Control of boiler with Opentherm

[Chris Pitman]

Has anyone linked an Opentherm boiler to loxone, only after basic temp control Theben do an opentherm to knx but its expensive a couple of boiler manufacturers do a 0-10v to opentherm controller.

Basically want to be able to control the output temp of the boiler based on demand ie lower for heating and full for hot water tank. 

[Aldert]

Hello Chris,
I installed the Theben OT/KNX gateway last month.
The result is great. I have a Nefit boiler and therefor had to install an additional gateway Bosh EMS to OT
Together with the Loxone miniserver it looks a bit like a Christmas tree but I am very satified with the result.
The biggest advantage is the priority value you can set in the Theben box.
When there is a need from my living room (underfloor heating) the max setpoint to the boiler is 60C
But if it comes from one of the rooms upstairs the setpoints can go up to 80C
This is because the convectors in the bedrooms need a higher temperature then underfloor heating to be efficient.
For the investment was modest because I alreasdy had a running KNX system in combination with the miniserver for control on mobile devices.
If anyone needs adduditional info, please let me know.

[mosseltje]

Hey Aldert,

Like Chris I'm looking to 'do' something with my OpenTherm devices. Both my boiler(Vaillant) as my suncollector ( also Vaillant) as my ventilation system have the OT possibility.

My set-up is a complete loxone system so no knx. So some questions.

1. Is one theben ot-box-s enough for 3 devices or is it one per device?

2. Do you know if it allows you to read and control all the devices parameters?

3. Its controlled via the knx gateway on the loxone but since I don't have any knx experience I can't imagine how it works. Is it via blocks like Loxone or is it via a programming language?

Thanks.

[Aldert]

Hey,

As far as i know, OT is a point to point connection.
The OT box-s is build for heating and cooling.
It is also able to control a second heating/cooling circuit.
The OT box reads a fixed number of variables (like boiler and outside temp)
You can't use it to parameterize your boiler. But you can switch on and off domestic hot water as an example.
Knx is basically a very simple protocol, but you need the right tools (software) for the configuration.
It does not run on function blocks like Loxone. The core is run on group-adresses. If an input and an output are on the same group adress data is exchanged. The functionallity on the knx side is in the physical units. You could say these are also a kind of function blocks which can be parameterized.
It is possible to add sotware blocks like in the miniserver. You will have to buy an other piece if hardware to add functionallity. You can also run a knx installation withouth a server. An actuator to switch on the light and a digital wall "switch" are enough!
I hope this helps

[mosseltje]

Thanks for the info Aldert.
After reading this I'll probably abandon the OT solution.
It seems like a lot of pricy components are needed in order have some limited info from these devices.