Using demisters without heating

BarryH

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I always use the front Demi’s tee button if the screen fogs. The interesting thing is that it turns on the air on and the blower at full power. BUT you can turn the blower down to minimum so is a useful way to have heater and air on on at the same time. I haven’t managed to find any other way.
I find the opposite. Hitting the demister turns on the AC to dry the air and the airflow onto the screen and turns up the fan speed but without increasing the Heat setting. I, therefore, hit the demist and turn up the heat to full and hey presto clear screen in less than you would expect. I do wonder why though that the Demister overrides the Recirculate since My old Renault would turn "Recirculate" ON when Demist selected and would therefore progressively dry the air as it recirculates through the AC and warms the car very quickly.
 
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BarryH

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I now have 3 x 1kg and two smaller car dehumidifier bags in the car and have cleaned the interior and exterior of all the windows with Rain-X window cleaner and have virtually no misting up. I don't have to use the demister as I used to on rainy days, I just set both the heat and fan to 3 blobs to keep it clear if it's a bit cold.
I presume these dehumidifier bags are the ones you reactivate by drying in the oven?

I wonder how much more kWh that process adds to your energy bill at high daytime rates than the small amount of electricity to operate the AC in the car from the electricity you put there at the cheaper off-peak rate? Not to mention the fuss an bother!
 

Kithmo

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I presume these dehumidifier bags are the ones you reactivate by drying in the oven?

I wonder how much more kWh that process adds to your energy bill at high daytime rates than the small amount of electricity to operate the AC in the car from the electricity you put there at the cheaper off-peak rate? Not to mention the fuss an bother!
By my reckoning, please correct me if I'm wrong.
Microwave. 600W for 6 minutes x 8 (I usually do the 1kg ones twice).
48 minutes at 600W = 480Wh (0.48kWh)
HVAC on demist is around 4-5kW lets say 4.5kW
3 minutes at 4.5kW = 225Wh (0.225kWh)
The bags last a month minimum before they need recharging and I use the car every day.

Using the HVAC.
31 (days) x 0.225kWh = 7kWh

So demister bags = 0.5kWh/month
HVAC = 7kWh/month

Even if it doesn't mist up every day, say only half the time, it's still 3.5kWh a month using the demister.
 

Slipstream

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I now have 3 x 1kg and two smaller car dehumidifier bags in the car and have cleaned the interior and exterior of all the windows with Rain-X window cleaner and have virtually no misting up. I don't have to use the demister as I used to on rainy days, I just set both the heat and fan to 3 blobs to keep it clear if it's a bit cold.
No need for all this stuff if the hvac system is used correctly. EVs are no different to ice vehicles when it comes down to heating and ventilation.
 

Dave

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No need for all this stuff if the hvac system is used correctly. EVs are no different to ice vehicles when it comes down to heating and ventilation.
Not the same. A BEV uses battery power to generate heat which impacts range. An ICE uses some of that wasted 60% to 70% of power to heat the cabin with no impact on range.
 

BarryH

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I don't think we are comparing apple with apples here. HVAC is the whole Heating and Ventilation and Air Conditioning System. There is no way that the use of AC to dry the air directed at the screen draws 4 to 5 kW. The heater is substantial but are you going to drive around with the whole HVAC turned off all winter of course not. Why on earth buy a modern car then not use the facilities you paid to have in the car? Last I checked on a full charge switching the HVAC system off even with the heater control and fan speed to minimum made about 10 to 20 miles difference to the range indicated (today when at 36 miles range HVAC made only 3 miles difference) but with the HVAC system turned on, the AC function makes no difference to range indicated. The compressor only draws a few watts and runs intermittently in any case.

When I first had an ICE car with AC I was always having people say to me that it would kill my consumption by anything from 4 mpg to 10 mpg and saying the just drove with the windows down in summer. So I set out to prove the thing one way or another by driving the same route twice on one day in same very light traffic once with AC and once with front windows down. The impact according to the trip computer was that the fuel economy was 10-12% worst at 40 mph with windows down. The AC on an ICE car is more powerful than on the ZS and drains more power from the engine so I'm not going to stop using it for every day driving.

With regards to microwave power calculations if you use a 600 Watt oven you can't use 600 watts in the calculation as that is the output power. I have a 900 watt microwave but the power draw is something like 1200 to 1400 watt.
 

Tim Green

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It’s my phone that dyslexic, not me! The main point I was trying to make is that when the demist button is pressed it will clear the screen fast, but by turning down the heat control and the fan speed it seems it is possible to have heat and air on on at the same time, which you cannot do by any other means. This is required for proper humidity control all year round.
 

djenson

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By my reckoning, please correct me if I'm wrong.
Microwave. 600W for 6 minutes x 8 (I usually do the 1kg ones twice).
48 minutes at 600W = 480Wh (0.48kWh)
HVAC on demist is around 4-5kW lets say 4.5kW
3 minutes at 4.5kW = 225Wh (0.225kWh)
The bags last a month minimum before they need recharging and I use the car every day.

Using the HVAC.
31 (days) x 0.225kWh = 7kWh

So demister bags = 0.5kWh/month
HVAC = 7kWh/month

Even if it doesn't mist up every day, say only half the time, it's still 3.5kWh a month using the demister.
The MGs AC system is using 4.5KW?? That's like triple the amount my heat pump uses (1.63KW) when its on 100% modulation (i.e never). Seems like a hella inefficient system or car AC systems are weird and out of my understanding. Would love to know more.
 

Kithmo

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The MGs AC system is using 4.5KW?? That's like triple the amount my heat pump uses (1.63KW) when its on 100% modulation (i.e never). Seems like a hella inefficient system or car AC systems are weird and out of my understanding. Would love to know more.
That's when it's on full heat and full fan.
Mine normally draws about a tenth of that on my usual settings of 3 blobs fan and 3-4 blobs heat.
 

N2STY

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I use to get 3 blobs of rice pudding 4 would be to much 🤮
 

Dave

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You rich southerners with your rice pudding and plum jam !
 

Kithmo

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I’ll have a kipper tie while yow is doin it.
tea GIF

Does your tongue reach the bottom of the tin?
Aye, if I oppen t'other end. (y)
 

djenson

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That's when it's on full heat and full fan.
Mine normally draws about a tenth of that on my usual settings of 3 blobs fan and 3-4 blobs heat.
Ahh, full heat. That explains it. thanks Kithmo :)
 
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