How to lay a cable heated floor - choosing a heating cable, do-it-yourself installation

The “warm floor” heating system is popular both among city residents and owners of country houses. This is due to the fact that, thanks to the optimal vertical temperature distribution (from floor to ceiling), it helps to create comfortable conditions in the house. One of the options for a heated floor can be an electric one, with a heating cable laid in a sand concrete screed. Many users have questions about how to properly make such a system, avoid installation errors and pour a reliable and durable sand-concrete screed. In this article, with the help of a specialist from LafargeHolcim, we will tell you:

• How to choose the right “pie” of an electric heated floor with a heating cable.
• What should be the thickness of the sand concrete screed when using a heating cable.
• How to choose high-quality sand concrete and cement.
• How to make your own mortar from sand and cement.
• Why is fiber added to sand concrete?
• The main stages of work on pouring sand concrete onto a heated floor screed with a heating cable.

Resistive cables

Such heating elements are produced in single- and double-core versions. They are connected to the network using special couplings. The principle of operation of these cables, regardless of the number of cores, is similar: heat begins to be released when current passes through them.

However, there is a difference - this is the connection method. In single-core elements, the current passes through one conductor and in order to make the circuit closed, both ends of the coil must be connected to the power supply.

The installation process is as follows:

1. The adapter coupling is attached at the connection point (this is prohibited from doing near the thermostat).
2. The cable is unwound and laid so that its other end, located near the coupling, is placed in the installation box.

When both couplings are connected, a closed loop is obtained and the wiring is completely ready for use. In this case, the couplings are on the floor and are filled with screed.

Connecting a resistive two-core cable is simpler, since one end is connected and a plug is placed on the other. To make the circuit closed, there is a second current-carrying core.

The design of both types of cables has much in common: one or two insulated cores, to give greater rigidity, a metal protective braiding against damage, and on top everything is covered with an outer insulating layer. In some products, the cores may be drainage, which serve to reduce the efficiency of electromagnetic radiation.

The price of two-core products is higher, but it is still in great demand for two reasons:

• It is easier to lay the cable, since the second end is not connected to the thermostat;
• electromagnetic fields of lower intensity are formed.

But both types of resistive conductors have a big drawback, which is the constant amount of thermal energy released. If heat is not removed for any reason, overheating occurs. This ends with a breakdown of the floor heating system.

Therefore, the resistive cable is not laid under furniture and make sure that there are no voids in the screed. The fact is that air has low thermal conductivity and in the area where the bubble appears, heat begins to be removed at a low speed, and this leads to an increase in the temperature of the cores, which fail.

Pros and cons of a self-regulating cable

When planning the installation of a heated floor with self-regulating properties, you should remember that the price of the conductor is high, significantly higher than the price of a conventional wire. However, with a correctly designed project, such a device will cost 40 percent more, no more. Despite this, the system is considered profitable, since it is more economical, and installation costs will quickly pay off.

The main advantages of self-regulating heated floors:

1. High reliability, unlike floors with resistive cords. This wire does not overheat, so the likelihood of fire or failure is low.
2. 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 conventional wire.
3. Simple installation, using simple regulators.
4. Can be used in areas where the use of explosive devices is prohibited.
5. Energy savings, as only cold areas are heated.
6. Independence of specific power from length.
7. Inaccuracies during installation do not affect the quality of the floor, and even overlaps do not lead to overheating.

It is worth saying that self-regulating floors also have disadvantages:

• high price;
• are not able to warm up the room completely, but only the floor surface;
• the possibility of laying only in a screed of at least 35 mm;
• periodic wear of the fuel matrix;
• service life is only 10 years;
• the starting currents of such a cable are high, especially in the presence of large cold sections, so 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 operating condition.

Self-regulating cables

Thanks to their special structure, heating wires of this type do not overheat. A self-regulating cable for underfloor heating consists of small segments connected in series. Each of them has two conductive cores, between which there is a polymer that generates heat.

Self-regulation of this type of electric floor is based on the properties of the polymer, whose electrical resistance largely depends on the temperature regime. The higher it is, the greater the resistance.

For this reason, as the polymer heats up and the degree of resistance increases, the current flowing through the element decreases, which means the amount of thermal energy released decreases. This is how the heat transfer of each segment is regulated. In this case, the temperature of neighboring elements does not depend on each other. The cost of such wiring under heated floors is much more expensive than resistive cables.

