How to choose the right wire (cable) for heating concrete in winter

Winter weather presents a number of difficulties for construction projects, especially when it comes to concrete pouring. Low temperatures have the potential to impede or completely stop the curing process, resulting in weaker concrete that doesn’t adhere to specifications. Using special heating cables to ensure that the concrete cures properly even in freezing conditions is one practical way to solve this problem.

It’s important to select the appropriate wire or cable for this use. Selecting the appropriate type guarantees even heating and aids in preserving the temperature required for proper concrete setting. Choosing the best option can be confusing, though, because there are so many options available. When making a decision, factors like the power output, longevity, and safety features of the cable are all important considerations.

We’ll go over the important factors to take into account in this guide when choosing heating cables for concrete during the winter. Knowing these variables will assist you in selecting the best solution, whether you’re a seasoned contractor or a do-it-yourselfer. This will guarantee that your concrete projects go smoothly and satisfy the highest requirements for quality and safety.

Criteria Description
Wire Type Choose a heating cable specifically designed for concrete curing, such as electric resistance or induction heating cables.
Power Requirements Consider the power output needed to maintain the desired temperature. The cable should provide consistent heat distribution across the concrete surface.
Temperature Range Ensure the cable can operate effectively within the temperature range required for concrete curing, especially in winter conditions.
Durability Look for cables with robust insulation and construction to withstand the harsh conditions of a construction site and resist damage.
Length and Flexibility Check that the cable length suits your project size and can be easily laid out in the concrete pour area.
Safety Standards Verify that the cable meets safety standards and regulations to ensure safe operation during the concrete curing process.

Why is concrete heating necessary

The temperature of the surrounding air affects the processes that take place in concrete as it hardens. Concrete hydration issues arise from water freezing in the winter when temperatures drop below zero. In this instance, the raster only freezes in some areas, so it does not fully harden. The water will melt and the solution’s solidity will be disturbed as the surrounding temperature rises. This procedure will cause the structure’s durability to decrease and its integrity to be violated after it has hardened.

The concrete must be electrically heated using a variety of wire types to avoid the effects mentioned above.

The homogeneous structure in this instance results from the absence of extraneous processes in the mixture, which enhances the concrete’s strength and durability.

Types of heating wires and cables

PNSV cables (decoding: heating wire, core material: steel, insulation: PVC) are typically used for electrical heating of concrete during the winter months because they are the least expensive and easiest to install of all the cables.

When it comes to how often it is used, the PNSP cable for heating concrete comes in second. Unlike PNSV with PVC insulation, it has polypropylene insulation, which is its primary distinction from the wire previously shown. The cable’s thermal conductivity can be slightly increased thanks to this material. However, because of its higher cost, it is only utilized in situations where the cable’s length is crucial. Typically, this kind of wire is set up as a heated floor.

These kinds of wires are challenging to install since precise measurement of their length is necessary. The supply voltage can be changed to fix any small mistakes that were made during the design phase.

Types and features of KDBS and VET cables

If PNSV or PNSP cable is to be used for wintertime electric heating of concrete, then additional control equipment must be incorporated into the system. This will allow the network’s power to be adjusted to regulate the production of heat. You can use two-core heating cables, such as the Finnish VET or Russian KDBS, that regulate heat transfer independently to simplify the system by removing unnecessary equipment from it.

These cables connect straight to the 220 volt network; additional devices do not need to be installed in order to make adjustments.

Although the designs of the two manufacturers are identical, there are some technical differences between them:

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

Pros and cons of PNSV

The most economical method for heating concrete is to use PNSV wire for electric heating. This is because the wire itself is inexpensive and uses comparatively little electricity. This kind of cable can also be used in a variety of challenging environmental conditions because it is resistant to acidic and alkaline environments.

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

These substations (PT) are highly expensive. Since you will be paying at least 10% of the total cost for renting equipment, it is not recommended as they require constant operation. Using welding machines is a possibility in certain situations. They do not, however, work well on large construction sites because they break down easily under heavy workloads.

Heating technology using PNSV

Many people think that laying the cables and connecting them to the electrical network is sufficient to heat concrete using PNSV wires. This strategy is essentially incorrect. Precise power regulation, which considers numerous factors, is required for adequate heating with wires. The structure will be destroyed by both too high and too little solution temperatures.

Naturally, the concrete solution won’t boil because the wire sheath melts at 80 degrees. A short circuit could result if the wire comes into contact with the metal reinforcement if it completely vanishes.

It is important to carefully consider the heating wire connection diagram. One of the best choices, "star," is shown below.

  1. At this stage, most of the total volume of water in the solution is absorbed, after which a crystalline structure is formed. In this case, the temperature of the concrete mass reaches 55 degrees (the heating duration depends on the ambient temperature). In order for the heating process to be continuous and uniform, it is necessary to maintain a voltage of 95 volts.
  2. At this stage, the value of the supplied voltage is reduced to 75 volts for crystallization of the concrete solution. The temperature inside is maintained the same (55 degrees) due to the inertness of the solution. It is important to note that if at this stage the ambient temperature decreases sharply, it is necessary to increase the value of the supplied voltage by 10 volts.
  3. This stage can be called cooling. In this case, the wire for warming concrete PNSV will be heated by no more than 20 degrees. At the last stage, the concrete solution gains up to 80% of its strength.

