Resistive cables for underfloor heating are simpler in design and are single-core or two-core metal (copper, brass or nichrome) conductors, enclosed in heat-resistant insulation layers and a sheath, as well as a screen. The disadvantage of resistive cables is the possibility of overheating.
Self-regulating heating cable for underfloor heating differs in that the heating element in it is not a core, but a semiconductor matrix. The resistance value on the self-regulating cable is not the same, due to which the temperature equalizes when overheating. It is believed that a self-regulating cable for underfloor heating is more reliable.
What is a self-regulating underfloor heating?
In a warm field with a self-regulating function, the cable looks like a simple insulated two-core wire, in it two parallel-placed conductors are closed in a circuit. It is equipped with busbars that help distribute the voltage along its entire length.
The design features of the floor protect it from overheating. And the presence of a conductive matrix makes it possible to cut the cable so that there are no cold zones.
In cases of overheating of the matrix, the number of conducting bonds decreases, thereby blocking the flow of electricity. When the floor cools down, the feed resumes.
A feature of a self-regulating floor - it can adjust the power supply itself, starting from the degree of heating.
Find out how to call or make your own repair of electric underfloor heating.
Types of cable for underfloor heating and their characteristics
Today the range of cable products is huge. It is divided into groups depending on the purpose, power and material from which it is made.
Resistive heating cable
This heating cable is resistively loaded and elongated. A conductor with constant resistance, it is higher than that of the power and installation wire. Heating is carried out using insulated copper or special alloy conductors. In addition, the product is equipped with a copper or foil shield with a drain core.
Screen functions:
- Reduces electromagnetic radiation, which is necessarily present in a conductor with current.
- It grounded, and in case of insulation breakdown, the electricity will be closed by the screen and go into the ground, this helps to protect a person from electric shock. In addition, circuit breakers and an RCD device are triggered.
Resistive cable products are:
- Single-core - there is only one conductive core in it. This type is one of the most inexpensive, but the installation is rather complicated, since both ends must be brought out to the same point and connected to a thermostat.
- Two-core - has two parallel conductors, enclosed in a screen. The variants of the conductors can be different, two heating or one heating type, and the second supplying. At the end, the section has a sleeve, it connects the two cores and insulates them. The advantage of this type is the ease of connection, since such a wire only needs to be placed according to the planned scheme, and there is no need to bring the other end to the thermostat. In addition, a two-wire cable produces a minimum of electromagnetic waves. Naturally, the price of cable products is much higher.
Resistive cables are manufactured in pre-fabricated sections with a fixed size and cannot be changed.The main characterizing indicator of any cable is the specific power of one meter, it should be 10 - 20 W / m, the excess is not permissible, this can disable the heating elements.
The length of the section should be selected taking into account the calculations performed. And since the cable is produced in different sizes, from 10 to 110 m, it will not be difficult to choose the right length. Sometimes the product is sold wound on spools, it is permissible to cut a wire of any length from them.
Pros of the model:
- Acceptable price.
- The invariability of the main characteristics.
- There is no inrush current, so there is no need to install special circuit breakers.
But the resistive cable also has disadvantages:
- If the installation is not done correctly, then there is a possibility of overheating, which can provoke a failure of the system.
- It is impossible to change the length of the wire without adjusting the characteristics.
- Needs to ensure the required heat transfer performance.
Resistive zone cable
In the process of development of the cable industry, a sectional type of resistive model was invented - zonal. In the center are two insulated conductors. They are wound with a high voltage wire helix. This wire, through each meter, is connected to one of the central conductors in turn. Moreover, all sites are independent.
Among the positive aspects of the zone cable are:
- the same power density along the entire length;
- starting does not require large currents;
- invariability of characteristics.
Negative aspects of this type:
- local overheating is possible;
- the need for heat transfer;
- the cost is the highest, in contrast to the usual resistive cord.
Heating mats
Heating mats are a construction consisting of a cable fixed on a special mesh with a certain pitch. The use of these mat makes the installation of underfloor heating easier, it is enough to roll them out on an even basis. It is allowed to lay them in a layer of tile adhesive. Different types of cables can be used in the mats.
Important! When fixing them in a layer of glue, the formation of air bubbles must not be allowed - this can provoke local overheating.
The main disadvantage of heating mats is the difficulty of laying them in rooms with a non-standard, geometrically complex layout.
Self-regulating cable
The most technologically advanced type of heating cables for underfloor heating is self-regulating. He is able to change the temperature based on the heating level of the room.
The presented model consists of two conductors, with a polymer matrix placed between them, which performs the function of a semiconductor. It is similar to a normal cable, but it is flattened rather than round in shape and can be of different lengths.
