HOW IT WORKS ? CENTRAL BOILER HOUSE PIPING NETWORK SATELLITE STATIONS BUILDINGS CONNECTED MULTI-ENERGY SAFE, CLEAN      COST-EFFECTIVE HEATING	The piping network proper comprises a double pipe which runs underground either bare or in a dedicated duct. One pipe conveys hot water from the central boiler plant to the delivery points. The other pipe returns the water to the boiler plant. On the outward leg, the hot water or steam circulates at a temperature between 90°C and 180°C, whilst on the return leg, the average is between 80°C and 100°C. To keep heat losses between the boiler house and the furthest satellite-station down to a few degrees, the pipes are heat-insulated, or lagged. This technique is also used for conveying chilled water in the district air-conditioning networks.