Filling with water heating system
The system of water heating is one of the most common. Several factors contribute to this:
- Universality of heat sources (electricity, gas, coal, firewood, etc.);
- Uniform heating of rooms;
- Security;
- Does not affect the composition of air in the room.
Work principles
The essence of the operation of any water heating system is as follows. The heat carrier is heated in the boiler, then circulates through the piping system through the rooms, where it cools in the radiators, giving heat to the rooms, and returns to the boiler for the next cycle. Boilers can be any, or their whole complex. The carrier of heat is most often water, also use antifreeze, special coolants. With the use of special coolants, the service life of the system is prolonged, the probability of defrosting is excluded, etc.
By the type of circulation of the coolant are distinguished:
FROM natural circulation . The heated coolant has a higher pressure than the cold one. Due to the pressure difference, circulation occurs. For such a system it is necessary to lower the boiler as low as possible. The lower the boiler, the more created pressure (located in the basement). The internal diameter of the circulation pipes must be at least 32. The pipes must have a slope (at least 1 cm per meter of main line) from the entry point to the last radiator. Either directly above the boiler at the highest point of the entire system, an expansion tank is placed and wiring is made from it. It is not recommended to plan a system with natural circulation with a contour length of more than 30 meters;
With forced circulation. A circulating pump is installed in the system. In this case, the diameter of the pipes, the location of the boiler and various gradients are not so important. When miscalculating in pipe diameters, it is possible to increase the pump power to improve circulation.
By pipe wiring:
- Single-tube. In fact, the heating radiators are connected to the annular pipe, or the heating circuit goes through the radiators;
- Two-tube. On the premises, there are two rings: separate feed and return. Heating radiators are connected to both.
On tightness:
- Open systems. An open expansion tank is installed;
- Closed Systems. There is no contact with the surrounding atmosphere.
On the contours:
- Single-circuit;
- Multi-contour. Are used for large areas and the need to adjust the temperature in different branches.
Planning of the water heating system
1. Select a species. For small rooms, heating systems with natural circulation are possible. Absence of the pump will require accuracy of realization and a larger diameter of the pipes. Circulation systems are more flexible in management. The same applies to two-pipe and multi-circuit. Open and closed type the difference is unimportant. In the case of an open type, accommodation will be required expansion tank at the top of the system;
2. Heating radiators. There are a lot of "wise" calculations of the number of radiators in the network. We suggest using rational. The total surface area of the radiators is 10% of the area of the heated room (with standard room characteristics: ceiling height, insulation rate, etc.). This norm does not depend on the declared power of radiators, heat losses and other. It is this calculation that allows for uniform heating of the room, and the power is largely determined by the temperature of the coolant. You can use any radiators. With decentralized heating, there will be no significant difference. In centralized heating systems, cast iron radiators have a slight advantage (they retain heat longer and maintain higher pressure during long operation). It is better to plan the installation of radiators as much as possible in the area of the room. For a more even warm-up, the most optimal pipe system is instead of radiators, but this is not entirely aesthetically pleasing;
4. Circulation pipes. For systems with natural circulation it is desirable to use metal pipes - they do not deform under the influence of heat, as a result of which there is no additional resistance. The diameter is not less than 32 mm, the longer the annular contour of the system, the greater the diameter of the pipes. For systems with forced circulation, the diameter of the pipes plays a lower value, however, the diameter of the main pipes must not be less than 25 mm. Taps to radiators are allowed a smaller cross section (20, 16 mm). It is more convenient to make a heating system from polypropylene pipes: low cost, easy installation and repair;
5. The collector. When choosing a system based on polypropylene pipes, the inlet and outlet manifolds are cooked independently from larger diameter pipes and splitters, the regulating valves are installed on the contour pipes. Collectors allow you to switch off various branches of the heating system and repair them without stopping the entire system as a whole;
6. Security systems. When the system is closed, the installation of safety valves is mandatory, installation of instruments is desirable: a pressure and temperature gauge on the delivery pipe and return temperature;
7. Circulation pump. The selection of the pump depends on many parameters. First of all, the heights. But if the resistance is large (many circuits, the diameter of the pipes is not enough), the pump's power, even for a single-storey heating system, may not be enough. Rough calculation: for every 10 meters of the circulation ring - 0.6 meters of pump head, the flow for every 100 square meters of area - 0.5 cubic meters of pump capacity.