A decrease in temperature promotes compression of the matrix, in which heat-conducting paths with increased resistance are formed. The current, flowing, heats up the matrix and the cable. As the degree of heating increases above the required level, the polymer expands and the number of current passes decreases, as a result, there are very few of them, and the floor heating stops. At the same time, all sections work autonomously.
The semiconductor is protected by a layer of heat-resistant insulation. Then comes a shield made of copper or steel, covered with additional insulation. Each cable should be selected based on the performance characteristics.
Comparison of heater types
Both types of resistive cable include a heating conductor that is protected by a sheath. Wire or foil can be used as insulation. The only difference between these cables is that the first has one heating core, and the second has two. The main difference between wires lies in the material from which they are made.
Do not forget to calculate the cable length
As a rule, brass, nichrome and copper are used as materials.Each of these metals has different properties and has unequal electrical resistance.
When deciding which cable is better to choose, it is worth considering not only the level of its electrical resistance, but also parameters such as the total length and the recommended distance between the heating elements of the wire. This data will allow you to provide the most suitable floor heating.
The permissible distance between the heating elements is determined and indicated on the product box by the manufacturer. Self-activity in this matter, at best, can render the entire floor system unusable. As a rule, manufacturers regulate a step of no more than 12 centimeters. Heating wires are sold in a certain length, which implies correct calculations. At the stage of mounting, it will no longer be possible to add or remove any part.
Another significant parameter that requires special attention when choosing a cable is the number of heating conductors.
Can I use a self-regulating cable for underfloor heating?
The main function of a self-regulating heating cable is to reduce the supply of electricity when the required heating degree is reached, while the quality and uniformity of surface heating does not suffer. This feature allows the model to be successfully used in the construction of underfloor heating in any premises, from living rooms to bathrooms and toilets.
In addition, in the presence of underfloor heating with a self-regulating cable, you can rearrange the furniture in the apartment, since it has the ability to regulate the heating level, in contrast to the resistive one. That is, it is permissible to reduce heating under heavy furniture. It is impossible to change the heat supply for a resistive wire, thereby overheating of the surface may occur, which will lead to the exit from the standing system.
It is worth noting the simplicity of the construction of a self-regulating floor, since this electrical cord can be cut anywhere, and the end can be sealed with oneself. At the same time, all connections, if properly installed, can last for more than one year.
Naturally, like any self-regulating electric floor, you need to connect to the power supply observing all standard protection methods. That is, the system must have a circuit breaker and an RCD, the leakage current in which is not more than 30mA. The samreg cable must have a screen and a power of 30 - 40 watts. At the same time, the laying step of the heating element is 15 - 20 cm.
For your information! A huge achievement is the use of the self-regulating properties of the material in foil floors.
Previously, this function was not possible due to the small size of the film. Infrared film with 30% self-regulating ability is produced in Korea today.
Application features
However, despite the simplicity of the installation of a self-regulating underfloor heating, some features of its construction should be noted:
- Cutting must be done during the installation of the underfloor heating. In this case, the length of the self-regulating circuit can be either several centimeters or several tens of meters. For different types of cord, the maximum length is different, and ranges from 70 to 160 meters.
- When installing underfloor heating with a self-regulating cable, it should be borne in mind that there is a large difference in currents between the nominal and starting value, 2 to 4 times. This should be taken into account when choosing ballasts.
Adhering to these expert advice, you can make the correct underfloor heating design with your own hands.
Alternative heating methods
If, for some reason, the location of the cables is not possible, then the house can be equipped with electric mats. Such heating devices are very convenient for arranging underfloor heating, while they require minimal financial costs.If the cost of one meter of a self-regulating wire is in the range of 5-10 dollars, then electric mats are much cheaper, and their efficiency is not inferior to a heat cable.
You can find carbon and cable mats on the market. They differ in technical parameters, installation method, production material and operating principle. They are similar to each other only externally. Each of the mats is a long, thin track that can be easily rolled into a roll.
Cable mats
If you carefully consider how the cable mat works, you can understand that this is, in fact, a single-core cable. The only difference is that it is fixed on a special mesh like a "snake". The required distance is maintained between each turn. This kind of heater is best suited for tiled floors, since its entire thickness does not exceed 3 cm.
This heating mat is placed on the floor. The area underneath should be free of bumps and debris. This requirement is due to the fact that the mat is fixed through a special adhesive base located on the underside of the mat. The roll is unrolled starting from the temperature controller. When it is necessary to turn the mat, it is allowed to cut the reinforcing mesh, while the wire should never be touched. It can only be rotated to the required angle.
After that, the temperature controller is mounted, the wires are laid and the base is glued. Then the system is checked for operability, after which the film is glued to the floor and covered with tiles or laminate.
