Winter weather

[Alb]

I found this problem/design feature on my other car and its predecessor (both from new).
The ventilation system on many cars is designed such that dehumidification is an integral part of normal functioning so use of A/C during wet weather becomes necessary rather than optional if you want a mist free screen.

 

[BarryH]

Condensation is a classic sign of water ingress.

Getting into a sealed box with wet clothes is water ingress isn't it?

I’m still not convinced that aircon actually works with heating. It cools air on cold but when heat is applied i don’t think there is any aircon. I can’t see any difference in both clearing the windows or drain on the battery with aircon on or off when heat is used. Others i know feel differently.

The HVAC set up in a car is such that the air coming into the HVAC whether from the outside or recirculated will pass through the chiller matrix which will extract by means of condensing it and also pass the air through the heater matrix. If the AC button is selected then the AC system will circulate the refrigerant through the chiller matrix collecting heat and cooling the air. The refrigerant then goes to the heat exchanger at the front of the car positioned in front of the coolent radiator. There is also a large cooling fan there to blow air through the Heat Exchanger if the car is stationary or the AC is working hard. The Refrigerant to go round the circuit needs a compressor pump. When the car is stationary turn on the AC and after about 30 seconds you'll hear a pump droning away. It is normal for this to stop and start again at intervals depending on the external temperature. If you turn the heater to a warmer setting then you still hear the compressor pump stopping and starting because it is chilling and dehumidifying the air passing through it. The normal arrangement is that the chilled air then passes through the heating matrix (or depending on the car an electric resistive heater) to warm the air coming into the cabin.

However, When the air coming into the heater is very cold the AC part isn't very effective if at all at extracting moisture i.e. dehumidifying and so many systems disable the system as it would also be prone to icing up the chiller matrix and blocking the airflow. AC systems cutoff is usually around 5C to 7C. One workaround of this problem is to have the air first pass through the heater element and then the chiller which prevents icing, although this can make it difficult to set the temperature you want, others add in a small electric heater to prevent defrosting. Done correctly if you have the heater on warm on a rainy day the vet temperature will rise as the AC kick in.

What I have found is that if you have recirculated on windows will quickly mist up but turn on the AC and they will quickly clear even when the outside temperature is low because the air drawn into the HVAC is warmer than the outside air so the AC cooling matrix isn't so prone to icing.

 

[Cocijo]

Getting into a sealed box with wet clothes is water ingress isn't it?

The HVAC set up in a car is such that the air coming into the HVAC whether from the outside or recirculated will pass through the chiller matrix which will extract by means of condensing it and also pass the air through the heater matrix. If the AC button is selected then the AC system will circulate the refrigerant through the chiller matrix collecting heat and cooling the air. The refrigerant then goes to the heat exchanger at the front of the car positioned in front of the coolent radiator. There is also a large cooling fan there to blow air through the Heat Exchanger if the car is stationary or the AC is working hard. The Refrigerant to go round the circuit needs a compressor pump. When the car is stationary turn on the AC and after about 30 seconds you'll hear a pump droning away. It is normal for this to stop and start again at intervals depending on the external temperature. If you turn the heater to a warmer setting then you still hear the compressor pump stopping and starting because it is chilling and dehumidifying the air passing through it. The normal arrangement is that the chilled air then passes through the heating matrix (or depending on the car an electric resistive heater) to warm the air coming into the cabin.

However, When the air coming into the heater is very cold the AC part isn't very effective if at all at extracting moisture i.e. dehumidifying and so many systems disable the system as it would also be prone to icing up the chiller matrix and blocking the airflow. AC systems cutoff is usually around 5C to 7C. One workaround of this problem is to have the air first pass through the heater element and then the chiller which prevents icing, although this can make it difficult to set the temperature you want, others add in a small electric heater to prevent defrosting. Done correctly if you have the heater on warm on a rainy day the vet temperature will rise as the AC kick in.

What I have found is that if you have recirculated on windows will quickly mist up but turn on the AC and they will quickly clear even when the outside temperature is low because the air drawn into the HVAC is warmer than the outside air so the AC cooling matrix isn't so prone to icing.

Your knowledge clearly surpasses mine in this area.
From a practical experience I can see no difference in the ZS when clearing windows in winter with heat and aircon on compared to aircon off.
All cars I’ve had with aircon have made a big difference in drying the air and demisting in winter. The ZS makes no discernible additional drain on the battery or any aircon noises that I can hear when used with heat. With the cold setting there is a drain and you can hear the pump working.
MG call the ‘aircon’ button the ‘cooling on/off button’ which is interesting. I have the view that any aircon is disabled when heat is used on the ZS to try to improve cold weather range…

 

[Kithmo]

In Winter, icy or just heavy condensation, I use full heat, front demist, recirculate and no AC to get heat into the car first. Then when everything is toasty, I turn recirculate off and front demist off (if the screen is clear) and turn the heat down to my usual setting.

