But you do mention a lot of air in the system.wildeman said:I am not sure if that would cause the issue but it has been piped like that since the house was built.
If you improve the contrast on the pic you will see it it OKYou show T7 connected to the N, whereas it should be Programmer 1 and the grey wire, meaning you don't have a neutral to the pump and boiler in the htg only mode.
So it's unlikely to be the valve. Which leaves us with a fault in the rest of the system.I have already replaced the valve body and actuator three weeks ago.
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