2023 Author: Philip Bishop | [email protected]. Last modified: 2023-08-25 07:54
- Pipe requirements
- Pipe manufacturers
- Pros and cons of pipe materials
- What is the best option?
The underfloor heating system has become an excellent solution that allows owners of new houses or apartments to abandon traditional heating pipes. Underfloor heating can be both the main source of the space heating system, and be part of the systems combined with radiators if the climate is rather harsh.
Over time, electrical systems were replaced by water systems, which, although more difficult to install, are much safer and more economical than electrical ones. And it is important to be able to understand how to approach the choice of pipe material for a water-heated floor and what to look for when choosing.
First of all, you need to understand that the pipes will be used to heat the room, which means that there is no place in the system for ordinary pipes used for cold or hot water supply. The main factor that heating pipes should have is durability, because temperature and pressure drops will constantly load the entire system.
In order for the installation to be of the highest quality, pipes for a warm floor must have high resistance to bending, that is, they must not allow cracks or breaks. Elasticity is another important quality that heating pipes should have, because all installation work will be done manually, which means that the pipes will have to be bent by hand.
During operation, the heating system must be protected against oxidation, which means that the pipes must be well insulated and completely sealed. These factors will also help minimize corrosive effects on the system.
If we talk about the final choice of material, then all the listed characteristics correspond to pipes from:
- cross-linked polyethylene;
All pipes produced for water underfloor heating systems are made with a diameter of 16-20 mm, withstand temperatures up to 120 degrees Celsius and a pressure of 5 bar.
A special place when choosing a pipe, regardless of the material chosen, will play the name of the manufacturer. A good reputation will allow you to be confident that the products are guaranteed to fulfill their intended purpose, and the likelihood of a defect will tend to zero.
Popular brands include Rehau (famous for XLPE pipes), Valtec (metal-plastic and polypropylene pipes), KERMI (metal-plastic pipes) Oventrop, Wieland, Q-Tec (copper and polypropylene pipes).
Pros and cons of pipe materials
For a water heated floor, they are made of metal polymers, polypropylene, copper and cross-linked polyethylene. Consider the main characteristics and features of the use of each of these materials.
The popularity of pipes made of metal-plastic is due to the cheapness of the material, as well as the absence of the need for additional equipment to connect them - a wrench and human strength are enough to connect using compression fittings. The pipes can withstand temperatures up to 95-110 degrees and a very high pressure indicator - operation up to 20 atmospheres is possible.
The structure of pipes made of metal-plastic consists of two layers of polyethylene, between which there is a metal tube made of aluminum. Between the layers of aluminum and polyethylene there is an adhesive composition that connects all layers into a single structure.
The aluminum tube is designed to give strength to the structure and also to keep oxygen out of the system. It is also designed to reduce the relative change in the length of the pipe due to temperature changes, due to the low coefficient of thermal expansion. Polymers protect aluminum from corrosion and the negative influence of the coolant.
We also note other advantages of pipes made of metal-plastic:
- low price of pipes and ease of installation;
- good flexibility - a bend radius of up to 7 pipe diameters is possible;
- low weight of the structure;
- good sound insulation characteristics.
Unfortunately, metal-plastic pipes have a number of disadvantages. First, due to the fact that polyethylene and aluminum have different coefficients of expansion, pipe delamination is possible during operation due to poor-quality adhesive composition connecting the layers. This can also lead to weakening of the connections, due to which pipes can leak at the fittings.
Secondly, metal-plastic pipes are very unreliable in terms of mechanical strength. Any minor damage can form cracks, which will begin to leak over time. This must be taken into account when assembling the system, without pinching the pipes at the joints, in order to avoid an incision, which will necessarily leak.
And thirdly, although the pipes themselves are quite cheap, the total cost of a system including fittings can be higher than, say, polypropylene systems. Given this, the use of metal-plastic may not be the most profitable option.
The pipes are supplied in diameters of 16, 18 and 20 mm, the length of one pipe is 50, 100 and 200 meters, with a thickness of 2 mm.
