Technology and scheme for laying PNSV wire for heating concrete

Heating plays a critical role in maintaining the functionality and durability of concrete structures, particularly in colder climates. A useful technique to accomplish this is by employing "Polymer-Nickel-Silver-Vinyl" (PNSV) wire. This kind of wire is perfect for concrete applications because it is made specifically to heat materials consistently and effectively.

A carefully thought-out procedure that incorporates the PNSV wire into the concrete slab is required when heating concrete with wire. To guarantee that the entire surface is heated evenly, the wire is arranged in a particular pattern before the concrete is poured. This is not only about comfort; it’s also critical to avoid problems that could jeopardize the concrete’s structural integrity, like uneven curing and cracking.

The technology for laying PNSV wire is simple in practice, but it needs to be done carefully. To get the best heating effects, the wire is usually arranged in a grid pattern with great care taken in its spacing and alignment. This configuration facilitates even curing and improves the overall quality of the completed slab by distributing heat across the concrete surface efficiently.

You can make sure that your concrete projects stay sturdy and durable even during harsh weather by incorporating PNSV wire into them. It’s a dependable method that improves concrete performance and maintenance in the short- and long-term.

The principle of operation and types of wires

In the winter, a wire with a specific cross-section and voltage is laid on the working surface to warm up the concrete before the solution is poured (after the reinforcement cage is laid). Subsequently, the concrete mixture is poured, and either the heating cable or the transformer is directly connected to it. This causes the concrete to get heated, which accelerates its hardening process. You shouldn’t be concerned that the mixture will start to bubble or crack because the structure of the solution does not alter when temperatures change.

For this kind of work, three types of heating cables are used nowadays:

• KDBS (two-core cable for concrete in sections). When using this cable, it can be connected to a 220V network, which eliminates the need to use a transformer. In addition, the KDBS cable is the easiest to install (does not require cutting), and thanks to special couplings, it is easy to lay according to the selected scheme. However, such wires are quite expensive (from 1020 rubles per linear meter). Another disadvantage is that the cable is used only once, since after the concrete mass has hardened, it cannot be dismantled.
• BET is a two-core cable developed using Finnish technology. Such cables also work without a transformer and are connected directly. The BET cable is distinguished by its cost-effectiveness, since about 20-25 m of wire will be required to heat 1 m3 of concrete surface.
• PNSV (single-core heating wire with a steel core and vinyl insulation). This is the cheapest concrete heating system (from 1 ruble per linear meter), so it is most often used in construction in the private sector. To use the PNSV heating wire, a connection to a transformer is required (under certain conditions, a direct connection is possible). However, after heating the concrete, the wire can be reused (for example, as a “warm” floor system or “anti-ice” for stairs).

We will go into more detail about the most common method used in the construction industry, which is heating concrete with a PNSV wire.

Features of PNSV heating wires

A steel core measuring 1.2 to 3 mm in diameter and 0.6 to 4 mm2 in cross-section makes up the PNSV cable, which is insulated with polyester or PVC. This insulating substance prevents the wire from bending, breaking, and from catching fire.

Electric heating is typically accomplished with wires that have a minimum diameter of 1.2 mm. Practice, however, indicates that using PNSV at 3 mm is preferable, particularly if you intend to manually compact the solution. As a result of the stronger insulation in this type of cable, there will be less chance of overheating even with a subpar power source.

It’s also important to note that this particular type of heating cable has another distinguishing characteristic: "cold ends." These branches reach past the edges of the slab of concrete. Use wires with aluminum conductive cores, or APVs, to connect the cable to the power line for "cold terminations."

This article will examine the ways that cutting-edge methods and contemporary technology are transforming the PNSV wire laying process for heating concrete. Our goal is to present a clear and useful guide for attaining the best possible outcomes in concrete heating projects by looking at the most recent techniques and tools utilized to install these wires efficiently. Gaining knowledge of these developments will help guarantee effective, long-lasting, and high-performing heating systems in a variety of concrete applications.

Characteristics of PNSV

When it comes to the wire’s technical specifications, the PNSV wire is distinguished by the following indicators:

• resistance of 0.15 Ohm/m;
• temperature range from -60 to +50 o C;
• flow rate of about 50-60 m per 1 m 3;
• the possibility of laying the wire at a temperature from -25 to +50 o C (however, installation work is recommended to be carried out at a temperature not lower than -15 o C).

In this instance, the heating wire embedded in the thickness of the concrete is operating at 14–16 A.

Crucial! Only when the wire is inserted straight into the concrete mass do the working current indicators "work." It will burn out the concrete heating system if you connect it outside.

