Temperature Sensors for HVAC & Refrigeration

Heating, Ventilation, Air Conditioning (HVAC), and refrigeration systems rely on a vast network of temperature sensors to maintain environmental comfort, protect sensitive perishable goods, and optimize massive energy loads.

While the temperature extremes in this sector are generally moderate compared to heavy industry, the demands for long-term stability, rapid response to ambient changes, and seamless integration into Building Management Systems (BMS) are paramount.

The application dictates the sensor design. Duct sensors monitor the temperature of moving air in supply and return plenums. Immersion sensors monitor chilled or heated water circulating through hydronic loops. Pipe-surface sensors are strapped externally to refrigeration lines to monitor superheat or subcooling.

In industrial refrigeration and cold storage, sensors must operate reliably at sub-zero temperatures, resisting the ingress of condensation and ice formation, which can quickly short out improperly sealed electronics.

Because the operating temperatures rarely exceed 150°C (and frequently drop below freezing), Platinum RTDs (Pt100 or Pt1000) and precision NTC thermistors are the overwhelming choice. They offer superior accuracy, linearity, and stability compared to thermocouples in this narrow temperature band.

For duct applications, specialized probes with perforated sheaths or extended lengths are used to measure the average air temperature, avoiding false readings from stratified airflow. For chilled water lines, direct immersion in a thermowell provides the most accurate reading, though well-insulated pipe-surface sensors offer a non-intrusive alternative.

When installing strap-on pipe sensors, the contact area must be clean and coated with thermal paste. Crucially, the sensor and the pipe must be heavily wrapped in insulation after installation to ensure the sensor measures the fluid temperature, not the ambient air of the mechanical room.

For cold storage and refrigeration applications, connection boxes and cable entries must be completely sealed. The cycling of temperatures around the freezing point causes condensation; if moisture penetrates the sensor housing and freezes, it will mechanically destroy the RTD element.

• Dramatically reduces building energy consumption by providing accurate feedback to variable frequency drives (VFDs) and chillers.
• Prevents product spoilage in cold storage by ensuring tight, reliable adherence to setpoint temperatures.
• Optimizes compressor efficiency by allowing precise calculation of refrigerant superheat and subcooling.
• Lowers maintenance costs through the use of highly stable RTDs that do not require frequent recalibration.