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A heating boiler is a device that, by means of the combustion of fuel (or electricity), heats the coolant.
The device (design) of the heating boiler: heat exchanger, thermally insulated housing, hydraulic unit, as well as safety elements and automation for control and monitoring. For gas and diesel boilers, a burner is provided in the design, for solid fuel boilers - a firebox for firewood or coal. Such boilers require a chimney connection to remove combustion products. Electric boilers are equipped with heating elements, do not have burners and a chimney. Many modern boilers are equipped with built-in pumps for forced circulation of water.
The principle of operation of the heating boiler- the heat carrier, passing through the heat exchanger, heats up and then circulates through the heating system, giving off the received thermal energy through radiators, underfloor heating, heated towel rails, and also providing water heating in the indirect heating boiler (if it is connected to the boiler).
Heat exchanger - a metal container in which the coolant (water or antifreeze) is heated - can be made of steel, cast iron, copper, etc. Cast iron heat exchangers are resistant to corrosion and quite durable, but are sensitive to sudden temperature changes and have big weight. Steel can suffer from rust, so their internal surfaces are protected by various anti-corrosion coatings to increase their service life. Such heat exchangers are the most common in the manufacture of boilers. Corrosion is not terrible for copper heat exchangers, and due to the high heat transfer coefficient, low weight and dimensions, such heat exchangers are popular, often used in wall boilers, but usually more expensive than steel.
In addition to the heat exchanger, an important part of gas or liquid fuel boilers is a burner, which can be various kinds: atmospheric or fan, single-stage or two-stage, with smooth modulation, double. ( Detailed description burners are presented in articles about gas and liquid fuel boilers).
To control the boiler, automation is used with various settings and functions (for example, a weather-compensated control system), as well as devices for remote control of the boiler - a GSM module (controlling the operation of the device via SMS messages).
Main technical specifications heating boilers are: boiler power, type of energy carrier, number of heating circuits, type of combustion chamber, type of burner, type of installation, pump availability, expansion tank, boiler automation, etc.
To determine required power heating boiler for a house or apartment, a simple formula is used - 1 kW of boiler power for heating 10 m 2 of a well-insulated room with a ceiling height of up to 3 m. Accordingly, if heating is required basement, glazed winter garden, rooms with non-standard ceilings etc. boiler output must be increased. It is also necessary to increase the power (about 20-50%) while providing the boiler with hot water (especially if heating the water in the pool is necessary).
We note the feature of calculating the power of gas boilers: the nominal gas pressure at which the boiler operates at 100% of the power declared by the manufacturer for most boilers is from 13 to 20 mbar, and the actual pressure in gas networks in Russia can be 10 mbar, and sometimes below. Accordingly, a gas boiler often works only at 2/3 of its capacity, and this must be taken into account when calculating. When choosing the power of the boiler, be sure to note all the features of the thermal insulation of the house and premises. In more detail with a table for calculating the power of a heating boiler, you can
So which boiler is better to choose? Consider the types of boilers:
"Middle class"- average price, not so prestigious, but quite reliable, standard standard solutions. These are Italian boilers Ariston, Hermann and Baxi, Swedish Electrolux, German Unitherm and boilers from Slovakia Protherm.
"Economy class" - budget options, simple models, the service life is shorter than that of boilers of a higher category. Some manufacturers have budget models of boilers, for example,
The efficiency of the heating system depends on many factors. These include the rated power, the degree of heat transfer of radiators and the temperature regime of operation. For the latter indicator, it is important to choose the right degree of heating of the coolant. Therefore, it is necessary to determine the optimal temperature in the heating system for water, radiators and the boiler.
What determines the temperature of the water in the heating
For correct operation heat supply requires a graph of the temperature of the water in the heating system. According to it, the optimal degree of heating of the coolant is determined depending on the influence of certain external factors. It can be used to determine what water temperature in the heating batteries should be in a certain period of time the system is running.
It is a common misconception that the higher the degree of heating of the coolant, the better. However, this increases fuel consumption, increasing operating costs.
Often, the low temperature of the radiators is not a violation of the norms for heating the room. A low-temperature heat supply system was simply designed. That is why the exact calculation of water heating should be given Special attention.
Optimum temperature water in heating pipes largely depends on external factors. To determine it, the following parameters must be taken into account:
- Heat loss at home. They are decisive for the calculation of any type of heat supply. Their calculation will be the first stage in the design of heat supply;
- Boiler characteristics. If the operation of this component does not meet the design requirements, the water temperature in the heating system of a private house will not rise to the desired level;
- Material for the manufacture of pipes and radiators. In the first case, it is necessary to use pipes with a minimum thermal conductivity. This will reduce heat losses in the system during the transportation of the coolant from the boiler heat exchanger to the radiators. For batteries, the opposite is important - high thermal conductivity. Therefore, the temperature of the water in the radiators central heating, made of cast iron, should be slightly higher than that of aluminum or bimetallic structures.
