Can you run a scroll compressor at reduced speed?

[strantor]

I was gifted a scroll compressor module (ATSL-165E) out of an Atlas Copco industrial skid compressor and I want to use it for my home shop compressor, but I can't justify throwing much money at it. It's just a 5HP 230V/460V 3ph motor and a scroll compressor mounted to a plate, coupled to each other by a couple of V-belts.

I have some 3HP motors and VFDs but no 5HP VFDs. I was thinking I will just replace the one or both of the pulleys (maybe the motor too) for a lower gearing solution; sacrifice some volume to work with what I have. But I'm not sure if you can do that. I know that piston compressors need to be run at a certain speed for splash lubrication to work, but I don't think that's a concern with a scroll compressor. But there might be some other thing I don't know about. Maybe the scroll has to run at rated speed to develop pressure? Maybe the compressor can't cool itself at reduced speed? Any gotchas?

 

[den-den]

I worked with some fairly large scroll compressors in the oil & gas industry, changing speeds was not a problem. I am sure there is a limit to how slow they can go but going from 5hp to 3hp does not seem like it would be an issue.

 

[Ulma Doctor]

In my experience, scroll compressors operate at higher speeds than the piston counterparts.
Be sure that the 3hp motor you intend to use is of similar rpm to the 5hp .
You are unlikely to be able to run the compressor at full capacity due to the reduced hp.
Pulley selection could substitute torque for hp, but the output will offer less than the 5hp .
Most likely, you’ll operate the compressor at about 70(ish)% of its potential

 

[strantor]

In my experience, scroll compressors operate at higher speeds than the piston counterparts.
Be sure that the 3hp motor you intend to use is of similar rpm to the 5hp .
You are unlikely to be able to run the compressor at full capacity due to the reduced hp.
Pulley selection could substitute torque for hp, but the output will offer less than the 5hp .
Most likely, you’ll operate the compressor at about 70(ish)% of its potential

So I was thinking torque is fixed; it takes a certain amount of torque to develop 120PSI so I have to supply that torque. So my only option is to either get a 5hp VFD or slow down the compressor (less CFM, same PSI).

But it took me reading your reply to realize, I don't have to hit 120PSI. I could set it around 75-80PSI and then I wouldn't have to change anything. I could still get the full CFM. Thanks!