Heat pumps in the MG4

[RP67]

As I said, I might have too much expectation to see things work. Probably I got used to it with my 2017 Mazda CX5... I don't know.

Just out of curious, when you using your heater, on a longer journey, and set it to the desired temperature (even the value on the screen is off by 5 deg), it is holding the temperature within I'd say 2 degrees C , I mean by feel? You are not experiencing excessive overshoot, then cold air to compensate the heat? What you saying, you set it and it holds on that temp for an hour...

 

[Rolfe]

I set it and it stays there. If I drive a long time it can get warmer just because the whole of the interior of the car has heated up and then I'll probably reduce the temperature by 1-degree increments to keep it comfortable, but that's all. I certainly don't get excessive overshoot. It takes a long time to get to the point where I want to turn it down, maybe an hour in cold weather, and it never blows cold air of its own accord. Indeed, it doesn't blow cold air when I turn the temperature down, it just gets a little cooler.

I know that you aren't the only person to have reported this fault, I have seen several others say exactly the same thing. But in the light of the way my car behaves I believe it is a specific fault peculiar to the cars in question. I have actually been impressed by the heating/aircon on the MG4. It doesn't blast me with hot or cold air the way my old Golf (and indeed every ICE car I ever owned) did, instead it gets the whole cabin to a nice temperature and keeps it there. It may take more electricity to do this, but it works.

I don't have a heat pump though, do you?

 

[RP67]

Does anybody has heat pump in the MG4? I thought all of them with PTC heater.

 

[siteguru]

EU models certainly come with a heat pump - at least for the Luxury (Trophy/Essence) models and above.

 

[RP67]

siteguru, you make me envy.

 

[siteguru]

UK isn't in the EU

We don't get the heat pump - not even as an option So you've nothing to be envious about.

 

[RP67]

Thanks for the clarification. I keep forget about politics can re-draw maps (well, at least borders). From here, looks like the UK is in Europe. That is sucks though, you've got the same cold as Europe, but not the same heater as Europe...

 

[Corindikev]

Dunno what is in the Australian version. I assume a heat pump as it doesn't get very cold here except around the Alpine areas and Canberra.

The thing is a reverse cycle air conditioner is in fact a heat pump. They just don't call them that in Australia. So all that is required is to have a process to reverse the cycle of the aircon compressor. In cool mode it expels the heat back in to the atmosphere. In heat mode it removes the heat from the air even if it is very cold & sends this into the car & the very cold air is released back in to the atmosphere.

In countries with very cold sub zero temperature Winters, a Heat pump would not work so the heater needs to be either PTC or Resistance as there is no coolant to use as a heat source in an EV. A heat pump (reverse cycle aircon) will work between about +45 degrees in cooling mode and -10 degrees in heating mode.
So in countries like Norway in mid Winter a car with a heat pump won't keep you warm.

 

[JimD]

In countries with very cold sub zero temperature Winters, a Heat pump would not work so the heater needs to be either PTC or Resistance as there is no coolant to use as a heat source in an EV. A heat pump (reverse cycle aircon) will work between about +45 degrees in cooling mode and -10 degrees in heating mode.
So in countries like Norway in mid Winter a car with a heat pump won't keep you warm.

I'm pretty sure that's wrong. Norway is one of the biggest users of heat pumps to heat their homes.

Even very cold air still has heat energy in it. True, it can't be extracted as efficiently, but it's still there.

 

[tsedge]

Thanks for the clarification. I keep forget about politics can re-draw maps (well, at least borders). From here, looks like the UK is in Europe. That is sucks though, you've got the same cold as Europe, but not the same heater as Europe...

While we are off-topic: it is worth knowing that this was MG UK's decision: the local importer gets to decide which models are offered and what specifications are appropriate to their market. So we can't blame anyone else.

Having said that, I am not bothered about not having a heat pump - PTC heater is just fine for the southern UK.

 

[Corindikev]

I'm pretty sure that's wrong. Norway is one of the biggest users of heat pumps to heat their homes.

Even very cold air still has heat energy in it. True, it can't be extracted as efficiently, but it's still there.

