Design of an open heating system: basic requirements for the circuit, components and installation. Installing an expansion tank for open heating How to fill a closed system

The working volume of coolant in the heating network may decrease due to a number of reasons - leakage, evaporation, steam discharge through an automatic valve, repair work. In an open type scheme, the main riser is emptied and filled with air from the expansion tank; when closed, the pressure is significantly reduced. In any case, the heating system needs to be recharged, which can be done in several ways.

Signs of a critical coolant shortage

Not all owners of private houses monitor the technical condition of their water heating; it works - and that’s okay. When a hidden leak occurs, the system continues to function for some time until the amount of coolant drops to a critical level. This moment is monitored by the following criteria:

1. In an open system, the expansion tank is first emptied, then the main riser rising from the boiler is filled with air. Result: cold batteries when the supply pipeline overheats; turning on the maximum speed of the circulation pump does not help.
2. The lack of water during gravity distribution manifests itself in a similar way; in addition, the gurgling of water in the riser can be heard.
3. On a gas heater (open circuit) there are frequent burner starts/switching on - clocking, the TT boiler overheats and boils.
4. The lack of coolant is reflected on the pressure gauge - the pressure gradually decreases. Wall-mounted models of gas boilers automatically stop when they fall below a threshold of 0.8 Bar.
5. Floor-standing, non-volatile units and solid fuel boilers continue to regularly heat the remaining water in a closed system until the volume vacated by the coolant is filled with air. The circulation will stop, overheating will occur, and the safety valve will operate.

Important clarification. When a TT boiler operating in an open gravity system boils, there will be no explosion, since the coolant communicates with the atmosphere. The water heated by the heater will evaporate, and then a fire will start in the boiler room. Although the described process takes a lot of time, such situations are far from uncommon.

We will not explain why the system needs to be recharged - this is an obvious measure to maintain the functionality of the heating. All that remains is to choose a method for replenishing the heating network.

Selecting a refueling option

Several methods are used to replenish the coolant supply:

1. Manual recharge is the cheapest and most versatile option, suitable for all types of wiring.
2. Automatic replenishment from the water supply is practiced only in systems operating under pressure.
3. To fill a closed network with non-freezing coolant, a manual pressure test pump is also used. The design of an automated circuit with an electric pumping station connected to a container with antifreeze is practiced in industrial boiler houses.

Note. If the radiator network and heated floors are filled with antifreeze, simple replenishment is done with a small hand pump. But most often, filtered tap water is used in the heating system, because of the price of non-freezing coolants (especially harmless propylene glycol).

The operating principle of the automatic make-up unit is based on the operation of a pressure reducing valve that responds to a decrease in pressure in the heating network. When it drops below the set value, the valve mechanism opens and releases water from the main line. A pumping station operates in a similar way, pumping antifreeze from a separate tank.

1. The unit consists of 2-3 inexpensive elements and will never turn on without the knowledge of the homeowner.
2. No matter how reliably and efficiently the heating network is installed, there is a possibility of leakage and valve operation.
3. Situation: pipe break, prolonged leakage of coolant in the absence of the owners. A completely autonomous “smart” recharge will flood the entire house, ruining the flooring and causing expensive repairs.
4. Imagine an identical situation in an apartment building - a leak from an individual system and the activation of automated replenishment will flood the neighbors below.
5. Fine sand will accumulate under the valve seat and the element will lose its seal over time. Under pressure from the water supply of 4-7 bar, spontaneous replenishment will begin. The most harmless scenario is the release of excess coolant through the fuse on the boiler safety group.

To eliminate the consequences of the described troubles, it is better to allocate a little time for personal control over your heating. Having discovered signs of loss of coolant, you will make your own decision - to recharge the system immediately, look for a leak, or make repairs. For a negative example of using such automation, watch our expert’s video:

Manual recharge scheme

The simplest option for filling the system is implemented in 90% of double-circuit wall-mounted boilers, where a cold water supply pipe is a priori connected. A manual valve is installed inside the housing, connecting this line with the heating return line. Often, a boiler feed tap is found on solid fuel heat generators with and without a water circuit (for example, heating units of the Czech brand Viadrus).

Reference. On some models of gas heaters equipped with a DHW heat exchanger (in particular, Beretta), instead of a manual tap, manufacturers install an automatic make-up valve with an electromagnetic drive. If the coolant pressure drops below 0.8 Bar, the boiler itself draws water to the required level.

