77 and run the A/C for an hour lunch break in 100-degree sun using only about 1/2 kWh. There's no way that it was running the A/C compressor and heat pump for an hour on 1/2 kWh.

goldbrick said:

Nubo said:

It seems to me LEAF varies the compressor RPM as opposed to ICE vehicles with mechanical compressors that are either ON or OFF. The service manual confirms this (range is 0-9000 rpm). It's one of the advantages of an electric compressor.

Click to expand...

Some ICE cars use variable displacement compressors (ie the number of pistons being used varies) but even then the aim is just to keep the low and high pressures in the AC system at the right operating point. The amount of evaporation will vary based on the amount of heat being absorbed in the condensor so a closed loop system is required. I agree that an electrical compressor system is far better though, even to the point of wondering why ICE cars don't use them more. Of course I'm sure the answer is 1) cost and 2) 'we've always done it this way'

Edit to correct info. AFAIK, all variable ICE compressors are variable displacement.

Click to expand...

That makes sense, especially as how they're slaves to engine RPM.

The LEAF has a hermetically sealed variable speed compressor (much like a high efficiency home heat pump). The compressor speed varies to supply appropriate pressure to the evaporator (less cooling needed results in lower compressor speed with less power draw and higher air discharge temperature). If things are working correctly, the air discharge temperature will not be too cold once desired cabin temperature is reached.

The ICE vehicles I have owned cycle the compressor to avoid evaporator freezing and the air flow is adjusted so some flows through the heater core when the temperature control is set higher (effectively raising the temperature of the mixed cooled and heated air which reaches the discharge vents).

It was warm enough today to play with the A/C a little bit. I confirmed that discharge air temperature can be modulated by adjusting the temperature setting while keeping the fan speed fixed (tried both low speed setting an high speed setting) in manual mode (auto mode controls everything). I am not sure how the S+ works, but the SL+ with heat pump routes the intake air (either from the cabin in recirculate mode or outside in fresh air mode) through the filter first, then the evaporator, then through the air blend doors which send the air around the inside condenser (to avoid adding heat to the air), through the inside condenser (to heat the air) or through both paths to modulate the discharge temperature. The air then flows to the defrost vents, dash vents, floor vents, or a mix of vents depending upon control settings.
Refrigerant valves control the flow of refrigerant to the evaporator, inside condenser, and outside condenser/evaporator (outside coil functions as condenser in cooling mode and as evaporator in heating mode).

GerryAZ said:

I am not sure how the S+ works, but the SL+ with heat pump routes the intake air (either from the cabin in recirculate mode or outside in fresh air mode) through the filter first, then the evaporator, then through the air blend doors which send the air around the inside condenser (to avoid adding heat to the air), through the inside condenser (to heat the air) or through both paths to modulate the discharge temperature. The air then flows to the defrost vents, dash vents, floor vents, or a mix of vents depending upon control settings.
Refrigerant valves control the flow of refrigerant to the evaporator, inside condenser, and outside condenser/evaporator (outside coil functions as condenser in cooling mode and as evaporator in heating mode).

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Have you seen a flow schematic of the latest "heat pump" systems? I'd like to better understand my 2021 SV plus system and how it operates. I was able to download all the service/repair manuals for my 2012 Leaf (e.g. HAC manual), but have not found such "free" downloads for my 2021.

You can buy the service manual (on CD or DVD) on the Nissan Publications web site. The disk for my 2019 is configured to prevent copying and the encryption makes it difficult to save page images in a format that could be posted.

GerryAZ said:

You can buy the service manual (on CD or DVD) on the Nissan Publications web site. The disk for my 2019 is configured to prevent copying and the encryption makes it difficult to save page images in a format that could be posted.

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You can't do a "print screen" and save as a .jpg or use the (Windows) snipping tool?

GerryAZ said:

You can buy the service manual (on CD or DVD) on the Nissan Publications web site. The disk for my 2019 is configured to prevent copying and the encryption makes it difficult to save page images in a format that could be posted.

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Likely you have to "accept terms" that make it illegal to copy.

SBCLeaf said:

There's no way that it was running the A/C compressor and heat pump for an hour on 1/2 kWh.

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Are you aware that there is not two separate components in your system? A heat pump compressor functions as a A/C compressor when the refrigerant flows in one direction & then operates as a air source 'heat pump' when the flow of refrigerant is reversed via a 3 way valve to control said refrigerant flow.

In this system whether a vehicle or a home based product the traditional exterior 'compressor' becomes the 'exchanger' when the flow is reversed and vice-versa. And using a DC based compressor allows for a huge speed range(10%-100%) which allows for a variable refrigerant flow and the slower flowing refrigerant in the mechanical sized for 100% operating in say 10%-25% flow is where a significant portion of the efficiency savings are realized in any of these systems.

That's why as already mentioned you see a 1500w-2500w power draw during initial cabin cool down & then around a 400w-600w to maintain because the COP(coefficient of performance) at lower speeds is typical around 3.5-4.5 so for 500w of energy consumed you are receiving around 1750w or more cooling performance.