Tado 3 zone?

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My set up is a 3 zone system (upstairs, downstairs and hot water). I have a secure channelplus H37XL programmer with upstairs and downstairs set to permanently on and a Tado wired thermostat attached to those rooms. The hot water is just set to a normal schedule.

I have a Tado extension kit from my previous house, and was wondering how I could incorporate it into the set up to control the hot water in the system.

Presumably the hot water is just like the central heating circuit, and just needs a closed circuit to call for hot water (assuming programmer and cylinder stat are also calling for it).

The question is about how the Tado extension kit works. When HW is set to on does it close the circuit? If so could it be wired in series with the HW channel (terminal 5 I think) on the current programmer, then the HW set to always on? Then the extension kit could provide the control of the HW through the app. If so what should I select when setting up the extension kit during the install? Is there a generic HW on off programmer that is in the app?

Thanks in advance and happy to clarify any points!