The Modbus icon
What Is Modbus?
Modbus is a serial communications protocol originally published by Modicon (now Schneider Electric) in 1979 for use with its programmable logic controllers (PLCs). Modbus is a de facto standard communication protocol, and is now commonly used to connect industrial electronic devices. 
More about Modbus…
Benefits Of Modbus
Some benefits of using Modbus are that:
- Modbus has been developed with industrial applications in mind
- Modbus is openly published and royalty-free
- Modbus is easy to deploy and maintain
- Modbus moves raw bits or words without placing many restrictions on vendors
- Modbus allows communication between up to 247 devices on the same network.
Why Is Modbus Used?
Before the introduction of Modbus, control of air conditioning was handled by enabling and disabling a unit based on temperature. When a unit was enabled, it would operate with its own local control (setpoints, heating/cooling modes etc.).
Modbus control provides an interface directly to the panel of the unit, allowing direct changes to settings and hence full control of the unit. On most units the panel can be 'locked out' to prevent local overrides.
Basic Modbus Rules
Each Modbus device has a 'slave address'. This is a unique identifier on the Modbus network. Different manufacturers may be used on the same network so as long as slave addresses do not clash. Each Modbus AC slave can have its own units. For example, the FDP3 can have up to 16 units on one slave address.
Modbus Driver Support
WEMS supports the following Modbus drivers:
Air Conditioning
- A1M: Mitsubishi 1 Unit Interface
- A32M: Mitsubishi 32 Unit Interface
- A50M/IP50: Mitsubishi 50 Unit Interface
- BM50: Lennox AHU Interface
- EMICON: Emicon Unit Interface
- FDP3: Toshiba/Daikin Interface
- LTX51: Toshiba VRF Interface
- TRANE: Carel Controller Interface
Metering
- EM21: Carlo Gavazzi Meter Interface
SMARTheating Zone Or Object
Modbus can be set up either as a SMARTheating Zone or as an Object.
- Modbus as an Object: The setup has no temperature links and is enabled (turned on or off) based on time. The unit is controlled to its own setpoints against its own integrated temperature sensors.
- Modbus as a SMARTheating Zone: Control is based on WEMS temperature sensors instead of sensors integrated in the unit. This offers a better chance to save energy by keeping the unit switched off.
Modbus Discover Wizard
To set up Modbus, see the Modbus Discover Wizard.
To set up Modbus using a custom template, see Generic Modbus.
Modbus Configuration
Once the Modbus Discover Wizard is complete, the Modbus can be configured through its icon on the Floorplan. For more information, see Modbus Configuration.