Prevention

Complication of mycotic eczema

Mycotic eczema is a chronic disease and tends to recur regularly. How long the remission will last depends on the patient himself, on how well he follows preventive measures. Eczema can be complicated by a long course and rashes all over the body, and wounds on the skin often become infected, suppuration appears, and in advanced cases, sepsis develops.

Prevention of relapses of mycotic eczema lies in the correct lifestyle. The patient needs to eat a balanced diet, excluding the consumption of allergenic foods, exercise regularly, harden and strengthen the body’s immunity in every possible way.

It is also very important to monitor the condition of the skin, immediately treat wounds and treat any rashes on the integument. Avoid exposure to household chemicals; all manipulations must be carried out with gloves.

It is necessary to maintain personal hygiene, regularly wash your hands and the whole body.

Nuances of arranging cable floor heating

If any heating wire is damaged, the system loses its functionality. For this reason, heated floors constructed using cables are laid in a screed. At the same time, its thickness is selected so that the high load from the cement layer does not damage the wiring located under it.

In addition, a screed that is too thick in this case will greatly reduce the efficiency of the heating system, making it inertial. A thicker layer can cause a lot of trouble, since the floor will not heat up even when the power is set to maximum.

In the electrical cable laying diagram for heated floors, it is always necessary to provide for the placement of a thermostat and a floor surface temperature sensor. You can do without these devices by directly connecting the cables to the power source. But then the heat supply system will not work for long.

This is especially true for resistive cables. Therefore, when installing a wired underfloor heating system, you first need to install a thermostat.

First of all, it is necessary to measure the resistance and insulation of the wire. Since each bay is accompanied by a passport, which indicates the technical characteristics of the cable for heated floors, it is necessary to compare the indicators obtained during the measurements with the data in the document. If the deviations do not exceed 10%, then installation work can continue.

Common Mistakes

How to install electric floors correctly with your own hands - this question often arises for beginners who want to do this heating at home.

The main mistake is installing floors under large furniture. Underneath, the surface is not cooled, which leads to overheating and then failure of the system.

You cannot bend the cable either, as this will disrupt the functioning of the device. When laying cable mats, cutting the wire is unacceptable, so you should correctly calculate the size of the heated area.

A common mistake when constructing electric floors is inappropriate control of the insulation resistance during installation. The indicator should not exceed that specified by the manufacturer by more than 10%.

When using a film heated floor, it may stop heating if the film is damaged. Its current-carrying parts must be properly insulated, otherwise electric current will leak and the system will eventually shut down.

If we talk about the temperature sensor, then you should not pour it into the screed. In case of breakdown, replacement will be difficult. It is placed in a corrugated pipe.

Installation of thermostats

First of all, you should determine the location of the thermostat. It must be mounted on one of the walls of the room at a distance of at least 30 centimeters from the floor surface. Typically, thermostats are located close to switches. A recess is made in the wall the size of a standard socket box.

After installing the installation box, the power supply is supplied without connection - zero, phase and ground. Then lay the groove in the direction from the thermostat to the floor. Several sections of pipe or corrugated hose are placed in it. 1 – 2 segments are taken out of the wall near the floor surface and connecting wires from the cables are placed in them.

The section of pipe located between them must be laid along the floor to a mark located 50–100 centimeters from the wall. Now, if the sensor breaks down, it can be replaced without any problems; to do this, remove the thermostat panel and remove the damaged element by the wires from the pipe. Then the new product is inserted and connected.

Installation of heated cable floors

When installing cable floor heating, proceed as follows. First, the base is cleaned and leveled. If necessary, a screed with a thickness of 3–7 centimeters is poured for this purpose. A level base is important.

If this requirement is neglected, then heating will not be uniform. When an air bubble appears under the resistive cable due to unevenness of the base, it will soon burn out.

On a prepared, clean base, in order to reduce heat loss, install thermal insulation, consisting of two parts: a tape laid around the perimeter of the room, and insulation. When choosing an insulating material, pay attention to its heat resistance - it should easily withstand temperatures up to 100 degrees.

If there is a cold basement below the room, a thicker layer should be created, and if there is another apartment, then 2 centimeters will be enough. If the heat insulator is not used, a third of the system’s power will go down.

When choosing insulation when laying a cable in a heated floor screed, it is better to give preference to a material that has a metallized surface. As a result, the heat going down will begin to be reflected and heat not the ceiling between the floors, but the screed located above the wiring.

