SERIES RESISTIVE HEATING CABLES
The first heating cable that was produced was of a series resistive type. Today there are several types series resistive heating cable available. These are manufactured in qualities from PVC to mineral insulated high-temperature cable with rustless sheath. The biggest advantage with these is the possibility to obtain long element lengths, from only one point of connection.
In contrary to parallel resistive and self-limiting heating cables which maximum length are limited by the voltage drop in the conductors, this is used as a heat emitting part in a series resistive cable. The heating conductor is manufactured of an alloy that gives required resistance per meter. By combining a required length with the available cable resistances and supply voltages can advantages be obtained such as varying outputs, lengths from a couple of meter to lengths on 800-1000m from one point of supply.
It is a disadvantage that the cable normally must be finished on the factory, which means you have to know the pipe lengths in advance to be able to pre-order required lengths. (At long high-temperature lengths where the heating conductor contains copper (cc-cables) shall consideration be taken to the temperature coefficient of the heating conductor which influence the output of the length negatively).
For installations within the Ex-surface a number of supplementary safety devices is required and exemption from the touched authorities.