Norms and optimal values ​​of the coolant temperature. The return of the heating battery is cold - device, causes, remedies

Let's start with a simple diagram:

In the diagram we see a boiler, two pipes, an expansion tank and a group of heating radiators. The red pipe hot water goes from the boiler to the radiators is called DIRECT. And the lower (blue) pipe through which more cold water comes back, so it's called - REVERSE. Knowing that when heated, all bodies expand (including water), an expansion tank is installed in our system. It performs two functions at once: it is a supply of water to feed the system and excess water goes into it when it expands from heating. Water in this system is a heat carrier and therefore must circulate from the boiler to the radiators and vice versa. Either a pump or, under certain conditions, the force of the earth's gravity can make it circulate. If everything is clear with the pump, then with gravity, many may have difficulties and questions. We dedicated a separate topic to them. For more deep understanding process, let's look at the numbers. For example, the heat loss of a house is 10 kW. The operating mode of the heating system is stable, that is, the system neither warms up nor cools down. In the house, the temperature does not rise or fall. This means that the boiler generates 10 kW and the radiators dissipate 10 kW. From a school physics course, we know that we need 4.19 kJ of heat to heat 1 kg of water by 1 degree. If we heat 1 kg of water by 1 degree every second, then we need power

Q \u003d 4.19 * 1 (kg) * 1 (deg) / 1 (sec) \u003d 4.19 kW.

If our boiler has a power of 10 kW, then it can heat 10 / 4.2 = 2.4 kilograms of water per second by 1 degree, or 1 kilogram of water by 2.4 degrees, or 100 grams of water (not vodka) by 24 degrees. The formula for boiler power looks like this:

Qcat \u003d 4.19 * G * (Tout-Tin) (kW),

where
G- water flow through the boiler kg / s
Tout - water temperature at the outlet of the boiler (possibly T direct)
Тin - water temperature at the inlet to the boiler (possible T return)
Radiators dissipate heat and the amount of heat they give off depends on the heat transfer coefficient, the surface area of ​​the radiator and the temperature difference between the radiator wall and the air in the room. The formula looks like this:

Qrad \u003d k * F * (Trad-Tvozd),

where
k is the heat transfer coefficient. The value for household radiators is practically constant and equal to k \u003d 10 watt / (kv meter * deg).
F- total area of ​​radiators (in sq. meters)
Trad-average temperature of the radiator wall
Tair is the air temperature in the room.
With a stable mode of operation of our system, the equality will always be satisfied

Qcat=Qrad

Consider detail work radiators using calculations and numbers.
Let's say the total area of ​​their ribs is 20 square meters (which approximately corresponds to 100 ribs). Our 10 kW = 10000 W, these radiators will give out with a temperature difference of

dT=10000/(10*20)=50 degrees

If the temperature in the room is 20 degrees, then the average surface temperature of the radiator will be

20+50=70 degrees.

When our radiators have large area, for example 25 square meters(about 125 ribs) then

dT=10000/(10*25)=40 degrees.

And the average surface temperature is

20+40=60 degrees.

Hence the conclusion: If you want to do low temperature system heating do not skimp on radiators. The average temperature is the arithmetic mean between the temperatures at the inlet and outlet of the radiators.

Тav=(Тstraight+Тоbr)/2;

The temperature difference between the direct and return is also an important value and characterizes the circulation of water through the radiators.

dT=Tstraight-Tobr;

Remember that

Q \u003d 4.19 * G * (Tpr-Tobr) \u003d 4.19 * G * dT

At a constant power, an increase in water flow through the device will lead to a decrease in dT, and vice versa, with a decrease in flow, dT will increase. If we ask that dT in our system is 10 degrees, then in the first case, when Tav=70 degrees, after simple calculations we get Tpr=75 deg and Tobr=65 deg. The water flow through the boiler is

G=Q/(4.19*dT)=10/(4.19*10)=0.24 kg/sec.

