In the case of piles or other foundation structures, closed circuits of DN 20/2.0 or 25/2.3 PE piping are incorporated in the concrete. These are used to circulate the heat transfer medium and transport the thermal energy to the central building services control system. Providing that the conditions are right, the fluid used can be water or mixture of water and antifreeze. The piping units are either attached to the reinforcing cages at the factory or on site. The pipe spacing is derived from the calculation of energy use; the dimensions and lengths of the piping systems are derived from the hydraulic calculations. As a rule, a pipe circuit (water circuit) will have a length of 150m - 300m from manifold to header block. The type of pipe connectors used are usually thermofusion connectors. The rigged cages are then placed in the locations determined by the structural engineer and cast in the concrete. The individual circuits are subsequently joined up via connecting lines to the manifold and header blocks. Pipes are laid primarily in the ground slab and along the exterior face of the outer wall of the building which is in contact with the soil. The work is usually carried out in phases as the walls of the basement must be completed before the connecting lines can be installed. The shaft to house the distributor blocks should be located above groundwater level and, if possible, in the building services room. The distribution system consists of a manifold and header block to which the flow and return lines of the piping circuits are connected. It is often necessary to include intermediate manifolds and/or ring circuits based on the Tichelmann system. This will largely depend on the size and shape of the building. The circuits are kept under a pressure of 6 bar throughout the complete construction phase so that they can constantly be checked for possible leaks. The pressures are tested and recorded in test reports prior to and after pouring the concrete. For further information (PDF file) on the system, please click here * ). * ) To view PDF files you will need the Adobe Acrobat Reader. If you do not have this software, you can download the Acrobat Reader here free of charge.