Gutters and roof drains

Heating cables are ideal to prevent ice and heavy snow in gutters and roof drains. It has an important safety aspect, as it prevents damage that might be caused by snow, ice and icicles falling down.
Warm or cold roof
Examine the roof construction: Warm or cold roof?
Warm roof is a poorly insulated roof where the heat loss through the roof construction causes a positive temperature on the roof surface under a layer of snow.
Water from melting snow will end up in the cold roof drains and freeze.
Cold roof is a well-insulated roof where the problem of ice is caused often in the late winter. Sunshine will melt the snow on the roof while the roof drains and gutters may be in the shadow. The melting water will then freeze.

Planning and calculation
Due to the high loads and varying gutter and drain lengths, TXLP drum type single conductor cable is used. Sum up the total length of roof drain and gutters. If needed the loop, in the drain is to go down to frost proof depth.
Multiply this length by 2, and this gives the cable length (load). Select the correct length and resistance value by using the calculation program Nex Calc. As the cable is laid in a loop, the load per meter cable has to be the W/m roof drain/pipe divided by 2.

The cable is installed in a continuous loop in the gutter/drain. The cable is fastened on top of each drain by using a stainless steel suspension bracket.
For the control, use an outdoors waterproof thermostat placed on the shadow side of the building. The thermostat is to disconnect at approx. + 5°C (41°F). With cold roofs a thermostat disconnecting at approx. - 10°C (14°F) can also be used for energy saving purposes.
In many countries it is also required to use a ground fault circuit interrupter, disconnecting at max. 30 mA.

Cables on roof surfaces
In some difficult situations with warm roofs it may be necessary to install heating cable loops on the outer part of the roof in addition to the cable in the gutters/drains. The linear cable load is to be limited to 16-18 W/m per meter cable.  

Cold roof: 1) Good ventilation 2) Sufficient insulation in ceiling
Warm roof: 1) Heating cable 2) Little or no ventilation 3) In substantial insulation in ceiling