To assemble a classic make-up unit suitable for any type of system, you will need the following parts:

• tee with side outlet DN 15-20, corresponding to the material of the heating main pipe - fitting for metal-plastic, polypropylene, and so on;
• disc (spring) ;
• ball valve;
• couplings, fittings.

The purpose of the check valve is to prevent water from the heating network from flowing back into the water supply system. If we are talking about pumping antifreeze using a pump, you cannot do without a valve. The fittings are installed in the order listed:

1. The tee cuts into the heating return after the circulation pump.
2. A check valve is connected to the outlet pipe of the tee.
3. Next is a ball valve.

Advice. If there is no fine filter at the entrance of the water supply to a private house, it is advisable to provide one on the make-up line. The element will protect the heating network from the entry of fine sand and rust particles that accumulate on the check valve plate and in the seats of three-way valves.

The operating principle of the unit is simple: when the tap is opened, water from the centralized main flows into the heating pipelines, since its pressure is higher (4-8 Bar versus 0.8-2 Bar). The filling process of a closed system is monitored by a boiler or safety group pressure gauge. If you accidentally exceed the pressure, use the Mayevsky tap on the nearest radiator and bleed off excess water.

To control the amount of coolant in the expansion tank of an open heating network located in the attic of the house, the tank must be equipped with 2 additional tubes with a diameter of ½ inch:

Comment. If you are interested in calculating the minimum volume of the expansion tank, follow the link.

The circuit with a check valve and shut-off valve is also applicable for filling solar systems (solar collectors) and geothermal circuits of heat pumps with antifreeze. How to use the boiler make-up valve is described in the video:

Automatic make-up unit

If you are firmly confident in the reliability and quality of the system, you can install an automated circuit that adds water from the cold water pipe. What you need to buy:

• pressure reducing valve (simpler - reducer);
• 3 ball valves;
• 2 tees;
• pipe for the bypass device.

Important point. The water entering the reducer must be pre-cleaned with a coarse strainer, otherwise the valve will quickly become clogged. If such a filter is not provided at the entrance to the building, install it in front of the make-up unit.

The main executive element of the circuit - the gearbox - consists of the following parts:

• fine filter on the inlet pipe;
• spring seat valve with rubber seals;
• pressure regulator handle with printed scale, range – 0.5…4 Bar (or higher);
• manual shut-off valve;
• check valve at the outlet.

Note. There are more expensive models of make-up reducers with a built-in pressure gauge that measures the pressure on the side of the heating system. Since this device is already in the security group or boiler, there is no point in spending extra money and duplicating it. The exception is the situation when the make-up is installed far from the heat source (read the next section).

As you can see, the pressure reduction machine already contains all the necessary elements - a filter, a check valve and a regulator. All that remains is to assemble a simple circuit with a bypass and service taps intended for removing and servicing the gearbox.

Operating the valve is simple - use the regulator to set the minimum pressure threshold in the heating network, open the direct line taps, and close the bypass. How to properly adjust the automatic valve is shown in a short video:

Advice. If you plan to install a coarse filter in front of the gearbox, provide an additional service tap in order to clean the mesh without turning off the water in the entire house.

To organize the automatic addition of antifreeze to the system, you can adapt a “hydrofor” - a water station with an electric pump designed for water supply from a well. The pressure switch of the unit must be reconfigured to a minimum pressure of 0.8 Bar, a maximum pressure of 1.2...1.5 Bar, and the suction pipe must be directed into a barrel with non-freezing coolant.

The appropriateness of this approach is highly questionable:

1. If the “hydrofor” works and starts pumping up antifreeze, you will still have to look for and eliminate the cause of the problem.
2. If the owners are absent for a long time, replenishment will also not save the situation in the event of an accident, since the size of the container is limited. The pumping station will extend the heating operation for some time, but then the boiler will turn off.
3. Placing a large barrel is dangerous - you could flood half the house with toxic ethylene glycol. Non-toxic propylene glycol is too expensive, as is spill cleanup.

Conclusion. Instead of additional pumps and automatic gearboxes, it is better to purchase an electronic unit of the Xital type. After a relatively inexpensive installation, you will be able to control the heating operation via a cell phone or computer and quickly respond to emergency situations.

