The control system is the brain of a radiant heating system. It is responsible for modulating the boiler, polling the outdoor temperature sensor for boiler reset and communicating with the home thermostats. When a room thermostat temperature falls below the designated room temperature, the system controller is responsible for opening the manifold actuator allowing warm water to flow to that room radiant flooring. A microprocessor control system can be as simple as a thermostat or as sophisticated as a Tekmar TN4 system.