24V Electronic Single Stage Temp. Control

The Johnson Controls A421GBF-02C is a single-stage, electronic temperature control designed for a wide variety of HVAC and refrigeration applications. It operates on low-voltage 24 VAC power and features a single-pole, double-throw (SPDT) output relay. The unit is housed in a high-impact thermoplastic Type 1 (NEMA) / IP20 enclosure suitable for both surface and DIN rail mounting.

Key Features

• Easy-to-Read Interface: Features a bright, adjustable backlit LCD screen and a three-button touchpad for intuitive setup.
• Precise Control: Allows for adjustable On/Off temperature setpoints, anti-short cycle delays, and sensor offsets.
• Temperature Setback: Includes a user-configurable setback mode controlled via an external switch, ideal for energy-saving schedules.
• Security: Offers a restricted user adjustment mode to prevent unauthorized tampering with settings.
• Versatile Mounting: Designed for simple snap-fit DIN rail installation or standard surface mounting.

Technical Specifications

• Model Number: A421GBF-02C
• Supply Voltage: 24 VAC, Class 2
• Output Relay: SPDT (Single-Pole, Double-Throw)
• Temperature Control Range: -40°F to 212°F (-40°C to 100°C)
• Power Consumption: 1.8 VA Maximum
• Enclosure Rating: NEMA 1 (IP20)
• Included Sensor: A99BB-200C PTC temperature sensor with 6.6 ft (2.0 m) cable

Typical Applications

• Boiler and chiller pump control
• Cooling tower fan control
• Condenser fan cycling
• Supply or mixed air temperature control
• Temperature monitoring and alarms