Heat pumps using the sub terranian earth temperature works in much colder climates than those using the ambient air temperature. The earth retains heat built up over the summer so until it gets to several metres deep permafrost, yes there is heat to be extracted. Not so with air at minus 10 degrees C

 

[JimD]

Heat pumps using the sub terranian earth temperature works in much colder climates than those using the ambient air temperature. The earth retains heat built up over the summer so until it gets to several metres deep permafrost, yes there is heat to be extracted. Not so with air at minus 10 degrees C

Not according to Viessmann (who make both gas boilers and heat pumps). They say (as do many other sources) that heat pumps are effective down to -20C. I don't know where you're getting your information from.

What temperature is a heat pump not effective? | Viessmann UK

Heat pumps take the heat out of the ground or air, but what happens when it’s less than 0 ℃ outside?

www.viessmann.co.uk

 

[siteguru]

Are you talking Air Sourced Heat Pumps (ASHPs) or Ground Sourced Heat Pumps (GSHPs)? In a car it's an ASHP.

 

[WonkoTheSaneUK]

Are you talking Air Sourced Heat Pumps (ASHPs) or Ground Sourced Heat Pumps (GSHPs)? In a car it's an ASHP.

I think the range of a GSHP-equipped car might be a little limited.

 

[YaR]

Heat pumps are great technology for houses, and while they may be more efficient than PTC heaters (which are actually pretty efficient themselves) over long time periods, they tend not to be able to put out as much immediate heat over short time spans so I suspect most cars that have them, other than for long journeys, are mainly using the PTC heater for the first 15 mins or so of heating anyway then the heat pump for maintaining the temp so the energy saving probably isn't that significant relative to the total used to move the car.

 

[Corindikev]

Yes in very cold climates an air sourced heat pump will be completely ineffective below about -10 deg C. In warmer climates as in Australia for most areas it will work very well. PTC heaters are pretty efficient and work very quickly. Heat pumps take a bit longer to get going but once they do they are more efficient than PTC but not by a huge margin.

I remember early ICE car heaters were pretty poor but they are very good now. In the 70s I owned an early Mitsubishi Colt & it had an electric resistive heater element that came on until the coolant temperature was hot enough to take over.

 

[securespark]

I think the range of a GSHP-equipped car might be a little limited.

Love it!!

 

[jiiikoo]

Yes in very cold climates an air sourced heat pump will be completely ineffective below about -10 deg C. In warmer climates as in Australia for most areas it will work very well. PTC heaters are pretty efficient and work very quickly. Heat pumps take a bit longer to get going but once they do they are more efficient than PTC but not by a huge margin.

I remember early ICE car heaters were pretty poor but they are very good now. In the 70s I owned an early Mitsubishi Colt & it had an electric resistive heater element that came on until the coolant temperature was hot enough to take over.

Not sure where you're getting your info from but as a Finn, I can tell you with confidence that there are ASHP's that work well to heat a home even at -25C temps and colder (efficiency does drop but they still work).

 

[fnegroni]

I don’t know you, but my mg4 seems to be quite well thermally insulated. Even if parked outside in the cold, it takes a long time for the interior temperature to lower significantly, to the point where repeated short journeys throughout the day benefit from the initial blast of warm air.
I also find the heater reasonably effective even on ECO.
In my specific Mg4, the climate control temperature is 3 degrees out, not 5.
If I set it to 21 or 22 on a cold morning, it will keep 18 or 19 degrees through the journey.
This is using Auto and directing the front vents down.
I think the positioning of the interior temperature sensor is also an issue. It seems to be affected by the air flow more than needed.
It would be good to see a wiring diagram to understand where it gets its reading from.
All the Mazda’s in my past (including a weekend test drive of a CX-30) have been brilliant in the way they managed their climate control, better then several BMW and Mercedes I’ve been into which were amongst the best.
The Kia Stonic I have is reasonably good but requires a bit of adjustment on occasion on a trip, but chooses the vents in a way that suits me (windscreen and feet are preferred over front vents)
The mg4 benefits from manually overriding the air flow to be windscreen and feet and excluding the front vents. All other functions will stay on auto, just the airflow isn’t automatically adjusted. Although I do leave it on full auto most of the time, if I detect some excessively frequent fluctuation, only then I manually set the airflow.

 

[Robf]

Not sure where you're getting your info from but as a Finn, I can tell you with confidence that there are ASHP's that work well to heat a home even at -25C temps and colder (efficiency does drop but they still work).

They will have pre-heat, actually air source in my experience starts to struggle below 6c. Its to do with the exhaust air (usually extracted from the wet rooms) being below freezing and condensate freezes in the vains, the system then has to go into reverse to melt.