I have the thrumometer and the therminator fed by a march pump which is connected to the brew kettle. P have an ice chest full of ice water to chill the plate chiller. I have a ball valve after the thrumometer to control the flow rate. I usually circulate back into the kettle for 10 minutes to sterilize the plate chiller. I then reduce the flow rate and turn on the pond pump that pushed the icewater through the plate chiller. I continue to adjust the flow rate and monitor the thrumometer to hit a my target temp. This can be pretty tricky and I don't have it nailed yet, but that is the gist of how I do it.