A421ABJ-02C Johnson Controls Temperature Control

Overview

The Johnson Controls A421ABJ-02C is a single-stage electronic temperature control unit equipped with a factory-wired 120 VAC piggyback power cord. It is designed to deliver precise temperature control for heating or cooling systems in refrigeration and HVAC applications. The unit features a high-impact plastic Type 1 (NEMA) / IP20 enclosure suitable for surface or DIN rail mounting, and it includes a remote A99BB-200C temperature sensor with a 6.6-foot cable.

Features

• Backlit LCD screen with adjustable brightness and custom system status icons.
• Simple three-button touchpad interface for basic and advanced programming.
• Adjustable on and off temperature setpoints that determine heating or cooling mode.
• Adjustable anti-short cycle delay to protect compressors from short cycling.
• Switch-activated temperature setback and sensor offset capabilities.
• Restricted user adjustment mode to lock down settings.
• LED indicator providing visual confirmation of the output relay’s on/off status.

Specifications

• Supply Voltage: 120 VAC
• Switch Type: Single-Pole, Double-Throw (SPDT) output relay
• Temperature Control Range: -40°F to 212°F (-40°C to 100°C)
• Enclosure Rating: Type 1 (NEMA), IP20 high-impact thermoplastic
• Sensor Type: Positive Temperature Coefficient (PTC) A99BB-200C sensor
• Cable Length: 6.6 feet (2.0 meters) with a 2-inch probe
• Power Connection: 6-foot single power cord with a combination male/female grounded piggyback plug

Applications

• On/off control of commercial refrigeration equipment and walk-in coolers.
• Heating and cooling management for HVAC systems, boilers, and chillers.
• Control of chiller pumps and cooling tower fans based on water temperature.
• Supply, makeup, and mixed air temperature monitoring.
• Condenser fan and temperature-actuated valve adjustments.