If we reduce the water flow exactly by half, and leave the boiler power the same, then the temperature difference dT will double. In the previous example, we set dT to 10 degrees, now when the flow decreases, it will become dT=20 degrees. With the same Tav=70, we get Tpr-80 deg and Tobr=60 deg. As we can see, a decrease in water consumption entails an increase in the direct temperature and a decrease in the return temperature. In cases where the flow rate drops to some critical value, we can observe the boiling of water in the system. (boiling temperature = 100 degrees) Also, boiling of water can occur with an excess of boiler power. This phenomenon is extremely undesirable and very dangerous, therefore a well-designed and thought-out system, competent selection of equipment and high-quality installation exclude this phenomenon.
As we see from the example temperature regime heating system depends on the power that needs to be transferred to the room, the area of ​​\u200b\u200bradiators and the flow rate of the coolant. The volume of coolant poured into the system with a stable mode of operation does not play any role. The only thing that affects the volume is the dynamics of the system, that is, the time of heating and cooling. The larger it is, the longer the heating time and the longer the cooling time, which is undoubtedly a plus in some cases. It remains to consider the operation of the system in these modes.
Let's go back to our example with a 10 kW boiler and 100 fin radiators with 20 squares of area. The pump sets the flow rate at G=0.24 kg/sec. We set the capacity of the system to 240 liters.
For example, the owners came to the house after a long absence and began to heat. During their absence, the house cooled down to 5 degrees, as did the water in the heating system. By turning on the pump, we will create water circulation in the system, but until the boiler is ignited, the temperature of the direct and return will be the same and equal to 5 degrees. After the boiler is ignited and reaches a power of 10 kW, the picture will be as follows: The water temperature at the inlet to the boiler will be 5 degrees, at the outlet of the boiler 15 degrees, the temperature at the inlet to the radiators is 15 degrees, and at the outlet of them a little less than 15. ( At such temperatures, radiators practically do not emit anything) All this will continue for 1000 seconds until the pump pumps all the water through the system and a return line with a temperature of almost 15 degrees comes to the boiler. After that, the boiler will already give out 25 degrees, and the radiators will return water to the boiler with a temperature slightly less than 25 (about 23-24 degrees). And so again 1000 seconds.
In the end, the system will warm up to 75 degrees at the outlet, and the radiators will return 65 degrees and the system will go into stable mode. If there were 120 liters in the system, and not 240, then the system would warm up 2 times faster. In the case when the boiler is extinguished and the system is hot, the cooling process will begin. That is, the system will give the house the accumulated heat. It is clear that the larger the volume of the coolant, the longer this process will take. When operating solid fuel boilers, this allows you to stretch the time between reloads. Most often, this role is taken over by, to which we devoted a separate topic. Like various types heating systems.

Can the water in the well freeze? No, the water will not freeze, because. both in sandy and artesian well water is below the freezing point of the ground. Is it possible to install a pipe with a diameter greater than 133 mm in a sandy well of a water supply system (I have a pump for a large pipe)? It does not make sense when arranging sand well install a larger diameter pipe, because sand well productivity is low. The Malysh pump is specially designed for such wells. Can rust steel pipe in a water well? Slow enough. Since when arranging a well suburban water supply it is sealed, there is no oxygen access to the well and the oxidation process is very slow. What are the pipe diameters for individual well? What is the productivity of the well with different pipe diameters? Pipe diameters for arranging a well for water: 114 - 133 (mm) - well productivity 1 - 3 cubic meters / hour; 127 - 159 (mm) - well productivity 1 - 5 cubic meters ./hour; 168 (mm) - well productivity 3 - 10 cubic meters/hour; REMEMBER! It is necessary that n...

They mean to divide the specifics of the heating operation into two types:

• independent, here the source of heat energy is located directly in the room - they are used in individual house or in high-rise buildings elite type;
• dependent, where a network of pipelines is connected to the heating complex - they are used in most urban areas and urban-type settlements.

According to the specifics of the circulation of the heat carrier, water is mainly used, where the speed of the water in the heating system directly affects the temperature in the radiators. The circulation is divided into natural (according to the principle of gravity) and forced (heating system using a pump). By distribution, it is customary to distinguish between a heating system with lower and upper pipe wiring.

Temperature

Despite the rich selection of heating systems provided, the options for heat supply and return are quite few. It must also be installed according to the rules Maximum temperature in the heating system to avoid further malfunctions.

Radiators are connected to the heating system in one of three ways: bottom, side or diagonal.

Also, the lower connection is also called differently: "", saddle. According to this scheme, the return and supply are installed at the bottom of the battery. In most cases, it is used when pipes are laid under the baseboard or under the floor surface. The return temperature in the heating system must not differ from the supply temperature.

Water speed

If there are few sections, heat transfer will be extremely inefficient compared to other schemes - the water velocity in the heating system decreases, which leads to heat loss.

Lateral heating is the most popular type connection of radiator batteries to heating. Water is supplied as a heat carrier in the upper part, and the return is connected from below, so that the return temperature in the heating system is considered equivalent.

To avoid a decrease in the efficiency of this type of connection with an increase in radiator sections, it is recommended to install an injection tube.

Pressure

The diagonal type of connection is also called the side cross scheme, because the water supply is connected from above the radiator, and the return line is organized at the bottom of the opposite side. It is advisable to use it when connecting a significant number of sections - when a small amount the pressure in the heating system rises sharply, which can lead to undesirable results, that is, heat transfer can be halved.

