Honeywell Home · Equipment controller
THM5421R1021 Equipment Interface Module
RedLINK equipment interface for compatible Prestige IAQ and VisionPRO thermostats.
Will this work with my system?
Match your equipment to these requirements before ordering.
Works with
- Staging: Heat pump: Up to 4 heat / 2 cool; Conventional: Up to 3 heat / 2 cool
Documented compatible models
Follow the configuration requirements below. Models not listed here have not been verified by this list.
System requirements
- Supply voltage: 18–30 Vac
- Power: Hardwired
- Connection: RedLINK
Check before you buy
- Match the full THM5421R1021 model number and hardware revision to the manufacturer's equipment manual and accessory list.
- Compare the equipment terminals, control voltage and required operating sequence with the model-specific installation diagrams.
Installation & configuration details
- THM5421R1021 is already included in the YTHX9421R5085WW kit.
- The newer 69-2758EFS-05 guide also covers Wireless FocusPRO. Confirm the applicable hardware revision and its sensor restrictions before selecting that pairing.
Manufacturer documentation (1)
Use these documents to compare your exact model and configuration.
Overview
Part of the Honeywell Home RedLINK system. See the system overview for component roles and selection requirements.
The THM5421R1021 connects compatible wireless thermostats to heating, cooling and supported IAQ equipment. Install the module near the HVAC equipment and follow the appropriate thermostat and EIM setup sequence. The current guide also covers Wireless FocusPRO configurations, with specific sensor restrictions. This is an equipment interface, not a standalone thermostat.
Selection and installation
Use the linked manufacturer documentation for the exact equipment configuration, wiring and commissioning requirements. Accessories and controls must be matched by model and electrical characteristics.
Product details
- Manufacturer
- Resideo
- SKU
- 365481
- Model / MPN
- THM5421R1021
- Condition
- New
- Lifecycle
- Current
Specifications
- Supply voltage
- 18–30 Vac
- Power sources
- Hardwired
- Stage modes
- Heat pump: Up to 4 heat / 2 cool; Conventional: Up to 3 heat / 2 cool
- Communication protocols
- RedLINK