Johnson Controls A421AEC-01C Electronic Digital Temperature Control, SPDT, 120V, 0.25m Cable

The A421 Series Electronic Temperature Controls are single-stage controls with a single-pole, double-throw (SPDT) output relay.

Line-Voltage Type 4X Electronic Temperature Control: Type 4X (NEMA), IP67 weathertight enclosure for surface-mount applications.
Rated for 120/240 VAC.
Includes an A99BB-25C temperature sensor with 9-7/8 in. (0.25 m) cable

A421 Controls feature a bright backlit LCD with adjustable brightness and a three-button touchpad interface that can be set up to restrict user adjustments. An LED indicates the output relay's On/Off status. Standard A421 Series control modules have simple On and Off temperature settings for heating or cooling, an adjustable anti-short cycle delay, temperature setback, and sensor offset capability. The temperature control range is -40 to 212°F or -40 to 100°C.

The A421 controls are available in (NEMA), IP67 (CE) watertight, corrosion resistant surface mount enclosures

Applications
The A421 Electronic Temperature Control can be used to control a wide variety of single-stage refrigeration or HVAC equipment. Sample temperature control applications include:
temperature monitoring and alarming
on/off control of boilers and chillers
boiler and chiller pump control
heating and cooling control
floating temperature control of damper and valve actuators
cooling tower fan control based on water temperature
supply, makeup, and mixed air temperature control
temperature actuated valve control
supply and makeup air damper and fan control
condenser fan control based on condenser temperature