Underfloor heating in a private house: schemes and installation rules

Recommendation points

• Selection of pipes for floor heating
• Ensuring circulation
• Manifold assembly
• Temperature preparation unit
• Insulation and storage layer
• Installation nuances

Unlike an electric floor heating on a liquid heat carrier, it requires more complex calculations for integration into the heating system. The service life and efficiency of the system directly depend on the correct choice of materials, fittings, installation and heating operation scheme.

Selection of pipes for floor heating

In contrast to popular belief, the choice of pipes for installing a heat exchanger in the floor is not so wide. There are two options in total: XLPE and copper. The most obvious advantages of special materials are durability, deformation resistance, low coefficient of linear expansion. But the main advantage is the oxygen barrier, which ultimately prevents the formation of sediment on the inner surface of the pipes..

The meaning of the use of copper in the high thermal conductivity of the tubes and resistance to corrosion. An obvious disadvantage is the complexity of installation and a high risk of failure in the presence of solid particles (sand) in the coolant. Despite the fact that soldering requires only an inexpensive gas lamp and flux, bending the coil correctly is a difficult task. This is despite the fact that there can be several tens of turns of the copper tube and one mistake that leads to a break leads to the rejection of the entire segment or the need for additional soldering.

Polymer (polyethylene) pipes have a higher coefficient of thermal expansion, in addition, they lose their strength properties when heated above operating temperatures, however, in warm floors, in principle, the coolant does not heat up above 40 ° C. Ease of installation is an obvious plus. Easy to bend and fit in a spiral or coil. The pipe is delivered in coils of 200 m each, allowing you to install underfloor heating without a single joint in the entire volume of the future screed. Most branded polyethylene pipes involve the use of special tools for crimping and welding.

Ensuring circulation

Hot water heating systems with underfloor heating do not work according to the gravitational principle and are always volatile. Because of this, overheating occurs: failures in the circulation and recirculation system can supply even 70–80? C, so the funds from saving on the use of polymer pipes should at least partially be spent on improving automation and auxiliary mechanisms.

The flow rate of the coolant in the tubes is strictly regulated by the manufacturer; assigning this task to the general circulation of the system means increasing the risk of malfunctions. A forced circulation device must be installed in front of the collector unit, then each of the circuits is adjusted to adjust the required flow rate. This determines the maximum loop length of each circuit and the temperature difference at its beginning and end..

For pumping water in the system, circulation pumps are used, designed for radiator heating systems. The diameter of the nozzles is determined by the required throughput of the pipe with which the pump is connected to the manifold. The lift height (or injection pressure) is determined by the total hydrodynamic resistance of the pipes declared by their manufacturer for different loop configurations and bending radii. Each connection requires an increase in the lift height. Speed ​​control for underfloor heating pumps is not required, however, with accelerated circulation, more intensive pumping of the system is possible to quickly enter the mode.

Manifold assembly

When using more than one branch for floor heating, the presence of a manifold assembly (comb) is strictly required. Self-soldering of the collector, even for two loops, will not give the desired result, it is almost impossible to balance the lines in the absence of uniform distribution and valve regulators.

The collector is selected both by the number of branches and by the total throughput. Essentially, it is a multi-channel flow regulator. Of the body materials, stainless steel and high-quality brass are preferred. For underfloor heating, two types of collectors can be used. If the difference in the length of the circuits is less than 20-30 meters, ordinary brass valves with ball valves are suitable. With a larger spread of hydrodynamic resistances, a specialized collector with flow regulators at each branch is needed.

Please note that it is not necessary to buy a double (supply + return) collector. You can install a high-quality mixer with flow meters on the supply line, and a cheaper one with valve (not ball) valves on the return. Separately, it is worth paying attention to what type of pipes the manifold unit is designed for. Most cheap products imply the connection of MP pipes, which are poorly suited for a warm floor and therefore are used less and less. For polyethylene circuits, it is better to spend money on reliable and proven REHAU collectors, for copper pipe systems – Valtec and APE. The connection of copper pipes to the manifold is recommended through a flare and / or a threaded fitting; direct soldering is not recommended due to the low maintainability of such connections.

Temperature preparation unit

The manifold itself is not the entire collector. When assembled, the mixing unit is completed with special fittings, which ensure the adjustment of the water temperature before entering the system. Both hot and cold water can be mixed, which fundamentally determines the specifics of the work of two types of mixing.