Is it possible to independently determine what temperature should be in the radiators? It depends on the characteristics of the system components. To do this, you should familiarize yourself with the properties of the batteries, the boiler and the heat supply pipes.
In a centralized heating system, the temperature of the heating pipes in the apartment is not an important indicator. It is important that the norms for heating the air in living rooms.
Heating standards in apartments and houses
In fact, the degree of water heating in pipes and heat supply radiators is a subjective indicator. It is much more important to know the heat dissipation of the system. It, in turn, depends on the minimum and Maximum temperature water in the heating system can be reached during operation.
For autonomous heat supply, the norms of central heating are quite applicable. They are detailed in the resolution of the PRF No. 354. It is noteworthy that the minimum water temperature in the heating system is not indicated there.
It is only important to observe the degree of heating of the air in the room. Therefore, in principle, the temperature regime of operation of one system can be different from another. It all depends on the influencing factors that were mentioned above.
In order to determine what temperature should be in the heating pipes, you should familiarize yourself with the current standards. In their content there is a division into residential and non-residential premises, as well as the dependence of the degree of air heating on the time of day:
- In rooms during the daytime. In this case, the standard heating temperature in the apartment should be +18°C for rooms in the middle of the house and +20°C in the corners;
- In living rooms at night. Some reduction is allowed. But at the same time, the temperature of the heating radiators in the apartment should provide, respectively, + 15 ° С and + 17 ° С.
Responsible for compliance with these standards Management Company. In case of their violation, you can request a recalculation of payment for heating services. For autonomous heat supply, a table of temperatures for heating is made, where the values \u200b\u200bof the heating of the coolant and the degree of load on the system are entered. At the same time, no one bears responsibility for violation of this schedule. This will affect the comfort of staying in a private house.
For centralized heating, it is mandatory to maintain the required level of air heating in the landings and non-residential premises. The temperature of the water in the radiators must be such that the air is heated to a minimum value of +12°C.
Calculation of the temperature regime of heating
When calculating the heat supply, the properties of all components must be taken into account. This is especially true for radiators. What is the optimal temperature in the radiators - + 70 ° C or + 95 ° C? It all depends on the thermal calculation, which is performed at the design stage.
First you need to determine the heat loss in the building. Based on the data obtained, a boiler with the appropriate power is selected. Then comes the most difficult design stage - determining the parameters of heat supply batteries.
They must have a certain level of heat transfer, which will affect the temperature curve of the water in the heating system. Manufacturers indicate this parameter, but only for a certain mode of operation of the system.
If you need to spend 2 kW of thermal energy to maintain a comfortable level of air heating in a room, then the radiators must have no less heat transfer.
To determine this, you need to know the following quantities:
- Permissible maximum water temperature in the heating system -t1. It depends on the power of the boiler, the temperature limit of exposure to pipes (especially polymer pipes);
- Optimal the temperature that should be in the heating return pipes - t This is determined by the type of wiring of the mains (one-pipe or two-pipe) and the total length of the system;
- Required degree of air heating in the room -t.
Tnap=(t1-t2)*((t1-t2)/2-t3)
Q=k*F*Tnap
Where k- heat transfer coefficient of the heating device. This parameter must be specified in the passport; F- radiator area; Tnap- thermal pressure.
By varying the various indicators of the maximum and minimum water temperatures in the heating system, you can determine the optimal mode of operation of the system. It is important to correctly initially calculate the required power of the heater. Most often, the indicator of low temperature in heating batteries is associated with heating design errors. Experts recommend adding a small margin to the obtained value of the radiator power - about 5%. This will be needed in case of a critical decrease in the temperature outside in the winter.
Most manufacturers indicate the heat output of radiators according to the accepted standards EN 442 for mode 75/65/20. This corresponds to the norm of the heating temperature in the apartment.
Water temperature in the boiler and heating pipes
After performing the above calculation, it is necessary to adapt the heating temperature table for the boiler and pipes. During the operation of the heat supply, emergency situations should not occur, common cause which is a violation of the temperature graph.
The normal indicator of water temperature in central heating batteries can be up to + 90 ° С. This is strictly monitored at the stage of preparation of the coolant, its transportation and distribution to residential apartments.