Installation of heating system
For a basis we shall take polypropylene pipes, a multi-loop, closed, two-tube system.
For installation it is required:
- standard set of tools: screwdriver, pliers, hammer, tape measure and so on;
- soldering iron for polypropylene pipes;
- pipe knife.
- Situationally - a puncher, a drill and so on.
From materials:
- pipes, fittings, taps;
- radiators of heating, plugs, adapters, cranes of Majewski, temperature regulators for radiator;
- circulation pump, main filter;
- security systems ( safety valve, pressure and temperature meters), valves for automatic air release;
- expansion tank.
Mounting of radiators
We install radiators of the heating system in place. Radiators are connected as follows. In the lower part of the output in obroatku, on the other hand, the lower part is muffled. At the top - on one side there is an entrance from the supply pipe, on the other hand a tap of the Majewski for bleeding air.
For better temperature control, it is recommended to install a faucet - no difference in the flow or return of each radiator. Installation of two cranes does not make much sense, when the radiator goes out of operation, the coolant merges without any difficulties from the entire contour. The crane can be used with automatic temperature control.
On the first radiators of the circuit it is recommended to install instead of the Mayevsky valve - a valve for automatic air release. As practice has shown in the operation of the heating system, the first radiators are often often airborne during operation.
When implementing a heating system based on polypropylene pipes, it is not recommended to install radiator connectors with "American" circulation pipes. Over time, the following pattern is observed: The rubber sealing ring coarsens and loses elasticity, during the heating season, the hot coolant expands the rubber and when cooling (the boiler has ceased to work for some reason), the joint is not sealed, as a result, the coolant from the system begins to leak out.
Installation of circulating pipes
The usual installation and installation of polypropylene pipes. Pipes should preferably be used for hot water with reinforcement, they are less susceptible to thermal expansion. Also it is not recommended to use pipes with external reinforcement - additional troubles for cleaning before soldering.
Mounting of collectors
The inlet and outlet manifolds are soldered from polypropylene pipes, tees, crosses, and cranes. Each tap of the contour has its own faucet. This allows you to flexibly manage the temperature and allows you to work with a separate circuit without stopping the entire heating system. You can buy a ready-made header.
The collector is a splitter. Input - from one supply pipe from the boiler to different circuits. Output - from different circuits into a single return pipe, going to the boiler.
Installing the expansion tank
The expansion tank in a closed system can be installed anywhere. It is recommended to install and connect the tank directly before entering the boiler, or before the pump. At the inlet of the expansion tank, a safety valve is required. Do not install cranes between the tank and the system.
Installation of a security group
The safety group can be located in different places (on the boiler, near the expansion tank, in front of the collector, etc.). The safety group includes: a safety valve for increased pressure, a valve for automatic air release, and can also be supplemented with pressure and temperature meters.
The requirements for the security group are as follows:
Should be located immediately after leaving the boiler without finding any devices between it and the boiler;
Do not install a crane between the safety group and the boiler output.
Installation of the circulation pump
The circulation pump is installed in the return duct immediately before entering the boiler. Before the circulation pump, a main strainer is installed to prevent particles of rust, scale and other large litter from entering the pump and the boiler. The circulation pump is installed strictly in accordance with the instructions to it (vertical, horizontal position, direction of movement of the carrier).
When installing two temperature meters (at the inlet and at the return) in the system, one can judge the sufficiency of the pump power. If periodically the difference between the temperatures reaches 20 - 30 ºС and higher - this may indicate a pump power failure, especially if you have to slow down the boiler, or the automatic boiler switches off the heating itself.
Full scheme of heating
For understanding, we give a complete scheme of heating, starting from the boiler.
The heat carrier is heated in the boiler. Then he enters the system. To this point without cranes are connected security system. To the same point is connected the inlet pipe of the input manifold. In the collector there is a branching of the coolant along the contours, the flow is regulated by separate cranes.
