How to ensure high-quality hardening of concrete in winter: PNSV, VET and KDBS cables

Pouring concrete in winter has its own difficulties. The main problem is the normal hardening of the solution, the water in which can freeze and it will not gain technological strength. Even if this does not happen, the low drying rate of the composition will make the work unprofitable. Warming up the concrete with a PNSV wire will help resolve this issue.

Electric heating of concrete in winter is the most convenient and cheapest way to achieve the desired hardness of the material. It is permitted by the standards of SP 70.13330.2012, and can be used when performing any construction work. After the concrete hardens, the wire remains inside the structure, so the use of cheap PNSV provides an additional economic effect.

Warm-up technology

The locations of communications and the location of holes in the concrete surface must be thought out before starting to pour the composition. After installing the system and covering it with a cement mixture, any work on the surface may damage the wires. For example, before diamond drilling into a material, you need to make sure that the hole will not pass through the concrete heating cable.

Rules for laying the system

Before placing the heating system, reinforcement and formwork are installed. Then the PNSV layout is carried out; there should be an interval of 8-20 cm between the turns of wires. The size of the gap depends on the wind, outside temperature and humidity.

The cable is attached with clamps to the fittings, without tension. The optimal radius of bends is more than 25 cm. The current-carrying conductors should not intersect, the distance between them is 1.5 cm, this arrangement avoids short circuits.

The following points must be checked before pouring the solution:

• the temperature of the prepared mixture is above +5 °C;
• there is no ice in the formwork;
• the circuit is connected correctly;
• cold ends have an optimal length.

The PNSV cable comes with instructions, which are important to follow when installing the heating system. There are two options for connecting via busbars - star and delta.

In the first method, three cables of the same type are combined into a node, then the free three contacts are connected to a transformer. The power supply is located at a distance of up to 25 m from the connection point. The area of ​​material that will be heated is protected by a fence.

The system is connected only after the solution has been poured. The use of a heating cable for concrete PNSV includes the following steps:

1. Warming up is underway; the temperature should increase by 10 °C per hour. High speed will disrupt the uniform heating of the material.
2. Heating is carried out at a constant temperature value. Concrete needs to gain half of its technological strength. The optimal temperature is 60 °C, the maximum possible is 80 °C.
3. The material cools slowly. Its cooling rate should not exceed 5 °C per hour, otherwise cracking of the structure will occur.

If all work was carried out correctly, the concrete will reach the appropriate strength grade. After heating, the cable remains in the material and plays the role of an auxiliary reinforcing structure.

VET and KDBS cables can be connected through a socket or panel board to a 220 V network; they are also divided into sections, which prevents overloads. But their cost is significantly higher than PNSV wires.

Concrete can also be heated using a tubular electric heater (TEH) and electrodes. The fittings are inserted into the solution and connected to a power source - a welding machine or other step-down transformer. This option does not require a heating cable, but will require significant energy expenditure. Water acts as a conductor in concrete, and as the material hardens, the resistance will increase.

Calculation of the length of the PNSV

Several factors influence the determination of the length of the PNSV cable. The amount of heat that will be applied to the material for hardening is of great importance. This indicator is affected by thermal insulation, air temperature, shape and size of the structure, and humidity.

The length of the loop should be on average 28−36 m. If the temperature is above -5 °C, then laying is done in increments of 20 cm. When cooling, every 5 degrees the gap between the cores is reduced by 4 cm. At around -15 °C it will be equals 12 cm.

The power consumption of the PNSV cable is also important; it depends on the diameter:

• 1.2 mm - 0.015 Ohm/m;
• 2 mm - 0.044 Ohm/m;
• 3 mm - 0.02 Ohm/m.

To do this, the squared current is multiplied by the resistivity. The total power is found from the product of the obtained value and the total length of the wire. The transformer voltage is calculated in a similar way. The current is multiplied by the resistance to get the operating voltage.

