How many floor heating systems can be connected to one TH115 Floor Heating Thermostat?
This is dependent upon the amperage of the units that you are trying to install. Each TH115 Floor Heating Thermostat can carry a load of 15 amps.
Once this limit is reached, a relay must be installed (and multiple relays after that, dependent upon the amperage of the units).
Please note that while the relay needs to be accessible, it does not need to be in plain sight.
You may hide it in a cabinet to avoid having two thermostats visually available in the room.
With that being said, if you are not interested in having a master and a relay and would prefer to have just one thermostat installed, you may have you electrician install a contactor panel to help carry the extra amperage load.