Quote Originally Posted by omdaddi View Post
How would I do this?

Thanks for taking the time to help me out.

(I am slowly working this out. Once I put the hot water relay in I realised I had made the (common) error of setting up the zone valves as boiler control. I have just set them up (I have three zones) by binding them at the same time when setting up the guided configuration. I worked out that there is < 10 litres in each circuit with all the TRVs closed downso am not going to worry too much.

All a bit of an adventure really, though not sure it is going to save money. The kids are delighted they can crank up the temperature in their rooms!
Someone more experienced than me will be able to tell you for sure, but my understanding is the Megaflo temp stat has an overheat stat built into it (effectively wired in series). It has a reset button on the front if it activates. So, in theory, as long as the stat is wired in series between your BDR91 and your motorised valve, the valve should close when the stat (or the overheat stat) open.

This is a very important safety feature and actually illegal to work on if you're not G3 qualified. This is not to scare you, but rather to make apparent to you that if you do insist on DIY, make sure you are 110% confident in what you are doing.