PNSV wire is the cheapest option for heating concrete mix. But its use requires special equipment and relevant knowledge. Thermal insulation also reduces the cost of heating the material and improves the quality of concrete due to uniform cooling.

https://youtube.com/watch?v=Mi9bK_pcfcI

Application of heating elements

Negative temperatures crystallize water in concrete, and hydration of the material stops.
When frozen, the liquid expands and breaks the bonds formed in the cement. Even if the temperature rises, the material will no longer reach the required strength. At a temperature of 20 °C, optimal and uniform hardening of the composition occurs, and its important characteristics are preserved. To maintain the required technical conditions in winter, PNSV concrete heating cable and its analogues are used. It can be useful in the following situations:

• thermal insulation of the formwork and monolith is not fully ensured;
• the monolith has large dimensions and cannot warm up evenly;
• work is carried out at negative temperatures, and water freezes in the solution.

PNSV wire

A universal and affordable way to warm up concrete in winter using a high-resistance cable and a step-down transformer. When linking the frame from the reinforcement, a heating cable is laid; the size and shape of the structure does not matter.

This heating method is applicable both at the construction site and for home builders. Let's tell you in a little more detail how to heat a concrete mixture with a PNSV wire at home.

After reinforcing the frame of the structure or laying the beacons under the self-leveling floor, the wire is laid in a snake no closer than 20 centimeters from each other (the optimal laying step). The length of one loop ranges from 28-36 meters. A welding machine can be used as a voltage source. The connection diagram in this case will look like this:

The nuance of warming up is that the PNSV cannot be connected without being covered with a solution, because Without heat absorption due to the high temperature outdoors, it will burn out. To avoid burnout, switch to an aluminum cable, leaving the output ends of the PNSV heating wire 10 cm out of solution. The manufacturer recommends a current in the cable of 11-17 amperes, which can be controlled with current clamps. We talked about how to use current clamps in a separate article.

For home construction, a PNSV with a diameter of 1.2 mm is sufficient. Its characteristics:

• resistance 0.15 Ohm/m;
• operating current immersed in solution 14-16 amperes;
• laying temperature from -25 to 50 °C.

Wire consumption per cube of concrete is 60 linear meters. The temperature to which concrete is heated is 80 °C, it is controlled by any thermometer. The rate of temperature rise of the solution should not exceed 10 degrees per hour. To avoid pointless expenses on electricity bills, the heated area is covered with any material that prevents the heating of the atmosphere, for example, covered with sawdust. To obtain an excellent result, the concrete mixture is also heated before pouring; the temperature of the mixture should not be lower than +5 °C. Following these instructions, you can warm up concrete in winter with your own hands. The technology is labor-intensive, but even an inexperienced person can do it. How to lay a heating cable in the foundation is described in the video tutorial:

Heating the foundation with wire

By the way, instead of the PNSV wire, you can also use the BET cable to heat the concrete. The video below briefly describes the instructions for installing the heating conductor:

How heating with BET cable works

The article does not indicate all methods of heating concrete in winter. There are induction, infrared and other methods, but we do not consider them due to their low prevalence and complexity. We gave a general idea of ​​the technology for constructing concrete structures, and the possibility of home craftsmen using methods for heating screeds and walls. By the way, the use of PNSV wire is possible not only during the heating of the structure under construction, but also after that. It can be used as a ready-made warm floor or anti-ice on stairs or sidewalks. Short sections are connected through a step-down transformer from 400 to 1500 watts. To connect directly to a 220 volt network, the length of the wire will be more than 120 meters.

That's all I wanted to tell you about why concrete is needed to be heated in winter and how to do it using heat guns, electrodes or PNSV wire. We hope our instructions were clear to you. You can get more information by watching the video tutorials in the article.

We also recommend reading:

• Heating of tracks with a heating cable
• How to save energy at home
• How to choose a heat gun by power
• Temporary power supply for construction site

Types and features of KDBS and VET cables

If you plan to electrically heat concrete in winter using a PNSV or PNSP wire, it is necessary to include additional control equipment in the system, with the help of which you can change the power in the network to regulate heat release. To simplify the system by excluding additional equipment from it, you can use two-core thermal cables that regulate heat transfer independently: Finnish VET or Russian KDBS.