The feed pipe in the circuit runs along all the radiators and ends at the entrance to the last of this circuit. Through the radiators, the coolant enters the return pipe of the circuit. The return also passes along all the radiators, starting from the extreme and ending with the inlet to the output manifold through the tap. Each radiator can be equipped with a separate crane at the outlet or at the inlet.
The heat medium is collected from all circuits in the outlet manifold and fed to a common return pipe. By reverse pipe The cooled coolant passes through the main filter, enters the circulation pump. To the same point the expansion tank is connected without cranes. It is also acceptable to connect the expansion tank to the boiler outlet. The pump generates pressure and pushes the coolant to the boiler inlet.
Each room, regardless of its intended purpose, needs heating. If earlier the main method of heating houses was considered to be a fireplace or furnace method, now it has become the least effective and in demand: the carrier is not able to provide enough heat because of the increase in heated facilities. One of the most progressive variants of heating is considered to be water heating. The standard system of water heating includes a boiler connected to the radiator via the mains. Water is used as the coolant.
The standard operating principle of the system is as follows: the heat carrier, in this case water, enters the radiators through the pipeline and gives the room heat; after that the water is returned to the boiler for heating again. The systems of water heating are divided into systems with natural circulation and forced circulation.
The heating system with natural circulation has become widespread in the pre-war period due to its efficiency, simplicity and reliability. Most often this type of heating system is used in dachas, as well as in country houses due to frequent power outages on such facilities. Such systems are conventionally divided into two types - with the lower and upper water supply. To determine the type of heating system, you need to consider their differences, characteristics and scope.
Schematic diagram of heating with natural circulation of coolant
Heating systems with top water supply
The heat carrier - in this case water - must be heated and supplied to the upper part of the heating system by means of a pipeline. The pipe used to feed water must have a larger diameter than the pipes that are responsible for supplying water to the radiator. This is necessary to achieve the greatest resistance to heat exchange. Horizontal pipes should be installed with minimal bias within one centimeter on a fitting meter.
The expansion tank must be installed in the upper part of the system: it will perform the function of receiving steam and excess heat - this is necessary because of the water's property to expand when heated and pass into the vapor state. On the tank there must be a drain cock and a cover or valve in its upper part. After the water is heated, it is distributed through the supply pipe to the vertical risers and into the radiators.
Tip: if you intend to use a heating system with natural water circulation, remember that the radiators must be connected using a diagonal method
After direct heating of the room, the water passes into the boiler through a specialized return pipe. Here it is re-heated and the water cycle is repeated. The heating boiler is located in the lowest part of the system, under the radiators. Usually, these elements are installed in the boiler rooms, for which the basements are allocated.
Heating systems with lower water supply
A system in which the heating medium is fed from below is usually used for heating houses where there is no attic space or access is denied to it. The main difference between the presented heating system is that the pipes are laid under the radiators. There is also an expansion tank, which is installed in the upper level of the system; usually for this purpose economic premises are applied. If there is no circulation of water in the heating system, which must occur naturally, then it is created by compulsory means.
The standard heating system with forced circulation functions through the same connection methods. The difference is that because of the long length of this system or the lack of natural conditions for creating the slope of the pipes, it is necessary to include a pump in the system. The pump for circulation is mounted to the main pipe - this helps to extend the life of the heating system. Using a pump helps not only to increase the efficiency of heating, but also to reduce the number of highways. The system with forced circulation has the ability to heat not just a few rooms, but even a house with several floors.
In order to produce high-quality work of this type of system, continuous power supply is needed. Installation of the pump for circulation in the heating system is required in order to create forced circulation of water in a closed loop. In this type of systems, the pump is the central component among equipment. It should be noted that the circulation pump may not be distinguished by a significant performance: its power is only needed to direct the liquid into the supply pipe. The same pressure pushes the water in the opposite direction, since the system is closed.
The circulation pump is necessary to ensure the uninterrupted operation of the heating system, therefore it must fully comply with the system in which the installation is to be carried out. Due to its functionality, this type of pump can be universally applied in a wide variety of pipelines.
Selecting a circulation pump for the heating system
In order to select a circulation pump for the heating system, it is necessary to make the appropriate calculations. Please note that within an hour this element will run three times more water than its total volume in the system. Thus, the total volume of a suitable amount of liquid on average is 10 liters per kilowatt of boiler output. The required model of the pump for the heating system and its power is determined from the pressure and consumption parameters. The head should be equal to the hydraulic resistance of the heating system.