How to connect to the heating system

With a closed circuit, there is not much difference where to connect the make-up pipeline - to the supply or return. We recommend using the classic proven method - the insertion point should be located on the return line next to the boiler, after the circulation pump and expansion tank. Causes:

• the unit is located in the combustion room, next to the equipment and instruments;
• pumping water into the return line is immediately reflected on the pressure gauge installed in the supply behind the boiler;
• the insert is located at the lowest point, the flow is distributed in 2 directions - into the boiler and radiators, the air is squeezed out evenly.

The piping of solid fuel units involves the installation of a condensation protection circuit with a three-way valve. You cannot make makeup in front of this valve - cold water will immediately close it and the boiler pressure gauge will begin to lag in readings. Cut inside the circuit, between the 3-way valve and the heat generator.

In a similar way, the make-up flows into the return line of the open system. The second option is to add coolant directly to the tank; the disadvantage of this method is to lay the supply pipe into the attic.

Connecting the make-up line is also allowed at other points:

• to a separate fitting of a solid fuel boiler, provided by the manufacturer;
• to the bottom of the hydraulic arrow;
• to the return manifold of the distribution comb;
• to the outlet of the indirect heating boiler.

These options are usually implemented in complex and extensive systems of country cottages. Connecting the make-up to the boiler is demonstrated in the next video:

Finally, about the safe addition of coolant

When filling water or partial replenishment, follow our recommendations:

1. Replenish the heated system slowly by opening the valve a quarter of the lever stroke. In this way, it will be possible to avoid the formation of air locks and protect the boiler heat exchanger from temperature shock.
2. Refill from scratch with the heat generator not working and the circulation pump turned off.
3. Check the pressure in the expansion tank and go through all the radiators, opening the Mayevsky taps for.
4. If your boiler is equipped with modern electronics, be sure to study the instructions regarding make-up. Often it is necessary to activate a special service mode in the unit.
5. Excess pressure is easily released through the nearest air vent.

Reference. Cast iron heat exchangers easily crack from sudden temperature changes, and steel fireboxes become covered from the inside with condensation. The latter mixes with soot and forms a dense coating.

Injecting antifreeze with a hand pump does not have any pitfalls. Pressure testing units are equipped with their own pressure gauge, which allows you to monitor the current pressure at the insertion point.

Over the past few years, closed heating systems have become increasingly popular. Heating equipment is becoming more and more expensive, and you want it to last longer. In closed systems, the possibility of free oxygen getting inside is practically eliminated, which extends the life of the equipment.

Closed heating system - what is it?

As you know, any heating system in a private home has an expansion tank. This is a container that contains some coolant removal. This tank is necessary to compensate for thermal expansion under various operating conditions. By design, expansion tanks are of open and closed type, respectively, and heating systems are called open and closed.

In recent years, a closed heating scheme has become increasingly popular. Firstly, it is automated and works without human intervention for a long time. Secondly, it can use any type of coolant, including antifreeze (it evaporates from open tanks). Thirdly, the pressure is maintained constant, which allows the use of any household appliances in a private home. There are several more advantages that relate to wiring and operation:

• There is no direct contact of the coolant with air, therefore, there is no (or almost no) unbound oxygen, which is a powerful oxidizing agent. This means that the heating elements will not oxidize, which will increase their service life.
• A closed-type expansion tank is placed anywhere, usually close to the boiler (wall-mounted gas boilers come immediately with expansion tanks). An open-type tank should be located in the attic, and this means additional pipes, as well as insulation measures so that heat does not “leak” through the roof.
• The closed type system has automatic air vents, so there is no airing.

In general, a closed heating system is considered more convenient. Its main drawback is its energy dependence. The movement of the coolant is ensured by a circulation pump (forced circulation), and it does not work without electricity. It is possible to organize natural circulation in closed systems, but it is difficult - it requires regulating the flow using the thickness of the pipes. This is a rather complicated calculation, which is why it is often believed that a closed heating system only works with a pump.

To reduce energy dependence and increase heating reliability, install uninterruptible power supplies with batteries and/or small generators that will provide emergency power supply.

