Digital Refrigerator Thermostat
Johnson Controls A421
The A421 series controls are single-stage, electronic temperature controls with a Single-Pole, Double-Throw (SPDT) output relay. They feature a lockable front-panel touchpad for setup and adjustment, and a Liquid Crystal Display (LCD) for viewing the temperature and status of other functions. A Light-Emitting Diode (LED) indicates the controls output relay On/Off status.
The A421 controls have heating and cooling modes, adjustable setpoint and differential, an adjustable anti-short cycle delay, and a temperature offset function. The setpoint range is -30 to 212F (-34 to 100C). The controls feature remote sensing capability and interchangeable sensors. The A99 temperature probe is 2" long and 1/4" diameter.