Quick Summary
The HTW-31-F13-4KN Modbus Thermostat is designed for 4 pipe fan coil systems. It controls a 3 speed fan and separate heating and cooling valves. This Modbus Thermostat supports Modbus communication, keycard input, and programmable control for stable and efficient HVAC operation.
This page explains how this Modbus Thermostat works in real FCU projects, including control logic, wiring reference, and key parameters. It also outlines project fit, customisation options, and typical questions to support selection and deployment decisions.
Key Features
(This section explains the core control functions and their practical value.)
(01) 3-speed fan control with auto mode
This Modbus Thermostat supports manual and automatic fan speed control. It adjusts airflow based on room demand. This improves comfort and helps reduce energy use in daily operation.
(02) 4 pipe system control
This Modbus Thermostat controls heating and cooling valves separately. It suits buildings with simultaneous heating and cooling supply. This improves flexibility and avoids seasonal switching errors. If you need standalone thermostat for 4 pipe system, please refer to this link: HTW-31-F13-4.
(03) Modbus communication
With Modbus communication, this Modbus Thermostat can connect to a BMS system. It allows central monitoring and control. This is useful in hotels, offices, and large buildings.
(04) Keycard energy saving function
The keycard function detects room occupancy. When the card is removed, the system can reduce operation. This helps save energy and improves control in hotel applications.
Product Design and Display
(This section shows the product’s dimensions and the interface layout.)

Technical Specifications
(This section lists the key parameters for reference and project confirmation.)
| Parameter | Value |
|---|---|
| Power Supply | 100~250Vac |
| Frequency | 50/60Hz |
| Power Consumption | 1.5VA |
| Accuracy | ±0.5°C |
| Sensor | NTC 3950, 10K |
| Setpoint Range | 5~50°C |
| Ambient | 0~50°C |
| Protection Class | IP30 |
Wiring Diagram
(This section provides the wiring reference diagram for correct installation.)

Model Code Guide
(This section explains what configuration the model code refers to.)
| Fan coil series | xx stands for |
| EC | EC fan |
| 2/4 | 2 for 2-pipe on/off; 4 for 4-pipe on/off system |
| M | Modulating valve control |
| W | Wi-Fi |
| N/B | N for Modbus; B for BACnet |
| K/E | K for Keycard; E for External sensor |
| Example HTW-WF11-FC-xx: if xx = 2EN, it stands for a 3-speed fan, 2-pipe system with on/off valve control, external sensor function, and Modbus communication. Most sub-models are ready-made. Kindly contact us to confirm availability. | |
Project Fit & Customization
(This section explains where the product can be used, its limits, and OEM/ODM options.)
This Modbus Thermostat is suitable for 4 pipe FCU systems requiring BMS integration and keycard energy control. It is not suitable for modulating valve systems or projects needing 0–10V output control.
Despite these limits mentioned above, ODM function customisation can be discussed. This may include protocol adjustments, control logic changes, or sensor integration depending on project needs and feasibility.
OEM customisation is also supported. Options include logo printing, colour changes, and label design. These help match project branding and maintain consistency across installations.
Certificates and Compliance


Frequently Asked Questions
Q1: Can this Modbus Thermostat connect to a BMS system?
Yes, it supports Modbus communication and can be integrated into a BMS for central control and monitoring.
Q2: Is it suitable for hotel projects?
Yes, the keycard function helps manage occupancy and reduce energy use, making it suitable for hotel applications.
Q3: Does it support both heating and cooling?
Yes, it supports 4 pipe systems with separate heating and cooling control for stable operation.
Q4: What is the MOQ and can we get samples?
We support sample orders. Standard MOQ is 300 units. Smaller quantities may be discussed for trial purposes.
Q5: How do we place an order?
Please contact us with your requirements. We will provide a PI. Payment supports TT, PayPal, Visa. Terms include EXW, FOB, DAP.
Q6: How is delivery arranged?
Courier delivery takes about 7 days. Air freight is similar. Sea shipping takes around one month depending on destination.
Related Thermostat Models
For projects with WiFi or Modbus needs, contact us to confirm the most suitable thermostat for your application. You can refer to below links as well:
This Modbus Thermostat is a strong fit for 4 pipe FCU projects that require central control and energy-saving logic. It is best suited for hotels, offices, and managed buildings. 【More models: fan coil thermostat】