Carbon option
The carbon mat assumes the presence of rod heating elements, connected to each other like a rope ladder. They have special coatings that, when electric voltage passes through them, make it possible to emit infrared radiation, which is thermal energy.
Each element of this chain works independently and is not influenced by other rods. The undoubted advantage of this system is that if one of the elements is out of order, this will not affect the work of the rest. In addition, such a device, like a self-regulating cable for underfloor heating, is able to autonomously monitor the external temperature to the situation and adequately respond to it. Moreover, the cost of such devices is much cheaper, and the service life is no less.
There are many options for electrically heated flooring. Of course, in each case, the choice of the heating element takes place individually, taking into account the characteristics of the floor, its external coating, the complexity of the installation of the system and financial capabilities.
Pros and cons of self-regulating cable
When planning the installation of an underfloor heating with self-regulating properties, it should be remembered that the price of a conductor is high, much higher than the price of an ordinary wire. However, with a properly drawn up project, such a device will cost 40 percent more, not more. Despite this, the system is considered profitable, as it is more economical, and the installation costs will quickly pay off.
The main advantages of self-regulating underfloor heating:
- High reliability, unlike floors with a resistive cord. This wire does not overheat, so there is little chance of fire or failure.
- The heating circuit is not limited to a certain length, which allows it to be laid on any area, even less than a meter, this is not possible with a conventional wire.
- Simple installation, using the simplest regulators.
- The ability to use in rooms where the use of explosive devices is prohibited.
- Saving energy, as only cold areas are heated.
- Length-independent power density.
- Inaccuracies in installation do not affect the quality of the floor, and even overlaps do not lead to overheating.
It is worth saying that self-adjusting floors have disadvantages:
- high price;
- are not able to warm up the room completely, but only the surface of the floor;
- the possibility of laying only in a screed not less than 35 mm;
- periodic wear of the fuel matrix;
- the service life is only 10 years;
- the starting currents of such a cable are high, especially in the presence of large cold areas, therefore, there is a need for class C circuit breakers.
Important! It is necessary to take into account the readings of the protective blocks from the network, if the temperature around the cable is low, then the current at start will be 1.5 times higher than in working condition.
Features of heating cable installation
If you decide to lay the underfloor heating cable, there are several steps to be taken. Work should be carried out on a prepared concrete base, which is usually equipped at the stage of major repairs. Installation involves pouring a screed prepared from cement and sand, 3 cm thick. In order to lay a cold wire that will connect the thermostat to the underfloor heating system, it is necessary to make a channel with a diameter of 20 millimeters. Among other things, a socket for the thermostat is installed.
In the place where the cable is supposed to be laid, it is necessary to cover a heat-reflecting substrate, which will shorten the heating-up period of the system, and also minimize the cost of electricity.
Which cable to choose
The choice of a cable product is influenced not only by its characteristics, but also by the rating of the company that produces it. You should give preference to trusted manufacturers who produce quality products.
Among these manufacturers, the following companies can be noted:
- "Devi" (Denmark) - produces resistive heating cables Deviflex 18T, which are designed for the arrangement of a heated floor of the main or additional type. The length of the wire is 105 meters, the power is 1880 W. The company's products are reliability, quality and a guarantee up to 20 years.
- "Ceilhit" (Spain) - produces inexpensive and effective devices that can create a comfortable indoor environment. The main product of the company is a two-core shielded cable with a power of 220 - 230 W. The manufacturer's warranty for the product is 16 years.
- GK "Teplovye sistemy" (Russia) is a reliable company specializing in the production of heating cables for underfloor heating: self-regulating and resistive. The products are manufactured using modern equipment and new technologies. At the same time, the price for heating products is reasonable.
How to calculate the power and the amount of cable for heating the room
Before proceeding with the installation of a self-regulating underfloor heating, it is necessary to calculate the power and length of the circuit. We also propose to find out how much electricity the heated floor consumes per 1 m2 per hour, month.
Power calculation
It is necessary to calculate the thermal power of a self-regulating heating system taking into account the characteristics of heating. That is, the warm floor will act as the main or additional source of heat.
But as mentioned above, the self-regulating cord performs periodic stress relief to maintain the floor surface in a comfortable state. Therefore, the heat will not be enough to heat the room, and it is not advised to use a self-leveling floor as the main one.
As an auxiliary heating, it is recommended to use a cable for such a floor with a power of at least 110 - 140 W per square meter. Moreover, in order for the heating level to be at a height, it is required to make thermal insulation.
The size of the room in which the heating element will move is also of great importance. It is not recommended to place the circuit under heavy furniture and plumbing fixtures, this is an unnecessary waste of electrical energy.
