Underfloor heating control with Evohome

[ansaar99]

Hi
I have an evohome system, and im currently installing tiling throughout my ground floor. Ive decided to install wet ufh under the tiles. Im now wondering the design for controlling the ufh and making it work seamlessly with evohome. The lounge (large through room around 43m sq) will have two loops connected to a 2port manifold. I want to control it as one zone though.

My existing central heating is setup as two zones, with honeywell motorized valves. One zone is essentially all the rooms in the house (where all the evohome stuff is). The BDR92 is connected to this motorized valve. The other valve operates to heat a conservatory with a manual separate room stat.

I could add a HR91 on the return of the manifold, but then how do I power the pump to only come on when the HR91 for the ufh is calling? Not a problem for the radiators in the house, but an issue for the ufh.

Ansaar

[Richard]

UFH with the evohome system needs to be specified correctly to work flawlessly.

The control side is pretty easy to understand, this section on our website (https://theevohomeshop.co.uk/22-underfl ... g-controls) details the evohome UFH products we use for UFH control. Basically, with a multi zone UFH system, the HCC80R controls the UFH components (pump, zone valve and thermal actuators) and then you have a room thermostat in each UFH 'zone'. The loops on the manifold are not classified as 'zones', the rooms are the zones and can have multiple loops/thermal actuators serving them (depending on the rooms size).

HR91 and HR92's are called 'radiator controllers' and we don't use them for UFH control.

As for setting up evohome for UFH, you need an evohome system configured correctly for it. The system hierarchy for UFH control is as follows...

BDR91 (Boiler Demand Relay)
HCC80R Zones | Single Zones Only | Hot Water Control
Radiator Multi Zoning (with HR91/HR92)
Sensors (DTS92E/T87RF/HCF82/CS92A)

The key thing with UFH is that you get your flow rates correct and the heating system pipework designed correctly to prevent the UFH system passing too much flow through the boiler or starving your radiator circuit. You really need an installer that knows heating systems well and knows evohome too.