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Westaflex WAC Binding

westaflex edited this page Mar 12, 2014 · 137 revisions


Table of Contents


Our WAC Usage documention describes the protocol in detail and is the starting point for understanding everything else. It contains the fundamental ModBus knowledge you need in order to adapt successfully with our Binding. With this foundation in place, you will be ready to apply the ModBus network rules, so that your home appliances can interoperate with those produced by other manufacturers as part of the OpenHAB ecosystem. This will free consumers to choose the devices that best match their needs, and combine them in novel ways with other compatible devices. See below for guidance as to what to look out for in each section. The possibilities are endless.

Binding configuration

A key feature of ModBus that distinguishes it from other protocols is that any given node in the network can act as the master for one channel, and as the slave for another channel.  This allows complex network topologies to be formed.

Item Binding Configuration

This section describes how the host (MCU, PC interface etc) can interface with the WAC chip. Extended messaging is also introduced, which is useful if you need to include additional information such as the Device Number. Note that extended messaging does not extend the size of the data payload, which is fixed at 8 bytes and cannot be altered.

Name Modbus function Data address Values
Heat 01h_Read_Coils 0 1-active, 0-passive
Plate heat exchanger frost protection function
Fire 01h_Read_Coils 1 1-active, 0-passive
Fire alarm
Filter 01h_Read_Coils 2 1-active, 0-passive
Dirty filter alarm
Fan 01h_Read_Coils 3 1-active, 0-passive
Fans alarm
LowPower 01h_Read_Coils 5 1-active, 0-passive
Low voltage
Textract 01h_Read_Coils 6 1-active, 0-passive
Temperature sensor alarm
Texhaust 01h_Read_Coils 7 1-active, 0-passive
Exhaust air temperature sensor alarm
Timit 01h_Read_Coils 8 1-active, 0-passive
Supply air temperature sensor alarm
RH 01h_Read_Coils 9 1-active, 0-passive
DTJ(100) humidity sensor alarm (controller works in determining the moisture content of 70%)
ReturnWater 01h_Read_Coils 10 1-active, 0-passive
Return water temperature sensor alarm
ToutDoor 01h_Read_Coils 11 1-active, 0-passive
Outside air temperature sensor alarm (controller continues to work in determing ToutDoor less than zero degree)
MotorActive 01h_Read_Coils 12 1-active, 0-passive
Fans ON
InDumpper 04h_Read_Input 13 0-90
Outside air damper actuator
Preheater 01h_Read_Coils 14 1-active, 0-passive
Preheater indication
Heater 01h_Read_Coils 15 1-active, 0-passive
Heater indication
Speed 06h_Write_Holding_Register 16 0, 1, 2, 3
Fans speed setting
TsetPoint 06h_Write_Holding_Register 17 0-30
Supply air temperature set
RH_value 04h_Read_Input 18 0-99
DTJ(100) humidity sensor value
Motor1 04h_Read_Input 19 0-3
Motor 1 fan speed value
Motor2 04h_Read_Input 20 0-3
Motor 2 fan speed value
Tlimit 04h_Read_Input 21 Hex: E0
Supply air temperature value
Texhaust 04h_Read_Input 22 Hex: E0
DTJ(100) temperature sensor value
Textract 04h_Read_Input 23 Hex: E0
Exhaust air temperature sensor value
ToutDoor 04h_Read_Input 24 Hex: FFEC
Outside air temperature sensor value
Twater 04h_Read_Input 25 Hex: FFEC
Return water temperature value


to handle many slaves in RTU mode, non blocking connections and RTS flow control.....

modbus_t *mb;

  uint16_t tab_reg[32];
  mb = modbus_new_tcp("", 1502);
  /* Read 5 registers from the address 0 */
  modbus_read_registers(mb, 0, 5, tab_reg);

See Examples of typical WAC Bindings, if you have any suggestions or questions don't hesitate to contact us or use our Github account. The snapshot version of our industry4.0 binding can be downloaded, together with the rest of openhab.


Congratulations! You should now have a good general understanding of how the WAC ModBus protocol works, which will give you a strong foundation for all the work you do with OpenHAB. Be Inspired →by our genuine Apps...

feature overview


Setup intro

Linux and OS X





User Interfaces



(link to openHAB forum)



Application Integration



A good source of inspiration and tips from users gathered over the years. Be aware that things may have changed since they were written and some examples might not work correctly.

Please update the wiki if you do come across any out of date information.

Binding configurations

Use case examples

Item definition examples

Sitemap definition examples

Collections of Rules on a single page

Single Rules


Syntax highlighting for external editors

Release Notes

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