Free Shipping on orders over $99 | FREE 365-DAY RETURNS
Filters Fast Logo Header
Free Shipping Item Banner

Honeywell 2-Wire IAQ White Thermostat w/ RedLINK


Retail: $399.99 /ea
You Save: 18%
As low as
Retail: $399.99
You Save: 18%
Ships in 5 to 6 business days.

The Honeywell 2-Wire IAQ White Thermostat with RedLINK features a 7-Day programmable feature and has three assignable sets of universal IAQ contacts to control humidification, dehumidification and ventilation. The wireless range of the equipment interface module can be extended by connecting a THM4000R1000 Wireless Adapter to the ABCD terminals. This high definition, 2-wire color touch screen thermostat is used for residential or light commercial applications designed with RedLINK technology. The Honeywell 2-Wire IAQ White Thermostat with RedLINK keeps a searchable history of alerts and setting changes to the thermostat which helps to determine if there is a system malfunction or by user error. This RedLINK thermostat has four assignable sensor inputs on the equipment interface module that can be used for wired sensors or dry contact devices. It also comes standard with a return and discharge air temperature sensor to measure Delta T.


  • Brand: Honeywell
  • Part Number: THX9421R5021WW
  • Pack Size: 1
  • Dimensions: 3 1/2" (High) x 4 1/2" (Wide) x 7/8" (Deep)
  • Applications: Up to 4 stages of Heat/2 Cool with Heat Pumps or 3 Heat/2 Cool with Conventional Systems
  • Operating temperature: 32 degrees Fahrenheit (0 degrees Celsius) to 120 degrees Fahrenheit (48.9 degrees Celsius)
  • Power Method: Hardwired
  • Color: Black front and black sides

Additional Features:

  • 2-Wire IAQ
  • 5-year warranty
  • RedLINK wireless communication
  • 7-Day Multiple Day Programming or Non-Programmable
  • Used with THM5421R1021 Equipment Interface Module and RedLINK accessories

The Honeywell 2-Wire IAQ White Thermostat with RedLINK is the correct component used with the following:

  • Used with RedLINK accessories
  • THM5421R1021 Equipment Interface Module

Product Availability

Please provide your e-mail address below to receive a notification when this product becomes available:


Thanks! We'll send you a notification when this product is available!