Usually, the fluid head velocity in systems with forced circulation rather low, which gives the right to judge the low losses of hydraulic resistance, which usually do not exceed 2 meters. The exact resistance is not easy to calculate, so the capacity of the circulation pump is determined from the midpoint. In order to calculate the performance, the dimensions of the area of the heating object and the power that the source of electricity possesses are also taken into account. It should be remembered that the pump is only needed in a system with forced circulation, a system with natural circulation does not need it.
Installing a circulation pump: what should I look for?
To install the circulation pump yourself, use the following guidelines:
- to extend the life of the entire system, install a liquid filter before the circulation pump. the filter must be installed on the suction pipe;
- do not select a circulation pump for the heating system high power and performance than required. Otherwise, there is a risk of encountering additional unpleasant noise during its operation;
- Never turn on the pump before filling the heating line with water and removing air from it, this can lead to equipment failure;
- install the pump in the area closest to the expansion tank;
- when installing the pump in closed system heating, if possible, install the pump on the return. This is due to the fact that this section of the highway has the lowest temperature.
Tip: Before starting the heating system, it is necessary to rinse it with water to remove various foreign particles. Do not forget that even short-term operation of the circulation pump idle in the absence of liquid in the system can result in failure of the pump itself and other elements of the system.
Almost all circulating pumps, presented in the modern market, are equipped with a connection with automatic regulation of boilers for heating. This function allows owners to adjust the temperature of the air in the heated object by changing the speed of the water in the heating system. In order to take into account the level of heat consumption in the rooms, special meters are installed, due to which the heat losses due to the wear of the mains are monitored. The heating circuit itself is not subject to any changes.
You can familiarize yourself with the way of installing the circulation pump yourself by watching the video:
As has been repeatedly mentioned, the main disadvantage of a heating system with natural coolant circulation is the low circulation head (especially in the apartment system) and, as a result, the increased diameter of the pipes. It is enough to make a little mistake with the choice of pipe diameters and the coolant is already "clamped" and can not overcome the hydraulic resistance. "Unscrew" the system can be without any significant alterations: to include in it the circulating pump (Figure 12) and to transfer the expansion tank from the feed to the return flow. It should be noted that the transfer of the expander to the return is not always necessary. With a simple conversion of an uncomplicated heating system, such as a room heating system, the tank can be left where it stood. If the new system is properly reconstructed or the new system is installed, the tank is transferred to the return flow and replaced from the open to the closed one.
Fig. 12. Circulation pump
What capacity should the circulation pump be, how and where to install it?
Circulating pumps for household systems heating have a low power consumption - about 60-100 watts, that is, as an ordinary light bulb, they do not raise water, but only help it overcome local resistance in the pipes. These pumps can be compared with the propeller (screw) of the ship: the screw pushes the water and ensures the vessel's progress, but at the same time the water in the ocean is not reduced and added, that is, the overall water balance remains the same. The circulation pump attached to the pipeline pushes the water, but no matter how much it pushes it out, on the other hand it receives the same amount of water, that is, the fear that the pump will push the coolant through the open expander is in vain: the heating system, the closed loop and the quantity the water in it is constant. In addition to circulating in centralized systems may be included boost pumps that raise the pressure and are able to raise water, they actually need to be called pumps, and circulating, in the language of translation, and it's hard to call pumps - so ... fans. No matter how long the ordinary household fan drives the air around the apartment, everything it can do is create a breeze (air circulation), but it can not change the atmospheric pressure even in a tightly closed room.
As a result of the application of the circulation pump, the range of the heating system considerably increases, the diameters of the pipelines are reduced, and the possibility of connecting the systems to boilers with increased heat carrier parameters is created. To ensure quiet operation of the water heating system with pump circulation, the velocity of the coolant should not exceed: in pipelines laid in the main premises of residential buildings, with conditional passages of pipes 10, 15 and 20 mm or more, respectively 1.5; 1,2 and 1 m / s; in pipelines laid in auxiliary premises of residential buildings - 1.5 m / s; in pipelines laid in auxiliary buildings - 2 m / s.
