What still has not been mentioned is either what this change will actually do! What is the stated benefit?? That is what I have not seen even mentioned yet. Does it somehow use the boiler to heat the tapwater?? The expense of any piping changes will certainly be greater than the claimed savings in fuel costs. Unless your domestic water heater is either electrically poweredor has poor efficiency.

And a bit of caution: That "shelly 3" device that Y shows still needs to be installed INSIDE a suitable enclosure to satisfy most electrical code requirements. Exposed mains voltage wires must be inside a suitable enclosure here in the USA. My guess is that the UK has similar rules, especialy since 220 volts undoubtedly gives worse shocks than the 120 volts in my locality.

 

What still has not been mentioned is either what this change will actually do! What is the stated benefit?? That is what I have not seen even mentioned yet. Does it somehow use the boiler to heat the tapwater?? The expense of any piping changes will certainly be greater than the claimed savings in fuel costs. Unless your domestic water heater is either electrically poweredor has poor efficiency.

And a bit of caution: That "shelly 3" device that Y shows still needs to be installed INSIDE a suitable enclosure to satisfy most electrical code requirements. Exposed mains voltage wires must be inside a suitable enclosure here in the USA. My guess is that the UK has similar rules, especialy since 220 volts undoubtedly gives worse shocks than the 120 volts in my locality.

It's just a replacement of the control system. The Shelly device will interface to Home Assistant and allow "smart" operation based on whatever relevant factors the TS wants to integrate (e.g.: time of day, day of week, month of year, occupancy, outdoor temperature, voice command, and more.)

Yes the control circuitry should be enclosed.

 

OK, now I see that the "home assistant" software would gain control by means of the added relays. Very interesting. AND it still leaves the description of exactly what exact functions the system would control.
My statement that providing a heat exchanger in the domestic water heater supply line, capturing heat in the heating system return line, is an option that will require no electrical control at all.