Based on this, the calculation of the load looks like this - the area of the heated room is multiplied by the norm per square meter.
Determining the length of the contour
To calculate the required size of the kennel, you need to look in the passport of the cable product. It reflects the power per meter of wire. It ranges from 5W to 150W. Such a variation in the voltage of a self-regulating cable is caused by the huge scope of its use.
Let's consider the definition of the contour length using an example. When heating the electrical cord to 28 degrees, and the bottom surface of the floor covering up to 25, a wire with a power of 17 watts is required. An area of 10 m2 will require 70 meters of heating circuit.
Self-adjusting system
The self-regulating wire has the best technical parameters. Its composition and mode of operation are completely different from the principle of operation of the cables described above. This wire contains two conductive cores that are in contact with a matrix made of a special polymer material. Due to this semiconductor device, the heating is regulated. When the temperature rises, the conductivity of the semiconductor decreases, thereby reducing the heat transfer capacity. From the outside, the matrix is covered with insulating materials, between them there is a special shielding braid.
Such a cable will serve you enough not to think about repairing it.
For a more accurate understanding, it is worth describing in more detail the principle of operation of such a wire:
- When the temperature in the room drops, a polymer material shrinks in the middle of the cable. This gives a boost to the electricity passing through the cable, and as a result, heat dissipation increases.
- When the temperature in the room decreases, a reverse reaction occurs, which provokes a decrease in the current strength. As a result, the amount of heat generated is reduced.
Self-regulating floor heating cable is very popular. This is due to the many advantages of this type of device over analogues:
- the ability to independently change the strength of heating, responding to the level of room temperature;
- stable multi-layer protection against mechanical stress;
- the uniqueness of the cable design provides protection against overheating, automatically extending the life of the heating element;
- does not involve frequent repairs.
The technical parameters of the electric heater make it possible to use this kind of cable in different rooms without taking into account the peculiarities of the flooring and the areas where the furniture is located. Each of the sections of the structure works independently, independently reacting to external influences and maintaining the temperature specified by the user.
If, under the influence of pressure, which can be exerted by household appliances or furniture, the temperature reaches a maximum, then the area of the overloaded cable will turn off on its own. In this case, the rest of the contour sections will continue their work.
When the disabled area cools down, it will maintain the required temperature again. Self-regulating wires are often chosen in living spaces, they are placed under laminate, parquet or tiles.
Installation of electric underfloor heating with self-regulating wire
Installation of any underfloor heating should begin with the acquisition of the necessary material, in accordance with the calculations made.
The process of arranging a heating structure with a self-regulating cable is similar to the installation of any electric underfloor heating:
- A thermostat is installed - its location on the wall is determined, the distance from the floor is at least 30 cm, preferably not far from the switch. A recess is made in the wall, where the thermostat is mounted. A strobe is made from it to the floor, in which the corrugated hose is placed.
- The base is being prepared - it needs to be leveled and cleaned of debris. If the floor has large differences, then it is better to fill it with a thin layer of rough screed.
- Work on hydro and thermal insulation is being carried out - two layers of material are laid. First, waterproofing - it can be a polyethylene film, on top - heat-resistant thermal insulation, preferably with a metallized surface. Before their installation, the perimeter of the room is glued with a damper tape to compensate for the thermal expansion of the screed when heated.
- A self-regulating cable is laid - it is laid according to the planned scheme ("snake" or "snail"). It must be complete, it should start from the thermostat. An important point is the step of laying the heating element. The smaller it is, the faster the floor heats up. And big steps will lead to colder zones. The recommended distance from the walls is 15 cm.
The cable is fixed to the reinforcing mesh, which is laid on the thermal insulation, or using a special adhesive tape to the substrate.
- A floor temperature sensor is mounted - the electrical cord from it should be brought to the thermostat through a corrugated pipe. A thermal sensor is installed in the center of the room, between two wires.
- The finishing screed is poured - the concrete layer should be at least 6 cm. The floor is poured in one approach, and after leveling the mortar, the concrete surface is left for 4 weeks to fully harden.
Important! The screed should be poured only after checking the cable for functionality. The resistance in the wire is checked using a tester. The indicator must coincide with the passport data, a deviation of 10% is permissible.
- The heating element is connected to the thermostat - this is done using special clamps.
- The finishing coat is laid - any material (tiles, laminate) that can be adjacent to heating.
The use of a self-regulating cable in underfloor heating is beneficial and convenient. Indeed, in such a design there is no risk of overheating of the heating element, this makes it safer. And the ability to independently regulate the temperature level allows you to easily create a comfortable atmosphere in the house.
