Johnnytoxic's Winter Weather Motoring Tip
- Thread starter Johnnytoxic
- Start date
I think your misunderstanding how A/C works, (the following is not a scientific/technical example, just a very simple explanation) Air conditioning doesn't cool the air this is a big misconception, it removes the heat from it lowering the temperature, the outcome is the same but the method is different to say, fresh air ventilation.
The air from the room is drawn into the indoor unit over a coil which then removes heat from it and the cooler air then goes back out into the room. The heat is transferred from the coil in the indoor unit to the coil in the outdoor unit via the pipework and then blown off into the atmosphere. This is why the outdoor unit appears to be blowing out hot air (and you wouldn't believe the calls we get from customers believing this is a fault).
When you turn the temperature up and the unit switches to heating it simply reverses the process and pulls heat from the outside air and dumps it into the room, a modern system can do this even when its -14 outside.
I fail to see why car systems are so different.
*edit*
Ok having read through this thread multiple times I am willing to believe I may have been wrong about the car A/C systems, back in like the 1960's fixed systems couldn't be used to heat either. However if that is the case I don't understand why a modern car uses A/C technology that's over half a century old. If they were fitted with a modern system they would be greener as using A/C to heat requires 1/4 the power of electric heating so all those cars that it was said use electric heater matrix's for instant heat would be able to run more efficiently.
Anyway sorry if I annoyed anybody, like I said I don't work on car A/C systems because there's no money in it but I always assumed they were the same as fixed systems, my apologies.
Soldato
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Kennysevenfold's top tip, Wake up at 8:59 and call in sick and go back to sleep. 
A office/house AC unit is a bit different from a car unit for a start, most units are bigger than a Car Engine so wouldnt really fit in the engine bay
. Again, we are going over the same rubbish from a few pages ago. The compressor does NOT reverse direction, it has valves (and different pipes) that send it (the fluid/gas) the opposite direction. A car AC unit is a simple one way loop, it DOES NOT reverse direction. I do not 100% know how AC works, but judging from the last few pages in this thread, i know more than you?The reason they use "old technology" is space and costs.
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Soldato
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The only work would be fitting and repairing and thats not a lot as the systems are pretty damn simple other than changing bought in components from a supplier. Theres plenty of money working in product development.
A heat pump is probably in the region of 1/3 of the energy to direct heating by electric, hence it was used on the EV1 and Rav 4 EV. Your ignorance to cars include the fact that around 30% of the energy released from the fuel gets dumped into the cooling system, at cruise its similar to a household gas boiler, and hence cars do not have electric heaters. You are conjecturing an energy saving for a system that does not exist on the bulk of mass produced cars.
Jesus I said I was wrong no need for the abuse.
It DOES reverse direction, it uses an electronically controlled valve to switch coolant flow within the unit reversing direction, I can link you a schematic if you would like, the are just two pipes from the indoor unit to the outdoor unit.
On a modern system its actually less than 1/9 the energy usage compared to direct heating by electric. 30% of the fuel used for the A/C are you sure about that? I had been told (admittedly by a Mitsubishi salesman) that on their new cars the systems effect on mpg was comparable to the drag caused by opening the windows. My comment on it being a better solution that electric heaters was based on the information given to me on page 4 which said most Renaults and some Audis use electric aux heaters.
*EDIT*
My spelling sucks
A office/house AC unit is a bit different from a car unit for a start, most units are bigger than a Car Engine so wouldnt really fit in the engine bay
It DOES reverse direction, it uses an electronically controlled valve to switch coolant flow within the unit reversing direction, I can link you a schematic if you would like, the are just two pipes from the indoor unit to the outdoor unit.
On a modern system its actually less than 1/9 the energy usage compared to direct heating by electric. 30% of the fuel used for the A/C are you sure about that? I had been told (admittedly by a Mitsubishi salesman) that on their new cars the systems effect on mpg was comparable to the drag caused by opening the windows. My comment on it being a better solution that electric heaters was based on the information given to me on page 4 which said most Renaults and some Audis use electric aux heaters.
