Book - School of Science and Technology

Radiant heating 185FinishScreed andpipe coilsDamp proofcourseInsulationFigure 7.10 Embedded floor panel (note extent of insulation)2 mm thick walls, in coil lengths of 120 m. The methods used in laying the coils are muchthe same as those previously noted except that metal strips holding plastic clips are laid onthe base slab, at right-angles to the coil line, to form a locating grid; various alternativeproprietary securing methods are also available. An emulsifying agent is added to thescreed mix to improve contact with the coils. It appears that problems have arisen fromgaseous diffusion inwards through the walls of the tube originally used, even under waterpressure, leading to corrosion of metal parts elsewhere in the system. To overcome thisproblem oxygen diffusion barriers are available for polyethylene tube, or substitutematerials, incorporating barrier films of either other plastics or metal foil.A well-established alternative to fully buried pipe coils was offered by `Panelite', aproprietary arrangement of steel pipe coils encased in split asbestos cement covers orsheaths, as shown in Figure 7.11. This arrangement allows freedom for expansion andcontraction and the air gap between the pipe and the covers acts as an insulant. As aresult, higher water temperatures may be used, Table 7.1, than with the wholly embeddedRound coversRound/ovalsyphonRound/ovalbendSpring clipsOvalcoversRound coverOval coverFigure 7.11 Details of sheaths for `Panelite'