Versatiled Series PI Control Thermostat

The Versatiled Series PI Control Thermostat is a versatile room temperature controller designed for precise heating and air-conditioning terminal control. It uses a proportional-integral (PI) control algorithm to continuously adjust valve output according to the difference between the room temperature and the target setpoint.

The 0–10V output can control compatible electric modulating valves in fan coil units, fresh air units, air handling units, and heat exchangers. Selected models also support RS-485 communication and Modbus-RTU, allowing integration with building automation (BA) systems.

The Versatiled Series provides multiple configurations for 2-pipe and 4-pipe FCU systems, different actuator types, AC three-speed or BLDC fan control, remote temperature sensing, scheduling, and valve control. This makes the series suitable for both standalone terminal control and integrated HVAC automation projects.

What Is a PI Control Thermostat?

A PI control thermostat uses proportional and integral control to regulate the output according to the current temperature deviation and accumulated temperature error.

Compared with simple on/off control, PI control continuously adjusts the control output. This can provide smoother temperature regulation and reduce unnecessary valve movement when controlling modulating HVAC valves.

For valve-based HVAC applications, PI control is particularly suitable when the objective is to maintain a stable room temperature through continuously adjusted valve output. West Control Solutions also describes PI control as a proportional-integral method used for modulating valves, without the derivative action associated with PID control.

Precise Temperature Control with 0–10V Output

The Versatiled Series PI Control Thermostat provides a 0–10V analog output for compatible modulating valves.

Instead of simply switching a valve fully open or fully closed, the thermostat can adjust the valve output according to the calculated temperature demand. This allows the connected valve to regulate heating or cooling capacity more progressively.

Typical applications include:

• Fan coil units
• Fresh air units
• Air handling units
• Heat exchangers
• Hydronic heating systems
• Commercial HVAC terminal units
• Building automation systems

The 0–10V control signal is especially suitable for HVAC equipment using proportional or modulating electric valves.

Modulating Valve Control for HVAC Terminals

The thermostat's PI algorithm regulates the 0–10V valve output according to the required heating or cooling capacity.

This makes the Versatiled Series suitable for applications where stable room temperature and smooth valve regulation are important.

The thermostat can be applied to:

Fan Coil Units

For FCU applications, the thermostat can regulate room temperature while controlling compatible modulating valves and fan operation.

Models are available for both 2-pipe and 4-pipe FCU systems, allowing selection according to the hydronic system design.

Fresh Air Units

The thermostat can be used to regulate compatible modulating valves in fresh air systems where temperature control is required.

Air Handling Units

For air handling applications, the 0–10V output can provide proportional control of compatible electric valves according to the required temperature conditions.

Heat Exchangers

The thermostat can also be used for temperature regulation in hydronic heat exchanger applications using compatible modulating valves.

2-Pipe and 4-Pipe FCU Compatibility

The Versatiled Series includes models designed for different FCU configurations.

2-Pipe FCU

A 2-pipe system generally uses a common water circuit for heating or cooling depending on the operating mode.

The thermostat can regulate the connected valve and fan according to the configured temperature control requirements.

4-Pipe FCU

A 4-pipe system provides separate heating and cooling water circuits. This allows heating and cooling functions to be managed through separate hydronic circuits.

The Versatiled Series provides corresponding models for both system configurations, helping HVAC system designers select the appropriate thermostat for different terminal unit architectures.

AC 3-Speed and BLDC Fan Control

Selected models support AC three-speed fan control, while the series also includes BLDC motor fan control functionality.

For conventional fan coil units, three-speed fan control allows users or the control system to select different airflow levels according to room requirements.

For compatible BLDC motor applications, the thermostat can provide the corresponding control required by the selected configuration.

The combination of temperature control, valve control, and fan control allows the thermostat to function as a complete room-level FCU controller.

RS-485 and Modbus-RTU Integration

Selected models are equipped with an RS-485 interface and support Modbus-RTU communication.

This enables the thermostat to communicate with compatible building automation systems and become part of a centralized HVAC control architecture.

A typical system can be structured as:

Room Temperature Sensor → PI Control Thermostat → Modulating Valve / FCU → RS-485 Network → BA System

This architecture allows local room temperature control while providing the possibility of centralized monitoring and management.

HaiLin Controls provides a broader HVAC and building automation product portfolio covering thermostats, DDC controllers, sensors, gateways, valves, and management systems. This enables the Versatiled Series to be incorporated into complete building automation projects rather than operating only as an independent room thermostat.

Programmable Schedule and Timer Control

Selected Versatiled Series models provide programmable scheduling and on/off timer functions.

Scheduling can help coordinate HVAC operation with building occupancy and operating periods.

Typical applications include:

• Office working hours
• Hotel occupancy schedules
• Residential daily routines
• Commercial building operating periods
• Public building schedules
• Energy management strategies

Programmable operation can help avoid unnecessary HVAC operation when spaces are unoccupied.

Remote Temperature Sensor

Selected models support a compatible NTC10K B=3950 remote sensor.

A remote sensor can be useful when the thermostat cannot accurately measure the required control point because of installation conditions or room layout.

Depending on the application, the sensor can be positioned at a more representative location for temperature measurement.

Anti-Condensation and Anti-Freezing Protection

The Versatiled Series includes anti-condensation and anti-freezing functions.

These functions provide additional protection for HVAC applications where temperature and moisture conditions may affect equipment operation.

The exact protection behavior and applicable settings should be confirmed according to the selected model and installation instructions.

User-Friendly Thermostat Design

The Versatiled Series combines practical HVAC control functions with a compact wall-mounted design.

Key user interface features include:

• Press Button Operation
• White Backlight
• Button Lock
• Power Restoration Function
• On/Off Timer
• Programmable Schedule

These functions provide convenient local operation while helping prevent unwanted setting changes in managed environments.