Review on Efficient Temperature Control with Grundfos 595444 3/4-Inch Clip-On Aquastat Control by George Karadimas

I bought a Grundfos 595444 3/4" clamp-on aquastat controller with a specified heat range of 85-105 degrees Fahrenheit to turn the water heater's circulation pump on and off. . The pipe that the sensor is attached to is made of copper and the temperature at the attachment point is 116 degrees. The regulator does not open at this temperature. I added thermal paste to the fitting and it still does not open and does not turn off the pump. Finally I isolated the controller and still no luck. Haven't tested the open/close range of the controller but am pretty sure it's not what is advertised. I bought a timer and installed it instead.