Heating foil for heating buildings - has heating conductor paths of lead-tin alloy, and at least one alloy safety path of tin, lead and antimony or lead and bismuth

摘要

The heating foil comprises a current path-like heating conductor, having defined specific resistivity per length, sandwiched between two polyethylene and polyester foils. The heating conductor comprises a narrow layer of hard lead core alloyed with 0.5-6 (2)%Sb having an Sn coating on both sides; and at least one conductor path formed as a sandwich of a narrow layer of alloy contg. 55.5-78.5 (61.5)% Sn, 20.7-43.7 (37.7)% Pb and 0.3-2.0 (0.8)% Sb, and another narrow layer formed of hard lead core alloyed with 0.5-6 (2)% Sb, having Sn coating on the free sides of the layers. The layers comprise 10-100% of the total thickness of the conductor and the Sn coatings comprise 0.5-3.5 (1)% w.r.t. hard lead core. Alternatively, the first narrow layer of the conductor path consists of a low m.pt. alloy contg. 27-47 (37)% Bi and 53-73 (63)% Pb. The heating foil is used for heating buildings, partic. wooden buildings. The foil has the required electrical resistance and thermal conductivity and minimum Sn content, to reduce costs. The safety conductor path, which stops power supply by melting if excessive temps. occur, has reduced width.