Thermostats and Controllers

A421 Series

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Product Bar End

A421 Series

Single-Stage Electronic Temperature Control A421 Series

Single-Stage Electronic Temperature Control


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


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QtyModelDescriptionIn StockList PriceInternet Price
A421ABC-02C TSTAT/LINEV/NEMA1/-40 TO 212/120VAC/6.6FT SEN In Stock203.00162.40
A421ABC-03C TSTAT/LINEV/NEMA1/-40 TO 212/120VAC/9.75FT SEN INFO205.00164.00
A421ABC-04C TSTAT/LINEV/NEMA1/-40 TO 212/120VAC/13.1FT SEN INFO216.00172.80
A421ABC-06C TSTAT/LINEV/NEMA1/-40 TO 212/120VAC/19.5FT SEN INFO217.00173.60


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  • • Easy-to-read, bright, adjustable backlit LCD screen displays the temperature, parameters, and status clearly and allows you to adjust LCD brightness for the ambient light conditions. Custom icons on the display provide visual cues on system and control status.
  • • Basic and advanced programming menus allow you to easily set up your control application on the LCD using a simple three-button touchpad interface.
  • • Adjustable On and Off temperature setpoints enable easy to set up cooling or heating control applications on the three-button touchpad, eliminating the need to remove the cover and reposition jumpers for reverse or direct control actions.
  • • High and low temperature setpoint adjustment stops allow you to set up your application for your desired range of adjustment and restrict user adjustment to just the desired temperature adjustment range.
  • • Displayed temperature offset allows you to adjust the displayed temperature to the actual sensed temperature in applications where the resistance error in long sensor cable leads cause a deviation in the displayed temperature from the actual sensed temperature.
  • • Adjustable anti-short cycle delay keeps the output relay Off after the Off setpoint is reached for a user-defined time delay, which helps avoid short cycling, hard starts, and nuisance overload outages on compressors and other inductive applications.
  • • Temperature setback/offset control enables the control to shift the On and Off setpoint values by a user-defined offset when an external switch closes the binary input control circuit. Using a switching timer enables you to set up occupied/unoccupied temperature setback schedules for your applications.
  • • High-impact, thermoplastic Type 1/IP20 or Type 4X (NEMA)/IP66 watertight, corrosion-resistant enclosures increase application options, allowing surface and snap-fit DIN rail mount, or watertight surface mount.

Supply Voltage:

 :Low Voltage Models 24 VAC (20 to 30 VAC), 50/60 Hz, Class 2 or Safety Extra-Low Voltage

 :Line Voltage Models 110/120 or 208/230/240 VAC, 50/60 Hz

Power Consumption :Max. 1.8 VA

Accuracy (Temperature):< ± 1.8℉ 1.0℃)

Operating Temperature:

 :Operating Type 1 Models: -40 to 150℉ (-40 to 66℃)

 :Type 4X Models: -40 to 140℉ (-40 to 60℃)

 :Shipping and Storage -40 to 185℉ (-40 to 85℃)

Operating Humidity:0 to 95% RH

Enclosure Rating:Type 1/IP20 high-impact thermoplastic or Type 4X/IP66 watertight, corrosion-resistant, high-impact thermoplastic


 :North America: cULus Listed; UL 60730, File E27734, Vol. 1; FCC Compliant to CFR47, Part 15, Subpart B, Class B Industry Canada (IC) Compliant to Canadian ICES-003, Class B limits

 :Europe: CE Mark – Johnson Controls, Inc. declares that this product is in compliance with the essential requirements and other relevant provisions of the EMC Directive 2004/108/EC and the Low Voltage Directive 2006/95/EC.

 :Australia: Mark: C-Tick Compliant (N1813)

Warranty: N/A


Download Additional Data

document   A421 Datasheet
document   A421 Installation Guide