I use a Steca solar controller (TR0301U) as a differential temperature controller to decide when to charge storage. It has a sensor in the tank and another on the wood boiler outlet. When the boiler is hotter than storage by the set threshold the controller energizes the zone valve to the storage tank heat exchanger. I have had a problem with this controller ever since I set this system up. I wanted to compare notes with others that have this controller in their system before I seek a warranty replacement. The problem I have is that the temperature readings on the Steca jump around. The readings will change by as much as 5 degrees in the matter of a few seconds. It only seems to do this after it has been charging the tank for a while. When the system is idle, it will usually read +/- 1 degree. The large jumps when charging will cause it to stop charging the tank when it should not. I am wondering if this is normal for these controllers of if I have a dud. I have tried to isolate some external cause of this problem, but it appears to be the controller itself. Thanks, Scott B.