There are a couple of systems for central heating and one of them is what is called a sealed system. What does this mean? Well, a sealed central heating system is one that is filled with water and then sealed with the water inside. The system is usually filled up by the cold water mains through a temporary hose connection which is shut off on completion. An Enfield Plumber is trained to work on both types of heating systems An example of one of these systems is a combi boiler. This system removes the filling hose to negate the chances of contamination from cleaners being fed in. This is prohibited by Water Regulation Authorities. Vented System.The sealed system is not under any outside pressure influences. This is known as a loop. Now a system called (a vented) system requires a loft tank, and is able to provide a controlling effect on the amount of water in its system as needed. This is achieved through a float type valve situated in its tank which is known as a feed and expansion. It works by containing expanding water in a bladder, fitted internally or externally.The sealed system is good for small space operation as it doesn’t require a tank to operate The sealed system has its uses for instance if you live in a small flat where space is limited, this system without a tank is ideal. Enfield Plumbers service and repair these systems on a regular basis. Safety features:Non -return valve to prevent backflow of hot water through to the cold water line.Temperature limiting valve to prevent dangerous increase in operating temperature.Pressure relief valve to open in case system pressure rises above the normal running pressure.Expansion relief valve in case the expansion vessel fails to operate.