Components and their purpose

In general, a closed heating system consists of a certain set of elements:

• Boiler with safety group. There are two options here. The first is that the safety group is built into the boiler (gas wall-mounted boilers, pellet boilers and some solid fuel gas generators). The second is that there is no safety group in the boiler, then it is installed at the outlet in the supply pipeline.
• Pipes, radiators, convectors.
• Circulation pump. Ensures the movement of coolant. It is installed mainly on the return pipeline (the temperature is lower here and there are fewer possibilities of overheating).
• Expansion tank. Compensates for changes in coolant volume, maintaining stable pressure.

Now in more detail about each element.

Boiler - which one to choose

Since the closed heating system of a private house can operate autonomously, it makes sense to install a heating boiler with automation. In this case, having configured the parameters, you do not need to return to this. All modes are supported without human intervention.

The most convenient gas boilers in this regard. They have the ability to connect a room thermostat. The temperature set on it is maintained with an accuracy of one degree. It dropped by a degree, the boiler turned on, heating the house. As soon as the thermostat is activated (the temperature is reached), the operation stops. Comfortable, convenient, economical.

Some models have the ability to connect weather-dependent automation - these are external sensors. Based on their readings, the boiler adjusts the power of the burners. Gas boilers in closed heating systems are good equipment that can provide comfort. The only pity is that gas is not available everywhere.

Electric boilers can provide a no less degree of automation. In addition to traditional units, induction and electrode units have recently appeared on heating elements. They are distinguished by their compact size and low inertia. Many believe that they are more economical than boilers using heating elements. But even this type of heating unit cannot be used everywhere, since power outages in winter are a common occurrence in many regions of our country. And provide the boiler with electricity. 8-12 kW from the generator is a very difficult matter.

Solid or liquid fuel boilers are more versatile and independent in this regard. An important point: to install a liquid fuel boiler, a separate room is required - this is a requirement of the fire service. Solid fuel boilers can be installed in the house, but this is inconvenient, since a lot of debris falls from the fuel during combustion.

Modern solid fuel boilers, although they remain periodic equipment (they warm up during combustion, cool down when the fuel burns out), but they also have automation that allows you to maintain a given temperature in the system, regulating the intensity of combustion. Although the degree of automation is not as high as that of gas or electric boilers, it is there.

Pellet boilers are not very common in our country. In fact, this is also solid fuel, but boilers of this type operate in continuous mode. Pellets are automatically fed into the firebox (until the stock in the burner is finished). If the fuel quality is good, ash cleaning is required once every few weeks, and all operating parameters are controlled automatically. The only thing holding back the spread of this equipment is its high price: the manufacturers are mainly European, and their prices are corresponding.

A little about calculating boiler power for closed-type heating systems. It is determined according to the general principle: per 10 sq. meters of area with normal insulation take 1 kW of boiler power. It’s just not recommended to take it “back to back”. First, there are unusually cold periods during which you may not have enough rated power. Secondly, working at maximum power leads to rapid wear of the equipment. Therefore, it is advisable to take the boiler power for the system with a margin of 30-50%.

Security group

A safety group is placed on the supply pipeline at the outlet of the boiler. She must control its operation and system parameters. Consists of a pressure gauge, automatic air vent and safety valve.

The pressure gauge makes it possible to control the pressure in the system. According to recommendations, it should be in the range of 1.5-3 Bar (in one-story houses it is 1.5-2 Bar, in two-story houses it is up to 3 Bar). If you deviate from these parameters, appropriate measures must be taken. If the pressure drops below normal, you need to check if there are any leaks, and then add some coolant to the system. At increased pressure, everything is somewhat more complicated: it is necessary to check in what mode the boiler is operating, whether it has overheated the coolant. The operation of the circulation pump, the correct operation of the pressure gauge and the safety valve are also checked. It is he who must discharge excess coolant when the threshold pressure value is exceeded. A pipe/hose is connected to the free branch pipe of the safety valve, which is discharged into the sewer or drainage system. Here it is better to do it in such a way that it is possible to control whether the valve works - if water is discharged frequently, you need to look for the reasons and eliminate them.

The third element of the group is an automatic air vent. Air trapped in the system is removed through it. A very convenient device that allows you to get rid of the problem of air locks in the system.

Security groups are sold assembled (pictured above), or you can buy all the devices separately and connect them using the same pipes that were used to wire the system.

