Flexit Nordic S4 modbus communication


I am wondering if I could be able to control the ventilation system in my house through Homey.

It can be externally controlled through the modbus-protocol (english instructions starts at page 12): https://www.flexit.no/globalassets/catalog/documents/111398_fdv_117989.pdf

Here are the instructions that I would be able to use: https://www.flexit.no/globalassets/catalog/documents/111400_modbus_nordic_basic.xlsx

The question is, will I be able to use Modbus in Homey? What kind of Modbus RTU should I use? Assuming that TCP/IP is the way to go? Are there Modbus integrations vs homey that could be reused?

Assuming that I would have to write an app to support the RTU?

Grateful for all help and support.



Hi there!

I’ve got the same wish to get an app to Flexit Nordic S4 via modbus communication.

I’ve asked the developer of NibePi to look into this.
I believe it can be done, but I have too little knowledge to help you out.

Since I have a Nibe S1255 that will fully support modbus TCP/IP anytime soon I think its possible.
Probably by doing it over MQQT.

In other words, by using a Raspberry Pi (Zero or whaterver) and a RS485 HAT
then install NodeRed and and configure it (or re-do) the NibePi to fit the needs of FlexIT S4 Nordic, then to send via MQQT to the Homey.
Thats how the Nibe F-users do it (One can also use the User Interface of NodeRed in the Raspberry)

I’ve let my S1255 to be a guinea pig for the development of the upcoming version that has the option of TCP/IP, but the progress of development has been slow due to Covid-19. (The developer has been busy feeding his 3d-printers for hospital equipments, making more than 1000 visirs…)
Hopefully the new version of NibePi (supporting nodered/modbus fully) will see the light within weeks (its in beta-version now)

if you get anymore info, please reply here or send me a PM. :slight_smile:

This is possible. Tom Heine has made an app to do this with a TCP-modbus konverter (webpage in Norwegian): Flexit Nordic S4/S3 og Homey – tomheine.net
To use this app you need CLI access to Homey Pro. That prosess is explained here: Getting Started | Homey Apps SDK
Is it not an ease process if you are not a developer. You need a PC or Mac with admin rights to do this.