How to connect Floor Heating Systems with Home Connected Hubs and Apps (Alexa, Google Home, HomeKit, etc)
Floor Heating Systems do not connect directly to Home Connected Hubs and Apps like Alexa, Google Home, HomeKit, etc.
Floor Heating System may be connected to a home-automation compatible low-voltage thermostat that will be used to control a floor heating system through an integration kit (with potentially a need of external transformer).
Here are the links to compatible thermostats for each home automation platform:
Google Home: Nest Thermostat , Honeywell thermostat, or a thermostat connected to SmartThings. (Note for Honeywell thermostats: Google Home supports Total Connect Comfort thermostats only. Lyric thermostats aren't supported.)
HomeKit: Nest (3rd Generation), ecobee3, ecobee3 lite, Honeywell Lyric Round, Honeywell Lyric T5 thermostat, iDevices Thermostat, First Alert Wi-Fi Onelink.
RC840T or Integration Kit Transformer Rating is 24 VAC / 40 mA / 1.2 VA, so any low-voltage thermostat that is compatible with this voltage and power will work with RC840T, if the power consumption (draw) is higher, then additional transformer is needed. Here's an example: Honeywell's Transformer AT120B1028 that provides 24VAC / 20VA