Honeywell TFM428KNM/U thermostat for 4-pipe FCU systems with Modbus RTU, ON/OFF valve control, 3 fan speeds, ±0.5°C accuracy. Officially supplied by DLK.

Honeywell TFM428KNM/U Thermostat – Technical Overview and Applications

1. General Introduction

The Honeywell TFM428KNM/U thermostat is a digital ON/OFF controller designed for 4-pipe Fan Coil Unit (FCU) systems. It supports independent heating and cooling valve control, 3 fan-speed outputs, and integrates Modbus RTU over RS485, making it suitable for buildings requiring centralized HVAC supervision.
The device is officially supplied in Vietnam by DLK – DLK TRADING SERVICE COMPANY LIMITED, the authorized Honeywell distributor.

2. Operating Principle

The TFM428KNM/U operates using ON/OFF SPST outputs to control both heating and cooling valves in a 4-pipe FCU system. A built-in microprocessor applies an enhanced control algorithm (FUZZY logic) to reduce temperature overshoot and maintain the setpoint with an accuracy of ±0.5°C.

The thermostat features:

• An LCD screen displaying room temperature, setpoint, operating mode, and fan speed

• Remote temperature sensor input (NTC 10k)

• RS485 communication using Modbus RTU, allowing real-time monitoring and integration into Building Management Systems (BMS)

Its wide supply range of 90–264 VAC ensures stable operation across various environments.

3. Practical Applications Across Industries

Commercial and Office Buildings

The TFM428KNM/U provides precise local temperature control with 3-speed fan output, making it ideal for multi-zone systems in commercial towers and office complexes. Modbus RTU enables easy connection to centralized BMS platforms for monitoring and scheduling.

Hotels and Hospitality Projects

In hotel guestrooms, the thermostat supports multiple operation modes—cooling, heating, automatic, and manual—allowing guests to adjust comfort settings easily. Through Modbus communication, the device can be integrated into PMS/HMS systems for energy optimization.

Manufacturing Plants and Cleanrooms

Industrial environments requiring stable and accurate temperature control benefit from the thermostat’s ±0.5°C precision. When used with remote sensors, it ensures consistent climatic conditions for inspection rooms or clean production lines.

Data Centers and Server Rooms

With Modbus connectivity, the thermostat allows continuous monitoring of cooling performance for perimeter FCUs supporting server rooms. This reduces temperature fluctuations and helps maintain safe thermal conditions for IT equipment.

4. Key Benefits of the Honeywell TFM428KNM/U

• Accurate temperature regulation with ±0.5°C stability

• Independent heating & cooling control for 4-pipe FCU systems

• RS485 Modbus RTU communication for BMS integration

• 3-speed fan output for flexible airflow control

• Clear LCD interface for quick setup and operation

• Supports remote temperature sensing

• Durable design with long mechanical service life

5. Technical Specifications Summary

6. How to Select the Correct Model

• Choose TFM428KNM/U when you need:

  • 4-pipe heating and cooling

  • Modbus RTU communication

  • 3-speed fan output

• Choose TFM428KN/U when communication is not required.

• Choose TFM428KNB/U when BACnet communication is needed.

Selecting the right model ensures compatibility with existing systems and optimal energy performance.

7. Why Choose DLK – Official Honeywell Distributor

DLK provides:

• Genuine Honeywell products with complete certification

• Technical consultation for HVAC/BMS projects

• Support in model selection, installation, and commissioning

• Stable stock availability and reliable after-sales service

With official authorization from Honeywell, DLK ensures consistent product quality and strong engineering support for contractors, OEMs, and building integrators.