Cables of this type are connected directly to a 220 volt network; installation of additional devices for adjustment is not required.

The design of the cables from both manufacturers is the same, but some of their technical characteristics are different:

1. Linear power, W/m (VET – 35-45, KDBS – 40).
2. Recommended bending radius, mm (BET – 25, KDBS – 35).
3. Nominal diameter, mm (BET – 6, KDBS – 7).
4. Section sizes, m (BET – 3.3-85, KDBS – 10-150).

Technical data

Structure

PNSV cable element diagram

The heating wire for concrete has a simple structure:

1. A steel core consisting of a single wire, capable of conducting electric current and having a round shape. Its diameter can be from 1.2 mm to 3 mm.
2. An insulation layer usually made of polyvinyl chloride or polyethylene.

Performance characteristics

Has high resistance to temperature changes. It does not lose its qualities and is able to work properly in the range from -60 degrees Celsius to +50, which in the case of our climate means always.

Low temperature makes the core shell less elastic and prone to fracture

• Polyethylene or PVC coating provides high water-repellent properties and can withstand exposure to a twenty percent salt solution and thirty percent alkali.
• When laying the cable, you will probably have to roll and bend it. If you overdo this, the metal wire may break off inside the insulating sheath. To prevent this from happening, the bending radius should not be less than twenty-five millimeters.

An example of the correct installation of a heating wire with your own hands

The instructions also require maintaining a minimum distance between wire elements of at least fifteen millimeters. Overheating can lead to damage to the insulating coating, followed by a short circuit. Sufficient indentation will save you from worrying about this.

Maintain the required gap between the heating elements even with such a chaotic arrangement

• During operation, the cable must operate in intermittent or long-term mode.
• The connection to the power supply must be made with “cold” ends and the soldering points must be taken outside the heating area.

Electrical indicators

1. The resistance of the product in question depends on the thickness of its section, decreasing as it increases:

• 1.2 mm – 0.15 Ohm;
• 1.4 mm – 0.1 Ohm;
• 2 mm – 0.025 Ohm;
• 3 mm – 0.005 Ohm.

1. The supplied AC voltage is allowed up to 380 V.
2. The power supply in this case is considered most suitable around 65 V.
3. The amount of heat generated depends on the presence of reinforcement in the structure:

• Reinforced concrete mass - 30-35 watts per linear meter.
• Ordinary concrete without metal inserts - 35-40 watts per linear meter.

1. The required heating cycle is usually three days.

Principles of use

The technological map of this process should take into account the following nuances:

• The cable cores are made of steel, which has a high resistivity, which means it gives off more heat. In air at such temperatures, the insulation melts, so direct connection of the heating cable to the network is carried out using a conductor with lower resistivity.
• The minimum distance between wires is 15 mm. Otherwise, all the insulation will melt.
• The cable is laid like a snake. The minimum radius of curvature is 25 mm.
• The minimum air temperature at which work can be carried out: -15 degrees Celsius, since the insulation of most wires is made of plastic, which loses its flexibility. As a result, it may crack.
• To ensure uniform heating, the wires are covered with foil.
• Warming up is carried out in stages.

Warming up concrete with PNSV wire

Professional construction is a process that does not stop in any weather: neither in rain, nor in snow, nor in severe frost. One of the main components of any construction process is concrete, for accelerated hardening of which various technologies, methods and devices are used. The most common technical means for accelerating the process in this way are: heating the concrete solution and structures made from it using special thermoelectric construction mats (TEMS) and wires for heating the concrete.