To ensure the system's noiselessness and delivery of the required volume of coolant, it is necessary to make a small calculation. We already know how to approximate identify the required boiler output (in kilowatts), based on the area of the heated premises. The optimal flow of water passing through the boiler, recommended by many manufacturers of boiler equipment, is calculated by a simple empirical formula: Q = P, where Q is the heat carrier through the boiler, l / min; Р - power of the boiler, kW. For example, for a 30 kW boiler, the water flow is about 30 l / min. To determine the flow rate of the heat carrier in any part of the circulation ring, we use the same formula, knowing the power of the radiators installed on this section, for example, we calculate the flow of water for the radiators installed in one room. Suppose that the power of the radiators is 6 kW, which means that the coolant flow rate will be approximately 6 liters per minute.
By the flow rate of water, we determine the diameters of the pipelines (Table 1). These values correspond to the practical correspondence of the pipe diameters with the flow rate of the heat carrier flowing through them at a speed of no more than 1.5 meters per second.
Table 1
Next, we determine the power of the circulation pump. For every 10 meters of the length of the circulating ring, 0.6 meters of pump head is required. For example, if the total length of the pipeline ring is 90 meters, the pump head should be 5.4 meters. We go to the store (or we select according to the catalog) and get a pump with the pressure that suits us. If pipes of smaller diameters than those recommended in the previous paragraph are used, the pump capacity should be increased, as the thinner the pipes, the greater the hydraulic resistance in them. And accordingly, when using large diameter pipes, the pump capacity can be reduced.
In order to ensure constant circulation of water in heating systems, it is desirable to install at least two circulating pumps, one of which is a working pump, the other (on the bypass) is a standby pump. Either one pump is installed on the system, and the other is in a secluded place, in case of a quick replacement if the first one fails.
It should be noted that the calculation of the heating system given here is extremely primitive and does not take into account many factors and features individual system heating. If you build a cottage with a complex architecture of the heating system, then you need to make accurate calculations. It can only be done by heating engineers. To build a multi-million dollar building without executive documentation - a project that takes into account all the features of the building is extremely unreasonable.
The circulation pump in the heating system is filled with water and undergoes equal (if the water does not heat up) the hydrostatic pressure from both sides - from the inlet (suction) and outlet (discharge) nozzles connected to the heat pipes. Modern circulating pumps made with water-lubricated bearings can be placed on both the supply and the return pipeline, but most often they are put on the back. Initially, this was due to a purely technical reason: when placed in a more cold water the service life of the bearings, the rotor and the stuffing box, through which the pump shaft passes, is extended. And now they are put on the return line rather by habit, since from the point of view of creating an artificial circulation of water in a closed circuit, the location of the circulation pump is indifferent. Although placing them on a supply line, where there is usually less hydrostatic pressure, is more rational. For example, the expansion tank is installed in your system at a height of 10 m from the boiler, so it creates a static pressure of 10 m of water, but this is true only for the lower pipeline, the upper pressure will be lower, since the water column here will be smaller. Wherever the pump is located, it will be subjected to the same pressure from both sides, even if placed on a vertical main feed or return riser, the pressure difference between the two pump nozzles will be small, since the pumps are small in size.
However, everything is not so simple. The pump, which operates in a closed loop of the heating system, enhances circulation by pumping water into the heat pipe from one side and sucking it from the other. The level of water in the expansion tank when starting the circulation pump will not change, since a uniformly running pump only circulates with an unchanged amount of water. Since under these conditions (the uniformity of the pump and the constant volume of water in the system), the water level in the expansion tank remains unchanged, it does not matter whether the pump is running or not, the hydrostatic pressure at the point of attachment of the expander to the pipes of the system will be constant. This point is called neutral, since the circulation pressure developed by the pump does not in any way affect the static pressure created by the expansion tank. In other words, the pressure of the circulation pump at this point is zero.
