Wireless Modbus Applications

Wireless Modbus Applications

If you are a building manager in a medium-sized commercial building, you may have controllers, thermostats, sensors, and control panels that are wired for Modbus RTU, or BACnet  MS/TP (Master-Slave/Token Passing) communication.

When it comes to retrofitting or doing repairs, it is easier to add wireless communication to these devices. Time can be saved through avoiding difficult wiring that can be replaced by a wireless link.

Here is an example application of a wireless Modbus with Mitsubishi MelcoBEMS MINI ( PAC-UKPRC001-CN-1 ) and a MelcoREMOTE.

This is an example connection when monitoring/controlling M-Series or P-Series units through the MelcoREMOTE device using Mitsubishi’s MelcoREMOTE phone application:
  1. The M-Series, and P-Series units allow for M-NET control of heat pump and air conditioning systems.
  2. The MelcoBEMS MINI ( PAC-UKPRC001-CN-1 ) connect to these units on the CN105 port to convert Mitsubishi’s  M-NET protocol to Modbus or BACnet protocol for management systems that do not use M-NET protocol (learn more about protocol converters here.
  3. MelcoBEMS MINI connects to MelcoREMOTE via Modbus.
  4. MelcoREMOTE has an Ethernet for remote server connection or cloud platform connectivity (use MelcoREMOTE app to do remote control).

See below images showing sample wired connection between MelcoBEMS MINI and MelcoREMOTE

wiring overview between indoor unit, MelcoBEMS, and MelcoREMOTE
Connection overview for MelcoBEMs and MelcoREMOTE

RS-485 connection between MelcoBEMS and MelcoREMOTE

RS-485 Connection between MelcoBEMS and MelcoREMOTE


Consider using Wireless Modbus  connectivity between the MelcoBEMS MINI and MelcoREMOTE with this Lumenradio’s W-Modbus device.

See image below where, in case an existing wiring has an issue, it is possible to use wireless adapters that can communicate the Modbus signals (or BACnet protocols for BACnet MS/TP).


W-Modbus application in wireless modbus connection between MelcoREMOTE and MelcoBEMS

Complementary to the W-Modbus is the wireless BACnet ( W-BACnet ) device that can convert a wired BACnet MS/TP to a wireless BACnet network. Because the Mitsubishi MelcoBEMS also supports BACnet protocol, you can use the W-BACnet gateway/node to connect the M-Series or P-Series systems to a BACnet MS/TP network.

Another example application for the wireless modbus ( W-Modbus ) and wireless BACnet ( W-BACnet ) devices can be in building management systems with Variable Air Volume (VAV) systems, FAN coil systems, heat pump systems, or between network controllers and system controllers.

For Prolon devices for example, you could interface the W-Modbus  between PL-VC2000 controller in a VAV box/terminal and the T1000 room sensor as shown below.


wired connection between VAV controller and sensor

Wired case


W-modbus devices connecttion between VAV controller and sensor

Wirelessly interfacing VAV controller and sensor with W-Modbus adapter


Another alternative to Lumen radio’s W-Modbus is Prolon’s PL-TREE-COM wireless Modbus adapter which is backward compatible with most Prolon controllers. See below sample applications:

1. Between VAV controller and a room sensor

PL-TREE-COM wireless communication between Prolon controller and sensor

2. Between a Master controller and follower controllers e.g between a rooftop controller (Prolon’s PL-M2000) and VAV systems for rooftop unit serving multiple zones.


PL-TREE-COM wireless communication between Prolon rooftop controller and VAV controller


Consider other Modbus gateway/adapter like Novus’s AirGate-Modbus suitable for creating a network of wireless sensors (Converts Modbus protocol to 802.15.4 protocol – utilizes ISM2.4GHz for wireless communication .


Has long range and possible to connect an external antenna  for improved wireless links. For configuration, use DigiConfig software which is a free.

For custom HVAC control solutions, feel free to  contact  our HVAC Control Engineering team for assistance or learn more on our  HVAC Controls  website.

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