Characteristics and features of the wire

To heat concrete, in most cases, a wire marked PNSV is used, which stands for: “heating wire, steel core, vinyl sheath.” In some cases, PTPG 2x1.2 is used. The PNSV cable for electrical heating of concrete consists of a steel core, in some cases additionally galvanized, with a diameter that can vary from 1.2 to 3 mm. On top it is covered with an insulating shell made of polyvinyl chloride or its subtypes. This type of insulation allows you to avoid fractures and kinks of the internal veins, and also protects against fires. A cable for heating concrete, depending on the core diameter and electrical resistance, can withstand a load of 80-160 watts per meter. PNSV type wire is optimally used for heating monolithic concrete, for example, when pouring foundations or walls.

Another distinctive feature of the heating cable is the presence of so-called cold ends. These are special branches that extend beyond the concrete surface. For them, APV wires are used, connecting the heating cable PNSV and the supply line from the heating transformer.

Heating wires are fixed to the reinforcement frame and supplied with current through step-down transformers, consisting of several stages, which allows you to change the level of surface heating depending on the ambient temperature. The most common heating substations are SPB-80 or KTPTO-80/86, each of which can heat about 20-30 m3 of concrete solution. The stations are connected to a three-phase network with an operating voltage of 380V, with mandatory grounding of the housing and the neutral (zero-phase) wire.

New warm-up method

More recently, it has become possible to heat concrete using a cable without a transformer. This became possible using BET thermal cable technology, capable of withstanding up to 40 W per linear meter and operating from a network with a voltage of 220V. A nichrome shielded thread is used as a heating element, ensuring a constant temperature of +80 °C and uniform heating of the solution. This cable is suitable for any type of foundation, be it a strip grillage or a monolithic one.

Wire prices

To expand the temperature range of cable use from -60 to +50 °C, as well as to increase the strength characteristics of the insulating layer, primary raw materials (primary) are used. The prices at which you can buy PNSV wire today for heating concrete made from such raw materials are presented in the table below:

How to heat concrete?

To warm up concrete, a certain sequence must be followed:

1. During the first two hours, the heating rate of the concrete composition should not exceed 10 °C per hour;

2. In the future, it is necessary to ensure that the temperature does not exceed +80 °C.

3. The last stage is cooling, and the temperature should not drop by more than 5 degrees per hour.

In the event that a separate heating station is used, a “star” connection diagram is suitable, designed for heating small areas. Installation must be carried out according to the technological map of the facility.

Installation of a wire that heats the concrete solution

There are different layouts for laying heating cables. But they all have the same things in common:

Installation of a heating cable when pouring a concrete slab

• They are connected to the voltage source through "cold ends". The core must have a minimum resistivity value.
• To improve the quality of heating the solution, the cable is wrapped in foil. Thanks to this, heat transfer increases and the concrete hardening period is reduced. This option is well suited for small volumes and areas.
• The minimum distance between adjacent “lines” of wires in the heating circuit should be 1.5 cm. Overlaps are not allowed. If these rules are not followed, then the cable sheath will melt.
• The temperature regime at which it is necessary to install the heating system for concrete mortar should not be less than -15°C.

At very low temperatures, the insulation may crack or break, causing a short circuit.

Related video: Cable for heating concrete without a transformer

Laying scheme

The main requirement is uniform heating; there should be no cold zones. The minimum distance between adjacent wires for heating concrete is 15 mm, the maximum is selected taking into account the characteristics and external conditions. The optimal horizontal gap is considered to be 20-40 cm, vertically - 8-10, it is not recommended to exceed it. The entire volume of the mixture and the main dimensions of the structures are taken into account.

The simplest design is a “snake” with a bending radius of at least 5 working diameters for PNSV and 10 for PTPG. It is placed along the reinforcement without tension (ideally with fixation with plastic clamps), overlaps and exits to the surface (the recommended distance to the edges is from 20 mm), the integrity of the insulation is monitored. Direct contacts of bare areas with mesh or metal rods cause a short circuit; in particularly dangerous places, laying with pieces of bitumen-impregnated paper or roofing felt is provided.

