A special version of Nest is available in Europe, which is capable of controlling 230 volt heating systems. The Nest is paired with a "Heat Link" device, which contains the circuitry required for controlling the mains-voltage heating system. The first release was the 2nd Generation Nest thermostat which the Heat Link controlled the central heating boiler. The 3rd Generation added support for OpenTherm and for controlling domestic hot water. The Nest E was made available to the UK in October of 2018. It has several major changes as the thermostat is stand mounted only, the Heat Link is grey and battery powered, the Heat Link loses the domestic hot water support, and lastly designed to be installed on the wall where the old thermostat was located.