Make a Honeywell Chronotherm IV modulation thermostat smart

At my parents house I made their current Honeywell Chronotherm programmable thermostat smart by using the TELE setting that is available. There are two contacts that when wires are are connected and making contact a TELE setting is activated. It’s possible to set the temperature of the thermostat in the TELE setting beforehand. I used this as an away mode.

Information from the Chronotherm manual (in Dutch)

Video of the configuration:

Webpage that inspired me (Dutch):

Screenshot of the dashboard. I added a DHT11 sensor for temp and humidity.

Wow I bet all those wires meet the FAF :slight_smile:

Oh wow, I have the same one, but never knew this was an option. Now I want this too!
Read the manual, but there was no information about the wiring. How did you do that?

Yeah, it works great. I connected the wires to a relay module, in NO mode, which is inverted whithin the home assistant configuration. The advantage is that, whenever the system crashes for whatever reason, the TELE setting will be turned off.

I found this image on the web of the backplate:

Source: Chronotherm IV vervangen door Chronotherm Touch | Honeywell Home - YouTube

And this one of the Chronotherm Touch:

Source: Thermostaat vervangen: Chronotherm III | Honeywell Home - YouTube

I can’t take a picture of my parents situation right now. The picture of the Chronotherm IV above is slightly different of the situation on my parents thermostat. They have a Chronotherm Modulation (uses OpenTherm). Which is different from Chronotherm IV (uses on/off). As you can see, there are two wires connected for signalling to the boiler. The backplate of the Chronotherm Modulation has more extra screws to attach more wires. I cannot tell you to which screws the wires should be attached at. I believed they were called TE, which you also see on the Chronotherm Touch picture.

It can depend from within the product range of the chronotherm if the TELE setting is available. The article on Bedien je verwarming op afstand – TD-er says a lot of Honeywell chronotherm thermostat after 1999 have it.

Thanks, I get the picture. If I understand it correctly, with the 2 wires connected the device will enter in tele mode and will be set to the pre configured temperature right? When it is disconnected it will continue in normal mode?

Yes. That’s right.

According to the manual, the TELE stetting does need to be active. I can’t recall whether this is the default setting.

You can check the Advanced menu by pressing the i-button and the copy day button for 5 seconds.

With the up ^ en down buttons you can select a setting and with the forward and back buttons (non rubber) you can change the value of a setting.

The setting number for Tele in the Chronotherm Modulation I am using is 6, the value should be 1 for it to be turned on.

To select the set temperature which should be set once the TELE setting is activated, press the i-button three times.

As described in below parts of the Dutch manual (couldn’t find an English version)

Awesome, it works now!
Also I managed to get it working without soldering to the Chronotherm itself (just the backplate).

Still very surprised that my 20 years old thermostat had a function like this. Didn’t knew this was a thing back then.

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for the sake of completeness, here are pictures of the backplate of the Chronotherm Modulation I am using. Two screws are available, named TE, to attach wires for the TELE setting