OTGW combined with Toon 2 thermostat

[georon]

Two questions about OTGW:

- Can this, combined with a rooted Toon 2 thermostat, control the central heating boiler in terms of modulation?
- Can the OTGW also control an on/off boiler (just for my curiosity)?

The situation is as follows:
- Now I have an old central heating boiler that does not support OpenTherm.
- A rooted Toon2 controls this (on/off).
- In HomeAssistant I determine the average heat demand in % of the zones (by reading my EQ3-MAX trv's).
- When there is a heat demand from the zones, I control a zigbee relay that turns the boiler on.

The boiler will be replaced soon (probably in the spring) by a new one that does support OpenTherm.
Then I want to replace the zigbee relay with an OTGW and then let the boiler burn in a modulated manner based on the heat demand of the zones?

The end game:
- Toon controls the 'living room' zone and thus also controls the trv's temp settings there.
- There are 10 radiator knobs, each of which controls its own zone and feed back their heat demand to HomeAssistant.
- Based on the heat demand of the zones, HomeAssistant should decide to instruct the boiler to start heating if it wasn't already, using the OTGW.

Thanks in advance.

[hvxl]

Controlling an Opentherm boiler is a bit more involved than controlling an on/off boiler. In addition to determining when there is a heat demand, you have to determine how much of a heat demand there is. From this number you have to derive a desired water temperature. Then you can use the OTGW to send this so-called control setpoint to the boiler.

The OTGW wasn't designed to control an on/off boiler.

[georon]

Thanks Schelte.

From the Equipment matrix I am unable to determine if the Toon is ok with another device changing the setpoint of the boiler. Note: this is my own imcompetence to read the message ids and their meaning

Could anyone guide me on this?

[hvxl]

The Toon really doesn't have a say in the matter.

While thermostats will most likely check that the boiler actually starts heating when they send such a request, I don't expect that any thermostat firmware will have implemented a check to make sure the heating is off when the thermostat doesn't request heating. Most likely the thermostat will still show an indication on its screen that the heating is on, based solely on the flags in the status message. But there is no reason to crosscheck if it requested that to happen. If it didn't, there's nothing it can do about it anyway.