Bed of sand
Application of heating cable in a bed of sand
A very frequently used method of applying heating cable is in a bed of sand. This method of application is universal and the surface coating can consist of different materials like asphalt, concrete plates, paving stone or ground bricks.
Types of cables to use: TCPR.
Limitation of powers: Max 20 Watt per meter cable.
Application: The cable should be applied in a well-compressed bed of sand with a depth of at least 50mm. The cable is then to be covered with sand, which is well stowed around the cables in order to obtain a good spreading of the heat. When working on this you have to be careful not to damage the cables. This layer of sand also has to be about 50mm thick.
Installation of the heating cables: The fastest ad easiest method is to apply a steel fabric or a chicken net to which you lash the cable with a fitting c/c-distance. When lashing a plastic coated lashing wire should always be used.
Another method is to fix the fixing strips in the first layer of sand by means of boards. These boards must not be applied in such a way that the cable can come into contact with the boards as the heating cable must not get direct contact with combustible materials. You can for example apply boards outside the heated area and stretch fixing strips between them. The cables are then mounted on the fixing strips with a required c/c-distance.
Check: The application of the cable should always be supervised by a competent engineer. Before the cable is covered it should always be tested (megatested and ohm-measured).
Control: At moisture/temperature control special sensors are mounted in the surface. A protective pipe for the sensor wire is then to be applied all the way to the sensor.
In asphalt, on concrete
Application of heating cables in asphalt on concrete
One method to apply the heating cables is to apply the cable directly in asphalt on for example cover of concrete. This method can be used in applications for example in handicap ramps and foot-bridges.
Type of cables: TCPRH, a variant of the ordinary TCPR-cable, is provided with an outer sheath of teflon, which means that it can stand the high temperature in hot asphalt (140-160°C).
Limitations: Max 30 W/m cable.
Application: The cable is fixed on special fixing strips which are nailed on to the concrete surface (c/c 500mm).
Check: The laying of the heating cable should be supervised by a competent engineer.
The cables should be tested (megatested and ohm-measured) by a responsible electrician before the asphalt is applied.
Covering: When the asphalt is applied by hand you have to be careful not to damage the cables with tools or other objects.