A simple scheme for switching on a warm floor. 1 – three-way valve; 2 – circulation pump; 3 – ball valve with a thermometer; 4 – distribution manifold with flow meters; 5 – return manifold with control valves; 6 – the contour of the warm floor. The temperature in the circuit is controlled manually and is highly dependent on the temperature of the coolant at the inlet.

The first type uses a closed circulation cycle, mixing hot water with a three-way valve as needed. The disadvantage of the system is that in the event of malfunctions in the operation of automation or the use of solid fuel boilers, a large amount of hot water can be supplied at a time, which negatively affects polymers, as well as the floor covering and the microclimate in the room. Therefore, hot water pumping is practiced mainly in systems with copper pipes..

A ready-made mixing unit for underfloor heating. The temperature control and the degree of mixing of the coolant are carried out fully automatically

For polyethylene circuits, more expensive collectors are preferred, which mix cold water from the return to reduce the incoming temperature. The complexity of such mixing units is due to the presence of an additional recirculation pump. Regulation can be carried out either by an adjustable two-way valve or by an electronic thermostat that controls the speed of the pump motor. The latter is an example of the struggle for accuracy and reduction of the system inertia, by the way, it is very successful. However, such systems are volatile..

Whether to take the collector assembly is a controversial issue. Of course, the availability of a guarantee is an obvious plus, but it is not always possible to find a model with the necessary strapping and the number of taps, in such cases you will have to assemble the device yourself.

Insulation and storage layer

The cake of a water-heated floor is as follows: polymeric foam insulation, heating pipes and a heat-accumulating screed in the order from bottom to top. The thickness and materials used for the main layers must be selected in accordance with the operating parameters of the system.

Insulation is selected taking into account the planned heating temperature, or more precisely, the temperature difference between the warm and the subfloor. They mainly use EPS or PPU plates with butting edges. This material is practically incompressible under distributed load, while the resistance to heat transfer is one of the highest. The approximate thickness of the polymer insulation is 35 mm for a temperature difference of 30 ° C and then 3 mm for every 5 ° C.

Ways to install a warm floor in a private house. Three options for fastening and distributing pipes are proposed: A – Use of special mounting mats for warm floors. B – Installation on a reinforcing mesh with a step of 10&nbs; cm using plastic ties. C – Laying pipes in prepared gutters in insulation using reflective screens. Underfloor heating construction: 1 – concrete base of the subfloor; 2 – insulation; 3 – damper tape; 4 – concrete screed; 5 – floor covering; 6 – reinforcing mesh.

In addition to protecting the pipes from damage, the screed regulates the inertia of the heating system and smoothes the temperature difference between the floor areas directly above and between the pipes. If the boiler operates in a cyclic mode, the heated concrete will give off heat, even if there is temporarily no hot water supply. In case of accidental overheating, the heat-absorbing screed will provide temperature removal, excluding pipe damage. The average thickness of the screed is 1 / 10–1 / 15 of the distance between adjacent tubes. By increasing the thickness, you can get rid of the heat-zebra effect with sparse piping. Naturally, the consumption of materials, as well as the inertia and the time the system reaches the mode, will increase..

When installing underfloor heating on the ground, it is necessary to pour a 15–20 cm incompressible layer of ASG. Crushed stone can be replaced with expanded clay for additional thermal insulation. On insulated frame floors, the underfloor heating can be laid directly on top of the waterproofing agent, with which the subfloor is covered in order to avoid the release of cement milk from the screed. In the best case, a thermal cut-off layer of polyurethane foam or EPS of 20–25 mm is arranged under the tubes. Even such a thin layer is enough to eliminate the cold bridges represented by the floor supporting structure, as well as to distribute the load from the screed..

Installation nuances

Installation of underfloor heating water should take place according to a pre-planned scheme. The collector requires a place equipped for installation, it can be either a boiler room or a compartment hidden in the wall. The rationale for installing intermediate headers depends on whether savings are achieved compared to laying pipes from a central distribution unit, and also whether such an increase in the length of the largest loop is acceptable. It is recommended to supply pipes to heating zones in rooms that do not require targeted floor heating: storerooms, corridors and others like them.

Fasten the underfloor heating pipes only to a special installation system. Perforated tape or mesh provides accurate adjustment of the installation step, reliable fixation during the mixture solidification and the gaps necessary for the temperature solution.

The fixing of the installation system to the floor is carried out through the insulation without significant pressure. You need to fix it in the holes formed after bending the petals to crimp the tubes. Thus, the attachment points are located most close to the heating elements, which excludes their floating, displacement or lifting of the entire system when pouring concrete.