What is Modbus?
Modbus is an open industrial communication protocol used to transfer data between electronic devices such as meters, sensors, controllers, PLCs, and Building Management Systems (BMS).
It is commonly used in Smart Buildings, energy management, and plantroom integrations where simple, reliable data exchange is required.
What Modbus does
Modbus enables devices to read and write data values such as:
- Energy consumption and power readings
- Temperatures and pressures
- Flow rates and levels
- Status signals and alarms
- Equipment run hours and counters
Why Modbus exists
Modbus was designed to provide a simple, lightweight, and reliable method of communication between industrial devices.
Its simplicity makes it ideal for energy meters, plant equipment, and legacy systems where complexity and overhead must be kept to a minimum.
Common Modbus types
- Modbus RTU – serial communication over RS-485
- Modbus TCP – runs over Ethernet and IP networks
- Modbus ASCII – legacy text-based format
Modbus vs BACnet
Modbus and BACnet are often used together in the same building, but serve different roles:
- Modbus – simple point-to-point or master/slave data exchange
- BACnet – rich object-based communication for full BMS control
In practice, Modbus is frequently used to bring energy meters and plant equipment into a BACnet-based BMS.
Where Modbus is used
- Energy meters and submeters
- Boilers, chillers, and plant equipment
- Variable speed drives (VSDs)
- Power monitoring systems
- Industrial and process environments
BMS platforms that use Modbus
Roles that work with Modbus
- BMS Engineers
- BMS Commissioning Engineers
- Controls Engineers
- Energy & Sustainability Engineers
- Plantroom Specialists
Why Modbus matters
Modbus remains widely used because it is simple, reliable, and supported by thousands of devices. It plays a critical role in connecting energy data and plant equipment into modern Smart Buildings.
Despite its age, Modbus continues to be a core building block in energy optimisation and system integration.