Expansion tank for closed heating system

The expansion tank is designed to compensate for changes in coolant volume depending on temperature. In closed heating systems, this is a sealed container divided into two parts by an elastic membrane. At the top there is air or inert gas (in expensive models). While the coolant temperature is low, the tank remains empty, the membrane is straightened (picture on the right).

When heated, the coolant increases in volume, its excess rises into the tank, pushing back the membrane and compressing the gas pumped into the upper part (in the picture on the left). This is displayed on the pressure gauge as an increase in pressure and can serve as a signal to reduce the combustion intensity. Some models have a safety valve that releases excess air/gas when a threshold pressure is reached.

As the coolant cools, the pressure in the upper part of the tank squeezes the coolant out of the container into the system, and the pressure gauge readings return to normal. That's the whole principle of operation of a membrane-type expansion tank. By the way, there are two types of membranes - disc-shaped and pear-shaped. The shape of the membrane does not affect the operating principle in any way.

Volume calculation

According to generally accepted standards, the volume of the expansion tank should be 10% of the total coolant volume. This means that you must calculate how much water will fit in the pipes and radiators of your system (it is in the technical data for radiators, and the volume of the pipes can be calculated). 1/10 of this figure will be the volume of the required expansion tank. But this figure is only valid if the coolant is water. If non-freezing liquid is used, the tank size is increased by 50% of the calculated volume.

Here is an example of calculating the volume of a membrane tank for a closed heating system:

• the volume of the heating system is 28 liters;
• expansion tank size for a system filled with water 2.8 liters;
• the size of the membrane tank for a system with non-freezing liquid is 2.8 + 0.5 * 2.8 = 4.2 liters.

When purchasing, select the nearest larger volume. Don't take less - it's better to have a small supply.

What to look for when purchasing

There are red and blue cans in stores. Red tanks are suitable for heating. The blue ones are structurally the same, only they are designed for cold water and cannot tolerate high temperatures.

What else should you pay attention to? There are two types of tanks - with a replaceable membrane (they are also called flanged) and with a non-replaceable one. The second option is cheaper, and significantly, but if the membrane is damaged, you will have to buy the whole thing. For flanged models, only the membrane is purchased.

Place for installing a membrane type expansion tank

Usually they place an expansion tank on the return pipeline in front of the circulation pump (if you look in the direction of flow of the coolant). A tee is installed in the pipeline, a small section of pipe is connected to one part of it, and an expander is connected to it through fittings. It is better to place it at some distance from the pump so that pressure differences are not created. An important point is that the piping section of the membrane tank must be straight.

A ball valve is installed after the tee. It is necessary to be able to remove the tank without draining the coolant. It is more convenient to connect the container itself using an American nut. This again makes installation/disassembly easier.

Please note that some boilers have an expansion tank. If its volume is sufficient, installing a second one is not required.

The empty device does not weigh much, but when filled with water it has a significant mass. Therefore, it is necessary to provide a method of mounting on the wall or additional supports.

Circulation pump

The circulation pump ensures the operation of the closed heating system. Its power depends on many factors: the material and diameter of the pipes, the number and type of radiators, the presence of shut-off and thermostatic valves, the length of the pipes, the operating mode of the equipment, etc. In order not to go into the intricacies of calculating power, the circulation pump can be selected according to the table. Select the nearest larger value for the heated area or the planned thermal power of the system, and find the required characteristics in the corresponding line in the first columns.

In the second column we find the power (how much coolant it can pump in an hour), in the third - the pressure (system resistance) that it is able to overcome.

When choosing a circulation pump in a store, it is advisable not to save money. The entire system depends on its performance. Therefore, it is better not to save money and choose a trusted manufacturer. If you decide to buy unknown equipment, you need to somehow check it for noise levels. This indicator is especially critical if the heating unit is installed in a residential area.

Strapping scheme

As mentioned earlier, circulation pumps are installed mainly on the return pipeline. Previously, this requirement was mandatory, today it is only a wish. The materials used in production can withstand heating up to 90°C, but it’s still better not to take risks.

In systems that can also operate with natural circulation, during installation it is necessary to provide for the ability to remove or replace the pump without the need to drain the coolant, as well as for the possibility of operation without a pump. To do this, a bypass is installed - a workaround through which coolant can flow if necessary. The installation diagram of the circulation pump in this case is shown in the photo below.

