# Thread: How Many BTU's in the average auto A/C

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Can't remember bben too many years since I read it.

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I have heard the figure 7 tons at highway speeds.

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Thanks

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re.: tmccar1665 's question of how btu in a car a/c

pardon the answer from wolfdog that it is 7tons at highway speeds (that's 84000 btu)I think wolfdog is thinking of a 50 passenger tour bus. Let us go back to a car. I believe it is between 4000 to 6000 btu. I do remember (years ago) hearing a 5300btu figure. Think about it; if you placed a bedroom size a/c in the car window, would it do a good job of cooling the car's interior? The car's interior volume is approx. 160 cu.ft. and the average bedroom is
1000 cu. ft. While the avg. bdrm. a/c is 5000btu and it does a good job on the 1000cu. ft. area. Of course there are a few factors to consider, but they are not needed at this time to get the idea across that 84000 btu would cool 3 row homes or 2 moderate single homes. yours truly, macgivor..

5. I must be way off base, but I thought it was a lot more than that in the big older cars, like over 12,000 BTU.

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Since you made this personal mcgivor,

I did a little research just for you.

The capacity of a compressor is directly related to the RPM, which varies on an automobile.

The convoluted logic you used to derive auto capacity is flawed. I'll leave you to figure out why.

The linked chart shows average 24,000 btu to as much as 40,000+ btu depending on the compressor.

http://www.heco.net/Compressors.pdf

7. I seem to remember an advertisement a while back-think it was for freightliner trucks-saying the vehicle had more cooling capacity than a 2000 sq. ft. home, or something to that effect.

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I've heard 5 tons at highway speeds. With no shade ,lots of glass and metal and vitually no insulation, I have no problem believing that high a capacity would be needed. They don't make different capacity systems for cars sold in different climates...one size fits all. in Phoenix's 116 degrees ya better have some capacity.

9. The problem is that some people think that same sized unit in their house should cool it off just as fast

10. 2-2.5 tons if i remember...been a long time.

11. Nobody has mentioned an important thing here. In your house you would not let your house get above 80°F. If for some reason it did get past 80 you would expect it to take a long time to get it back to a normal temperature.

Even in the great NE a car sitting in the sun can get up to a 140°F. It can fry a doggy. When you jump in your car you expect it to be half way comfortable by the time you hit the next traffic light. Since time is a big factor. And the heat load caused by the temperature difference it only stands to reason that you would need a lot of capacity from the air conditioning system. I would have (educated) guessed 7 ton.

[Edited by benncool on 08-09-2004 at 08:47 PM]

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## Capacity

12000 btu/hr-48000btu/hr

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why is it newer cars only hold a charge of 2.2 pounds of freon, and the older cars had like 4 pounds.

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