
Modbus is a communication protocol developed in the late 1970s for programmable logic controllers (PLCs). Today it is widely used to connect industrial electronic devices, including HVAC systems. Modbus is an open, license-free protocol that uses a simple client-server architecture where a client sends requests and a server returns responses.
/ˈmɒdbʌs/
Modbus is a communication protocol developed in the late 1970s for programmable logic controllers (PLCs). Today it is widely used to connect industrial electronic devices, including HVAC systems. Modbus is an open, license-free protocol that uses a simple client-server architecture where a client sends requests and a server returns responses.
What is Modbus used for in HVAC?
It connects HVAC controllers and devices so they can share data for monitoring and control.
Source: The Cooling Company

Simple, robust protocol for device communication.
Many HVAC systems use Modbus to connect controllers and devices for monitoring, alarms, and data collection in real time.
Ensure Modbus devices share the same baud rate and parity settings to avoid communication errors.
“Ensure Modbus devices share the same baud rate and parity settings to avoid communication errors.”
Modbus was created by Modicon (now Schneider Electric) and became a de facto industrial standard.
Is Modbus the same as BACnet?
No. Both are common building automation protocols, but they have different standards and capabilities.
Can Modbus run over Ethernet?
Yes. Modbus TCP/IP is a widely used Ethernet-based version.
Do all HVAC systems support Modbus?
No. Support depends on the manufacturer and controller options.
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