In any closed hydraulic system the circulation pump uses the expansion tank as a reference point in which the pressure developed by the pump changes its sign: up to this point the pump generates compression, water pushes, after it, causing a depression, water sucks. All heat pipes of the system from the pump to the point of constant pressure (counting in the direction of water flow) will refer to the pump discharge zone. All heat pipes after this point - to the suction zone. In other words, if the circulation pump is plunged into the pipeline immediately after the connection point of the expansion tank, it will suck the water out of the reservoir and pump it into the system, if the pump is installed before the tank connection point, the pump will pump the water out of the system and pump it into the tank.
Well, what kind of difference does the pump pump the water out of the tank, or pumps it into it, if only it turns it over the system. And there is a significant difference: the system is interfered with by the static pressure created by the expansion tank. In pipelines located in the pump discharge zone, the hydrostatic pressure should be considered as compared with the water pressure at rest. On the contrary, in pipelines located in the suction zone of the pump, it is necessary to take into account the pressure decrease, in which case it is possible that the hydrostatic pressure not only drops to atmospheric pressure, but even underpressure may occur. That is, as a result of the pressure difference in the system, there is a danger of sucking or releasing air or boiling of the coolant.
To avoid disturbance of water circulation due to boiling or sucking air during the design and hydraulic calculation of water heating systems, the rule should be observed: in the suction zone at any point in the piping of the heating system, the hydrostatic pressure must remain excessive when the pump is operated. There are four ways to do this rule (Figure 13).
Fig. 13. Schematic diagrams of heating systems with pump circulation and an open expansion tank
1. Raise the expansion tank to a sufficient height (usually at least 80 cm). This is a fairly simple method when reconstructing systems with natural circulation into the pumping circulation, but it requires a considerable attic room height and careful warming of the expansion tank.
2. Move the expansion tank to the most dangerous upper point in order to switch the upper line into the injection zone. Here it is necessary to make an explanation. In the new heating systemsthe supply pipelines with pump circulation are made with slopes not from the boiler, but to the boiler, so that the air bubbles move along with the water, as the driving force of the circulation pump will not allow them to swim "against the current", as it was in systems with natural circulation . Therefore, the upper point of the system is obtained not on the main riser, but on the most distant one. For the reconstruction of the old system with natural circulation in pumping, this method is rather laborious, as it requires reworking of pipelines, and to create a new system is not justified, since other, more successful options are possible.
3. Connect the expansion tank pipe near the suction pipe of the circulation pump. In other words, if we reconstruct an old system with natural circulation, we simply cut off the reservoir from the supply line and re-install it on the return duct behind the circulation pump and thereby create the most favorable conditions for the pump.
4. We depart from the usual scheme of placing the pump on the return and connect it to the supply line immediately after the point of connection of the expansion tank. When reconstructing a system with natural circulation, this is the simplest way: just cut the pump into the feed pipe, nothing else remaking. However, the choice of pump should be treated very carefully, yet we place it in adverse conditions of high temperatures. The pump will have to serve for a long time and reliably, and this can only be guaranteed by a solid manufacturer.
The modern market of sanitary and heating fittings allows to replace expansion tanks of open type with closed ones. In the closed tank there is no contact of the system fluid with air: the coolant does not evaporate and is not enriched with oxygen. This reduces the loss of heat and water, reduces internal corrosion of heating appliances. From the closed reservoir, the liquid will never spill out.
Expansion tank of closed type ("Expansomate") - capsule of spherical or oval form, divided inside a hermetic membrane into two parts: air and liquid. In the air part of the hull under certain pressure the nitrogen-containing mixture is pumped. Before filling the heating system with water, the pressure of the gas mixture inside the tank tightly presses the diaphragm against the water part of the tank. Heating the water leads to the creation of working pressure and an increase in the volume of the heat carrier - the membrane is bent towards the gas part of the tank. At the maximum operating pressure and the maximum increase in the volume of water, the water part of the tank is filled and the maximum compression of the gas mixture occurs. If the pressure continues to rise and the volume of the heat carrier continues to increase, the safety valve will reset the discharge of water (Figure 14).
Fig. 14. Expansion tank of membrane type
The volume of the tank is selected such that its useful volume is not less than the volume of the thermal expansion of the coolant, and the preliminary air pressure in the gas part of the tank is made equal to the static pressure of the coolant column in the system. This selection of the gas mixture pressure allows the membrane to be kept in an equilibrium (not tensioned) position with the heating system, which is filled but not switched on.
