is heat pump working?

[chibitomo]

Hi everyone, I'm new to the forum and got my new i3 last week. Such an awesome car, but have some noob questions I hope someone can help with! I got the non-Rex i3 with the heat pump, but when i can't find any switch to turn the heat pump on. Does it just turn on automatically when the cabin heating is on? How do I know it's working? I can see that the car is saying I can save 5 miles usually by turning the heater off - is that a better saving than i3s without the heat pump? (It's about 8 degrees Celsius at the moment here in the uk)

Thanks in advance

 

[jadnashuanh]

The heat pump is optional in the UK...but, if you have it, it comes on automatically unless it is too cold to function, and then it reverts to resistance heating. It should be able to provide decent heat down to maybe -20C or so (not sure of the exact number).

 

[chibitomo]

Thanks Jim!

 

[RJSATLBA]

Hi everyone, I'm new to the forum and got my new i3 last week. Such an awesome car, but have some noob questions I hope someone can help with! I got the non-Rex i3 with the heat pump, but when i can't find any switch to turn the heat pump on. Does it just turn on automatically when the cabin heating is on? How do I know it's working? I can see that the car is saying I can save 5 miles usually by turning the heater off - is that a better saving than i3s without the heat pump? (It's about 8 degrees Celsius at the moment here in the uk)

Thanks in advance

You should expect the potential saving from turning off heating to be less than for cars without a heat pump (which includes all REx cars) because your heating is already more efficient so less to gain from turning it off. So yes, it should be better but because it is lower not higher.

 

[peteinlongbeach]

Can someone explain which models have radiant, heat pump (part of the a/c compressor?), or both?
Also, when / why / how does each one work?
I have been unable to find this information anywhere....

 

[alohart]

In the U.S., all REx models have just resistance heating. All BEV's have heat pump heating. Heat pumps lose efficiency as temperatures drop, so I have read that i3's with heat pumps also have resistance heaters to help in very cold temperatures, but I don't know whether that's true.

REx models don't have heat pump heating due to a lack of space for a component of that system, so resistance heating is installed.

When the climate control's set temperature exceeds the cabin temperature and climate control is on, whichever heating system is in one's i3 starts producing heat.

 

[jadnashuanh]

The heat pump in the BEV sits where the gas tank is in the REx. Now, in theory, you could make the a/c compressor work backwards as a heat pump, but it's my understanding that the heat pump in the BEV is a separate unit than the a/c compressor. As a result, the REx, in the current configuration, never has a heat pump, nor does it get cabin heat from the REx engine like a normal ICE since it (hopefully) rarely runs. My guess is that in the winter, when the windows fogged up, you could not switch the single compressor back and forth to both dry then reheat the air for demisting the windows - thus, the two systems. As a result, unless they redesign the vehicles, the REx won't have a heat pump. Heat pump verses resistance heating can provide as much as a 3-4:1 energy advantage, so having one can make a difference on maximum range, depending on the ambient conditions.

 

[WoodlandHills]

Does setting the temp at 10 degrees below ambient use less energy than setting it 10 degrees above if you have a REx? I am assuming that the interior is not heat or cold soaked, but is at ambient temp so we are just looking at the energy load to maintain themp, not reach it. I guess that I am asking if it uses less range to cool the car than to heat it?

 

[jadnashuanh]

The conditioning system just moves heat from one place to the other. There's plenty of heat when you need to cool the car, so it's easier for the system to move it. The colder it is outside, if you can run the compressor as a heat pump (not available on the REx), the less efficient it is. So, short answer: cooling may take less energy than heating, but it depends on the delta how efficient it is in heating mode. BMW has indicated that at speeds above 30mph, running the a/c to cool is more efficient than having the windows open because of the increased drag that causes. Ideal case would be if you would be comfortable with the system turned off and could keep the windows closed. That is essentially the situation when you run in EcoPro+ mode.