• Control Front Panel LCD displays the temperature, parameters, and status and allows you to adjust the backlight intensity for ambient light conditions. Custom icons display the system and control status.
• Basic and Advanced Programming. Menu provides two levels of parameter adjustment and control setup, allowing you to set up advanced features in one menu and easily adjust basic parameters in the other menu.
• On/Off Temperature Adjustment allows you to select the temperature values at which the relay turns On and Off, which automatically defines the Heating or Cooling mode of operation.
• Switch-Activated Temperature Setback allows you to shift the On/Off temperature by an adjustable setback value. When a user-supplied switch closes the binary input control circuit, the control operates at the defined setback temperatures.
• Adjustable Anti-Short Cycle Delay allows you to select the minimum time the output relay remains off before the next on cycle; avoiding short cycling, hard starts, and nuisance overload outages on compressors and other inductive applications.
• Adjustable Sensor Offset allows you to adjust the displayed temperature to the actual sensed temperature.
• Optional Restricted Adjustment Mode allows you to restrict the On/Off adjustment to your defined temperature range.
• Sensor Failure Mode allows you to select the relay On/Off state in the event of a sensor or sensor wire failure.
• Backlight Brightness Level allows youto adjust the LCD backlight intensity.

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, 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.

Repair Information

• Do not attempt to repair or recalibrate theA421 Series Electronic Temperature Control.
• In case of a defective or improperly functioning control, contact your nearest Authorized Johnson Controls/PENN Distributor or Sales Representative.
• When contacting your Johnson Controls/PENN distributor, have the model number ofthe control available. This number can befound on the label inside the cover of the control