Real World Heat Pump Effect

[Uncle Paul]

I believe that Tesla has a computer on board that can determine the best way to generate the heat necessary to deliver the temps the driver asks for.

They can select between resistance heating, heat pump or scavage waste heat from the motors/battery excess.

Gonna be hard to give hard numbers, because there are so many variables, but believe your Tesla can choose between the heat sources it has available to provide cabin heat.

I looks like the heat pump can pull warmth generated by the working motors/gearbox or battery cooling to provide a very efficience transfer of that extra heat to the cabin. If none of that is available it will pull from ambient air. If it gets too cold for that to be efficient, last resort will be to use resistance heating.

Owners can still fall back to using available seat/steering wheel heat to add comfort efficiently.

 

[mongo]

I believe that Tesla has a computer on board that can determine the best way to generate the heat necessary to deliver the temps the driver asks for.

They can select between resistance heating, heat pump or scavage waste heat from the motors/battery excess.

Gonna be hard to give hard numbers, because there are so many variables, but believe your Tesla can choose between the heat sources it has available to provide cabin heat.

I looks like the heat pump can pull warmth generated by the working motors/gearbox or battery cooling to provide a very efficience transfer of that extra heat to the cabin. If none of that is available it will pull from ambient air. If it gets too cold for that to be efficient, last resort will be to use resistance heating.

Owners can still fall back to using available seat/steering wheel heat to add comfort efficiently.

Indeed.
The patent goes into all the different factors involved in the mode selection.
One note of potential clarification, there is no separate resistance heater on the Y. The compressor and blower are driven inefficiently to generate additional heat, if needed. So stator resistance heating and potentially drive electronics resistance.

 

[Uncle Paul]

Clever Tesla...

 

[mongo]

Clever Tesla...

Yeah, they side stepped the whole frost issue (on the low complexity system) and offset the cost of the cabin condensor and valving by removing the cabin PTC, wiring, fuses, and control electronics.

The best part is no part
-Elon

 

[aesculus]

It will be interesting to see this drift into the other cars over time.

 

[mongo]

@arnis, you can click disagree on my posts all you want, but there is no PTC heater on the Y.

X has a pack and cabin heater

3 has only a cabin heater

Y has neither

 

[MY-Y]

I hope the heat pump includes a resistive heater as well. They have very low thermal mass, so they make heat very quickly.

It would be interesting for a comparison on how quick and how hot the MY heat is compared to the M3.

 

[arnis]

There is no PTC heater or there is no PTC heater in HVAC box?

What random lists did you post?

 

[mongo]

There is no PTC heater or there is no PTC heater in HVAC box?

What random lists did you post?

No PTC at all, those are screen captures directly from the owner's manuals of the 3 vehicles.

 

[MP3Mike]

What random lists did you post?

They are from the Tesla First Responders guides.

 

[mongo]

I hope the heat pump includes a resistive heater as well. They have very low thermal mass, so they make heat very quickly.

It would be interesting for a comparison on how quick and how hot the MY heat is compared to the M3.

The compressor can be run inefficiently which acts like the PTC did. The cabin blower can also, but at a lower power level.

 

[MP3Mike]

Y has neither

OT: But notice that the Model Y uses a HV busbars for the charge port instead of cabling? (I wonder if that will positively impact the peak charge rate and how long it can hold it.)

 

[mongo]

OT: But notice that the Model Y uses a HV busbars for the charge port instead of cabling? (I wonder if that will positively impact the peak charge rate and how long it can hold it.)

Yeah, saw that. They double listed HV cables too.
Likely cuts cost and may be sized for higher charge rate. Doubt it impacts peak charge duration since thermal mass is pretty low.

 

[arnis]

Compressor wiring/windings/fuse might handle 1kW and even 2kW. but not 4kW.
There is no reason to remove PTC/resistive heater from the vehicle.
Though moving it from HVAC under the frunk has some advantages.

In some scenarios compressor has to stop. This is why second heating apparatus must be available.

 

[mongo]

Compressor wiring/windings/fuse might handle 1kW and even 2kW. but not 4kW.
There is no reason to remove PTC/resistive heater from the vehicle.
Though moving it from HVAC under the frunk has some advantages.

In some scenarios compressor has to stop. This is why second heating apparatus must be available.

You are incorrect, read the patent US20190070924A1 - Optimal source electric vehicle heat pump with extreme temperature heating capability and efficient thermal preconditioning - Google Patents

There is no situation where the compressor cannot run. The drive units current run at 3.5kW waste heat and those don't have the benefit of phase change of the coolant. The compressor can boil the refrigerant.
They put in both a cabin evap and condensor.
There is no reason to keep the PTC and its cost.

 

[arnis]

Heat pump outside condensers freeze and/or clog up for example.
"There is no situation where the compressor cannot run." Joker.

 

[MP3Mike]

Heat pump outside condensers freeze and/or clog up for example.
"There is no situation where the compressor cannot run." Joker.

Maybe you missed the fact that Tesla designed the system such that they can bypass the outside condenser when the conditions make it not suitable to use it.

There is a reason it took them "so long" to put a heat pump in their cars. They wanted to design, and test, it the best they could first. And up until the Model Y they thought that A/C and a PTC heater was the best choice available at the time.

 

[Feathermerchan]

In the diagram above #232 is "12V Heater" What is that?
In the patent #232 shows as "Low voltage cabin heater" so it's a smaller cabin heater because at 12V you're limited to the amount of power you can supply.
So you two are both right. No HV PTC heater but still a resistance cabin heater.

When the compressor is moving heat from the drive train/ battery to the cabin, heat does not have to be removed by the radiator so the shutters can be kept closed reducing drag.

 

[mongo]

In the diagram above #232 is "12V Heater" What is that?

That is the HVAC blower being driven inefficiently to produce heat, it has a 400W limit in the patent description.

Or not... per @MP3Mike

 

[MP3Mike]

In the diagram above #232 is "12V Heater" What is that?
In the patent #232 shows as "Low voltage cabin heater" so it's a smaller cabin heater because at 12V you're limited to the amount of power you can supply.
So you two are both right. No HV PTC heater but still a resistance cabin heater.

When the compressor is moving heat from the drive train/ battery to the cabin, heat does not have to be removed by the radiator so the shutters can be kept closed reducing drag.

They refer to it as a LV Heater:

This mode is also needed whenever the passenger and the driver comfort requests differ ; the LV cabin heater 232 cores can provide left / right differential heating

So it is how they handle the different temperature settings between the two sides. (Which people have reported is not currently available in the Model Y, so maybe the software isn't 100% done yet.)