We installed an 5 hp Ingersol Rand rotary screw comp. a couple of years ago. We also installed an IR refrigerated air dryer to match. I can't remember how we got by before on our antique piston-type without dryer.
Get the biggest reservoir you can. This cuts down on compressor short-cycling, which is hard on motors, and gives you the reserve for burst of air such as a keg washer uses. We installed compressor tanks at or near all of our high-use machines, too, which really helps.
Timm Turrentine
Brewerywright,
Terminal Gravity Brewing,
Enterprise. Oregon.