Controlling Itho CVE ECO ventilation with Domoticz

For ventilation our 17 year old house is equipped with an Itho air handler for mechanical ventilation. Exhausts in the kitchen, toilet and bathroom make sure that fresh air gets pulled in through ventilation inlets located over the windows. The air handler made a lot of noise for the past few years, so we mostly had it unplugged. Since that’s a terribly bad idea –too little fresh air, too much moisture– we decided to replace the air handler and add some home automation to the mix in the process.

Installing the Itho CVE ECO

We chose to replace the unit with the Itho CVE ECO, an updated model from the same manufacturer, because replacing it would be easy –the wall plate is exactly the same, down to the mounting holes– and they could confirm over mail that all three connectors would accept 230V without blowing up the device (more on that later). Installation took no more than 15 minutes. This updated model uses a low voltage DC motor instead of an AC one, reducing power consumption by over 80%. It also supports wireless remotes, but we’re not using them because 1) we want to be able to control the device programmatically, and 2) we’d rather not tape a bunch of devices to our walls. Instead, we’re using our Z-Wave based home automation setup.


In case you’re not from the Netherlands, Germany or Sweden, you may have never heard of Perilex. It’s a three-phase connector system. Essentially, it’s a wall socket with PE (protective earth), N (neutral) and three phase conductors (L1, L2 and L3). It’s usually connected to a three-way switch that will have two switching wires attached to it, for L2 and L3. L1 is always connected to a live wire, so it runs in the “low” mode (the device can’t and shouldn’t be switched off). When the switch is put into “medium” or “high” mode, it switches L2 or L3 in addition to L1. So in “low” mode current is applied to L1, in “medium” to L1 & L2, and in “high” to L1 & L3. That works well with a single wall switch, but we wanted to have a more versatile setup.

Enter Fibaro FGS-223

The Fibaro FGS-223 double switch is a Z-Wave module that packs two independent relays. They’re added to Domoticz as two separate switches. I attached one to the Perilex wall socket so L1 would always be live, while L2 and L3 could be switched on/off by the Fibaro module. Because of this, it can’t be guaranteed that both relays won’t be switched on simultaneously. Since we don’t want to blow up the module, I made sure to contact Itho to find out what would happen when current is applied to all three connectors. They confirmed my suspicion: in that case the device would simply function in “high” mode. Great!

Setting up Domoticz

Though we can apply current to all phases without issue, I still wanted to switch L2 off when L3 is switched on, and vice versa. Not because I’m afraid to damage the air handler, but because I want it to go into “low” mode after I go from “medium” to “high” and then switch off “high” (instead of falling back to “medium”). This was easy to fix in Domoticz with a simple device based Lua script:

Alright, we can now turn the air handler up to “medium” or “high”, or turn both relays off and have it run in “low” mode.

Adding the home automation

I added a double momentary wall switch next to the device, connected to the Fibaro module, so we can change modes manually (in case the Z-Wave network is down for some reason; I always try to have physical actors attached to my modules). Going up two flights of stairs to push a button, or getting out my phone to control the ventilation doesn’t really add much automation to the home. That’s why I installed a double momentary wall switch in the bathroom connected to a Fibaro FGS-213. It’s a single switch, but it does have the ability to connect a second switch to it to start a scene. In this new setup, switch 1 turns the bathroom light on/off, and switch 2 tells Domoticz to start a scene. The scene turns on the “high” mode for 30 minutes and then turns it back off again, defaulting to the “low” mode again. When hopping in the shower it’s a matter of switching on the light and pressing the second button, without having to open a window.

Future proof

This setup is future proof in that it enables us to add more controls later. We can add a switch to the kitchen for when we’re cooking, or catch a double-clicking action on an existing light switch. We could add a CO2 sensor to increase air flow when CO2 levels are high, or hook it up to our Z-Wave smoke/heat detectors to turn it down (and keep it at) the lowest level when there’s smoke.