Extension using two thermostat zones and one extension
I have currently got 2 smart thermostats in 2 zones alongside smart radiator valves both upstairs and downstairs. all was working well.
We recently had a new water boiler installed so I purchased the extension kit to use my water. they then wired up the extension kit and it seems it contains one zone and one water, the downstairs smart thermostat is wired into the zone and water. they have however wired the upstairs zone into the extension as well.
My issue is when I turn the water on my upstairs zone valve actuates heating my radiators upstairs, the smart thermostat is switched off so it is not in any way sending on/off signals.
My question is should the upstairs zone be also wired into the extension? I think it only needs the downstairs to control the on/off function and the upstairs should be on its original own zone.
Is this right please, with both zones in the water seems to be controlling the upstairs zone as well as water?
So extension should only have downstairs zone and water only