By using pipes made of polypropylene (PP marking), structures of any complexity can be achieved. Structurally, such pipes are a single body, unlike metal-plastic, they do not have a metal layer. This can result in an obvious disadvantage - polymers have a high coefficient of linear expansion.
To reduce the coefficient of expansion, pipes are reinforced with aluminum or fiberglass
The advantages are similar to those of metal-plastic:
- lack of corrosion;
- low cost of pipes;
- high temperature and pressure indicators that the system can withstand - up to 110 degrees Celsius and up to 20 atmospheres;
- high flexibility - bending radius can be 8-9 pipe diameters.
The connection is carried out using a welding machine, which translates into another advantage - no leaks at the joint. A similar process can allow the entire system to be monolithic, in contrast to reinforced-plastic pipes, which are not suitable for this.
The peculiarity of the polymer composition provides resistance to defrosting. This means that even if the liquid in the system is frozen, this will not affect the intactness of the pipes - when thawing, the form will return to its original form. However, there is a lower temperature limit at which installation can be carried out - not lower than 15 degrees Celsius.
Among polymeric materials, polyethylene (PE) is the leader in distribution in the environment of heating pipes. If earlier ordinary polyethylene was used to transport cold water, due to a decrease in strength at temperatures from 50 degrees Celsius, then towards the end of the 20th century it was possible to bind polyethylene molecules, or in another way "sew" them.
This material (XLPE is marked with PE-X) has the best strength and resistance to high temperatures and UV radiation. However, unlike polypropylene, pipes cannot be welded to each other due to the peculiarities of the chemical composition. However, XLPE has sufficient elasticity for the use of fittings, which will be characterized by high tightness.
There are different ways of "crosslinking" molecules, depending on which the characteristics of the material can change. It is recommended to choose pipes of the PE-Xb type, which have a crosslinking density of 65%.
XLPE pipes can withstand coolant temperatures from 0 to 95 degrees Celsius, and the installation of the system can be carried out even at negative temperatures (up to -15 degrees Celsius). The pressure in the system can reach 10-12 atmospheres. Bending up to 7 diameters can be achieved manually, but a building vein can be used if a larger radius is required. Separately, it should be noted that the material is well resistant to chemical and biological effects and corrosion.
The outer diameter of pipes for heating can be 16 or 20 mm, thickness - 2 mm, pipes are supplied in reels of 240-300 meters.
As for the use of all-metal pipes for a water-heated floor, copper is beyond competition. The highest temperature and pressure range that the system can handle makes copper pipes the most versatile material of all.
Copper pipes age for a very long time and are able to endure frequent freezing without damage, which is especially practical in domestic conditions - if the operating requirements are met, copper pipes will withstand 50 winters without repair or replacement. In addition, they bend well, manually you can achieve a bend of 6-8 pipe diameters, which is very convenient when installing the system.
Copper pipes operate at temperatures from -160 to 200 degrees Celsius and system pressures from 10 to 27 atmospheres
We also note the disadvantages of copper pipes:
- the coolant must have acceptable acidity and rigidity, which can cause pitting of pipes;
- frequent draining of the coolant from the system is undesirable;
- contact of copper with other materials should not be allowed, so that electromechanical corrosion does not appear.
Well, the most obvious drawback of copper pipes is their high cost. On average, manufacturers offer options that are 2-3 times more expensive than, for example, polyethylene pipes. The installation of the system will also be more costly - for work, you will need press machines to connect pipes using press fittings. Self-installation of pipes is also questionable, since the presence of specialists will be required for competent work with the equipment, which will also result in costs.
The diameters of copper pipes can be 16, 20, 26 and 32 mm, and the length is 100 or 200 meters. Pipe thickness - 2 mm.
What is the best option?
If the monetary component does not bother you, then underfloor heating from copper pipes will be the best option - high heat transfer and durability are important advantages. However, polyethylene pipes are also well suited - they are cheaper, and given that the pipes are selected for domestic houses and apartments, they are well suited for the required characteristics.
As for the installation of the underfloor heating system, almost all of the options presented have the ability to work independently. But, if we are talking about copper or metal-plastic pipes, then you may need the help of professionals so that in the future the mounted system can please you with warmth without problems.
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