We have a number of electric baseboard heaters in our house that I would like to smarten up. Eventually I intend to get rid of these baseboard heaters, and replace them with a better heating system, so ideally I want to use Ecobee smart thermostats, rather than a line-voltage baseboard thermostat such as the one from Mysa, so we can keep them for controlling the future heating system (also for other reasons, but this is the one that most justifies the cost).
As far as I can tell, the Aube RC840 series of relays appears to be the best option to enable this, though I’m very open to alternative options.
In my research, I’ve read that it’s possible to use one thermostat to control two baseboard heaters with Aube relays, but I want to know if it would be safe/reasonable to use a single Ecobee for three baseboards (they heat a single, large space, so an Ecobee with a smart sensor or two would work well; another reason to favor Ecobee over Mysa: fewer thermostats).
Also, in such a scenario would I want to use the RC840s with transformers, or without, and use a separate transformer at the thermostat for 24V power?