You can save money by purchasing regular insulation and laying a film with a reflective effect on top of it. At the same time, experts do not recommend using foil, since it will collapse in a few months. You can buy heat insulation in both rolls and slabs.

It is unacceptable to leave gaps between the sheets and strips of insulation: they are laid closely, since any gap creates a cold bridge through which heat leaks out.

Depending on the base, the following can be used to attach heat-insulating materials: double-sided tape, staples plus a construction stapler, and adhesive. For joining points, tape is used - it can be mounting tape, but the best choice would be metallized tape.

When there is often high humidity in the room, waterproofing is placed on top of the thermal insulation layer. To do this, use polyethylene film or other modern material.

Then you can proceed in one of two ways. In the first case, a small height preliminary screed is laid from a mixture of sand, cement and water. Thanks to its presence, heat is distributed more evenly and overheating of the floor heating cable is prevented.

The second method involves installing a mesh with cells of 10–15 millimeters or a special mounting tape on top of a polyethylene film. The tape must be placed with a laying step of 40–50 centimeters. The grids are mounted close to one another.

Thermal insulation

To prevent heat loss through the ceilings, thermal insulation is used. When choosing it, take into account the heat-shielding properties, on which the overall thickness of the screed depends. On the ground floor, slabs 5 cm thick are used as thermal insulation; if there is an apartment below with heating, insulating layers no more than 2-3 cm can be used.

The heat insulator is taken with a metallized coating. Aluminum foil does not withstand prolonged contact with the screed and is destroyed. It is necessary to use metallized coatings in the form of spraying with lavsan, etc.

The slabs are laid without gaps. The resulting cracks are filled with polyurethane foam, all joints are sealed with adhesive tape.

Perform power calculations for heating cables

When calculating thermal power for a cable system, the purpose of this heat supply method is taken into account. If the heating cable for a heated floor is planned to be used to provide auxiliary heating for a property, then 110-140 W will be required for each “square” of area. When the system is the main one, in this case 150 W or more is needed.

In addition, you should know the size of the area where the cable will be laid out. It should not pass under furniture, plumbing fixtures or objects located low above the floor surface. This is especially true for resistive cables, which are at risk of overheating, but for self-regulating wires there is no danger.

By subtracting the area of ​​these zones, you can find out the actual heat supply area and the power of the entire underfloor heating system, for which the heating area is multiplied by the norm for one square meter.

Next, you should calculate the length of the floor heating cable: in the passport for this product, manufacturers indicate the power of one meter. The required footage is determined by dividing the total power by the cable capacity. For example, the result of calculations was 93 meters.

You need to purchase several bays, the total length of which is close to the calculated value. It should be remembered: if there are extra meters of cable left, they cannot be cut off, since there are couplings at their ends, secured using special equipment.

You can make something similar yourself, but the service life instead of 10 - 20 years will be several years, and sometimes months. Therefore, the cable is laid along its entire length.

Laying heating cables

The power ends must be led to the wall to the thermostatic device. In this case, the couplings must be in the screed. Lay the floor heating cable according to the diagram in the shape of a “snail” or “snake”. The first method is more difficult to implement and has no advantages, so the second installation option is almost always used. Sometimes a double or triple “snake” is laid.

The size of the installation step is selected taking into account the required power: the closer the wires are located, the greater it will be. The maximum distance between adjacent conductors is 30 centimeters, and the minimum is 5 centimeters. A more precise step is determined based on the purpose of the room: in bedrooms and children's rooms it is usually larger, and in common rooms it is smaller.

In addition, if desired, the distance is reduced in areas near window and door openings, as well as in the center of the room. The main thing you should pay attention to when developing a wire layout is that they cannot intersect or touch, and the gap between the walls and cables must be at least 15 centimeters.

After completing the installation of the heating elements, you need to install a floor temperature sensor, the wires from which are connected to the thermostat via a corrugated hose. It is advisable to place it centrally between two wires. If the screed height is sufficient, the tube with the sensor can be placed on top and fixed. When the thickness is not enough, the subfloor has to be tapped.

Temperature sensor installation

Lay and secure a corrugated pipe in the groove from the box to the heating mat section. Select the diameter according to the size of the sensor.

The bending radius of the tube near the wall must be at least 5cm.