An unregulated wire is connected to a step-down transformer, special attention is paid to the cold ends, the current supply conductors must have a lower resistivity value than the heating ones, aluminum meets this requirement. When choosing a "triangle" circuit, the wires are divided into three equal groups, connected in parallel and combined into three output points

When distributing the load with a “star”, three segments of equal length at one end will be connected into one node, the rest - to the power station. All contacts are reliably insulated; for these purposes, double-sided electrical tape or heat-shrinkable tubes are used. The power of the transformer for heating is determined by the calculation; on average, 1 kW is required for 0.4-1 m3 of concrete.

Laying KDBS follows the same principle, but in slightly larger increments (consumption is 4 lm per 1 m2 along a screed or horizontal plane) and with direct connection to an outlet. It is completely immersed in concrete, only the supply terminal remains outside. Despite the higher cost of the cable and the increase in power consumption to 1.5 kW per 1 m3, this type provides the most uniform heating and stable performance characteristics. Once dry, it is simply cut off and left in the concrete. KDBS is selected for critical areas, when carrying out urgent repairs, with a large number of individual monolithic elements, or the need to use a vibrator. It is easier to install it for people without experience; the factory parameters exclude overheating or burnout.

Basic rules of heating technology:

• The minimum temperature of the poured composition is +5 °C.
• Power is supplied exclusively to wires buried in concrete, ideally through a voltage stabilizer.
• Due to cracking of the insulation, installation is not recommended at temperatures below -15 °C.
• The process is carried out with power control: smooth heating for the first 2 hours, maintaining within 50-60 °C for at least 3-4 days, gradual cooling.

Heating cable price review

Single- and double-core cables are sold in coils:

Prices for self-regulating cable in sections, respectively, are:

Concrete heating technology

System installation

The work is performed in the following order:

• First of all, you need to clean the surface of debris and various sharp parts that can damage the wire.
• Then the reinforcement or reinforcing mesh is laid, and the reinforcement is welded.
• Then the wire is installed. The easiest way is to lay it with a snake. Its value will depend on the area of ​​the fill and the length of the cable. At the same time, do not forget that laying wires on top of each other is strictly prohibited; in addition, you must ensure that the cable does not come into contact with the formwork and does not protrude beyond the surface of the concrete.

Wire installation

The optimal distance between cables is considered to be no more than 15 centimeters, especially if there is a long wire and the filling area is small.

Next, you need to check the system for functionality - connect it to electricity and make sure that the cable heats up. It is imperative to control the current power.

Do not exceed the indicators indicated by the manufacturer on the wire. If the system will be operated without a transformer that allows you to reduce the current, then PTPZh brand wire should be used, since it is more powerful.

• After this, you need to disconnect the cable and let it cool.
• The final stage is pouring the area with concrete.

Cable installation diagram

As we can see, installing a concrete heating system with wire is in many ways similar to installing a heated floor. Moreover, this cable can be used for these purposes as well. The only thing is that in this case it is more expedient to make a heating element from wire threads and wrap it with insulating material.

If a separate power station is used, then it is better to use a “star” connection diagram. It is more efficient than the “snake” and is well suited for heating small areas.

Star scheme

Procedure for heating concrete

Instructions for heating concrete with a cable are as follows:

• After the area is completely filled with concrete, the heating system starts. In this case, the rate of temperature increase should be no more than ten degrees Celsius in two hours.
• Next, the main warm-up period begins. At this stage, you need to ensure that the temperature does not reach 80 degrees Celsius.
• The final stage is cooling. The rate of temperature decrease should be no more than five degrees per hour.

This completes the concrete heating process. If the instructions are strictly followed, the material will be able to achieve the required level of strength even in conditions of very low temperatures.

Wire Requirements

The PNSV heating cable must comply with the parameters that have a direct impact on the functional qualities:

• Bandwidth. For houses and apartments, a current of 16 A is sufficient; if installation on an industrial scale is necessary, the figure must be increased.
• Section diameter. Its resistance to heat depends on the thickness of the cable; a wire that is too thin for heating concrete will burn out when the temperature increases to a certain limit. The recommended value for private use is 1.2 mm.
• Cold ends. This is the name given to the taps from the main core, which are located outside and connected to the power source. They are usually made of aluminum, the cross-sectional diameter of which is larger than the heating cable for pouring concrete in winter. The ideal option is the APV-4 wire.

