Fully Pumped Sealed System
Central heating systems currently being installed in the UK are increasingly of the sealed primary circuit type. This means the water heated by the boiler, which circulates around the radiators is held in a closed circuit under pressure. Such an arrangement has a number of advantages over 'open-, vented' or 'conventional' heating systems. Sealed systems are low maintenance, but are not maintenance free. Combination boilers invariably have sealed circuits.