Tekmar 071 Universal Sensor: Convenient 1' Wire Compatibility Review

I replaced the setpoint sensor in my hot water tank with this so I can monitor the actual temperature. It goes well with the existing sensor and appears to be working well.

I have 3 of these in a heating system with a hot water boiler. One measures the temperature of the outside air, another measures the temperature of the water circulating through my floors (80-100 degrees) and the third measures the temperature of the boiler circuit (typically 180 degrees). The boiler circuit sensor fails regularly every 5 years. The other two have been running without problems for 20 years. I keep 1 or 2 in reserve.

The original sensor 071 has proven itself as a boiler flow temperature sensor for many years. It eventually failed, which is understandable because it was subject to thermal cycling. At room temperature, the measured resistance is normal, 15.5 kOhm. But as the boiler flow temperature increased, the resistance decreased as expected (as it should work) and fell further below the threshold for the control 422 malfunction error. It is indecent that the DTC 422 for this error on my 422 controller is