Will try bypass valve fully open when I get back fom work tonight.
To clarify there is only 1 2 way valve in the heating circuit, the hot water circuit always has flow, eventually plan on implementing s-plan system with additional zone valve in hot water circuit.
With current setup cylinder stat will only really work to turn off boiler when running in hot water only mode, if heating is selected as well as long as the room stat is calling for heat the boiler will remain on and continue to heat hot water in cylinder.
To clarify there is only 1 2 way valve in the heating circuit, the hot water circuit always has flow, eventually plan on implementing s-plan system with additional zone valve in hot water circuit.
With current setup cylinder stat will only really work to turn off boiler when running in hot water only mode, if heating is selected as well as long as the room stat is calling for heat the boiler will remain on and continue to heat hot water in cylinder.