A421ABJ-02C | Single Stage Temp Controller with Sensor, Duty-Cycle Timer, 120/240VAC, NEMA1, 6' 7
Get Special Pricing!
Log In or Create an Account for the LOWEST PRICING on our most Popular Brands!
Brand: Johnson ControlsSKU: A421ABJ-02C

Web Price:

Availability: IN STOCK
Contact us for price breaks on large quantities!
Orders over $999 ship FREE*
The product is not cancelable or returnable unless found defective
*Free shipping applies within the continental US and weighing less than 50 lbs.
Shipping and Returns Terms
Image for Technical Expert

Speak With a Technical Expert

Call (847) 773-0645

Hours: 9am - 5pm CDT M-F

A421ABJ-02C | Single Stage Temp Controller with Sensor, Duty-Cycle Timer, 120/240VAC, NEMA1, 6' 7" lead, -40 to 212F, HTG/CLG | Johnson Controls

Johnson Controls | A421ABJ-02C
The photo is for representation purposes only and may not be a photo of product being purchased.
Search products similar to A421ABJ-02C

Documents and manuals

Johnson Controls A421ABJ-02C Documents


Details for A421ABJ-02C

Single Stage Temp Controller with Sensor, Duty-Cycle Timer, 120/240VAC, NEMA1, 6' 7" lead, -40 to 212F, HTG/CLG


The A421 Series Standard Electronic Temperature Controls are single stage, electronic temperature controls with a single-pole, double-throw (SPDT) output relay. The controls feature an adjustable backlit LCD for viewing the temperature and status of other functions, and a three-button touchpad for setup and adjustment. An LED indicates the on and off status of the output relay.

The A421 Controls are available in low-voltage 24 VAC and high-voltage 120 VAC or 240 VAC models, which provide options for most refrigeration and HVAC applications.

The A421 Controls provide heating or cooling control, sensor offset, temperature setback, adjustable antishort cycle delay, and a restricted user adjustment mode. The temperature units can display in °F or °C. The temperature adjustment range is -40°F to 212°F or -40°C to 100°C.

The A421 Controls are available in Type 1, IP20 highimpact plastic enclosures suitable for surface or DIN rail mounting and Type 4X, IP66 watertight, corrosionresistant surface mount enclosures. The factory-equipped power cords provide convenient plug-in connection and control of 120 VAC heating and cooling equipment.


You can use the A421 Control to manage a wide range of single-stage refrigeration or HVAC equipment. Sample temperature control applications include:

  • Temperature monitoring and alarming
  • On and 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.

Features and benefits

Control front panel LCD

Displays the temperature, parameters, and status. You can 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. You can set up advanced features in one menu and easily adjust basic parameters in the other menu.

On and off temperature adjustment

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

Shift the On or 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 (ASd)

Select the minimum time the output relay remains off before the next on cycle; avoid short cycling, hard starts, and nuisance overload outages on compressors and other inductive applications.

Adjustable sensor offset

Adjust the displayed temperature to the actual sensed temperature.

Optional restricted adjustment mode

Restrict the On or Off adjustment to your defined temperature range.

Sensor Failure mode

Select the relay On or Off state in the event of a sensor or sensor wire failure.

Backlight brightness level

Adjust the LCD backlight intensity.


Item Number A421ABJ-02C
Brand Johnson Controls
Housing NEMA1
Type Temperature Controller
Voltage 120/240VAC

Contractor Rewards Program

Learn more about POINTS PLUS Contractor Rewards Program

Already part of the POINTS PLUS Program?
Enter your Contractor ID # in the comment field of your order on Blackhawk Supply


People Also Searched
Johnson Controls A421ABJ-02C
A421ABJ 02C
Johnson Controls A421ABJ 02C
Johnson Controls A421ABJ02C
A421ABJ-02C price
Johnson Controls A421ABJ-02C price
A421ABJ 02C price
A421ABJ02C price
Johnson Controls A421ABJ 02C price
Johnson Controls A421ABJ02C price