Temperature is irrelivent, as the compressor doesnt use any more power if the air it is cooling is hotter.
Now your average 6pk drive belt tensioned correctly can achive about 14kw power transmission. a 3pk belt can achive up to about 3kw of power transmission. The subaru ac comp uses a 4pk drive belt, which can handle a max of 5kw power transmission before slipping.
Something that mechanics are taught at tafe. I take it that you arent a mechanic?
Now even more so. When i did my airconditioning training we set up a compressor on a test bench, with a cars evaporator, which was run by a 1.5hp motor. It achived normal gas pressures and cooled to the same standards as a car aircon, infact it was the same thing on a test bench.
The aircon compressor clutch is a magnetic clutch, which has too friction discs that are about 10mm wide, by 70mm dia. that drives a shaft which is about 8mm diameter. This shaft defiantly couldnt handle 15kw.
seriously how much power do you think a compressor can use?
Quote:
Originally Posted by Rossco
No offense taken, a house is a completely different scenario though.
Houses generally don't exceed 60+ degrees inside unless they're on fire. 
Let's compare some interesting numbers..... (sorry op)
Average automotive Hvac system:
20,000 Btu/hr (average)
Outside (fresh) air, Panel Vents
30 deg c Ambient + radiant heat absorbtion
50% relative humidity
= outlet temp 2-3 deg C
Note that the 20,000 BTU/hr works out to just less than 8 hp delivered (do the math), and assuming a reasonable compressor efficiency, this puts you back to the 10-15 kw region for draw from the compressor, not including the additional electrical (alternator) load added by the evap fan (100w), condenser fans (175w each) and the a/c clutch itself (50w).
Compared to a house a/c where a 12000-Btu/hr air conditioner is usually sufficient for approximately 550 to 650 sq. ft.
This is not too surprising really if you think about it for a second, it doesn't take long to pull down a 60 deg C car interior to something more reasonable.
/Infomercial
back on topic 
If the comp is failing the belt will start to scream/slip as the load goes through the roof.
check the tensioner pulley bearing also, it's only under real load when the a/c clutch is engaged.
Look around the engine bay for belt dust near the a/c belt's path. |