Pass the temperature sensor itself with wires through it. In this case, certain distances must be maintained:

• there must be at least 0.5-1 meter between the sensor and the wall

• the sensor itself should be located exactly in the middle between the turns of the heating elements

The pitch between the turns in the mats is maintained within strictly specified parameters (most often 7.5-8 cm). Due to this spread, the so-called “thermal zebra” under the tile is compensated.

That is, the heat is completely and evenly distributed over the surface of the tile, and with your bare feet you will never feel temperature dips between the cable lines and the empty space where there is none.

The cores from the temperature sensor are also stripped and crimped with tips. For the convenience of their further connection, mark them - DT.

To prevent the mortar from going into the corrugated tube, a plug is installed at its end. If it is not included in the kit, you can get by with electrical tape.

Sometimes a special brass tip is included. Many people have no idea what it is for. And it is precisely intended for installing the sensor head inside it.

After completing all the above work, be sure to measure the resistance again. What if you broke or shorted something during the installation process?

Final pouring of the screed

Before final pouring of the solution, you need to make sure that the cables are working properly. To do this, take a tester and measure the resistance. This parameter must match the data in the passport. Permissible deviation is maximum 10%.

When everything is in order with the heating elements, you can start pouring the screed. If thermal insulation was not installed, and the installation was carried out directly on the subfloor, then the height of the solution can be 3 centimeters.

If there is insulation, the concrete layer must be at least 6 centimeters. Only with such a thickness of the screed is it possible to ensure the required rigidity of the floor covering. The height can be made smaller provided that hard finishing materials are laid - parquet boards, laminate, etc.

After leveling the concrete layer, it is left for at least 4 weeks. Only then do they begin to connect the cables to the thermostat. It has clamps to which the heating conductors are first connected, and then the power wires. The electric heated floor is ready and all that remains is to install the floor covering.

To lay a cable for a heated floor with your own hands, you need to have the appropriate knowledge and skills, otherwise the best solution would be to contact specialists who provide this type of service.

Peculiarities

Electric underfloor heating is a modern type of residential heating system.
This design consists of heating mats and special regulators laid under the floor or between layers of concrete screed. The advantages of the scheme include:

• uniform heat distribution along the height of the building;
• absence of circulation disturbances in the form of convection currents - movement of heat in the air;
• simplicity and clarity of self-installation of the system;
• cost-effectiveness of professional installation;
• saving useful area of ​​heated space;

• no need for additional equipment;
• Possibility of installation under any floor covering;
• increased comfort and convenience;
• environmental friendliness;
• Possibility of use by people suffering from various types of allergies and bronchial asthma.

The disadvantages of electric heating are:

• high cost of 1 kW of electricity;
• creation of an electromagnetic field within a heated room;
• mandatory skills in handling temperature regulators;
• difficulty in diagnosing and repairing the system;
• existence of height restrictions for heated buildings;
• the need to improve electrical safety through grounding.

However, with rational design and proper installation, all these shortcomings are eliminated by themselves, which is why this system is becoming increasingly popular among consumers.

Cable underfloor heating and flooring

Warm electric floors may not be used with all types of floor coverings. When resistive cables are installed, the finish can be made from any tile, wood plank, laminate or linoleum. As for the last two types of flooring, they should not have a heat-insulating layer.

When purchasing laminate or linoleum, it is advisable to pay attention to the presence of such characteristics of the materials as suitability for heated floors. When the heating system is installed using a resistive cord for underfloor heating, the floor surface should not be covered with carpets or heating elements should not be placed under furniture.

But a self-regulating cable can be installed anywhere. If you are going to use glue, grout and adhesive composition, you need to purchase special ones. They are intended specifically for floor heating systems, since they have greater elasticity and better thermal conductivity.

Other options for arranging a warm electric floor

It will take a lot of time to make a warm electric floor; this work cannot be done in a short time. Most of the time is spent ensuring that the screed solution completely hardens. The mixture must be laid in a layer at least 6–7 centimeters thick.

A linear meter of cable is inexpensive, but to the costs of installing a heated floor, you should add the costs of installing a screed, thermal insulation, purchasing fastening tape and other materials.

Taking into account the above information, before making a final decision, it would not hurt to familiarize yourself with other options for arranging a warm electric floor, for example, using film and rod heaters. They emit heat in the infrared range, which is well perceived by the human body, which is their huge advantage.

When heating with infrared heated floors, the temperature seems comfortable, although it is several degrees lower than with thermal radiation. As a result, energy costs are reduced. Among the advantages of the infrared rod floor is its ability to self-regulate.