The Heatrae Sadia direct comb thermostat part is located within the thermostat section. The thermostat is a heating control that is used to manage the temperature of your central heating system. There are lots of different variations available and they don't all necessarily need to be attached.
Genuine replacement part for Heatrae
Technical specification
TypeThermostatManufacturer Model No1735757Brand NameHeatrae Sadia