Much the situation is more complicated with autonomous heating. In this case, control completely depends on the owner of the house. It is important to ensure that there is no excess of water temperature in the heating pipes that goes beyond the schedule. This may affect the security of the system.
If the water temperature in the heating system of a private house exceeds the norm, the following situations may occur:
- Pipeline damage. In particular, this applies to polymer lines, in which the maximum heating can be + 85 ° C. That is why the normal value of the temperature of the heating pipes in an apartment is usually + 70 ° C. Otherwise, deformation of the line may occur and a rush will occur;
- Air heating excess. If the temperature of the heat supply radiators in the apartment provokes an increase in the degree of air heating above + 27 ° C - this is beyond the normal range;
- Reduced service life of heating components. This applies to both radiators and pipes. Over time, the maximum temperature of the water in the heating system will lead to breakdown.
Also, a violation of the water temperature schedule in the autonomous heating system provokes the formation of air locks. This occurs due to the transition of the coolant from a liquid state to a gaseous state. Additionally, this affects the formation of corrosion on the surface of the metal components of the system. That is why it is necessary to accurately calculate what temperature should be in the heat supply batteries, taking into account their material of manufacture.
The most common violation thermal regime work is observed in solid fuel boilers. This is due to the problem of adjusting their power. When a critical temperature level in the heating pipes is reached, it is difficult to quickly reduce the boiler power.
The influence of temperature on the properties of the coolant
In addition to the above factors, the temperature of the water in the heat supply pipes affects its properties. This is the principle of operation of gravitational heating systems. With an increase in the level of heating of water, it expands and circulation occurs.
However, in the case of using antifreezes, the excess temperature in the radiators can lead to other results. Therefore, for heat supply with a coolant other than water, you must first find out the permissible indicators of its heating. This does not apply to the temperature of district heating radiators in the apartment, since antifreeze-based fluids are not used in such systems.
Antifreeze is used if there is a possibility of low temperature affecting the radiators. Unlike water, it does not begin to change from a liquid to a crystalline state when it reaches 0°C. However, if the work of heat supply is outside the norms of the temperature table for heating upwards, the following phenomena may occur:
- Foaming. This entails an increase in the volume of the coolant and, as a consequence, an increase in pressure. The reverse process will not be observed when the antifreeze cools;
- Formation of limescale. The composition of antifreeze includes a certain amount of mineral components. If the norm of the heating temperature in the apartment is violated in a big way, their precipitation begins. Over time, this will lead to clogging of pipes and radiators;
- Increasing the density index. There may be malfunctions in the operation of the circulation pump if its rated power was not designed for the occurrence of such situations.
Therefore, it is much easier to monitor the temperature of the water in the heating system of a private house than to control the degree of heating of antifreeze. In addition, ethylene glycol-based compounds emit a gas harmful to humans during evaporation. Currently, they are practically not used as a coolant in autonomous systems heat supply.
Before pouring antifreeze into the heating, all rubber gaskets should be replaced with paranitic ones. This is due to the increased permeability of this type of coolant.
Ways to normalize the temperature regime of heating
The minimum value of the water temperature in the heating system is not the main threat to its operation. This, of course, affects the microclimate in residential premises, but in no way affects the functioning of heat supply. In case of excess of norm of heating of water there can be emergencies.
When drawing up a heating scheme, it is necessary to provide for a number of measures aimed at eliminating a critical increase in water temperature. First of all, this will lead to an increase in pressure and an increase in the load on the inner surface of pipes and radiators.
If this phenomenon is one-time and short-lived, the heat supply components may not be affected. However, such situations arise under the constant influence of certain factors. Most often, this is the incorrect operation of a solid fuel boiler.
- Installing a security group. It consists of an air vent, a bleed valve and a pressure gauge. If the water temperature reaches a critical level, these components will remove excess coolant, thereby ensuring the normal circulation of the liquid for its natural cooling;
- mixing unit. It connects the return and supply pipes. Additionally, a two-way valve with a servo drive is installed. The latter is connected to a temperature sensor. If the value of the degree of heating exceeds the norm, the valve will open and the flows of hot and cooled water will mix;
- Electronic heating control unit. It records the temperature of the water in various parts of the system. In case of violation of the thermal regime, he will give the appropriate command to the boiler processor to reduce power.
These measures will help prevent incorrect operation of the heating for another initial stage the occurrence of a problem. The most difficult thing is to regulate the level of water temperature in systems with a solid fuel boiler. Therefore, for them, special attention should be paid to the choice of parameters of the safety group and the mixing unit.
The effect of water temperature on its circulation in heating is described in detail in the video:
