Opentherm

daveemitchell

Hello,

I've just had a 111w Viessman boiler installed. It has opentherm and needs a heating and hot water input.

I currently have it on a Nest v3, but I'm thinking of going to Tado because of the TRV's being able to 'heat on demand'.

This morning I've read that UK Tado no longer supports Opentherm and the EU doesn't have hot water hot water control.

Is this correct?

My current TRV's are Mihome ones, but they can't do HOD which I'd really like - any work around that I can use?

thanks

johnnyp78

It is a combi effectively, it should be fine, the boiler will manage the tank and you should be able to set the desired temperature using the app. I would still double check with Tado support to make sure it is compatible with Tado’s implementation of opentherm.

johnnyp78

Yes, you’re correct, however it’s rare to be able to use opentherm or ebus with system boilers unless the boiler is able to provide hot enough water to the tank while also modulating the heat requirement to the radiators. The old extension kits, which had both hot water relay and digital connections, could only do one or the other, not both.

daveemitchell

The 111w has a small tank and is working well with Nest, but I really want HOD…. Why can’t it just be simple??

johnnyp78

I’m a bit confused- is it a combi or a system boiler? If it’s a combi it’s easy to set up with Opentherm and you’ll get hot water control. If it’s system then it’s more complicated.

Just had a look and it appears to be a combi, in which case all you need is a connection with Opentherm control - either an EU wireless receiver, an old extension kit or a wired thermostat.

daveemitchell

It is confusing. They have a small water tank built into the unit (45l) So unlike a combi there is no delay for hot water.