to all, above is a drawing of my previous configuration using a “2-wire” thermostat, high voltage that is 220 240 Volts, directly connected to my gas heater.
couple of key points:
#1 the thermostat had batteries internally used to trigger the “dry switch” (now on the drawing).
#2 upon “heat” command (ambiant temperature below target) the “dry switch” basically closes the electrical path between Ls and Lr
#3 once Ls and Lr are connected together, this triggers the heater (gas + circulator)
#4 Ns connector is shown although not used in this configuration since thermostat operates from its own supply (internal batteries)