A421ABD-02C Johnson Controls Temperature Control

Overview

The Johnson Controls A421ABD-02C is a line-voltage, single-stage electronic temperature control designed to manage a wide range of single-stage refrigeration or HVAC equipment. It features an integrated off-cycle defrost timer, an adjustable backlit LCD screen, and a simple three-button touchpad interface for convenient configuration. Housed in a NEMA 1 (IP20) high-impact thermoplastic enclosure, it is suitable for surface or DIN rail mounting and includes an A99BB-200C PTC temperature sensor with a 6.6-foot cable and a 2-inch probe.

Features

• Single-pole, double-throw (SPDT) dry-contact output relay.
• Adjustable backlit LCD screen with customizable brightness and visual status icons.
• Advanced menu options including adjustable anti-short cycle delay, sensor offset, and temperature setback.
• Off-cycle defrost control to schedule regular, passive defrost periods from 1 to 99 minutes.
• Restricted adjustment mode to limit settings to a user-defined temperature range.
• LED indicator displaying the On/Off status of the output relay.

Specifications

• Supply Voltage: 120/240 VAC, 50/60 Hz
• Power Consumption: 1.8 VA maximum
• Temperature Control Range: -40°F to 212°F (-40°C to 100°C)
• Ambient Operating Temperature: -40°F to 150°F (-40°C to 66°C)
• Operating Humidity: 0% to 95% RH non-condensing
• Enclosure Rating: Type 1 (NEMA), IP20 high-impact thermoplastic
• Sensor Type: A99 PTC temperature sensor (1,035 ohm at 77°F)

Applications

• On/off control of boilers, chillers, and commercial refrigeration units.
• Temperature-actuated valve, damper, and cooling tower fan management.
• Condenser fan cycling control based on ambient or condenser temperature.
• Defrost cycle and temperature management for walk-in coolers, display cases, and reach-in boxes.