Step-by-step installation of TC 10 heating cable into the screed

This solution is mainly used for larger areas – the cable is tied to the mesh with plastic tie wraps at regular intervals of about 250 – 300 mm. The mesh also serves as reinforcement for the screed.

The third option is a double-sided mounting tape glued directly to the insulation boards, into which individual plastic clips are pressed at each bend of the cable. Regardless of the chosen method, the rule applies that the cable must be firmly fixed along its entire length so that it cannot shift, lift, or fold over itself during the pouring of concrete or during installation – crossing of the heating part of the cable is not allowed, as it causes localized overheating and may lead to premature failure.

Detail of cable mounting on a mounting strip

Step 5: Placement and installation of the floor sensor (probe)

A floor temperature sensor is part of the functional system, which measures the temperature of the screed and sends a signal to the thermostat to switch the cable on and off. The probe is placed in a protective tube (protector), one end of which is sealed (to prevent concrete from entering) and it is placed exactly between two adjacent loops of the cable, in the middle of the distance between them, at a depth corresponding to the height of the cable – that is, in the same plane, not deeper or shallower.

The reason the sensor is not placed directly on the cable or too far from it: too close to the cable would measure a distorted high temperature and the system would turn off before the entire area is heated; too far away (for example, near the wall outside the heated zone) would cause the cable to overheat while the sensor reports a low temperature. The protector must always be removable – this means that the probe can be pulled out and replaced in the future without the need to break the screed, which is one of the main advantages of a properly installed system.

Connection diagram of the cable, probe, and thermostat

The wires from the cable and the probe are led in separate protectors up to the location of the distribution box or junction box under the thermostat, usually routed in the wall or in a groove in the floor upwards. The cold ends of the cable must never be crossed or connected arbitrarily – the connection between the cold end and the heating part is waterproof from the factory and must not be damaged or wet before concreting.

Step 6: Measurement and testing before concreting

This is a step that is unfortunately often skipped in practice and is one of the most common causes of later complaints. Before concreting the screed, it is necessary to measure:

• Electrical resistance of the cable – using a multimeter, measure the resistance between the two conductors of the heating loop and compare it with the value stated by the manufacturer on the cable label or in the accompanying documentation (tolerance is usually ±5 – 10 %). A significant deviation indicates a damaged conductor.
• Insulation resistance – measured between the heating conductor and the grounding braid/shielding of the cable, the value should be at least 1 MΩ (in practice, new cables usually measure values in the hundreds of MΩ).
• Visual inspection – no visible damage to the sheath, no crossing, minimum distance from walls and from itself is maintained.

Record the measured values (best directly in the installation protocol together with a photo of the layout) – this record is proof that the cable was functional before concreting, which is crucial in case of a later complaint, if a fault is later discovered. A detailed procedure for measurement before and after concreting can be found in the article How to test the functionality of the TC 10 cable before and after concreting the screed.

Step 7: Screed pouring

After successful testing, the system is poured with a screed. Recommended thicknesses and procedures:

• The minimum thickness of the screed above the cable is 30 mm, commonly used is 40 – 50 mm, which ensures sufficient heat accumulation and mechanical protection of the cable.
• Cement-based screed with an additive improving thermal conductivity and preventing the formation of air bubbles around the cable, or anhydrite (flowable) screed, which has excellent thermal conductivity and self-leveling properties, is used.
• During pouring and especially during compaction (using a vibrating float or poking), be careful not to mechanically damage the cable – never step directly on the cable in areas where it is not yet concreted, and proceed carefully near it during compaction.
• The perimeter expansion strip must be installed around the entire room before pouring the screed, so that the screed can freely expand thermally without causing cracks.
• For larger areas (over approximately 40 m² or with an irregular plan), it is necessary to install expansion joints in the area according to the current standards for floor heating – usually at the transitions between rooms and along longer sides.

Time schedule of the installation step by step

Drying of the screed and the first start-up of the system

This is the phase where the most mistakes are made even by more experienced installers, as the investor's impatience pushes for an earlier start of heating. A cement screed needs at least 21 – 28 days of natural drying under normal conditions (air temperature around 18 – 20 °C, without wind or direct sunlight) to achieve sufficient strength. An anhydrite screed usually requires 7 days per millimeter of thickness to reach the phase of technological loading, but exact values are always provided by the manufacturer of the specific screed.

The first start-up of the heating cable is never done at full power immediately after the waiting period has passed. The recommended procedure of the so-called heating protocol (functional test according to STN, similar to that for water-based floor heating):

• Set the thermostat to a low temperature (about 25 °C) and let the system run for 48 – 72 hours.
• Then gradually increase the temperature by 5 °C each day until you reach the operating temperature (usually 27 – 35 °C on the floor surface depending on the type of floor covering).
• Ventilate the room throughout the entire process so that the moisture released from the screed can escape outside, not condense under the floor covering.
• Before laying the final floor covering (tiles, laminate, vinyl), let the system cool down to room temperature again to prevent thermal shock to the adhesives and materials.

Starting the system too quickly or too early at full power is one of the most common causes of cracks in the screed and subsequent damage to the cable, which is unfortunately a damage that can be easily avoided by observing the technological break.

Practical scenarios from implementations

In everyday practice with customer orders, similar situations repeat themselves, from which it is useful to learn:

Bathroom 6 m² during an apartment renovation – typically a lower power cable is used, such as HAKL TC 10/ 1030 W 2x connection cable, where the area is reduced to about 3.5 – 4 m² of real heating area after subtracting the bathtub, shower area, and sanitary facilities. A critical point is precisely avoiding the sanitary fixtures and maintaining minimum distances from the waste pipe embedded in the floor.

Living room with kitchen 24 m² – here, a power of about HAKL TC 10/ 2200 W 2x connection cable or higher is often selected according to the building's heat loss, while it is necessary to account for the area under the kitchen line (without a skirting gap) and for expansion in the area of transition between the kitchen tiles and the living room laminate, if they are treated as separate temperature zones.

Cottage or recreational building with intermittent operation – here it is worthwhile to choose a higher installed power, for example HAKL TC 10/ 2410 W 2x connection cable, because with sporadic heating (weekend operation), the system needs a faster rise to a comfortable temperature than a lower power spread over the same area could achieve.

Most common installation errors and how to avoid them

From experience with complaints and service interventions, the following mistakes are most commonly repeated:

• The cable is cut short or cut to size – the resistive cable TC 10 is never cut; it is delivered in the exact length for the given power, and any interference with the heating part of the cable will disable it.
• Skipping resistance measurement before casting – without recording the measured values, it is practically impossible to prove when the failure occurred during a complaint.
• Too thin a layer of screed over the cable – causes local overheating, cracking of the screed, and damage to the floor covering.
• Probe placed directly on the cable or outside the heated area – leads to incorrect temperature sensing and uneven heating.
• Starting the system too early after casting – risk of cracks and cable damage.
• Crossing the cable with itself during laying – local overheating at the crossing point.

A complete and detailed analysis of typical mistakes can be found in the separate article "Most common installation errors of resistive cables TC 10," where we also examine situations where the cable does not heat evenly or does not heat at all after casting. This topic is also covered in the article "Why the heating cable TC 10 does not heat or heats unevenly."

Comparison of TC 10 with other types of resistive cables

The cable TC 10 belongs to the family of simple resistive heating cables with a fixed (non-adjustable) power per meter, in contrast to self-regulating cables, which vary their power according to ambient temperature. For floor heating under tiles or screed, the fixed resistive cable of type TC 10 is a standard and proven solution due to the simplicity of installation, favorable price, and long service life (manufacturers commonly state a service life of 20 or more years with proper installation). A detailed comparison with other types of resistive cables can be found in the article "HAKL TC 10 vs other resistive cables – differences and advantages."

Maintenance after installation completion

The resistive cable embedded in the screed essentially does not require any regular maintenance – it contains no moving parts or consumable parts. The only thing to monitor is the functionality of the thermostat and the floor sensor, which is replaceable due to its installation in a protective housing. It is recommended to perform a control measurement of resistance and insulation condition of the cable once a year, preferably at the beginning of the heating season, if access to the connection terminals in the distribution board is available. More on this topic can be found in the article "Maintenance and service life of resistive heating cables TC 10."

Common questions about the installation of cable TC 10

Can the cable TC 10 be shortened if it is longer than needed?

No, the heating part of the cable must not be cut or extended. The cable is manufactured in the exact length according to the ordered power, which corresponds to the resistance of the conductor. If the cable is longer than the room area, the solution is to increase the spacing of the loops or to slightly extend the perimeter (within the minimum distances from the walls), not to physically shorten the cable.

Can I lay the cable directly on the old tiles without insulation?

Technically yes, if the base is flat and cohesive, but without thermal insulation, a significant portion of the heat will be lost downward, the system will be less efficient, and the temperature rise will be slower. We recommend at least a thin insulation layer or a reflective foil if the floor height does not allow for a thicker insulation.

How long do I have to wait before I can turn on the heating after casting?

With a cement screed, it is usually at least 21 – 28 days, with an anhydrite screed according to thickness and manufacturer's recommendation, often around 7 days per millimeter of thickness to the phase of first loading. The technical sheet of the specific screed used by the installer is always decisive.

What if I measure a different resistance before casting than the manufacturer states?

A deviation of up to approximately 5 – 10 % is normal and acceptable. A more significant deviation (for example, half or double the nominal resistance) indicates cable damage and it should be claimed before casting – after casting, replacement is much more complicated and expensive.

Do I have to use the exact recommended power, or can I choose a higher cable and regulate it with a thermostat?

It is a common and recommended practice to choose a cable with a slightly higher installed power than the minimum required, as the thermostat always regulates the actual operation according to the set temperature – the cable does not run continuously at full power. A higher installed power also ensures a faster rise to a comfortable temperature after heating is interrupted.

Can the cable TC 10 be used as the main (only) heating source for a room?

Yes, in well-insulated new buildings, resistive cables are commonly used as the only heating source for a room, but the power must be correctly dimensioned according to heat loss, not just area – this topic is covered in a separate article on power selection.

Conclusion

The installation of the heating cable TC 10 into the screed is a process that can be reliably completed even by oneself if the correct procedure is followed, but it requires attention to detail in each step – from good thermal insulation, through precise placement and fixing of the cable, correct placement of the floor sensor, thorough measurement before casting, to patience during the drying of the screed and gradual system start-up. Most reported faults do not result from the cable itself, but from incorrect or rushed installation procedures. If you follow this guide step by step and also use the other detailed articles from our Knowledge Center devoted to the calculation of spacing, fixing of the cable, or testing of functionality, you will get a floor heating system that will reliably serve for decades without the need for intervention in the floor structure.

Do you have a question on this topic?

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