Honeywell Home THM5421R1021/U Prestige 2-Wire IAQ Equipment Interface Module

Centralize and simplify indoor air quality (IAQ) and HVAC control with the Honeywell Home Prestige 2-Wire IAQ Equipment Interface Module (THM5421R1021/U). Designed for installers and facility managers, this equipment interface module expands thermostat capability to manage multi-stage systems—supporting up to 4-stage heat and 2-stage cool in heat pump configurations and up to 3-stage heat in conventional systems. Three universal IAQ contacts let you control humidification, dehumidification and ventilation equipment, while four sensor inputs accept wired sensors or dry contacts for environmental monitoring and integration with building security or surveillance systems. Wired connectivity and broad compatibility with Prestige 2-Wire IAQ and VisionPRO thermostats with RedLINK reduce setup time and ensure dependable operation across residential and light-commercial installations. Compact, gray housing and straightforward wiring make it easy to mount in equipment rooms or control panels. Ideal for contractors, integrators and building automation projects that require robust IAQ control alongside HVAC and security monitoring. Add this Honeywell Home equipment interface to your next project to improve comfort, compliance and system oversight — contact us to order or specify it in your design.

• Centralizes IAQ and HVAC control to simplify installation and reduce wiring for installers and integrators
• Supports up to 4-stage heat and 2-stage cool (heat pump) to handle complex multi-stage HVAC systems
• Three universal IAQ contacts for humidification, dehumidification and ventilation — enables proactive environmental monitoring
• Four sensor inputs for wired sensors or dry contact devices for flexible integration with indoor air quality and security systems
• Compatible with Prestige and VisionPRO thermostats with RedLINK for seamless building automation and reliable connectivity