a/c question

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Sep 14, 2010
S California
If my home a/c is rated at 3 tons, using the same metrics what would be the same kind of rating for my late model 4Runner a/c? It's not well insulated, has a lot of glass area and the a/c works well no matter how hot is may be outside.
I believe a car's AC is the same order as for a house, in the 2+ ton range for the reasons your list. Cars aren't well insulated and have a lot of glass.

Plus, you expect your car to cool off from sitting in the sun in 100 degree weather in a few minutes.

Try get your house at 80F down a few degrees, takes quite a while.
When I went to HVAC school years ago the instructor mentioned something like 3 or 4 ton, if I remember correctly, you want to cool the car almost instantly so makes sense.
Originally Posted By: Corvette Owner
3 tons equals about 14 horsepower. I read that a car's a/c uses about 8 horsepower, therefore it would be about 1.7 tons.

The amount of horsepower needed depends on several factors. In the 1960s, iron 1 and 2 cylinder compressors demanded far more power than more modern designs.
A 3 ton ac unit has a 3 hp compressor, or slightly under. The rule of thumb is 1 ton = 1 hp, not sure about automotive, I would guess most cars have a 1/2 - 1 hp compressor. I realize the power loss is much higher than 1 hp when being used, I have read up to 10 hp lost with ac on in automotive. Not sure why, maybe inefficient form of power transfer to turn compressor.
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