I would like to control Nest thermostat (3rd gen with heatlink) domestic hot water, however the API doesn't seem to be exposing neither it's controls nor it's status (https://developers.google.com/nest/device-access/api/thermostat). As there's clearly at least an internal API for that, which the thermostat itself is using: would it be possible to expose the same controls/stat for external use? Use-cases:
This Google help page suggests that the Nest Thermostat is using OpenTherm commands to control the water boiler. If so, then your water boiler must have an OpenTherm interface. You could use some other hardware to interface with your water boiler, for example this DIY OpenTherm gateway, which will allow you to control the boiler programmatically with OpenTherm commands. This would allow home assistant integration, or a DIY push-button for boost.
This is one of the worst aspects of Best, being able to bost hot water is essential, since it is in the app when is it not available though API. I realise this is probably because having separate water tanks that are controlled independently is not as common in the states and Nest us very USA centric, but the feature is key in the app.
Yes the Nest thermostats use an internal API to control domestic hot water. This API could be used to expose the same controls and stats for external use. However, I think you would need to use a third-party service to expose the controls/stats for external use.
