Honeywell YTHX9421R5101WW/U

Honeywell Prestige® IAQ Wireless Programmable Thermostat with RedLINK™ Technology, 40 - 99 deg F, 4 Stages Heat, 24 VAC


Manufacturer part number:




Honeywell Prestige® IAQ Programmable Thermostat, Wireless, 40 - 99 deg F, +/-1 deg F Differential, 4 Stages Heat, 2 Stages Cool, Temperature Settings Per Day: 4, Programs Per Week: 7, Terminal Designations: R, RC, RH, C, W-O/B, W2-AUX1, W3-Aux2, Y, Y2, G, A-L/A, U1, U1, U2, U2, U3, U3, S1, S1, S2, S2, S3, S3, S4, S4, A, B, C, D, System Switching: Auto/Manual, Fan Switching: Auto-On-Off-Circulate, High Definition Digital, Touchscreen Display, 24 VAC, Hardwired, Horizontal Mount, White, 3-1/2 Inch H x 4-1/2 Inch W x 7/8 Inch D, Includes: (2) Duct Sensors and Lithium Battery, Equipment Interface Module and Outdoor Air Sensor

  • Control heating, cooling and IAQ equipment with only 2 wires at the thermostat. Heating, cooling and IAQ equipment wires to the equipment interface module
  • Smart schedule - programs in seconds for any lifestyle
  • Patented interview based programming and installer setup
  • Light commercial - commercial language (occupied and unoccupied), schedule holidays and custom events, remote setback economizer and time of day
  • Delta T alerts and diagnostics informs customers when their system is not performing as expected with instructions to contact the dealer. Provides a sense of security and greater comfort while generating repeat business
  • All Prestige® IAQ kits come standard with a return and discharge air temperature sensor to measure Delta T
  • Multiple staging options to provide comfort or energy savings
  • Alerts and user interactions log - keeps a searchable history of alerts and setting changes to the thermostat to determine if there is a system malfunction or if the issue was caused by user error. Saves time in troubleshooting and points the technician in the right direction
  • Customizable service reminders allow dealers to remind their customers when its time to call for service, when their warranty is expiring and to provide customized alerts
  • USB port for transferring installer setup customizable reminders, custom events and holidays to multiple thermostats
  • USB port for adding the dealer's full color business logo on the screen
  • 3 assignable outputs to control humidification, dehumidification, ventilation and a stage of heating or cooling
  • Tri-lingual - english, french and Spanish display options
  • Precise temperature control (+/- 1 deg F) for reliable and consistent temperature

Application: Light Commercial or Residential

Products specifications
Attribute nameAttribute value
ApplicationConventional or Heat Pump
Brand NameHoneywell
Control Range40 - 99 deg F
Differential+/-1 deg F
Dimensions3-1/2 Inch H x 4-1/2 Inch W x 7/8 Inch D
DisplayHigh Definition Digital, Touchscreen
Fan SwitchingAuto-On-Off-Circulate
Mounting TypeHorizontal
Number of Stages4 Heat/2 Cool
Power SourceHardwired
Programs Per Week7
SeriesPrestige® IAQ
Stages Cool2
Stages Heat4
System SwitchingAuto/Manual
Temperature Settings Per Day4
Voltage Rating24 VAC