Don't forget about the required wire length. Taking into account the thickness of the section, the heating cable for heating concrete should be calculated based on the average value of 55 m of heater per 1 m3 of solution.

Pros and cons of PNSV

Electric heating of concrete with PNSV wire is the most cost-effective option. This is due to the low cost of the wire itself, as well as the relatively low consumption of electrical power. In addition, this type of cable is resistant to alkaline and acidic environments, making it suitable for use in a variety of harsh environmental conditions.

The concrete heating cable PNSV also has significant disadvantages:

1. The complexity of design work due to the need to accurately calculate the cable length.
2. The need to include a step-down substation in the system.

The cost of such substations (SS) is quite high. Their functioning is required constantly, so it is not advisable to rent equipment, because for this you will need to pay at least 10% of the total cost. In some cases, it is possible to use welding machines. However, they are only suitable for small construction projects, as they quickly break down during intensive work.

Using PNSV wire after hardening

Heating cable sections laid in a concrete structure remain in it forever and do not lose their resistive properties. Therefore, it makes sense to use them to improve the comfort of your stay. Often, the PNSV wire is specially laid in a concrete floor screed. However, this is not the best solution, although it is the most budget-friendly.

When placing the heating element under the floor covering, possible obstacles to the dissipation of the generated heat should be taken into account. In living rooms, these are places where cabinet furniture is installed, the base of which fits tightly to the floor. Local overheating zones appear in them.

With prolonged use, the wire gradually becomes thinner and eventually breaks. Replacing it is extremely difficult, as it requires removing the floor covering and destroying the concrete screed.

The solution to the problem is to use a self-regulating heating wire. Its design consists of two copper cores, between which there is a so-called thermal matrix - a semiconductor element whose conductivity changes as it heats up. The higher the temperature, the higher the resistance. This causes the current flowing through this area to decrease, causing it to cool down.

Such a heating element works at any size - from a piece a few centimeters long to a multi-meter section. It can be crossed with others similar to it (this is strictly forbidden to do with a PNSV wire due to the danger of melting the insulation and causing a short circuit). The main disadvantage of self-regulating heating wire is the cost. It is several times higher than a single-core resistive one.

https://youtube.com/watch?v=ITujT-WErts

Warming up the poured concrete mass using the PNSV heating cable allows you to reduce the time to achieve 80% of the structural strength from seven days to two to three days and not stop work with the onset of cold weather. However, the technology of this process is quite complex; usually its scheme is developed for each specific case. Therefore, do not be seduced by its apparent simplicity. Contact professionals, and in their absence, thoroughly study the issue yourself.

Physical hardening process

Concreting is one of the most common technological processes in construction. It is used not only to create foundations, but also various floors, supports and main walls. Hardening of a cement-sand or cement-gravel mixture occurs during a chemical hydration reaction, when water molecules and substances dissolved in it create a new chemical compound.

It is irreversible and is accompanied by the release of a certain amount of heat, which, at positive external temperatures, maintains the interaction of substances during the first seven days after pouring concrete into the formwork.

However, it may not be enough if construction is carried out during the demi-season, and even more so in winter, when outside temperatures drop significantly below zero. In this case, some of the substances do not enter into a chemical reaction, which significantly reduces the actual strength of concrete structures.

In addition, unspent water freezes and expands, destroying them from the inside. To prevent this from happening, various methods of heating the poured mass are used. The simplest and most effective is to lay a heat-generating electrical cable inside the array, which is the PNSV wire.

This is interesting: Water repellent - what it is and what it is like

Heating concrete with a 220 volt cable: features

To ensure that the solution poured into the formwork sets properly, a KDBS is used - a 220-volt heating cable for concrete. This is a two-core resistive heating cable, complemented by a connecting wire and a connector for connecting to the mains.

