Supply and return water temperatures are measured at the hot and cold water coils on a representative floor using matched-pair 10K Ω thermistors. These are the same type of sensor used in the weather stations. They are accurate to ±0.26°F (0.2°C). In this case the thermistor design allows the thermistors to be strapped to the outside of the pipe with conductive compound between the pipe and the sensor.

In the pilot IMDS it was determined that the best accuracy was needed in cooling plant measurements. For measuring chilled water and condenser water temperatures, glass-encapsulated thermistors with stainless steel thermowells and caps were used that are accurate to 0.01 °C. For chilled water, 10K Ω thermistors were used and for condenser water, 30K Ω. Supply and return temperatures were measured at both the evaporator and condenser.

Chilled water thermistor assembly

Cross-section of pipe w/thermistor