 

[BarryH]

In Winter, icy or just heavy condensation, I use full heat, front demist, recirculate and no AC to get heat into the car first. Then when everything is toasty, I turn recirculate off and front demist off (if the screen is clear) and turn the heat down to my usual setting.

I have just run some tests with the car parked up. In READY mode Fan speed 1 and Heat set to lowest setting and AC off. This draws 1A.

Turning on AC the other settings as before current drain initially jumped to 3A dropping back a little to 2A then 1A again and as the compressor cycled so does the current draw cycle up and down between 1A and 3A every few seconds.

Turning the heater up a few notches changed the cycling pattern with the compressor running slightly less frequently.

I lifted the bonnet and located the two refrigerant pipes [one larger than the other] where they pass through the bulkhead (on the passenger side of the car). The fatter of the two is the cold pipe entering the cabin. Checking this pipe just with my hand it was much colder than the smaller pipe coming from the cabin whether the heater was on the lowest setting or not. This was subjective as I didn't have my digital temperature gages to hand. I will repeat these tests and see by how much the refrigerant temperature changes at different heater settings.

Selecting the Screen Demist/Defrost setting will illuminate both the Screen Symbol and AC Symbol of course and override the Fan Speed setting and Air Distribution controls but not the Heater control which for effective defrost must be turned up high. Early morning Demisting I have found works best with heater set somewhere between 3/4 and Full and Recirculation ON so that progressively warmer and dryer air enters the system rather than cold damp air. Current drawn under these high fan speed and heater plus AC conditions cycled between 3A and 2A but the AC was still cycling on and off.

 

[Cocijo]

Interesting tests. So does your car definitely run the aircon when you have the heat setting applied? As I’ve said, on my car pressing the ‘cold air’ button when heat is on does nothing except to turn the button light in …

 

[Mike]

Having just got my first EV, I am interested to know you de-ice in winter? Can't start the engine to warm up with the blower on full. So what is the answer?

 

[Kev555]

Getting into a sealed box with wet clothes is water ingress isn't it?

The HVAC set up in a car is such that the air coming into the HVAC whether from the outside or recirculated will pass through the chiller matrix which will extract by means of condensing it and also pass the air through the heater matrix. If the AC button is selected then the AC system will circulate the refrigerant through the chiller matrix collecting heat and cooling the air. The refrigerant then goes to the heat exchanger at the front of the car positioned in front of the coolent radiator. There is also a large cooling fan there to blow air through the Heat Exchanger if the car is stationary or the AC is working hard. The Refrigerant to go round the circuit needs a compressor pump. When the car is stationary turn on the AC and after about 30 seconds you'll hear a pump droning away. It is normal for this to stop and start again at intervals depending on the external temperature. If you turn the heater to a warmer setting then you still hear the compressor pump stopping and starting because it is chilling and dehumidifying the air passing through it. The normal arrangement is that the chilled air then passes through the heating matrix (or depending on the car an electric resistive heater) to warm the air coming into the cabin.

However, When the air coming into the heater is very cold the AC part isn't very effective if at all at extracting moisture i.e. dehumidifying and so many systems disable the system as it would also be prone to icing up the chiller matrix and blocking the airflow. AC systems cutoff is usually around 5C to 7C. One workaround of this problem is to have the air first pass through the heater element and then the chiller which prevents icing, although this can make it difficult to set the temperature you want, others add in a small electric heater to prevent defrosting. Done correctly if you have the heater on warm on a rainy day the vet temperature will rise as the AC kick in.

What I have found is that if you have recirculated on windows will quickly mist up but turn on the AC and they will quickly clear even when the outside temperature is low because the air drawn into the HVAC is warmer than the outside air so the AC cooling matrix isn't so prone to icing.

I did mention Barry about the bit if your clothes aren't wet. I see you've done a lot of testing on the heating/ air con system, so I take it condensation/steam is down to just using the heater/aircon correctly? I am taking an MG5 out today for a 24hr or possibly a few days test drive to see if I have the courage to jump to full electric.

 

[Ron61]

I don't know why , but my EHS feels the same way.....if its a rainy day I get fogged up instantly , I have to set the blower to the windscreen and use the demist function. Never had that on my other cars.... Pretty weird

My BMW 320d did it all the time.

 

[Kithmo]

Interesting tests. So does your car definitely run the aircon when you have the heat setting applied? As I’ve said, on my car pressing the ‘cold air’ button when heat is on does nothing except to turn the button light in …

IIRC all car AC units don't operate when the ambient temperature is less than 3 or 4 deg C, to prevent the condenser evaporator icing up and damaging it.
I can feel a drop in temperature coming out of the vents when I switch AC on with heat if it's above 4 deg C outside. I've not actually measured this yet at the vents though with my thermometer, will do so next time I go out.

 

[Alb]

You'd be in trouble if the Condenser iced up, that's the hot part of the system!

