The Johnson Controls A99BB-400 Temperature Sensor is a precision PTC silicon sensor engineered for high-accuracy temperature monitoring in commercial refrigeration and HVAC systems. Designed for seamless integration with System 450 controls and Penn A419/A421 series controllers, this thermistor-style sensor features a linear resistance-to-temperature output, minimizing calibration drift in the field. The A99BB-400 is equipped with a 13-foot PVC cable and possesses an operational range of -40?F to 212?F (-40?C to 100?C), making it ideal for both evaporator coil sensing and high-ambient discharge air monitoring. The sensor probe is constructed with high-grade stainless steel to ensure rapid thermal response and resistance to moisture ingress. When replacing HVAC temperature sensors, the A99 series provides the reliability required for digital temperature control applications where maintaining tight tolerances is critical to system efficiency and compressor longevity. Key Benefits Linear PTC Output: Provides predictable resistance changes for precise HVAC diagnostics and control indexing. Submersible Probe Design: The stainless steel housing ensures durability in high-humidity environments and refrigeration sensor applications. Extended Lead Length: The 13-foot (4-meter) PVC lead wire allows for versatile mounting without the need for immediate splicing. Broad Compatibility: Native support for Johnson Controls A419, A421, and System 450 modules ensures a direct-fit replacement. Common Questions What is the resistance value of the A99BB-400 at room temperature? The A99 series uses a 1035 ohm reference point at 77?F (25?C), utilizing a positive temperature coefficient for stable readings across the scale. Can the 13-foot lead be extended in the field? Yes, the PVC cable can be extended using standard 22 AWG shielded twisted pair wire, though keeping the total run under 250 feet is recommended to maintain signal integrity. Is this sensor compatible with non-Johnson Controls thermostats? This is a proprietary PTC sensor; it is specifically designed for controllers calibrated for the A99 sensor curve and is not a standard 10k Type II or III NTC thermistor. 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.