The tank of the closed type can be put in any point of the system, but, as a rule, it is installed next to the boiler, since the temperature of the liquid in the place of installation of the expansion tank should be as small as possible. And we already know that the circulating pump is best installed immediately behind the expander, where for him (and for the heating system as a whole) the most favorable conditions are created (Figure 15).
Fig. 15. Schematic diagrams of heating systems with pump circulation and expansion tank of a closed type
However, with such a scheme of the heating system, we face two problems: air removal and increased pressure on the boiler.
If in systems with open expansion tanks the air was removed through the expander countercurrent (in systems with natural circulation) or in passing (in systems with pump circulation), this does not happen with closed reservoirs. The system is completely closed and air has nowhere to escape. To remove air plugs at the upper point of the pipeline, automatic air drifts are installed - devices equipped with floats and shut-off valves. As the pressure increases, the valve opens and bleeds air into the atmosphere. Or for each heat radiator are installed cranes Maevsky. This part, installed on the heating devices, allows you to lower the air plug directly from the radiators. The Maevsky crane is included in some radiator models, but is more often offered separately.
Fig. 16. Automatic air vent
The principle of operation of the air vent (Figure 16) is that, in the absence of air, the float inside the device keeps the discharge valve closed. When air is collected in the float chamber, the water level inside the air vent is reduced. The float is lowered and the exhaust valve opens, through which air is released into the atmosphere. After the air outlet, the water level in the air vent increases and the float floats up, which closes the exhaust valve. The process continues until the air again gathers in the float chamber and lowers the water level by lowering the float. Automatic air vents are manufactured different designs, shapes and sizes and can be installed both on the main pipeline and directly (L-shaped) on radiators.
The crane of the Majewski, unlike the automatic air vent, is in general a conventional plug with an air vent and a conical screw screwed into it: by turning the screw, the channel is released and the air exits outwards. Screwing the screw closes the channel. Also there are air vents, in which instead of a conical screw a metal ball is used, which covers the air discharge channel.
Instead of automatic air evacuators and Mayevsky cranes in the heating system, you can include an air separator. This device is based on Henry's law. The air present in the heating systems is partially dissolved and partly in the form of microbubbles. When water passes (together with air) through the system, it falls into the region of various temperatures and pressures. In accordance with the law of Henry in some areas, air will be released from the water, and in others it will dissolve in it. In the boiler, the coolant heats up to a high temperature, therefore, it is in it that the air containing the air will be liberated as much air as the smallest bubbles. If they are not immediately removed, they will dissolve in other places in the system where the temperature is lower. If you remove the microbubbles immediately behind the boiler, then at the outlet of the separator we get dehydrated water, which will absorb air in different places of the system. This effect is used to absorb air in the system and bring it into the atmosphere through a combination of a boiler and an air separator. The process continues continuously until the air is completely removed from the system.
Fig. 17. Air separator
The operation of the air separator (Figure 17) is based on the principle of merging microbubbles. In practice this means that small air bubbles adhere to the surface of special rings and come together, forming large bubbles that can separate and float up into the air chamber of the separator. When the flow of fluid passes through the rings, it diverges in a variety of different directions, and the design of the rings is such that all the liquid passing through them comes into contact with their surface, making it possible for the microbubbles to adhere and merge.
Fig. 18. Schematic diagrams of heating systems with pump circulation, expansion tank of closed type and air separator
Now a little distracted from the air and back to the circulation pump. In heating systems with extended pipelines and, as a consequence, with large hydraulic losses, quite often quite powerful circulating pumps are required, which create a pressure on the discharge pipe larger than that for which the boiler is designed. In other words, when placing the pump on a return just in front of the boiler, the connections in the boiler heat exchanger can flow. In order for this not to happen, powerful circulating pumps are installed not in front of the boiler, but behind it - on the supply pipeline. And then the question arises: where to place the air separator, behind the pump or in front of it? Leading manufacturers of heating systems have solved this issue and suggest installing a separator in front of the pump (Figure 18), to protect it from damage by air bubbles.
And now consider the heating systems with pump circulation in more detail.
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