UFH addition with weather compensation

[Rhyss]

Trying to research and figure out how this will be done. Although i'm not connecting up the UFH myself, i need an understanding to ensure access required is available, the schedule of works is right and that i only purchase what is necessary.

Current setup is Viessmann Combi 200w boiler with weather compensation, single zone circuit going to all radiators in the house all with TRV's.

Kitchen currently in progress and i'm putting down underfloor heating. As far as i understand with a conventional setup (i.e. central thermostat connected to boiler) the UFH would be at least split into two zones being the houses radiators so that itself can call for heat from its own room thermostat and manage.

However with weather compensation this isn't the case as there is no central thermostat.

My Q is:
- In my case does the UFH manifold get connected directly to the flow and return valve from the CH ? (i've seen people suggesting this sort of open loop way with ASHP)

Going to talk to my heating guy next week, but has anyone dealt with this before and can shine some light?

There seems to be bugger all out there relating to WC boiler with underfloor heating and radiators!

[B'stard Child]

What temp do you currently heat your rads with?

If above 40 then you'll probably need to blend the flow temp to the UFH with some of the return to keep the floor at a lower temp than the rads

Low temp systems with oversized rads and underfloor can be run at the same temp (ie no blending)

[LocoBlade]

Assuming you can't size your rads large enough that they can run at the same flow temps as the UFH needs (typically 25-35c), you can split it into two zones and either use a mechanical mixing valve on the manifold to lower the temperature compared to what the weather comp is setting for the radiator circuit, or the much better option is using an electronic mixing valve to mix the UFH circuit down on it's own weather compensation curve controlled by the boiler controls. This is far better because the electronic valve will vary the temperature of the water going to the manifold based on the outside temperature / demand so once the right curve for that zone is set can be left to run low and slow for long periods or constantly keeping the house at the required temperature without needing a schedule or even a thermostat in many cases.

We've got this setup with a Vaillant boiler running weather comp I went into quite a bit of detail in this thread
https://www.pistonheads.com/gassing/topic.asp?h=0&...

There's a Youtube video I linked to that Andrew Milward recorded during the install of our system which explains how it all works, and just looking at his channel this looks like he documented a similar setup on a Veissman like yours here:
https://www.youtube.com/watch?v=h37ZTCllhLM

Edited by LocoBlade on Wednesday 2nd October 20:20