I haven't tried Honeywell but I can confirm how Google Thermostat is
useless and had caused hundreds pounds of damage on repair and call out
charge. Their support is worst than their product.
I had exactly the same problem with my hot water not working and Gen 3.
Vaillant engineer diagnosed the problem caused by the heatlink (it shows
no error or anything so everything looks fine which of course is not).
We removed the heatlink and everyt...
