Heating cables in cast floors

Direct acting heating systems normally require 60-100 W/m2 (5.5 - 9 W/sq. ft). These systems require low thermal capacity, and the heating cables are placed as close to the floor surface as permitted by the national authorities.
Normally this means that the heating cable is placed in the lower part of a max 50-mm (2") thick screed on a high-grade thermal insulation. When renovating, or when space is essential, special thin screed solutions are used, allowing screed thickness down to 10-15 mm (3/8" - 5/8").

The heating cable is evenly applied at the pre-calculated center-center distance. Avoid concentration or overlap of cables as this could result in uneven floor temperature and damage to the cables during operation. When laying the heating cable ensure that it's not pressed into or in contact with the insulation below. This can be solved in several ways. For example:

  1. The heating cable is attached onto a layer of chicken wire covering the entire floor, or onto reinforcement bars.
  2. The heating cable is attached to a layer of solid cast, minimum 10mm. (Concrete/Screed).
  3. The heating cable is attached to non combustible plates (plasterboard, fibre plasterboard or similar)

In wet rooms as toilets, bathrooms and washing rooms plates withstanding moisture must be used.

Both TXLP and TKXP can be installed along reinforcement bars. Attach the cable longitudinally to the bars, and avoid stepping on the cable.

In all types of cast floors it's important with a correct mixture and to mix well (normally 1 part cement and 4 parts sand) before pouring. The cast must be compacted to avoid airpockets and to ensure the possible heat conductivity.

The cast is to dry and harden naturally, and the heating cable can be turned on after 6-8 weeks.

It is not recommended to use a dry cast, meaning the use of little water to decrease dry and harden time. If this method is used, ensure that mixing is done by machinery and compacting is done thoroughly.

Screeds and other casts have shorter drying and hardening time.