“Keep your head in the cold, and your feet warm” - folk wisdom that allows you to maintain health. This proverb is implemented by warm floors - one of the most technologically advanced types of space heating. But for the system to fulfill its responsibilities, it is necessary to calculate a warm water floor taking into account operating conditions.
What is a warm water floor
This type of space heating became widely used in Europe in the 80s of the last century. It was then that the mass production of polypropylene pipes began, which served as an impetus for the installation of such systems.
A warm water floor is a structure of pipes joined together that are inside a concrete screed. The water circulating inside evenly heats the floor, and he? in turn heats the room air. The water temperature is 26-40 ° C, which creates a comfortable temperature.
This heating works from boilers of any kind. But more often used gas. The temperature in the system is regulated by sensors installed in the room, as well as heat mixing valves.
Advantages and disadvantages
The basis is pipes made of polypropylene, metal, copper, corrugated stainless steel. Steel pipes are rarely used due to the complexity of installation and the high cost of the material. This type of heating has the following advantages:
- The room is heated evenly whole, and not locally, as when using radiators.
- The heating coming from the very bottom creates an air temperature that is the same at any height.
- A small amount of heating allows the use of various types of flooring.
- In the hot season, the water system can be used to remove excess heat from the room.
However, it must be taken into account that the water floor is more complicated and more expensive in its design than radiator heating. You also need to understand that installing a system in an apartment building does not work, because the consumer is forbidden to connect personal heating equipment to the engineering systems of the house.
Based on the above, we can conclude that this heating is suitable for private homes. But before installing it, you need to make a calculation of the warm water floor.
Initial data
The starting point for calculating the pipe for a warm water floor is the determination of the heat loss of a house per unit of time. The house consists of many elements, each of which has its own heat transfer. To find out how much heat the building is losing, you need to add the heat loss of the walls, floor, ceiling, windows and doorways. To the resulting number, add the losses associated with the ventilation of the room. This is another 10 to 40%. The calculation is done for the coldest time of the year.
Building materials have different heat transfer. Therefore, the main task is to determine how much heat goes out through each square meter of the building. Knowing the heat loss, you can choose the power of the boiler and calculate the length of the warm water floor. In addition, the thermal conductivity of the concrete screed and floor covering, which will retain heat, is taken into account.
To summarize, you need to list the parameters that are taken into account during design:
- Floor temperature. It should be heated to +30 ° C. This temperature should not be confused with the temperature of the coolant, which, naturally, is higher.
- The part of the floor adjacent to the external walls must be heated to +35 ° C to compensate for heat dissipation through walls and windows.
- In all places with high humidity (bathrooms, rooms for drying clothes), the floor temperature should not be lower than +33 ° C.
- Pipe laying configuration. Installation distances between branches are taken into account here.
- The materials from which the house is built.
- Flooring. The higher its thermal conductivity, the more quickly the floor and the room will heat up. The most optimal materials are tile, porcelain stoneware, marble slab. Materials from wood, as well as from its waste, do not transfer heat well.
Underfloor construction
The warm floor has a complex structure. In construction, it is called a pie because of the large number of layers. It consists of:
- Bearing base. It can be a rough floor or concrete slab.
- Waterproofing from a layer of plastic film, limited along the contour with a damper tape.
- Heat insulating layer. It does not allow heat to go under the floor.
- Pipes serving as a coolant conductor.
- Concrete screed.
- Flooring.
Types of pipe laying
Before starting the design, a warm water floor is calculated. The length of the pipe is the main characteristic that needs to be set. It depends on the required thermal power and on the material of the pipes, which have a different coefficient of thermal conductivity. The higher it is, the shorter the pipe can be used. The highest ratio is for a copper pipe. However, it is rarely used due to the high cost. The water circuit, depending on its length, is performed in several ways:
- Snail. The pipe is double stacked in a spiral starting from the center of the room to the periphery. The distance between adjacent branches is taken equal to 100 mm. This method is good because in a room of any size, the floor has the same temperature.