Calculation of length

If using a wire PNSV to warm up a concrete mixture, it is first required to determine its length based on multiple factors. The estimated thermal energy needed to heat the concrete mass to the necessary temperature is the primary deciding factor. The temperature outside, the air’s relative humidity, and the object’s size all affect how much heat is produced.

It’s critical to understand the primary PNSV characteristic—namely, the power consumed—when determining the length. The resistance is lower for cables with a larger cross-section; for example, a diameter of 2 mm equals 0.044 Ohm / m, and a diameter of 3 mm equals 0.02 Ohm / m.The most common diameter is 1.2 mm, which is equivalent to 0.015 Ohm / m. The obtained value needs to be multiplied by the cable’s length in order to determine the total amount of power needed.

The calculation of step-down transformers is similar. The overall resistance of 100 meters of 1.2 mm-diameter PNSV will be 15 Ohm. Given that the current is limited to 16 A, we can calculate the operating voltage by multiplying the current by the resistance; in this instance, the result is 240 V.

In winter, it’s important to choose the appropriate wire or cable for heating concrete by taking safety regulations, project type, and temperature requirements into account. With the correct cable, concrete cures correctly even in cold weather, avoiding cracks and guaranteeing durability. The quality and longevity of the concrete can be greatly impacted by the heating cable you choose, regardless of the size of your project or construction.

Installation of PNSV

The plan for installing the PNSV wire needs to be considered during the facility’s design phase. Installing it in the formwork prior to pouring the concrete mortar is crucial. The most common method for fastening the wire to the reinforcement is with aluminum wire.

Sections are mounted vertically and horizontally at equal distances from one another to guarantee as uniform a heating of the concrete mixture as possible. Adjacent ones should be spaced out by roughly 15 centimeters.

It’s crucial to remember that the segment should be 31 linear meters in length if the network voltage is 380 volts, and between 220 and 17 meters if it’s lower. The mixture will only be heated uniformly in this situation, giving it the greatest strength possible. The most remote places won’t receive the thermal energy if the section is mounted longer.

This is typically accomplished by connecting a cable with tight winding and aluminum cores. The wire stays inside the concrete mixture until it solidifies completely, at which point it can be utilized as a "warm floor."

Installation of sectional heating cable

This kind of cable is delivered to the job site as a completed section rather than coiled for heating concrete. The installation procedure is made somewhat easier by this fact, as cutting the wire is not necessary. Putting the system together following the following preparatory steps:

  1. Calculating the required power of one segment depending on the volume of concrete mix.
  2. Choosing the length of the wire.

Although installing the system is fairly easy, it does require some knowledge and expertise.

Here are some general guidelines that will help you install a sectional type wire for heating concrete quickly and correctly:

  • To heat one cubic meter of concrete mix, depending on the composition, 500-1500 W is required (depending on the ambient temperature). You can reduce the consumption of electrical energy by adding special additives to lower the freezing temperature of the mixture or by insulating the formwork.
  • If the concrete mix is ​​poured into a ceiling or any beam, the calculation of the electrical wiring is carried out taking into account the following initial data: 4 meters of wire per 1 square meter of the element surface.
  • The wire is reliably protected, so it can be attached to the reinforcement.
  • The wires should always be in contact with the formwork.
  • During installation, it is important to monitor the distance between the cables, otherwise the electric heating of concrete by the heating wire will be uneven.
  • It is necessary to maintain at least 4 centimeters between adjacent circuits.

It’s important to make sure the wires don’t cross over when installing.

A successful project depends on selecting the appropriate wire or cable for heating concrete in the winter. Especially in cold weather, the proper cable can aid in achieving the required concrete strength and durability. You can make an informed choice that will improve the concrete structures you use in the short and long terms by being aware of the different types of cables that are available, their features, and how they work with the requirements of your particular project.

Recall that voltage, insulation quality, and power output of the cable are the most important factors to take into account. The effectiveness and security of the concrete heating process are directly impacted by these factors. To further avoid any potential hazards, always adhere to the safety standards and guidelines provided by the manufacturer. Purchasing a high-quality, suitable cable is preferable to taking a chance on the integrity of your concrete with a less expensive, insufficient one.

In the end, the cable you choose will depend on the particulars of your project, like the concrete’s thickness and the surrounding conditions. Spend some time carefully evaluating these variables, and seek professional advice if necessary. Making the appropriate decision will guarantee that your concrete cures correctly, even in the worst winter weather, producing a final product that is robust and long-lasting.

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Anna Vasilieva

Journalist with a technical education, specializing in construction topics. I can explain complex technical topics in simple and accessible language.

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