Honeywell
Honeywell THM5421R1021 HVAC Control
Controls up to four heat and two cool stages for heat-pump systems, or three heat and two cool stages for conventional systems, with three universal IAQ contacts and four sensor inputs
- Controls humidification, dehumidification and ventilation with three universal IAQ contacts
- Works with Prestige IAQ and RedLINK VisionPRO thermostats for integrated system control
- Manages up to four heat and two cool stages in heat pump configurations
- Handles three heat and two cool stages in conventional HVAC systems
- Accepts four sensor inputs for wired sensors or dry contact devices
HVAC Equipment Interface Module
The Honeywell THM5421R1021 is an equipment interface module designed for residential and light-commercial HVAC systems. It provides the central control logic for multi-stage heating and cooling equipment. Installers use it to coordinate thermostats, sensors, and indoor-air-quality accessories in a single wired platform.
Sustained multi-stage operation
The module manages up to four stages of heating and two stages of cooling for heat-pump configurations. In conventional systems it handles three heating stages and two cooling stages. Four sensor inputs accept wired sensors or dry-contact devices for continuous monitoring. Three universal IAQ contacts drive humidification, dehumidification, and ventilation equipment during long duty cycles.
Replaces standalone staging boards
This unit consolidates separate staging relays, sensor terminals, and IAQ contact boards into one enclosure. The upgrade is worthwhile when a system adds multi-stage equipment or IAQ accessories that exceed the terminal count of an existing control board. It is not suited for single-stage-only installations that do not require the extra staging capacity or sensor inputs.
Highlights
- Controls humidification, dehumidification and ventilation with three universal IAQ contacts
- Works with Prestige IAQ and RedLINK VisionPRO thermostats for integrated system control
- Manages up to four heat and two cool stages in heat pump configurations
- Handles three heat and two cool stages in conventional HVAC systems
- Accepts four sensor inputs for wired sensors or dry contact devices
Specifications
| Brand | Honeywell |
|---|---|
| Model | THM5421R1021 |
Questions about this item
Does the THM5421R1021 generate audible noise or heat during continuous daily operation?
The module is a solid-state control board with no moving parts, so it runs silently and produces only minimal warmth inside the equipment cabinet.
Which thermostat models must I already own for the THM5421R1021 to function?
It requires a Prestige IAQ thermostat or a RedLINK VisionPRO thermostat to communicate and manage the HVAC system.
Will the THM5421R1021 work with my existing two-stage heat pump and single-stage furnace?
Yes, it supports up to four heat stages and two cool stages on heat pumps, and three heat stages with two cool stages on conventional systems.
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