Which are welding pipe materials

Heating pipes

Heating pipes: so that everything stays in motion

Heating pipes transport the water warmed up in the boiler into the radiators and also lead it back again. To keep everything flowing, you should definitely pay attention to the different materials, the diameter and, above all, the correct laying of the heating pipes - if you dare to do this yourself.

If you want to lay heating pipes yourself, you should not only be very familiar with the material, but also have welding skills. Often the technical knowledge, the regulations to be observed as well as the effort for the pipe assembly are underestimated. It is usually better to resort to the knowledge of a professional heating installer.

In heating technology, copper pipes and occasionally mild steel pipes are mainly used in single-family houses and the renovation of old buildings. Plastic and copper pipes are very often used for underfloor heating. The pipes are standardized on the basis of nominal diameter (DIN EN ISO 6708), nominal pressure and operating pressure (DIN EN 1333).

Pipe materials for heating pipes

Copper pipes

They can be installed quickly and easily and are corrosion-resistant. In addition, they have lower pressure losses due to pipe friction than steel pipes. All dimensions are standardized by DIN EN 1057. The laying of copper pipes often takes place in the screed or in skirting boards. It should be noted, however, that there is sufficient leeway, as copper pipe has a thermal expansion factor that is around 40% higher than that of steel pipe.

The connection of individual copper pipes or bends is made by brazing, welding, pressing or clamping. Copper pipes connected in this way are suitable for operating temperatures of up to 250 ° C. Soft-soldered copper cables are only permitted for operating temperatures of up to 110 ° C.

Steel pipes

Thin-walled and flexible steel pipes are also used for closed heating systems in single-family houses and old buildings. They are easy to use. In contrast to copper pipes, steel pipes can withstand higher pressure and are suitable for temperatures of up to 120 ° C. Instead, steel pipes are more susceptible to corrosion. For example, they are not suitable for areas that are at risk from moisture. Since there is usually no air inside the heating system, corrosion within the pipes is virtually impossible. Due to their thin walls, they must be well insulated from the outside by an additional covering.

If you want to minimize the risk of external corrosion, you can use stainless steel pipes. An additional advantage over copper pipes: the thermal expansion is significantly lower. Disadvantage: a significantly higher price compared to normal steel!

Plastic pipes

The use of plastic pipes is restricted. Operating temperatures of 80 ° C must not be exceeded here. The advantages are high corrosion resistance, easy installation and low friction losses due to smooth surfaces. The temperature sensitivity is a disadvantage. Here there can be major changes in length when the temperature changes. Plastic pipes also have a significantly lower resistance to overpressure.

Another disadvantage is a shorter service life compared to heating pipes made of metal. In addition, it cannot be ruled out that tiny plastic particles (microplastics) may detach over time and enter the water cycle. Plastic pipes are mainly used for underfloor and wall heating.

In order to guarantee the effectiveness of the heating system, the pipes used must be insulated if they are used purely as line pipes! The insulation of the heating pipes is required by law.

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Legal regulation

Section 69 of the Building Energy Act (GEG) stipulates that freely accessible heating lines in unheated rooms must be insulated. This also applies to existing heating systems! There is an obligation to retrofit. This requirement applies to both pipes for heat distribution in the heating system and for hot water distribution. The only exception to this is a clearly demonstrable inefficiency. Or owning a building with a maximum of two apartments, one of which the owner has been living in since February 1st, 2002.

The GEG specifies minimum requirements for the insulation thickness of pipes and fittings. All heating and hot water pipes must be sheathed with an insulation thickness that corresponds at least to the inner diameter of the pipe. This applies when using insulation materials with a thermal conductivity of λ = 0.035 W / (mK). When using insulation materials with higher thermal conductivity, the insulation thicknesses must be adjusted. Exceptions are described for some installation situations.

Types of installation of the heating pipes

The way in which heating pipes are laid depends on the building. There are two options: star-shaped as well as ring-shaped laying.

  • The circular laying is used especially in multi-storey houses. Here risers lead to the individual floors. From this riser, each radiator is connected to one another in a ring. In this form, the heating pipes are often laid in wall slots or special skirting boards.
  • The second option is that star-shaped laying. It is suitable for single-storey houses and apartments. In contrast to the ring-shaped installation, with the star-shaped installation, each radiator is connected individually. The heating pipes usually lead from the central heating system to the respective radiator. Since short pipelines are sufficient here, laying in the screed is ideal for a new building.

Laying the heating pipes

If you want to lay heating pipes yourself, you have to know exactly what you can and cannot do. Steel and copper pipes need to be welded. Copper pipes, on the other hand, can be soldered or pressed. Usually this work is done by a heating technician. If you do this work, the heating specialist should definitely take a look at your work. Because once the heating pipes have disappeared into the floor, wall or behind skirting boards, errors can only be remedied with great effort.

Those who lay heating pipes themselves should fall back on the technically simple technology. When it comes to the choice of pipes, those made of plastic have proven their worth. They are easier to shorten. When buying, you should already know how the pipes are to be laid. A corresponding number of connectors and T-pieces are required.

First, measure the distances between the connection and the respective radiators in order to determine the required number of heating pipes. Important: Include the waste. Take into account that you have to lay a supply pipe and a return pipe each.

Then the radiator valves are screwed into the flow and return. Attach a plastic connector to each valve. The pipe is welded on here. To do this, the end of the pipe and the connector are briefly heated. Then both are put together. The solid connection is created when the material cools down.

When laying heating pipes, the insulation must also be taken into account. The pipe insulation requires additional space. This means: If the pipes are on the wall, you have to keep a greater distance to the wall in order to be able to attach the heating pipe insulation.

The right diameter

The size of the heating pipes depends on the amount of heating water flow. How much heating water is required and how fast it flows depends in turn on the amount of heat required and the flow and return temperatures. A calculation that usually only a heating specialist can solve.

In the first step, it calculates the heating load. All heat losses are added up. The result provides the heat energy required to adequately heat each individual room. This value is the basis for dimensioning the radiator, foot or wall heating.

Once you have decided on a heating system, the next step is to determine the flow and return temperatures of the heating system. While for radiators, for example, 55 ° C in the flow and 45 ° C in the return, they are lower for surface heating systems. The difference between the flow and return temperature, the so-called spread, is then important for the design of the heating pipes.

Because the value of the required amount of heat and the spread gives the amount of heating water flow. Once this has been established, the pipe diameter can now be calculated. For heating pipes in living areas, a limit of around 0.2 to 0.5 meters per second applies.

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