Tado and Constant call for Heat in Two Zone System

[Harrison88]

Hi guys,

I have a two zone system with boiler and megaflo. A separate unit controls the hot water. The thermostats are wired and battery powered.

Current thermostat wiring looks like this:
https://imgur.com/a/EEeOAhR

Black into middle. Brown into bottom.

I took the Tado wiring and copied it - black into NC, brown into common.
https://imgur.com/tsIe38E

However, the Tado is immediately and constantly demanding heat. The Tado unit and app clearly slows that it doesn't need heat and isn't switching on the heating, but my zone valve is lit up and the radiators are hot - so someone is lying.

Have I got the wiring right?

Cheers!

[ericmark]

Not enough info really but original thermostat switches boiler on/off and Tado I think is OpenTherm so it turns boiler up/down and modulated the flame so completely different connections to boiler.

I think Tado can switch on/off but it does rather defeat the whole reason for fitting it.