As others have said, to go cooler change the relative rates that the wort flows and the water flows. The slowest wort flow and highest water flow will maximize the temp drop. When I used mine, I run the wort through a Blichmann thru-mometer to ensure I was getting where I needed to go. I don't use it anymore, so if you want the thru-mometer, let me know- I'll send it to you for cheap.