TEKMAR 401 and DHW

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Feeling the Heat
Sep 1, 2011
South Central PA
Does anybody have any experience with a Tekmar 401 House Controller? I am having a problem because the DHW pumps are running non-stop and I am trying to adjust the temperature setting in the Tekmar. I have attempted to adjust the temperature so that the circulator will stop running when the DHW is >/= to 135*. Using an external thermometer on the body of the HWH, I get a temperature of 139* so that tells me the circulators should stop running. I changed the setting in the Tekmar for the DHW to 100* and I placed the tank’s sensor on the supply side of the plate exchanger (168*). I expected this to kill the pump because it would appear that the DHW tank was above the set temperature. The circulators did not stop. The Tekmar has a “View” function that should allow me to see what the current value the tank sensor is providing, but I can’t get the value to display. Is there a way to test the sensor to verify that it is working properly? Am I missing something?