The concrete heating PNSV wire is connected to the reinforcing frame’s mesh and is powered by a step-down transformer; ideally, it has multiple stages so that the heating intensity can be adjusted based on the air temperature. The technical regulations state that a heating substation KTP TO-80/86 (SPB-80 is also frequently used) that can heat an area of 20–30 m 3 should be used for work. The transformer is wired into a 380 V three-phase network (the casing needs to be grounded).

It is much more practical and secure to use a substation if you intend to heat concrete directly from a 220 V network using a cable that is 120 m in length and does not require a transformer.

It is also important to keep in mind that the foundation base pouring principle affects the wire’s length. The values differ for structures that are reinforced and those that are not. Take note of the table below to determine the length of the heating wire.

However, in order to obtain more precise information, we highly advise you to consult the process map 37-03. This document also includes the calculation for heating concrete (which can take anywhere from 8 to 72 hours), based on the surrounding temperature and the structure’s modulus of strength.

Technology of laying and heating PNSV

The following tasks must be completed in order to prepare the area before the heating cable for concrete is laid:

• Install the formwork (it is possible to use an inverter) and reinforcement cage (make sure that there is no ice on these elements).
• At the level of the upper and lower reinforcement cage, lay out the cable (it is impossible to pull it too tightly) with a laying step from 80 to 200 mm (depending on the air temperature). Make sure that the wires do not cross or touch each other under any circumstances. The cable is fastened to the reinforcement using wire twists (1.2 mm), plastic ties or steel staples.

Practical! A "snake" arrangement is the best way to lay the wire, as the illustration illustrates. 28–36 meters for a loop.

• Install the transformer at a distance of 25 m from the work area and lay rubber mats next to it.
• Equip a fence around the area where the concrete will be heated with heating wires.
• Make busbar sections (according to the diagram below) and install them along the section.

• Connect the PNSV wires to the busbar sections.
• Connect the busbar to the transformer and test it at idle.

Connection diagram options

The "Star" or "Triangle" connection diagrams are the most often utilized when heating concrete via cable.

The cable is split into three identical groups of wires connected in parallel, as shown by the "triangle" diagram. The resulting sets are connected to the three output terminals of the KTP TO-80/86 by connecting them at both ends to form nodes.

In order to use the "star" connection diagram, three equal sections of wires must be connected to a node at one end. Three free "tails" must then be connected to nodes and the KTP’s output terminals.

Once everything is prepared, you can lay the concrete mixture and activate the heating wire.

Crucial! If only part of the concrete mixture is laid, the heating process cannot begin.

Heating technology

It’s important to be clear about the concrete’s heating time before connecting the equipment:

• Initial period – heating. During this period of time, the temperature should not exceed 10 o C in 2 hours.
• Intermediate stage – heating by isotherm. This is a very important moment during which temperatures of 80 o C and more should not be allowed.
• Final stage – cooling. During this period of time, it is important to ensure that the cooling rate of the concrete is no more than 5 o C/h.

Practical! It is not advised to keep the concrete heated after the solution has reached 50% strength.

As a result, depending on the features and nature of the construction site, the concrete will warm up over the course of several hours to three days.

Post-processing of concrete

Many inexperienced builders wonder whether it is possible to drill and cut concrete before it reaches its grade strength because it takes such a short time to heat the concrete mass.

It can actually be cut, but only if one subtlety is considered. Nothing significant will occur if you intend to cut using a diamond tool, which prevents the creation of cracks and uneven hole edges. However, you will have to wait until the concrete reaches the necessary strength grade in order to use impact loads.

When it comes to heating concrete, using PNSV wire offers an effective way to ensure that your concrete cures properly, even in cold weather. This technology helps to prevent issues like freezing, which can compromise the strength and durability of your concrete. By embedding the PNSV wire within the concrete, you create a reliable heating system that maintains optimal temperatures throughout the curing process.

A particular plan is followed when laying PNSV wire to guarantee even heating. Before concrete is poured, wire is carefully arranged in a grid pattern. By using this technique, cold spots that could cause uneven curing are avoided and the concrete is guaranteed to receive uniform heat throughout. To get the most out of this system, installation instructions and recommended spacing must be followed.

All things considered, heating concrete with PNSV wire is a workable way to improve the longevity and caliber of your concrete constructions. Through meticulous planning and execution, you can steer clear of common pitfalls and guarantee proper concrete setting. This technology increases productivity and protects the integrity of your work, particularly in inclement weather.

Video on the topic

Wiring a loop PNSV. For heating concrete. Machine quick method.

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Heating concrete with a PNSV wire video