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AC compresser

F

flying belgian

Well-known Member
I had the fan pulley go bad on the combine radiator. I found a used one and put it on. It is a 3 groove pulley, two being for the fan and one driving the ac compressor. The groove for the compressor is 6 inch dia. and the old one was 4 and half dia. Will that hurt to spin the compressor that much faster? I left the belt off for now as today was our last warm day so I don't need ac until next year. I really hate to change the pulley if I ever find the right one as it is a time consuming job. Takes about 2 hours.
 
You are reducing your compressor capacity by 67% for a given rpm. If your current compressor was cycling at the maximum heat load (which I doubt) you might get by with it.

If it was running full bore in an attempt to keep you cool, you will be getting hot and surely it won't take long for you to decide that the 2 hrs to change the pulley isn't that bad after all.

Mark
 
Bigger pulleys will spin the accessory slower... not faster... You're reducing your a/c capabilities...
 
Bigger pulley on the accessory will reduce rpm. Bigger pulley on the drive will increase the rpm. The way I read his post is he went fron a 4.5 inch pulley for the compressor drive pulley to a 6 inch which would speed up the compressor. DH
 
No, it's not going to hurt anything to run it a little faster. All it will do is increase the capacity a little bit. Even then the maximum capacity set by the expansion valve, or orifice tube, will be the determining factor in how much more the system will actually do.
 
One rule to remember!

Usually always what we don't want to do we end up doing anyway!! May not like doing it but the outcome is usually what we always want!!
 
I did some google research for pulley ratio. Follow the link below. Hope this helps everyone understand. One way to understand it better is to take two pulleys, one 6" and one 3". Put a mark on one side of each pulley then roll them each one revolution on the work bench and see which one travels farthest. The 3" will have to make more turns to go the same distance as the 6" pulley did. The smaller pulley always turns more rpms no matter if it's the drive or driven.
Pulley Ratio
 
The way I read this , the biger pulley he installed is a driven and a driver. Without knowing the size of the crankshaft pulley we will not know the effect on the air conditioner.
We do know however the fan will run slower as the 6 inch pulley is driven from the crank and then a bigger drive was installed to drive the compressor.
 
As the driven wheel gets larger in diameter (circumference increases), it takes more circumference of the driving wheel to complete one rev. As the circumference of the driven wheel increases to twice that of the drive wheel, the drive wheel has to make 2 revs to get one for the driven wheel, thus you have a 2:1 reduction gear. Since the engine contains the drive wheel and it has to run at a certain rpm to perform it's intended function, the AC compressor will run slower than it did.

I understood that the new compressor had the 3 groove chev on it which increased from 4" dia to 6" and it is the driven wheel. Obviously, if the two chevs swapped positions, the result would be just the opposite and yes the compressor would be putting out 1/3 more refrigerant and you could be looking at potential evaporator freezing problems.

Mark
 
Ok, I give.

I re-read the original post and yes the drive pulley is the one that increased in circumference. So the compressor WILL run faster and may not hurt anything, especially if the heat load is adequate to keep the evaporator above freezing.

Only problem there may be head pressure becoming excessive, which would require more hp to drive it, and no big deal on that application, but would put additional pressure on seals and hoses which could cause pre mature leaking problems of refrigerant.

Sorry for the brain-fart.

Mark
 
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