Our long-standing experience shows that the faults we are called upon to resolve are largely caused by recurring errors. This mainly concerns heating cables and heating mats installed as electric underfloor heating. Most often, this is due to a lack of knowledge of installation regulations; however, installation companies sometimes underestimate the potential risks and regard the requirements in the instructions as unnecessarily strict.
We believe that practical demonstrations will better highlight the risks involved in installing electric heating systems and help people understand the importance of the individual requirements set out in the instructions.
Unprofessional repairs
Repairs to heating cables carried out by unqualified personnel unnecessarily lead to significantly greater damage.
Sometimes, the heating cable is accidentally damaged before it is covered with screed or sealant. Such things can simply happen during construction, and if the fault is detected in time, an experienced electrician can repair the damaged area using a repair kit. The repair kit costs just under 300 CZK including VAT, so the repair costs will not exceed 1,000 CZK. A repair carried out to a high standard has no negative impact on the quality or service life of the heating cable.
Unfortunately, we sometimes find that the person who damaged the cable has attempted to repair it themselves without the necessary expertise. This is likely due to fears of possible penalties; ultimately, however, it leads to damage that is many times worse. Once the heating cable has been covered with screed and the floor covering laid, it is no longer possible to determine exactly where the cable is damaged without special equipment. To locate the fault, our service technicians must then be called out, and what was originally a repair costing a few hundred crowns suddenly becomes a repair costing over 10,000 crowns. An unprofessional attempt at repair is, moreover, clear evidence that the person concerned was aware of the damage.
Incorrect installation
The most common mistakes when laying heating cables and mats
A frequent cause of underfloor heating failure is a failure to follow basic installation guidelines. Sometimes the installation company carries out such a clearly unprofessional installation that the client contacts us to request an assessment even before the system is embedded in the screed or sealed. More often, however, the errors are not entirely obvious and are only discovered when a fault occurs. The installation company carries out the actual laying quite carefully; however, the mistakes they make show that they lacked the necessary experience and, unfortunately, had not studied the instructions.
Heating cable connectors
A very common fault is damage to or incorrect positioning of the heating cable connector.
The heating cable connector is used to connect the resistance wire (heating element) to the supply conductor – the so-called ‘cold end’ (SK). The connection is made using crimp sleeves, which are hard and inflexible. The connector must therefore not be subjected to bending stress – there is a risk that the crimp sleeve will literally cut through the resistance wire when bent. Mechanical damage can also occur if the cable is bent immediately behind the connector – the sharper the bend, the greater the risk.
Installation companies are also often unaware that the connector heats up in exactly the same way as the heating cable for the first half of its length (the point where the resistance wire connects to the supply conductor). Correct installation should therefore be carried out in such a way that the connector – not only along its entire length, but also plus 5 cm of heating cables before and 5 cm of cable after the connector – is laid completely straight and thoroughly encased in screed or flexible sealant.
The rules for positioning connectors apply not only to underfloor heating, but to all applications using heating cables or mats (outdoor applications for protection against snow and ice, protection of pipes against freezing, etc.).
