Cable for heating concrete: a key element of the internal

Cable for heating concrete without a transformer allows to significantly optimize the process of maintaining the optimum temperature in the hardening solution. Despite the fact that the conductors themselves of this type are more expensive than standard PNSV wires and their analogues, the total cost of the work is much lower.

In our article we will describe what the key features of such conductors are, and also describe their advantages.

Maintaining temperature in concrete

Standard technique

Concrete warming up with a cable is usually used if the work is carried out in winter. At the same time there is a risk of freezing of water in the solution, which leads to a slower hydration of cement and a decrease in the strength of concrete.

To avoid this, the instruction recommends that you proceed according to the following scheme:

• For heating the mass of the solution, a single wire PNSV wire is taken with a diameter of from 1.2 to 4 mm.

Tip! For reinforced structures, modification in PVC insulation is chosen, for non-reinforced structures - in polyethylene insulation. This is due to the fact that polyethylene can melt, and this will lead to a short circuit to the metal frame.

• The wire is cut into identical fragments (usually 28 or 17 m), which are twisted into compact spirals with a diameter of 30-40 mm.
• Spiral "threads" are interconnected in several identical groups and laid in the formwork inside the reinforcement cage.

• Since the characteristics of the PNSV cable do not allow it to be used in air, so-called “cold ends” of thicker wires are installed on the system’s terminals.
• The formwork is poured with concrete, and after the initial setting, the entire system is connected to the network through a step-down transformer. This device provides adjustment of the strength of the incoming current, which allows you to control the temperature of the conductors inside the solution.

Features of heating cables

The technique described above is quite effective, but it has several disadvantages. The key is the need to use a transformer to reduce the voltage.

Впрочем, можно обойтись и без этого громоздкого устройства. Естественно, при этом вместо стандартного провода ПНСВ нужно использовать специальные греющие кабели, такие как VET (Финляндия) или KDBS (РФ). Для подобных изделий характерны такие свойства:

Such devices are designed to operate from a normal power supply with a voltage of 220 V. High-quality PVC insulation provides reliable protection against short circuits and breakdowns, in addition, it does not become brittle even at a temperature of -35⁰C, which significantly expands the "climatic framework" of the use of such conductors.

В отличие от провода ПНСВ, кабели типа VET и KDBS не требуют подрезки. На краях секций устанавливаются концевые и соединительные муфты, что позволяет быстро собирать всю греющую систему с использованием минимального набора инструментов.

Installation recommendations

Preliminary calculations

The calculation of the cable for heating concrete is quite simple:

• According to the standards for heating one cubic meter of solution, it is necessary to build from 0.5 to 1.5 kW of power.
• To save electricity, you can add anti-frost additives to the concrete, as well as to equip insulated formwork. The price of additional materials will be compensated by the reduction of electricity costs.
• When pouring overlaps of standard thickness, up to 4 meters of heating wire per square meter is usually laid.
• When a bulk monolith is being poured, the conductors are stacked in a long way, with a gap of at least 30-40 cm

Laying of heating circuits

Assembling a heating system with your own hands is quite simple:

• First, we build the formwork and assemble the reinforcement cage.
• Then we estimate where the heating of concrete will be most relevant, and we collect cable products from sections of the appropriate length.
• Most often they warm up the surface of the material, the places of contiguity of horizontal and vertical planes, etc..

Note! It is undesirable to cross the expansion joints, as well as the areas where diamond drilling of holes in the concrete will be subsequently carried out.

• We put the cables inside the formwork in such a way that all the conductors lie at least 20 cm from the surface of the frozen concrete.
• To avoid the appearance of cracks and creases on polymer insulation, turns should be made smooth. The bend radius for different models will be different, but in most cases, experts make it equal to 40-50 mm - with a margin.
• To evenly distribute the temperature in the thickness of the concrete, it is advisable to lay the conductors at equal distances from each other.. The intersection of the wires is not allowed, and the minimum distance between two heating circuits is 40 mm.

After the layout we fix the conductors on the fixture. To do this, use the usual wire, tying it without undue effort and deformation of the insulation. You can also use plastic clamps.

Затем заливаем опалубку бетоном, стараясь не нарушить размещение термоэлементов. Кабели VET и KDBS допускают вибрационное воздействие, потому бетон вполне можно уплотнять.

All the laid elements are connected with contact wires to the system, and then - connected to the power source.

Conclusion

Warming cable for concrete, running from the network without the use of a step-down transformer, is very convenient to use. Of course, its cost is much higher than that of the PNSV wires, but on the other hand, it allows solving the set task - maintaining the optimum solution temperature - much more efficiently. You will find more information on this subject by studying the video in this article.