Roof gutters and downpipes

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Heating cables are very suitable for ensuring snow and ice free gutters and downpipes. They prevent the formation of snow and ice lumps which can be very dangerous if they were to hit a person when falling from the roofs or roof gutters. Frost protection of roof gutters and downpipes is therefore a question of safety of people on the ground below. In addition, damaged roofs, gutters and downpipes after frost are avoided.

Roof projection / eaves
In cases of "warm" roofs, it may be necessary to install a heating cable on the roof surface, in the area above of the eaves, so as to prevent water for the melting snow to freezes again on its way to the gutter. Linear power of the cable should in the range 16-18W/m, and an area power of around 100W/m2 will suffice.

Planning and design
In a roof gutter, series resistant heating cables will normally be installed in a loop ("back-and-forth”), so that the linear power the heating cable must be half of the calculated linear power for the roof gutter installation. The highest permissible installed power in a roof gutter depends, amongst other things, on the material from which the gutter is made.

A self regulating heating cable adjusts the heat emission relative to the ambient temperature, which means that the cable will emit high power when it is covered by snow or ice. As snow or ice melt, the cable will decrease the output power, and if the temperature rises even more, the cable will reduce the power even further. Note however that a self regulating heating cable never "switches off", and that a temperature control system, or a simple switch-off option, is almost always necessary.

Using self regulating heating cables do not required any calculations. The only designs parameter to observe is that the specified maximum lengths for the heating cable in question are not exceeded.

Mounting
The heating cable can lay in the roof gutter without any particular attachment or fixation, or it may be positioned, using special distance brackets in plastic, and hang freely in the downpipe (to the opening of the downpipe, or to frost free depth). The heating cable is suspended from the roof gutter edge, using a special suspension hook. On roofs, attachment must be carried out using equipment suitable for the roofing in question. On bitumen membrane roofs, the cable can be attached to the roofing using bituminous glue (or similar) but then the linear power shall not exceed 18W/m.

Thermal management
With a roof gutter thermostat for control and management of the heating cables, the energy efficiency of installed system is enhanced. Roof gutter thermostats ensure that the heating cables are only energized when moisture is detected and the current temperature may cause ice to form. This prevents unnecessary use of energy.

The heating cable is preferably controlled by a waterproof air thermostat, installed on a shaded side or part of the building. In “warm roofs”, where the temperature in e.g. the attic goes above freezing, due to poor insulation in the roof, a thermostat installed in the attic may be appropriate. This should switch on the heating cable system when the attic temperature reaches the point where snow on the roof begins to melt.