In the direct heating systems, the sealed radiator is placed in the boiler interior, heating the water directly. The radiator cannot be replaced without emptying out the boiler first.
A safety valve is equipped with a check valve that prevents the backflow of water into the mains water system.
Thermal insulation prevents heat loss into the surroundings. Materials such as polyurethane foam have very good insulating properties. Generally, the thicker the layer of insulation, the less heat is lost.