To finally stop at one of the connection options, you must be guided by the methodology for organizing the return. It can be of the following types: single-pipe, two-pipe and hybrid.

Which option is worth choosing will depend on a combination of factors. It is necessary to take into account the number of storeys of the building where the heating is connected, the requirements for the price equivalent of the heating system, what type of circulation is used in the coolant, the parameters of the radiator batteries, their dimensions, and much more.

Most often, they stop their choice precisely on a single-pipe wiring diagram for heating pipes.

As practice shows, such a scheme is used precisely in high-rise buildings of the modern type.

Such a system has a number of characteristics: they are low cost, easy to install, the coolant (hot water) is supplied from above when choosing a vertical heating system.

Also, they are connected to the heating system in series, and this, in turn, does not require a separate riser for organizing the return. In other words, water, having passed the first radiator, flows into the next, then into the third, and so on.

However, there is no way to regulate the uniform heating of radiator batteries and its intensity, they are constantly fixed high pressure coolant. The farther the radiator is installed from the boiler, the more heat transfer decreases.

There is also another wiring method - a 2-pipe scheme, that is, a heating system with a return. It is most often used in luxury housing or in an individual home.

Here is a couple closed loops, one of them is intended for supplying water to batteries connected in parallel, and the second for its removal.

With hybrid wiring, the two schemes described above are combined. This may be a collector circuit, where an individual wiring branch is organized at each level.

Although ordinary people believe that they do not need to know exactly what scheme the heating of an apartment building is equipped with, situations in life can really be different. For example,...

The choice of which coolant to buy for a heating system depends on the conditions of its operation. The type of boiler room and pumping equipment, heat exchangers, etc.

Heating was invented to ensure that the buildings were warm, there was a uniform heating of the room. At the same time, the design that provides heat should be easy to operate and repair. A heating system is a set of parts and equipment used to heat a room. It consists:

1. A source that creates heat.
2. Pipelines (supply and return).
3. heating elements.

Heat is distributed from the starting point of its creation to the heating block with the help of a coolant. It can be: water, air, steam, antifreeze, etc. The most used liquid coolants, that is, water systems. They are practical, since various types of fuel are used to create heat, they are also able to solve the heating problem. various buildings, because there are really many heating schemes, different in properties and cost. They also have high operational safety, productivity and optimal use of all equipment as a whole. But no matter how complex heating systems would be, they are united by the same principle of operation.

Briefly about the return and supply in the heating system

The water heating system, using the supply from the boiler, supplies the heated coolant to the batteries, which are located inside the building. This makes it possible to distribute heat throughout the house. Then the coolant, that is, water or antifreeze, after passing through all available radiators, loses its temperature and is fed back for heating.

The simplest heating structure is a heater, two lines, an expansion tank and a set of radiators. The conduit through which the heated water from the heater moves to the batteries is called the supply. And the conduit, which is located at the bottom of the radiators, where the water loses its original temperature, returns back, and it will be called the return. Since, when heated, the water expands, the system provides a special tank. It solves two problems: a supply of water to saturate the system; accepts excess water, which is obtained during expansion. Water, as a heat carrier, is directed from the boiler to the radiators and back. Its flow is provided by a pump, or natural circulation.

Supply and return is present in one and two tubular heating systems. But in the first there is no clear division into the supply and return pipes, and the entire pipe line is conditionally divided in half. The column that leaves the boiler is called the supply, and the column that leaves the last radiator is called the return.


In a single-pipe line, heated water from the boiler flows sequentially from one battery to another, losing its temperature. Therefore, at the very end, the batteries themselves will be cold. This is the main and probably the only disadvantage of such a system.

But the single-pipe option will gain more pluses: lower costs for the purchase of materials are required compared to the 2-pipe; scheme has more attractive appearance. The pipe is easier to hide, and it is also possible to lay pipes under doorways. Two-pipe is more efficient - two fittings (supply and return) are installed in parallel in the system.

Such a system is considered by experts to be more optimal. After all, her work is unsteady on the supply of hot water through one pipe, and the chilled water is diverted in the opposite direction through another pipe. Radiators in this case are connected in parallel, which ensures uniformity of their heating. Which one establishes the approach should be individual, while taking into account many different parameters.

Just a few general tips to follow:

1. The entire line must be completely filled with water, air is a hindrance, if the pipes are airy, the heating quality is poor.
2. A sufficiently high fluid circulation rate must be maintained.
3. The difference between the supply and return temperatures should be about 30 degrees.

What is the difference between supply and return heating

And so, to sum up, what is the difference between supply and return in heating:

• Feed - the coolant that goes through the water conduits from the heat source. This can be an individual boiler or central heating Houses.
• The return is water that, having passed through all the radiators, goes back to the heat source. Therefore, at the input of the system - supply, at the output - return.
• It also differs in temperature. The supply is hotter than the return.
• Installation method. The conduit that is attached to the top of the battery is the supply; the one that connects to the bottom is the return line.