*EDIT*
My spelling sucks
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Soldato
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I wasnt intending any abuse
I work on concept vehicles, including electric/hybrids. For most case studies we have looked at you are looking in the region of 1/3 of the electrical load using heat pump systems to generate cabin heat over electric cabin PTC heaters. These are automotive appropriate technolgies with the various restrictions, mainly bumper apertures, for the heat exchangers and the trade off against drag coefficients.
The 30% comment is simply how much heat the cooling system will have to dump from the water jacket to ambient air, I'm simply indicating how much of an excess is available to use as free heater, there is little need to provide auxillery systems, hence most cars dont.
I work on concept vehicles, including electric/hybrids. For most case studies we have looked at you are looking in the region of 1/3 of the electrical load using heat pump systems to generate cabin heat over electric cabin PTC heaters. These are automotive appropriate technolgies with the various restrictions, mainly bumper apertures, for the heat exchangers and the trade off against drag coefficients.
The 30% comment is simply how much heat the cooling system will have to dump from the water jacket to ambient air, I'm simply indicating how much of an excess is available to use as free heater, there is little need to provide auxillery systems, hence most cars dont.
Ahh I see, sorry if I was a bit rude about it. Have you considered using a multi split system with two external coils on a switchable circuit?, one of the external coils could be front mounted as normal so it can be used for cooling and the second could be heated by the exhaust gases, if the system had the ability to switch between the circuits for heating/cooling that would provide instant heat whenever needed (I am assuming here that the exhaust gas is hot as soon as the ignition is started?). This should add that much weight and although I realise this idea is totally superfluous for say a car sold in California but for a 4x4 in Scandinavia/Russia/Alaska/etc im sure instant heat combined with high energy efficacy would be useful no?
*** Before anybody assumes something stupid im not suggesting my car has the above system, merely theory crafting with Jonny
*** Before anybody assumes something stupid im not suggesting my car has the above system, merely theory crafting with Jonny
![[TW]Fox](/data/man-of-honor/2009.png){kind=avatar}
He is talking about CAR AIR CONDITIONING because this forum is called MOTORS.
[TW]Fox;17965056 said:
Actually he was talking about fixed building A/C units, then went on to explain how car ones were different, both the quote and my comment on it were aimed at the fixed ones, anyway A/C units have motors in them (im joking about with th last comment)
Soldato
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Prius 3 does something similar however the exhaust heat exchanger heats the coolant directly rather than any sort of compressor system which its self requires energy put into it. Capturing heat energy from the exhaust direct to coolant also helps emissions regardless of ambient conditions by getting the engine up to temp ASAP.
There is no point having a micro system that is efficiently optimised to the n'th degree when it compromises the whole vehicle system. Can you imagine the effect on a overweight of a building system on mass and subequently MPG, let alone the effects on vehicle dynamics... you may aswell just burn the fuel in its own little burner....
Which is exactly what most cold climates will have as option or indeed a block heater you plug in as its just a better way to do it.
I think the Audi A2 1.2 Tdi (3 Litre) has a block heater than runs when you start it just to get the engine temp up as soon as possible as the car is so efficient the thermal mass of the block takes time to give decent heat out and of course you want the oil up to teamp ASAP.
It does - some other cars have this as well. Our old 530d had it, IIRC most of the larger BMW diesels do on account of the fact they take so long to get up to temperature.
i was NOT talking about fixed building units. and either way im 90% sure the Pump/Compressor does not change pumping direction.
Caporegime
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Open front door
Open garage
Get in car and drive away.
Open garage
Get in car and drive away.
Probably the only person in the world who uses the garage daily
Nobody on my street has a car in their garage. In fact I don't they've EVER had one in (garages have been added later on as development on most houses)
Probably the only person in the world who uses the garage daily
Nobody on my street has a car in their garage. In fact I don't they've EVER had one in (garages have been added later on as development on most houses)
isnt a garage for storing loads of empty boxes that you are never going to use again?
Are you kidding? I quoted what you said, hell its further up the page, you clearly wrote "A office/house AC unit" then went on to attempt to describe how you thought they worked. I made a comment on this and Fox jumped for his caps lock to tell me this was the motors section.
But with regard to the compressor I think were arguing the same point using different terminology here, the compressor itself doesn't reverse its own flow it has valves that alter the coolant line route that it uses to reverse the system flow direction. It doesn't change its own pumping direction.