You can install the MTS200(for boiler/water system version) with your system according to the diagram below. The sensor connected to terminals 6,7 is optional. You can also follow up the Meross App step by step to set up your system.

1. Gas boiler heating system(Control the boiler with thermostat):

2. Water underfloor heating system(Control the thermal actuator with thermostat, support both 2-wire and 3-wire actuator):

3. If your old thermostat only has two wires and there are no other wires in the junction box, the MTS200 is NOT compatible as it does not have a live or neutral input.