Ventillation unit via phone cable

[sola]

Hi Everyone,

I would like to integrate a SystemAir Villavent VM 400 EV house ventilation unit into my OpenHAB / MySensors based home automation system (to intelligently control the strength of the air-flow for the rooms based on air-quality sensor data).

This model has no integration to any automation system (according to the local distributor) but has a wired remote control panel so I assume it is possible to decipher the commands sent on the wire between the control panel and the ventilation unit (looks like simple telephone cable).

How can I read / debug the commands ?

How can I build an Arduino + sketch to also send a command on the cable ?

Any help / pointers is appreciated !
Andras

[gohan]

Some HVAC systems use modbus protocol but in your case more research is needed. Most likely they use a standard protocol, not everybody wants to develop new protocol if not necessary. In your case a logic analyzer would help a lot but it is up to you to decide if it is worth it

[dbemowsk]

@sola See if you can get them to tell you what protocol it talks with first. Knowing that is the first step in knowing how to decipher it. Once you know what it is, then you have to find out if the protocol is defined somewhere that you can get your hands on a copy.

Years ago I had bought an RCS RS485 thermostat and I ended up writing a plugin for the automation software I was using at the time. I have since migrated that code to a MySensors bridge node to control it. Writing the initial plugin took a while, and I would have been dead in the water if I didn't have their protocol outline.

[Thucar]

@sola check this out: https://planetaklimata.com.ua/instr/Systemair/Systemair_Modbus_for_Residential_units_User_Manual_Eng.pdf

If my memory serves me, I have done Villavent 400 unit integrations with ModBus. They have a decent ModBus support with a good range of functions available. Keep in mind that it's ModBus RTU, not TCP so you'll need to connect it via RS485. By far the easiest method is to use a usb-to-RS485 dongle.

If your ventilation unit is located far from your home controller and it's not easy to set up direct wiring, look into a serial-to-ethernet converter

I would not use serial-to-wifi models, as they have proven to be way less reliable.

So the bottom line is: if your unit indeed supports ModBus, you do not need an Arduino to do the talking. Just connect the unit to your controller and use a ModBus plugin for OpenHAB

[sola]

@gohan
Thanks, I am thinking of buying a logic analyzer even if not needed for this particular task.

@dbemowsk
Thanks, I will investigate the protocol further. Based on Thucar's comment it seems that it actually has an integration protocol only the Hungarian distributor was not aware of it.

@thucar
Thanks, this is very promising.
I will look into the OpenHAB modbus integration and the Villavent docs you linked.

[Thucar]

@sola I know for a fact that I have used ModBus with Systemair ventilation units in three different occasions. I just can not remember the exact models. They all used the above linked documentation though, so that leads me to believe they are using either the same full controller on all their residential models, or at least the ModBus firmware is the same.

[Tomwor2]

@sola Wonder if you found a solution for this and would mind sharing some more details. I have the same unit and look for the same solution.

[sola]

@tomwor2
Hit Tomwor

I haven't got anywhere with this projec yet.

According to the local distributor, it is almost sure that this old model has no Modbus support (newer models do).

So signal analisis is the only way to go forward.

I have got my hands on a USB signal analyzer by now but lacking the free time to do anything with it.

[Tomwor2]

@sola Thanks for your prompt feedback.