2023 Author: Philip Bishop | [email protected]. Last modified: 2023-08-25 07:54
- Material calculation
- Surface preparation
- Thermal insulation
- Heating zone selection
- Underfloor heating cable
- Laying step
- Filling the screed
Electric underfloor heating is currently used everywhere, not only in living rooms, but also on balconies, bathrooms and kitchens. It can also be used as an additional source of heating in a room together with a radiator. Its attractiveness lies in its simple installation and rapid heating of the subfloor. But it is very important to study the technology of making a warm floor in a screed, so that in the future there are no difficulties with operation.
To install a warm floor, you should stock up on a certain set of tools, which will differ depending on the specific conditions and the list of work performed. Among the main ones are:
- Underfloor heating set, which includes heating elements, temperature sensors, RCD protection system.
- Wiring, selected cable option (single-core, double-core).
- Mounts and connecting wires.
- Copper cable serving as ground.
- Reinforcing mesh or module.
- Temperature controller and more.
As for the direct laying of the electric underfloor heating in the screed, then you will have to use pliers, special clamps, a hair dryer when connecting the heating cable, etc. When all this is available, you can start planning the surface, high-quality distribution of heating elements. This, in turn, will allow you to correctly calculate the required amount of warm floor.
Some manufacturers provide their consumers with ready-made tables that allow them to determine exactly how many elements of a warm electric floor should be purchased for high-quality installation.
Much will depend on the room itself, on its heat loss. This will allow you to determine the required step of laying the heating elements, which will cover the entire possible area. It should be noted that when using an electric underfloor heating as the main source of heat, the heating cable for a concrete screed must cover more than 70% of the area of the entire room.
It is easier to make calculations when using infrared underfloor heating. It is enough just to purchase the number of heating elements that will cover a predetermined area in the room.
The electrical cable is calculated based on its length for connecting to the wiring, to the thermostat, from the meter and other elements of the warm floor. It will not be superfluous to even have some margin, so that when installing a warm floor, you do not have to be distracted from work.
When installing an electric underfloor heating, you should immediately forget about the direct connection of all components directly to the outlet. It is strictly forbidden to do this for the sake of your own safety.
It will not be superfluous to check the electrical input in an apartment or house, which must withstand the entire load and with a margin from the warm floor. Otherwise, you will have to replace it with the appropriate one, as well as install the appropriate fuses (automatic machines).
Before starting the installation of a warm floor in the room, prepare the surface for work. In some cases, it will even be necessary to remove the old screed if it is very damaged and has serious defects. It is removed to the base, to the floor slab, if possible. After that, all debris and dirt are removed from the surface.
If there are slight differences in height along the floor in the room, potholes, cracks, then it is best to fill in a small layer of rough cement-sand screed. Further work can be started only after the solution has completely dried.
When everything is ready, a layer of waterproofing is performed. In addition to the base of the floor, the material should also go to the wall, about 10-15 cm. In the future, excess areas are easily cut off with a construction knife. We must not forget about the damper tape (vertical waterproofing), which is necessary to suppress the thermal expansion of the screed during the operation of a warm electric floor.
The insulating layer is created to retain heat inside the room, and not waste it in the lower rooms. The amount of material used will depend on the room itself, its configuration, and the type of surface in the room. Thermal insulation has its own goals, which must be manifested during operation:
- Underfloor heating can act as an additional source of heating in the room. In this case, the purchase of foamed polyethylene with a foil coating (penofol) is enough. This will act as a substrate under an electric underfloor heating under a screed during the installation process.
Extruded polystyrene foam or expanded polystyrene sheets will look great on the base of the floor when the lower floor is heated.
The corresponding thickness is also selected within the range of 20-50 mm. He can choose from the entire list and other insulation that has a sufficient level of strength. The main thing is that it has an appropriate thickness.
- The rooms below do not always have their own heating system. This mainly applies to basements and garages. Here the insulation should have a layer of up to 100 mm. An alternative material is mineral wool, which has similar qualities and characteristics.
Insulation can be installed along the walls. This will also help to damp the thermal expansion of the screed during the operation of the underfloor heating system. But here the insulation should be compressible and have a thickness of no more than 20 mm.
Further, the reinforcing mesh is laid, which not only creates a very durable "cake" of the warm floor, but also provides an opportunity to attach heating elements to itself. Instead of a layer of reinforcement, adding microfiber to the solution along with plasticizers is suitable.
Heating zone selection
The heat transfer in the room must be uniform over the entire surface. Otherwise, you may encounter overheating of the heating element and its failure. Then it will be necessary to make not only the repair of a separate area, but sometimes the entire warm floor. To avoid this, the cable is placed in a concrete screed that has an identical composition over the entire area and the same distance from the top of the fill to the cable wall. You should forget about light insulating materials like sawdust or expanded clay.
Much will also depend on the chosen option for the floor covering, the degree of thermal insulation it has. After all, the heat is initially transferred to the tile or laminate, and after that the air in the room is warmed up. On the floor surface, after the installation of an electric heated floor in a screed, bulky furniture, carpets and other objects that will create obstacles for the uniform transfer of heat should not be located. If furniture does have legs, then their height should be at least 15 cm.
