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I believe i understand this now 🙂
The black wire which enters to the bottom of the Room STAT/Timer block link is carrying power which is carried over through the link into the red wire leaving the bottom and activates the demand for central heating. Hence the boiler firing constantly.
By removing the link and placing the black wire in the 4th position (counting from the earth as number 1) as soon as the thermostats activate, power travels down the black wire and the demand for central heating fires the boiler.
Is my understanding correct?
Terminal (from left) 3 Shaun if terminal 4 is live with link removed?? (post 15).
Just like the attached ShaunCorbs?
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