The Johnson Controls A421AEC-02 is a heavy-duty single-stage electronic temperature control engineered for precision in demanding HVACR environments. This unit serves as the direct replacement for A419AEC-2 and A419AEC-2C, offering a critical upgrade for contractors maintaining refrigeration, space heating, and cooling systems. Housed in a NEMA 4X enclosure (IP66), this controller is built to withstand wash-down environments and high-moisture locations where standard controls fail. Operating on 120/240 VAC, it features a broad setpoint range of -40?F to 212?F (-40?C to 100?C), managed via a high-visibility front panel LCD and a rugged three-button touchpad. The SPDT output relay provides versatile switching for compressors, fans, or heating elements, while the integrated anti-short cycle delay protects equipment from rapid cycling. Flexible mounting options include DIN rail or surface mount, and the package includes an A99 temperature sensor to ensure out-of-the-box functionality for field installations. Rugged Environment Protection: The NEMA 4X watertight enclosure prevents corrosion and moisture ingress in walk-in coolers and industrial sites. Simplified Retrofitting: Designed as the primary A421 digital controller upgrade, it features a familiar interface for technicians moving from A419 legacy models. System Safeguards: Adjustable anti-short cycle delay and sensor offset capabilities prolong the lifespan of controlled compressors and motors. Universal Voltage Compatibility: Multi-tap 120/240 VAC input allows for site-wide standardization across different power configurations. Common Questions Is the A421AEC-02 a direct swap for the older A419 series? Yes, the A421AEC-02 is the direct replacement for A419AEC-2. Note that while functional specs align, you should verify terminal block locations as wiring positions may differ slightly from older legacy boards. Can this control be used for both heating and cooling? Yes. The SPDT relay and adjustable On/Off temperature settings allow you to configure the unit for either heating or cooling applications by simply adjusting the setpoint logic in the basic menu. What is the maximum distance for the temperature sensor leads? The included A99 sensor can be extended using standard 18 AWG or 22 AWG shielded cable. For long runs, ensure proper grounding of the shield to prevent electromagnetic interference from affecting the digital readout. 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.
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