It is effective in the temperature range from +5*C to -30*C and can be used not only for monolithic work, but also for temporary heating of the entire construction site.

Heating concrete using a heating cable has many advantages:

1. The concreting process at low temperatures accelerates, and the concrete does not freeze.
2. It is possible to maintain a high pace of construction work, reducing time and labor costs.
3. This is an economical solution that does not require significant financial investments.
4. Installation of a heating cable for concrete does not require the use of special equipment, is carried out without a technological map and can be carried out directly by specialists from a construction company.
5. To connect the line, a step-down transformer is not needed, since the concrete is heated with a 220-volt wire.
6. The maximum cable heating temperature is 60*C, which provides optimal conditions for concrete hardening. It does not overheat and does not boil, which means that so-called “sinks” and voids are not formed in it, reducing its strength.
7. Heating of concrete at 220 V is carried out using heating sections, which guarantee uniform heating over the entire area of ​​the poured structure.
8. The use of KDBS is absolutely safe, since the high-strength insulating coating reliably protects the steel core from mechanical damage.

Advantages and features of segmented cable

The main advantage of a segmented cable is that there is no need to include additional equipment in the system. This method of heating concrete is as safe as possible (unlike cases when electrodes are used), since the likelihood of electric shock is practically reduced to zero. Another advantage is the ease of installation and calculations when using the heating section. The material has already been divided into segments; all that remains is to calculate the required power.

Warming up concrete in winter with PNSV wire is much cheaper, so segmented cable, which is divided into sections of busbars, is used only on small objects, when the speed of construction and the accuracy of the work are a priority.

Carrying out treatment of concrete after heating

Many builders wonder whether it is possible to manipulate cutting or drilling concrete after it has gained strength. This question is due to the fact that at the time the heating stops, the structure has not yet acquired brand strength. The answer to this question can be positive, but with some reservations. Although cutting is possible, it is unacceptable to produce impact loads. The most suitable solution for this is the use of diamond tools. So, if you use diamond drilling at this stage, the holes in the concrete will have smooth edges and cracks will not appear. Moreover, if you drill through the concrete body using a diamond bit, then you will not have to change the tool at the moment of breaking through the reinforcement, which is true for reinforced concrete.

Types of heating wires

The modern market provides a wide range of such products with different performance characteristics.

The cable heating the concrete must have good insulation, otherwise a short circuit or fire may occur. A good insulating layer helps prevent kinks and fractures. As a rule, such products have one current-carrying core, but they are also found with two conductors.

Types of wire for heating concrete and their features:

• PNSV is the most accessible and well-known type. It has an attractive price, starting from 1 ruble per meter. Reusable use is possible, but can only be used with a transformer.
• The PTPZh wire is similar in technical characteristics to the PNSV, but it has two cores.
• KDBS - two-wire in sections. Expensive. Can be used without a transformer. Very easy to install and install. Applies once.
• VET - with two steel wires. Economical. You can work with it without a transformer.

https://youtube.com/watch?v=ITujT-WErts

In addition to products that heat concrete structures, there are series of heating wires used for other purposes. They can be resistive or self-regulating. Resistive conductors include the simplest ones, which are used in the construction of heated floors, as well as for heating pipes with a diameter of up to 40 mm. Large pipes and roof heating are carried out using a self-regulating cable, which independently regulates heating without sensors, reacting to temperature changes.

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Method of heating reinforced concrete

The main advantage of this technology over other heating methods is the absolute absence of heat loss, since thermal energy remains in the surrounding concrete mass. The costs of heating the cable and transferring heat into the body of the concrete structure are minimal compared to other heating technologies.

The next, undoubtedly, big advantage is the ease of implementation of this method. After calculations, it is enough to select the right heating element, connection and installation diagram, select the appropriate voltage, and the final result can be achieved without resorting to the services of builders and electricians.

The technology itself consists of several stages, the first of which is the construction of formwork or a form of the corresponding structure, into which the reinforced frame, heating wire will be laid and concrete will be poured, which must be compacted with an in-depth vibrator before applying voltage to the circuit.

