Features of calculating pipes for underfloor heating

Installation of underfloor heating pipes is impossible without preliminary calculations of the heating system operation. Correct calculations will ensure not only high-quality operation of the heating system, but also allow long-term use of the equipment without leaks..

Design features

Warm water floor is gaining more and more popularity. It has pushed even massive batteries out of the market due to its easy installation and wide range of products. Also, unlike radiators, it became possible to regulate the circulation of water in a metal channel using flow meters.

The design can be combined with ordinary heating radiators. Moreover, its action is focused on uniform heating of the air in the room. The radiator is not able to quickly heat the room, since in most cases it is limited by a small space due to the wall installation. At the same time, a system of warm pipes runs under the floor of the room, thereby preventing drafts and heat leaks..

The structure is based on a concrete screed, which quickly collapses under the influence of high humidity. To avoid unpleasant consequences after a leak, it is necessary to place sheet polystyrene or expanded polystyrene on the cement. However, if the pipes are laid immediately, then the porous materials will easily absorb heat.. For insulation, it is recommended to cover the foam layer with foil.

For reliable reinforcement in the floor structure, the pipe system is laid in an additional cement layer on top of the waterproofing coating of the main screed. So the structure is securely fixed under the floor covering without losing its properties..

Subtleties of calculation

In most cases, 5 m of pipes are consumed per 1 m2. In this case, the step length is 20 cm.

However, experts recommend laying pipes based on accurate calculations.. For this purpose, you need the formula L = S / N * 1.1, where:

  • S represents the area of ​​the plot;
  • N denotes the laying step;
  • 1.1 – spare pipe needed to create turns.

If you add twice the distance from the collector to the floor, you get a more accurate calculation. For a better understanding of the calculations, you can give an example:

  • suppose the area of ​​the site is 16 m2;
  • the distance from the collector to the floor – 3.5 m;
  • the laying step is 0.15 m;
  • following the formula: 16 / 0.15 x 1.1 + (3.5 x 2) = 124 m.

The increase in flow depending on the distance between adjacent pipes is presented in the following table:

Loop pitch, mm

Pipe consumption per 1 m2, m. P..











The layout of the warm floor limits the length of the pipe to 120 m, because there are a number of reasons for this:

  • the high temperature should not damage the floor covering;

  • heating in the circuit during operation (especially with a leak) can damage the cement screed;

  • dividing the surface into several areas for efficient heating.

When carrying out calculations, it must be remembered that the number of sections depends not only on the floor area, but also on its geometry..

By diameter

To correctly calculate the pipe diameter, the following calculations will be required:

  • 15kPa – pressure of the pump, which provides efficient heating;

  • pipe length is 85 m;

  • the heat carrier consumes 0.2 m³ / h.

Therefore, the calculation is made according to the formula D = 18 * (p / L * G2) – 0.19, where:

  • D denotes the diameter of the pipe for underfloor heating;

  • L – footage of the length of the product;

  • p is the pump pressure;

  • G is the flow rate of water that circulates in the pipes (described in the documentation);

  • D = 18 * (15/85 × 0.22) –0.19 = 13.6 mm.

Manufacturers produce 16 mm pipes – the most optimal option for installing the system. Snake and snail are considered suitable schemes for setting up a heat-insulated floor. Hot water during planning is red, cold water is indicated in blue.

Along the length of the contour

The heating system needs to be designed to maintain the most efficient air pressure and circulation. Therefore, the limit for the length of the water circuit is 80, maximum 100 meters. However, the room does not always correspond to the calculations, requiring its own parameters, sometimes exceeding 150 m. The problem is easily solved – just install a few circuits.

For example, if a room requires 240 m of pipe, then three structures of 80 m should be created. In this case, the contours do not have to correspond to each other. According to experts, the difference can be up to 15 meters.

When calculating, it is necessary to take into account the diameter of the pipe and the material of manufacture:

  • Metal-plastic products most in demand due to their low cost and easy installation. It is based on polyethylene with an aluminum interlayer, which increases the reliability of the structure. The metal has a high thermal conductivity, which attracts manufacturers who want to create optimal conditions for heat transfer. With a diameter of 16 mm, the length of the contour can reach hundreds of meters.

