T603 Modbus Thermostat for 2/4-Pipe Fan Coil Retrofit

Key Specifications

Parameter	Specification
Model	T603
Product Type	Standalone Fan Coil Thermostat
Fan Type Support	AC fan (3-speed) or DC fan (7-speed)
Communication	Modbus RTU via RS485 (A/B terminals) – passive monitoring only
System Compatibility	2-pipe / 4-pipe fan coil units, fresh air, floor heating

Ready to upgrade your HVAC control? Send us your project details (system type, quantity, destination country) now. We will reply within 24 hours with a quote and wiring guide.

Why Choose T603 Modbus Thermostat

Smart & Energy-Saving: Microcomputer chip with high-precision sensor automatically adjusts fan coil and valve.
2/4-Pipe Versatility: Works with 2-pipe and 4-pipe fan coil units. Supports AC/DC fan two-in-one configurations.
AC & DC Versions Available: AC100~240V version and DC24V version, for different power environments. Please confirm before ordering.
Standalone & Retrofit-Ready: Standard 86mm box for direct replacement. No central control required.
Modbus RTU Interface (RS485 A/B): Passive data monitoring only (no master control).
3.5″ Touchscreen: Clear TFT color display for easy operation.

Additional Information& Compatibility Notes

Our T603 Modbus Thermostat features an RS485 interface (A/B terminals) designed for basic Modbus RTU passive data monitoring. It is standlone thermostat and does not function as a full Modbus master or slave device. For more details on how Modbus RTU works, please read our guide:Modbus RTU HVAC Basics.

To properly integrate the T603 into your system, you will need the official Modbus Register Map (Protocol Document). Please contact us to request the latest register list and wiring guide for your project.

Fan Compatibility Note: The T603 supports both AC fan (3-speed) and DC fan (7-speed) control via the Advanced Mode menu. However, fresh air and VRF systems require AC fan mode only. Please confirm your system type and fan motor before ordering. Send us your wiring diagram if you are not sure.

Important Note on Modbus Functionality:
The T603 is a standalone thermostat. Its RS485 (A/B) terminals are designed for basic Modbus RTU passive data monitoring. It works as a passive monitoring Modbus slave only. It supports data reading by a matching external gateway and does NOT support full two‑way remote control for general BMS. If your project requires full Modbus RTU integration and remote command from a building management system, please choose our T605 Modbus Thermostat instead.

If your project requires full Modbus RTU integration with a building management system, please choose our T605 Modbus Thermostat instead.

All setting operations of the T603 Modbus Thermostat are listed below.

1. Clock Adjustment
– Enter: While on, press and hold the Fan Speed button for 5 seconds.
– Adjust: Blue text indicates the active setting. Press Fan Speed to cycle through minutes, hours, and day-of-week. Use Up/Down buttons to change values.
– Save & Exit: Press the Power button.

2. Timer Function
-Enter: While on, press and hold the Mode button for 5 seconds.
Adjust: Blue text indicates the active setting. Press Fan Speed to cycle through timer minutes, hours, and status. Press Mode to switch between timer-on and timer-off settings. Use Up/Down buttons to change values.
– Save & Exit: Press the Power button.
3. Child Lock
-Toggle: While on, press and hold both Up and Down buttons for 5 seconds to enable/disable. When enabled, all buttons except Power are locked.
4. Factory Reset
– Action: While on, press and hold the Power and Down buttons together for 5 seconds.
5. Fault Alarm
-Trigger: Sensor short-circuit or temperature outside -30 ℃ to 80 ℃ range.
-Display: Shows “E1” on the screen and disconnects all loads. Returns to normal after the fault is cleared. 6. Frost Protection
– Condition: Activated when the unit is off.
– Action: Output turns on if room temperature ≤5 ℃ and turns off once it reaches ≥7 ℃, repeating this cycle.
7. Temperature Control Logic
– Cooling / AC + Floor Cooling: Output turns ON when room temp > (set temp + start differential). Turns OFF when room temp ≤ (set temp – 1℃).
– Heating / AC + Floor Heating / Hydronic Heating: Output turns ON when room temp < (set temp – start differential). Turns OFF when room temp ≥ (set temp + 1℃).
– Note: Fresh air and refrigerant-based AC systems are not temperature-controlled.
8. Advanced Mode
– Enter: While off, press and hold the Mode and Fan Speed buttons together for 5 seconds.
– Navigate: Use Up/Down to select a category → Press Mode to enter → Adjust parameters with Up/Down → Press Mode again to return to the category list.
– Save & Exit: From the category list, press the Power button. (Note: You must return to the category list to exit.)

Application Guide
Not sure if the T603 is compatible with your fan coil system? Read our detailed guide:
T603 Fan Coil Thermostat: 2-Pipe vs 4-Pipe System Application Guide.

Ready Stock& Fast Dispatch

We work directly with factory to ensure fast dispatch. Every unit is tested and packed with a wiring guide before shipping.

FCU thermostat warehouse stock, production testing and assembly for T603 Modbus thermostat

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