Pouring the solution into the prepared form

https://youtube.com/watch?v=Mi9bK_pcfcI

Some features that PNSV or KDBS have, which are used to warm up the concrete mass, allow the circuit to more efficiently convert voltage electricity into heat, the main thing is to calculate everything correctly. This heat warms the concrete, speeding up its setting and hardening.

Professional builders know and understand the difference between heating wire and cable, and individual developers will find it useful to have an idea about this, which will help them use the technology correctly and more efficiently. The heating method using a cable is more expensive for the following reasons:

1. Heating of reinforced concrete is carried out by connecting the circuit to a reduced voltage through a special step-down transformer in order to prevent the leakage of dangerous voltage into the structure through wet metal reinforcement in the event of accidental damage to the insulation.
2. The heating KDBS can be connected to a network of at least 220V. Optimally - 220V or 380V without reducing the mains voltage.

Connecting PNSV or KDBS is easier in terms of organizing the workflow - connections are made through special couplings, and the cable does not need to be shortened or extended. But a heating cable is more expensive than a wire, so in individual construction it is used at the discretion of the owner. Another disadvantage of cables is that they cannot be reused.

KDBS for heating concrete

Wire differences:

1. Externally, a wire can be distinguished from a cable by the following characteristics: a wire usually has one core, a cable has two or more.
2. The wire has nominal temperature limits when heating concrete – ± 55°C.
3. Maximum current – ​​16 A.
4. The cross-section is 0.6-3 mm, which allows you to bend the wire in any direction and use complex laying patterns. You can use a special calculator to calculate the wire cross-section.
5. Wire consumption for heating 1 m3 of concrete solution is 50-55 m.

Length calculation

To calculate the length of the PNSV wire for heating concrete, several main factors must be taken into account. The main criterion is the amount of heat supplied to the monolith for its normal hardening. It depends on the ambient temperature, humidity, the presence of thermal insulation, volume and shape of the structure.

Depending on the temperature, the cable laying pitch is determined with an average loop length of 28 to 36 m. At temperatures down to -5°C, the distance between the cores or pitch is 20 cm, with a decrease in temperature for every 5 degrees, it decreases by 4 cm, at - At 15°C it is 12 cm.

When calculating the length, it is important to know the power consumption of the PNSV heating wire. For the most popular diameter of 1.2 mm, it is equal to 0.15 Ohm/m; for wires with a large cross-section, the resistance below a diameter of 2 mm has a resistance of 0.044 Ohm/m, and 3 mm – 0.02 Ohm/m. The operating current in the core should be no more than 16 A, therefore the power consumption of one meter of PNSV with a diameter of 1.2 mm is equal to the square of the current and the resistivity and is 38.4 W. To calculate the total power, you need to multiply this figure by the length of the laid wire.

The voltage of the step-down transformer is calculated in a similar way. If 100 m of PNSV with a diameter of 1.2 mm are laid, then its total resistance will be 15 Ohms. Considering that the current is no more than 16 A, we find the operating voltage equal to the product of the current and the resistance; in this case it will be equal to 240 V.

The use of PNSV wire is one of the cheapest ways to heat concrete. But it is more suitable for use by professional builders, since its connection requires special knowledge and equipment. This cable can also be used at home if you correctly calculate the power consumption. The use of thermal insulation materials will help reduce costs when heating the solution; in this case, heating will occur faster, and the temperature decrease will occur more evenly, which will improve the quality of concrete.

Recommendations for use

Sections 40 KDBS are economically and technologically feasible to use in the following typical areas:

• pouring a large number of small-sized monolithic structures and elements;
• critical fillings that require uniform heating of the reinforcement grids without boiling or burning out;
• production of columns, walls, etc. without the involvement of specialized teams for the monolith;
• using a vibrator;
• supplying concrete mixture from a mixer;
• urgent large-scale work in which it is impossible to regulate the heating power;
• the need for a large number of heating stations at the same time.

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