  • Polyethylene structures do not require an additional layer, crosslinking at the molecular level. The product bends easily and is resistant to high temperatures up to 95ºC and to various chemical solvents. With a diameter of 18 mm, the limit will be 120 meters.

  • Polypropylene has high rigidity and strength. It is not in demand on the market and is used primarily for production purposes. The length limit for the product is 90-100 meters.

  • Copper products have the highest thermal conductivity, due to which their price is the highest on the construction market. However, they need a professional installation, since at the slightest offense they leak.

  • Corrugated pipes made of stainless steel. The maximum contour length is 120 m with a diameter of 25 mm. Corrugated pipes are recommended to be purchased with a pre-calculated length sufficient for one circuit. Such a purchase automatically eliminates the possibility of leakage..

The choice of design should be guided by the parameters of the room. Otherwise, you will have to calculate the number of contours..

A large area should be divided into its constituent sections in a ratio of 1: 2. That is, its width will be 2 times less than its length. Therefore, in order to calculate the number of sites, the following measures will be required:

  • With a step of 15 cm, the number of m2 for the area of ​​the site does not exceed 12;

  • a step of 20 cm is suitable for 16 m2;

  • step 25 cm – 20 m2;

  • 30 cm – 24 m2.

Subsequently, with an increase in the step by 5 cm, the area accordingly increases by 4 m2. However, experts do not recommend calculating exact values.. To avoid leaks, take 2 m2 in reserve.

Installation diagrams

Before planning, you should calculate the number of pipes required for complete heating of the room. It is recommended for this purpose to use graph paper 1: 50 for drawing a room diagram, as well as for making the necessary calculations. When building a drawing, it is important to respect the scale.

For the correct calculation of pipes per square meter of surface, you need to plan a laying scheme in advance:

  • “Snake”. This type of installation is suitable for small rectangular rooms. In most cases, snake installation is used for water floors as an alternative heating method. The main disadvantage in this case is the uneven distribution of heat. The highest temperature points are concentrated in the places of pipe bends, close to the collector. With distance from the latter, the temperature will decrease.

  • Double “snake” is similar to the previous type. The only difference is in laying not one, but two pipes at once, parallel to each other..

  • Corner “snake” assumes the exit of pipes from the corners of the room.

  • “Snail” does not have heat loss due to the fact that it combines warm and cold pipes, thereby ensuring uniform heating of the area. Installation is carried out in cold rooms with a large area. In this case, the step is up to 35 cm.

When laying with a snake, adjacent pipes are located at a distance of 30 cm from each other. When approaching doors and windows, this distance is reduced to 15 cm.This position ensures pressure reduction and long-term operation.

It is important to remember that styling methods can be combined with each other. And also the installation method determines how many pipes should be used..

Useful Tips

Building professionals based on many years of practical experience recommend paying attention to the following details:

  • The flow rate of the number of pipes for a warm floor is influenced by the heat transfer coefficient and the plasticity of the structure. Therefore, before purchasing a product, you should pay attention to these parameters. The most suitable options are metal-plastic and corrugated structures..
  • Do not connect or install floor heating pipes under a concrete screed. These manipulations will lead to the destruction of cement from a strong temperature drop..
  • Contrary to the permissible parameters, experts recommend not using more than a hundred meters for one circuit, and the distance between the pipes must correspond to 20 cm. The pipes are displaced towards each other at the risk of large heat losses. Such places are windows and doors..
  • The circuit unit must not heat more than 20 square meters of the room.
  • It is necessary to strictly follow the instructions on the technology for installing a warm floor. Mandatory installation of a barrier, insulation and substrate.
  • When operating two circuits in the same room, it is recommended to observe the difference in their length. It should not exceed 15 meters.

Also, today there are online calculators that allow you to calculate according to given formulas. However, to calculate the parameters of the pipes, you still need to know the criteria for the placement..

It is important to remember that correct calculations will help save on materials, while maintaining high quality and long-term operation..

How to calculate and make a hydraulic floor with your own hands, see the next video.

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