- The snake. The pipe is laid out in parallel branches, sequentially filling the room area. This type of installation is simpler, but it has a drawback: the floor temperature varies depending on the distance from the heat carrier source. In a large room, the difference can be up to 10 ° C due to the gradual cooling of the water.
The location of the water circuit is first drawn on paper with markup. Then, according to the scheme, the required pipe length is found.
Calculation of the length of the pipe of a warm water floor
To calculate the length of the thermal circuit, 3 parameters are needed: the area of the room, the laying pitch, the pipe bending coefficient. The formula for the calculation will look as follows:
L = S / N x 1.1, where L is the length of the circuit, S is the area of the room, N is the distance between the turns.
From the distribution manifold to the return, the circuit is laid in a single cut. The thicker the pipe, the higher the heat transfer. Sizes from 16 to 25 mm are used. Concrete screed is made no more than 60 mm. If you do more, the heat will be absorbed by the concrete pad.
What temperature should the coolant have
The water temperature in the circuit depends on the temperature of the boiler’s water jacket. For the solid fuel boiler to function properly, the medium temperature must not drop below 55 ° C. Therefore, the calculation of the power of a warm water floor is based on this figure. This temperature is enough to warm the room to 25-27 ° C.
The amount of water passing through the system depends on the thickness of the pipe, as well as on the power of the pump. On average, it is 2 l / min per 10 square meters. m
Reduces the room temperature by reducing the capacity of the feed collector.
Calculation of thermal power
Calculation of a warm water floor is made to determine the necessary heat output. Building materials and room configuration are taken into account. The dependence of power on heat loss at home is expressed in the formula:
Mn = Q x 1.2, where Q is the total heat loss of the room in watts. A factor of 1.2 indicates that there should be a margin of power when designing the circuit.
To determine the heat loss, the materials from which the ceilings, windows, doorways, and their area are made are taken into account. The thermal conductivity of the materials is taken from the tables.
Floor heat loss is not taken into account. The area of wall ceilings is measured on the outside, taking into account the angles. Heat loss of each part of the room is calculated as follows:
Q = 1 / R x (t in - t n) x S x (1+ ∑ β), where:
- R is the thermal resistance of the material of which the floor is made. It is obtained by multiplying the tabular value of the resistance coefficient by the thickness: R = δ / λ;
- t in - the desired indoor temperature, t n - the minimum temperature in the region;
- S - area of overlap, calculated by multiplying the width by length. ∑β - the sum of heat losses associated with the location of the building relative to the cardinal points. Also, losses related to wind direction can be added to this category.
Calculation Example
The specific option makes it more clear how the formulas are applied. Take for example a wooden room with a total wall area of 80 square meters. m. The maximum temperature in winter is -35 ° C, the room temperature +25 ° C. We perform the calculation for warm water floors, the installation of which is planned in the north-western part of the house:
- We find the thermal resistance (R) of the wall ceilings. The value of λ is taken from the tabular data. For wood, it is 0.14 m² x C ° / W. Divide by the wall thickness of 0.2 m, we get 0.7 m² x C ° / W.
- We find the total heat loss of the walls of the room. Q = 1 / 0.7 x (25 - (-35)) x 80 x (1 + 0.1) = 7542 W.
R for the ceiling is calculated based on the thermal resistance of the ceiling insulation. The area is taken equal to the floor area. In addition, there is similarly heat loss for windows and a doorway. The sum of all the values found will be the total heat loss of the room. The resulting figure needs to be increased by 1.2 times. This work will be the necessary power for underfloor heating.
If the design of the water circuit does not provide the desired heat dissipation, then in this case additional heaters are installed to compensate for the missing power.
Computer calculation
To avoid studying the thermal conductivity tables, you can calculate the warm water floor in Valtec. It is free, does not require registration. In addition to heating, it can calculate data on water supply, sewage, hydraulics. And also calculate the aerodynamics of the chimney.
In addition to computer programs on the Internet, there are online calculators that, taking into account the size of the room, make up a pipe laying scheme for a warm floor, and also calculate the water floor heating over an area.
Another type of calculator determines the cost of underfloor heating based on the heated area, pipe pitch, and materials used. Such a program is more suitable for budgeting.