 

[Kithmo]

You'd be in trouble if the Condenser iced up, that's the hot part of the system!

Sorry I meant the evaporator, couldn't remember the name of it. (now corrected)

 

[Cocijo]

Again I must state I’m no expert on aircon. I thought during the winter turning on aircon dried the air and in doing so helped demist the car faster. I have always used aircon during the summer and winter months - winter along with heat to fast demist. On my ZS as I’ve said there is no difference using the aircon (or cold air button as MG call it) when the heat setting is on heat On cold i can hear the pump kick in and working - on heat nothing and no battery drain. I have put this down to MG trying to maximize range in winter or just poor design. Perhaps my car has a fault.

 

[Jaygee]

I’m still not convinced that aircon actually works with heating. It cools air on cold but when heat is applied i don’t think there is any aircon. I can’t see any difference in both clearing the windows or drain on the battery with aircon on or off when heat is used. Others i know feel differently.

What I’ve noticed with the air on running along with the heater is that the air coming through is not as warm. It is indispensable when it is raining or cold outside.
whilst I have not noted additional drain with the aircon I am aware that it has moving parts which will wear out with time. I am unsure as to how mg uk will look at this from a warranty point of view if it were to fail given their somewhat lack lustre customer service.

 

[BarryH]

What I’ve noticed with the air on running along with the heater is that the air coming through is not as warm. It is indispensable when it is raining or cold outside.
whilst I have not noted additional drain with the aircon I am aware that it has moving parts which will wear out with time. I am unsure as to how mg uk will look at this from a warranty point of view if it were to fail given their somewhat lack lustre customer service.

Clearly using AC with heating will send warm air to the vents (mainly "Screen" with regards to demisting). I know a lot of people think of AirCon only as a summer thing but when I got my first car with AirCon some 25+ years ago the AC engineer I took the car to for regassing told me to remember AC stands for Air CONDITIONING not Air COOLING and in UK it is every bit as important to "Condition" the Air by Dehumidifying it in winter as it is in summer and that he never switches his off. Car manuals usually also say to run the AC at least once a month.

 

[AnonymouseDriva]

remember AC stands for Air CONDITIONING not Air COOLING and in UK it is every bit as important to "Condition" the Air by Dehumidifying it in winter as it is in summer and that he never switches his off. Car manuals usually also say to run the AC at least once a month.

but...but... the manual specifically (and repeatedly) refers to this as the 'air cooling' function.

I'm with you on that one though. If my GCSE physics from, erm, a while ago, servers me correctly, the dehumidification is probably just a side effect of the cooling - in that the act of cooling the air reduces the amount of water vapour that the air can hold, resulting in condensation in the cooler unit (and therefore drier air). so effectively with both A/C and heating on we're cooling the air to 'dry' it out, then warming it back up again I guess...

 

[Cocijo]

I still remain unconvinced that the ‘cold air’ button does anything at all when using the heater. The pump doesn’t run there’s no battery drain and the impact on demisting and drying the air is nil.

 

[AnonymouseDriva]

I still remain unconvinced that the ‘cold air’ button does anything at all when using the heater. The pump doesn’t run there’s no battery drain and the impact on demisting and drying the air is nil.

I did wonder about that - whenever the system is set to 'auto' my A/C light is permanently on, but I've still noticed things getting a bit steamy.
A press of the 'Demist' button sorts that though,
Maybe the A/C button means that the system is 'active / available' but not necessarily 'on' unless the cabin temperature dictates that cooling is required or the 'demist' function is on?

 

[JoOLS]

It’s masking the issue though isn’t it? Another blot in the copy-book …….

I've had VW's, BMW's an Toyotas that have all misted up quite badly. Not sure it's an MG trait specifically.

 

[BarryH]

I've had VW's, BMW's an Toyotas that have all misted up quite badly. Not sure it's an MG trait specifically.

I don't think it is a trait of EV's as such but I think with modest range EV Drivers want to conserve as much as possible and therefore tend to turn AC off as unneeded because it is winter or not particularly hot. It is a false economy I believe because the AC compressor and fan uses surprisingly little power and drier air takes less electrical energy to heat the air going through the heater.

I think any car can mist up in British winters and most people turn their car heaters up to a higher temperature than they need to be comfortable just to keep the windows clear and that can lead to drowsiness on a long drive. Of course in an ICE car, it is seen as free heat turning the temperature up so why not, but EV drivers are perhaps more aware that it could be sapping range!

Better, therefore, to keep the AC on and you'll find you'll need a lower setting on the Heat Dial to have comfort, alertness and clear windows.

On a side note years ago I invested in a Dehumidifier for my home and lowering the Relative Humidity from the upper 70's to 80% RH. Reducing it to 50% made a massive difference to the heating bill. All that moisture suspended in the air in your home takes energy to keep it as warm as the 20+C you want in your home. Removing it makes it easier for my central heating to do its job.