on Friday I had the hot water cylinder replaced as there was a leak in the old coil. On completion plumber asked me to use programmable room thermostat, Vaillant VRT360f, that is WI-FI connected to VR65 Control Centre to heat water. Boiler fired up and port valve opened, all good but after about 30 seconds it shut off. Now it is possible to operate CH via the over ride, programmed timing of CH does not work and hot water does not work on either programmed time or override (using electric Emerson heater for hot water). There are no fault codes displayed on controller. LED light on inside of control centre is on constant suggesting it is working fine. Called Vaillant today and they suggested it was a performance issue. I am wary of spending upwards of £150 on a new programmable room stat if that is not the problem. Has anyone had similar experience? System has been working fine for several years. Can anyone suggest possible solution? Is there some sort of reset? How can I confirm that it is the programmable room stat that is broken?