From effective work heating system depends on how comfortable the temperature will be in the cold season in the house. Sometimes there are situations when hot water is supplied to the system, and the batteries remain cold. It is important to find the cause and eliminate it. To solve the problem, you need to know the structure of the heating system and the reasons for the cold return during hot supply.

Heating system device - what is a return?

The heating system consists of expansion tank, batteries, heating boiler. All components are interconnected in a circuit. A fluid is poured into the system - a coolant. The fluid used is water or antifreeze. If the installation is done correctly, the liquid is heated in the boiler and begins to rise through the pipes. When heated, the liquid increases in volume, the excess enters the expansion tank.

As heating system completely filled with liquid hot coolant displaces the cold, which returns to the boiler, where it heats up. Gradually, the temperature of the coolant increases to the required temperature, heating the radiators. The circulation of the liquid can be natural, called gravity, and forced - with the help of a pump.

The return is a coolant that, having passed through all the heating devices included in the circuit, gives off its heat and, cooled, enters the boiler again for the next heating.

Batteries can be connected in three ways:

1. 1. Bottom connection.
2. 2. Diagonal connection.
3. 3. Side connection.

In the first method, the coolant is supplied and the return is removed at the bottom of the battery. This method is advisable to use when the pipeline is located under the floor or baseboards. At diagonal connection the coolant is supplied from above, the return is discharged from the opposite side from below. This connection is best used for batteries with large quantity sections. The most popular way is lateral connection. Hot liquid is connected from above, the return flow is carried out from the bottom of the radiator on the same side where the coolant is supplied.

Heating systems differ in the way pipes are laid. They can be laid in one-pipe and two-pipe way. The most popular is the single-pipe wiring diagram. Most often it is installed in high-rise buildings.It has the following advantages:

• a small number of pipes;
• low cost;
• ease of installation;
• serial connection of radiators does not require the organization of a separate riser for draining liquid.

The disadvantages include the inability to adjust the intensity and heating for a separate radiator, the decrease in the temperature of the coolant as it moves away from the heating boiler. To increase the efficiency of single-pipe wiring, circular pumps are installed.

For organization individual heating a two-pipe piping scheme is used. Hot feed is carried out through one pipe. On the second, the cooled water or antifreeze is returned to the boiler. This scheme makes it possible to connect radiators in parallel, ensuring uniform heating of all devices. In addition, the two-pipe circuit allows you to adjust the heating temperature of each heater separately. The disadvantage is the complexity of installation and high flow materials.

Why is the riser hot and the batteries cold?

Sometimes, with hot supply, the return of the heating battery remains cold. There are several main reasons for this:

• incorrect installation;
• the system or one of the risers of a separate radiator is aired;
• insufficient fluid flow;
• the cross section of the pipe through which the coolant is supplied has decreased;
• the heating circuit is dirty.

Cold return is a serious problem that must be fixed. It entails many unpleasant consequences: the temperature in the room does not reach the desired level, the efficiency of radiators decreases, there is no way to correct the situation additional devices. As a result, the heating system does not work as it should.

The main trouble with cold return is the large temperature difference that occurs between the supply and return temperatures. In this case, condensate appears on the walls of the boiler, reacting with carbon dioxide released during the combustion of fuel. As a result, acid is formed that corrodes the walls of the boiler and reduces its service life.

How to make radiators hot - looking for solutions

If it is found that the return is too cold, a series of troubleshooting steps should be taken. First of all, you need to check the correct connection. If the connection is not made correctly, the downpipe will be hot, but should be slightly warm. Pipes should be connected according to the diagram.

In order to avoid air locks that impede the movement of the coolant, it is necessary to provide for the installation of a Mayevsky crane or a bleeder for air removal. Before venting, shut off the supply, open the valve and let the air out. Then the tap is closed, and the heating valves open.

Often the cause of the cold return is the control valve: the cross section is narrowed. In this case, the crane must be dismantled and the cross section increased using a special tool. But it is better to buy a new faucet and replace it.

The reason may be clogged pipes. It is necessary to check them for patency, remove dirt, deposits, clean well. If patency cannot be restored, clogged areas should be replaced with new ones.

If the speed of the coolant is insufficient, it is necessary to check whether there is circulation pump and meets the requirements for power. If it is missing, it is advisable to install it, and if there is a lack of power, replace or upgrade it.

Knowing the reasons why heating may not work effectively, you can independently identify and eliminate malfunctions. The comfort in the house during the cold season depends on the quality of heating. If you do the installation work yourself, you can save on hiring third-party labor.