Johnson Controls ST-W24 Temperature Sensor

The Johnson Controls ST-W24 is a professional-grade immersion temperature sensor designed for high-accuracy liquid temperature monitoring in hydronic HVAC systems and industrial process loops. Engineered with a precision 10K Ohm NTC Type II thermistor, this sensor provides a highly stable resistance output that is compatible with most Building Automation Systems (BAS) and digital controllers. The assembly features a 4-inch stainless steel probe that ensures rapid thermal transfer and long-term durability in demanding environments.

For technicians and contractors, the ST-W24 simplifies maintenance by including a heavy-duty brass thermowell with a 1/2" NPT fitting. This design allows for the removal and replacement of the temperature sensing element without the need to drain the system, significantly reducing downtime during service calls. The waterproof probe and conductive compound filling provide an accuracy rating of ?0.36?F (?0.2?C), making it an ideal choice for chilled water systems, boiler control, and cooling tower applications where precise thermal data is critical for HVAC energy efficiency.

• System Continuity: The included brass well allows for sensor swaps without depressurizing or draining the plumbing.
• Universal Compatibility: The 10K-2 NTC thermistor curve is the industry standard for JCI Metasys and other major HVAC control systems.
• Rugged Construction: A stainless steel probe prevents corrosion, while the galvanized enclosure (on specific configurations) protects terminations.
• High Precision: Delivers accurate readings within a wide operating temperature range of -40? to 221?F.

Is the ST-W24 compatible with non-Johnson Controls controllers?
Yes. While optimized for JCI hardware, the 10K Type II NTC thermistor is a standard resistance-based element compatible with most direct digital control (DDC) platforms that accept a 10K-2 signal.

Can this sensor be used in potable water systems?
This immersion sensor is typically utilized in closed-loop hydronic heating and cooling. For domestic hot water applications, verify local plumbing codes regarding lead-free brass requirements before installation.

What wiring is required for the ST-W24?
The unit typically ships with 8-foot 24 AWG pigtail leads. It is a non-polarized 2-wire resistive sensor, simplifying field wiring to the controller's analog input.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.