Previously, during the creation of a floor heating scheme on paper, all the described points should be provided. If there are such items, the areas where the heating cable will be absent are determined in advance. Laying the underfloor heating cable in the screed should be carried out in a place that is guaranteed to be open.
Underfloor heating cable
Each cable version has its own power and length. Cutting off a smaller piece of cable will immediately decrease the resistance required for 220 V. This will all lead to overheating and damage.
There are some recommendations, thanks to which you can choose the quality of the heating cable option. Much depends on the specific power of the product, which includes the number of watts required for each square meter of the room.
With such as laminate flooring, parquet or tube, the minimum power density should be 80 W / m 2. Tile or porcelain stoneware has high performance - at least 100 W per square meter. There may be cases of using a floor heating system as the main heating system. In this case, "cold" room should have a power density of 200 watts per square meters, and insulated Improvement - 150 W / m 2.
The length of the cable will be determined depending on how much area in the room will be covered by it. The production step of laying the heating element will also play a significant role. Since cables of standard length are presented in the store for sale, it is best to focus on them. When calculating, everything is done as follows:
When the room has an area of 15 m 2 and requires 1 kW of the specific power of the cable, a standard length of 80 meters is purchased on sale and a calculation is made: 15/80 and we get 0.1875 meters - the optimal laying step. The standard cable should remain unchanged in its parameters. It is better to slightly reduce or increase the laying step than not to get the necessary efficiency from the heating system later.
In addition, the cable can be single-core or two-core. This or that situation has its own peculiarities and subtleties. A single-core cable must be connected to the network at both ends. That is, it goes over the entire heated area in the room, after which it comes back.
It is better and easier to lay a two-core cable, where it is necessary to connect only the "cold" end to the network.
It is worth talking in more detail about the laying step directly, before pouring the screed onto the warm floor. From the boundary of the heated area of the room to the laid heating cable should be ½ of the laying step. The heated area is the area that stands out of the area of the entire room, where the underfloor heating is installed under the screed, from which the area of furniture items is taken away, under which the heating elements will not be installed:
S (heating) = S (room) - S (furniture)
Now you can begin to consider the choice of the optimal cable laying spacing. There is a certain formula for this:
H = S / L * 100
In the presented formula, a decoding of each component should be given: H - laying step, S - the area of the floor base that will be heated, on which the heating cable will be laid, L - the length of the heating cable used for installation.
It is best to choose the maximum laying step up to 20 cm. It is in this range that the best efficiency of heating the air in the room from the base will be. As for the heating cable, it should be at least 17 W per meter.
Filling the screed
The final stage of installing underfloor heating under the screed is the very filling of the solution, which must be prepared in strict accordance with the proportions of each component. In order not to waste your personal time preparing the solution, it is best to visit the store and purchase ready-made dry mixes specially designed for warm floors. Here it will be enough just to add a certain amount of water, which is indicated on the package. In this case, all additives and components will already be present in the composition of the solution, which will create a screed over the warm floor.
The optimum thickness of the concrete screed is 40-60 mm. Everything will depend on the specific situation, the chosen step of laying the heating elements. If, additionally, a layer of reinforcement made of a metal mesh is included in the "pie", then the thickness of the screed can be reduced to 30-40 mm.
There are other requirements for the screed, which should be paid special attention to:
- The length of one side of the tie must not exceed 5 meters.
- The maximum area of the heated screed is 20 m 2.
If the wall is larger in the room, or it is necessary to warm up a large area of the base of the floor, then it is best to use a second cable that will fit in a separate screed.
They should be separated from each other by thermal seams. In this case, crossing of heating cables is not allowed. The reason for this is the thermal expansion of the material used for installation. Heat seams located along the contour of each screed are filled with a heat insulator.
Since the screed will heat up during operation, a special additive should be added to it when preparing the solution. This will increase its elasticity, and also eliminate the likelihood of cracks on the surface during heating.
As for the proportion of mixing the solution, then 1 part of cement will require 4 parts of fine crushed stone and 4 parts of sand. In addition, a plasticizer is added, namely 0.01 parts. If the solution turns out to be very liquid, then the likelihood of cracking after laying the warm electric floor under the screed will increase. The formation of internal voids in the screed is also not allowed. This will lead to local overheating of the heating cable and its failure. You will have to spend money and time to repair the warm floor in the room.
You can turn on the heating system only after the concrete screed has completely dried, which usually takes 28 days. During all this time, conditions should be created for uniform drying and high-quality setting of the solution.
The process of performing a warm floor and further pouring a concrete solution does not take much time and does not require significant knowledge. All that is required is to follow the technology exactly and follow all the advice from the experts. The result is an excellent heating system that will transfer heat into the room from the floor itself. All this creates comfort for everyone who will be in the room. It is better to spend money once on the purchase of high-quality material than to throw out money for repairs later.
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