Is the heat pump reversible?

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Grimbo66
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Post by Grimbo66 »

Hi all. Can anyone tell me if the heat pump is reversible? Will it cool the cabin in summer as well? Thanks

CarterHounslow
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Post by CarterHounslow »

I'm confused by the question. Do you mean does the heat pump act as an air conditioner? Or are you asking if you pump heat out?
Last edited by CarterHounslow on Sun Jul 18, 2021 10:14 am, edited 1 time in total.
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Daveion
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Post by Daveion »

A heat pump has a reversing valve in the refrigeration circuit. It can capture heat from ambient air to heat the cabin or remove heat from the cabin and discharge to ambient. The 2 key components of an evaporator and condensor can exchange roles whereas in a standard AC curcuit that is not possible. The refrigerant gas boils at -20C or there about which is why heat can be extracted from ambient air below zero C but on a diminishing scale as you reach the boiling point of the liquid gas in the circuit.
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Raxacorico
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Post by Raxacorico »

Our home heating is an Air Source Heat Pump. In the Summer we can cool the house too; though we hardly ever need that here in Scotland!
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Daveion
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Post by Daveion »

Daveion wrote: Sun Jul 18, 2021 10:01 am A heat pump has a reversing valve in the refrigeration circuit. It can capture heat from ambient air to heat the cabin or remove heat from the cabin and discharge to ambient. The 2 key components of an evaporator and condensor can exchange roles whereas in a standard AC curcuit that is not possible. The refrigerant gas boils at -20C or there about which is why heat can be extracted from ambient air below zero C but on a diminishing scale as you reach the boiling point of the liquid gas in the circuit.
To be clear, it is not achieved by changing inside and outside air by voulme but by passing air over cooling or heating coils that have reversible functions in a Heat Pump.
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Andreas
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Post by Andreas »

Grimbo66 wrote: Sat Jul 17, 2021 10:15 am Hi all. Can anyone tell me if the heat pump is reversible? Will it cool the cabin in summer as well? Thanks
My understanding is that it is not, and serves only to heat the vehicle. Whether this is a hardware or a software issue I do not know. If the latter it might be fixable later. It's a strange oversight, if my understanding is correct, given the very significant range impact of the air conditioning system.

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MotMot
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Post by MotMot »

AC consumes about 1-1.5kwh at the moment (that’s what’s being used when the car is stationary). Yesterday I drove 200 miles (using 50kwh) in 4 hours - so really it doesn’t make that great a difference. Heating the battery in winter uses a lot more I understand (3-4kwh?) so it doesn’t surprise me the heat pump is primarily aimed at reducing that.
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Post by monkeyhanger »

MotMot wrote: Sat Jul 24, 2021 5:05 pm AC consumes about 1-1.5kwh at the moment (that’s what’s being used when the car is stationary). Yesterday I drove 200 miles (using 50kwh) in 4 hours - so really it doesn’t make that great a difference. Heating the battery in winter uses a lot more I understand (3-4kwh?) so it doesn’t surprise me the heat pump is primarily aimed at reducing that.
I'm pretty sure the heat pump only heats the cabin, not the battery array, which is the reason that the benefits of having one are tiny. On a typical UK Winter, you'll only see around an extra 5 miles of range for having one.
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Daveion
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Post by Daveion »

monkeyhanger wrote: Sat Jul 24, 2021 6:25 pm
MotMot wrote: Sat Jul 24, 2021 5:05 pm AC consumes about 1-1.5kwh at the moment (that’s what’s being used when the car is stationary). Yesterday I drove 200 miles (using 50kwh) in 4 hours - so really it doesn’t make that great a difference. Heating the battery in winter uses a lot more I understand (3-4kwh?) so it doesn’t surprise me the heat pump is primarily aimed at reducing that.
I'm pretty sure the heat pump only heats the cabin, not the battery array, which is the reason that the benefits of having one are tiny. On a typical UK Winter, you'll only see around an extra 5 miles of range for having one.
I read an article on the design of the ID3 and 4 HVAC system.
https://evflux.pro/id3-cooling-and-heating/

Its a sophisticated system. In the Heat Pump option the single compressor can cool the batteries whist heating the cabin or cool the cabin whilst heating the batteries. The battery coolant is separate to the HVAC refrigerant but with a series of heat exchanges, valves and some minor resistive heating the Heat Pump can juggle everything and use the medium of the refirgerant, CO2 Gas in a liquid or gas state delendent on cycle, to heat or cool batteries and cabin simultaneously.
Im not sure now in the thread if this answers the question of REVERSIBLE??
For me its confirmation of what I first thought.
The Heat pump has a single compressor.
It can heat or cool the cabin by reversing the function of evaporator and condensor.
It additionally can heat or cool the batteries via heat exchange coils that carry the CO2 refrigerant.
That is I guess why it is an expensive option.
Im not sure the efficiency overall is worth the money with a heck of a lot of things in such a system that can go wrong and good knowledge needed to trouble shoot faults. I think future repairs will be expensive as dealerships will have to use major component replacements as assembies will not allow further breakdown of a small failed components. All repairs of course will require careful handling of the high pressures associated with liquid CO2.
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Andreas
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Post by Andreas »

Thanks!

Would be interesting to see if heat pump users get a smaller hit on range indicated when they turn on AC, compared to those without.

All the best

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Daveion
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Post by Daveion »

Andreas wrote: Sun Jul 25, 2021 2:40 pm Thanks!

Would be interesting to see if heat pump users get a smaller hit on range indicated when they turn on AC, compared to those without.

All the best

Andreas
With so many variables in driving style, preferences etc, one will never know. On paper the heat pump is more efficient at heating the cabin, and I think the batteries from the description of the system in the link than a resistive heating system alone in models with standard AC.
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simonrg
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Post by simonrg »

With my car with heat pump, pre-heating the car in winter for 20 minutes having charged the car to 80% and still plugged into granny charger, the car still had 80% charge. So granny charger (2kW) was able to supply power needs of heat pump only 1.5kW. Whereas with a loan 1st Edition no heat pump, similar pre-heat only had 75% left, so heat pump certainly requires less power.
Benefit on air conditioning / cooling may be less, as non-heat pump air conditioning unit is basically the same as a heat pump just only able to cool, so only benefit would be higher efficiency of heat pump.
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