Traditionally, private houses have sloping roofs (e.g. “saddle roofs”), and it has primarily been commercial and industrial buildings which have had flat roofs. Flat, or nearly flat, roofs have, however, become more and more common also in private homes and cottages, and although they are dimensioned to withstand snow loads, it can be both comfortable and clever to remove snow using heating cables. This is particularly true for roofs which are covered with roofing membrane, normally not intended for manual snow cleaning (due to risk of damaging the membrane with snow shovels).
For snow melting on flat roofs, an area power of approximately 200W/m2 is recommended, with the linear power of the heating cable not exceeding 20W/m.
Attachment to flat roofs may be by using bituminous glue or similar, attachment bands, or sandwiching between two layers of roofing membrane. With the latter method, a temperature sensor should be installed in direct contact with the heating cable and used protection against overheating.
Nexans offers several products that are suitable for snow melting systems on flat roofs.
TXLP Single conductor heating cable
Single conductor heating cable (also called drum cable) is quite suitable for snow melting installation on flat roofs. Since the cable should be laid in such a way that the "end" of the cable comes back to the starting point of the installation, some planning of the installation is required. Single conductor heating cable systems should be calculated by a person possessing experience with such systems.
DEFROST PIPE self-regulating heating cable
DEFROST PIPE is a family of self-regulating heating cables. A major advantage of self-regulating heating cables is that they will never overheat, yet they will emit more power when needed, i.e. when they are covered by snow. The variant called DEFROST PIPE 20 yields 20W/m at 10°C, and will be very suitable for this application. Recommended distance between cable strings is about 10cm. Using a wider separation between the strings gives a risk of the heat emission of the cables decreasing, before the snow between the strings has melted. When using self-regulating heating cables, the power supply circuitry must be dimensioned with respect to the inrush current that may occur in such heating cables. Self regulating heating cable systems should be calculated by a person possessing experience with such systems.
TXLP Heating cable elements
TXLP Heating cable elements (17W/m) is well suited for this application. Used in conjunction with attachment bands, giving a distance between the cable strings of 10 cm, yields an area power of 170W/m2.