In closed systems with forced circulation, a bypass is not needed - without a pump it is inoperative. But two ball valves on both sides and a filter at the inlet are needed. Ball valves make it possible, if necessary, to remove the device for maintenance, repair or replacement. The dirt filter prevents clogging. Sometimes, as an additional element of reliability, a check valve is also installed between the filter and the ball valve, which will prevent the coolant from moving in the opposite direction.

Connection diagram (piping) of a circulation pump to a closed heating system

How to fill a closed heating system

At the lowest point of the system, usually on the return pipeline, an additional tap is installed to feed/drain the system. In the simplest case, this is a tee installed in a pipeline, to which a ball valve is connected through a small section of the pipe.

In this case, when draining the system, you will need to substitute some kind of container or connect a hose. When filling the coolant, a hand pump hose is connected to the ball valve. This simple device can be rented from plumbing stores.

There is a second option - when the coolant is just tap water. In this case, the water supply is connected either to a special boiler inlet (in wall-mounted gas boilers), or to a ball valve similarly installed on the return line. But in this case, another point is needed to drain the system. In a two-pipe system, this may be one of the last radiators in a line, with a drain ball valve installed at the lower free inlet. Another option is presented in the following diagram. Shown here is a closed-type single-pipe heating system.

Diagram of a closed one-pipe heating system with a system power supply unit

Designing a modern autonomous heat supply for residential buildings, apartments and industrial facilities is a serious job that requires correct calculations and coordination of the parameters of the installed equipment. For trouble-free operation of a heating circuit under load, it is important to choose the right expander and professionally install the expansion tank of the heating system. Let's consider the design nuances, specifics of connecting and servicing the device that compensates for the increase in coolant volume.

Why is it necessary to install an expansion tank in the heating system?

The physical properties of a liquid, which increases its volume with increasing temperature, are the cause of pressure surges that occur in a closed heating circuit. In this regard, connecting the expansion tank to the heating system is important, as it allows you to solve a number of serious problems:

• compensate for the thermal expansion of liquid in heating lines. The working capacity of the tank accepts excess water that appears during volumetric expansion of the liquid. The device does not allow increasing pressure to damage the boiler and ensures the integrity of the lines;
• smooth out hydraulic shocks associated with periodic turning on and off of the circulation pump. When the room temperature fluctuates, the coolant supply equipment operates cyclically, causing short-term pressure surges.

The working reservoir of the expander, being a kind of buffer for the heating circuit, provides:

• increased service life of heating elements;
• stabilizes the effect of excess pressure and temperature on equipment;
• increased reliability and safety of operation of units.

The above arguments confirm that installing an expansion tank in the heating system is a mandatory measure.

Determining the expander volume

Capacity or, as experts say, usable space of the expander is the priority parameter of the device. Its value must exceed by a margin the maximum amount of coolant that, as a result of expansion, fills the tank. This is due to the fact that as the intensity of boiler operation increases, the volume of liquid in the lines increases. It fills the damper tank, which receives an increased amount of coolant.

The capacity of the expander is affected by the type of liquid used. The following parameters are used to perform the calculation:

• the volume of the tank is 15% of the total amount of water filling the heating circuit;
• capacity increases to 20% when filling the heating system with antifreeze.

The algorithm for calculating the capacity of the expansion tank involves determining the total amount of working fluid. It is calculated by summing the volumes of individual structural elements:

• heating boiler. Information about capacity is contained in the technical passport of the unit;
• highways. The volume of pipes is determined by multiplying the internal cross-sectional area by the length;
• radiators. If there is no data in the passport, you can experimentally calculate the volume by filling the battery with water.

Having obtained, by calculation, the volume of the circuit, it remains to multiply the obtained value by a coefficient of 0.15 for water or 0.2 for antifreeze.

For example, with a capacity of lines and devices of 60 liters, a damping tank of the following volume will be required:

• 60 x 0.15 = 9 liters - when using water;
• 60 x 0.2 = 12 liters - when filled with antifreeze.

The given algorithm allows you to quickly make calculations to determine the main operating characteristics of the expander.

Where is the expansion tank installed in the heating system?

Depending on the design features of the heating, the location of the damper tank changes:

• in an open type design it is installed at the highest point, which is usually located in a room under the roof or in the ceiling area of ​​the boiler room. An open system is a vessel of complex configuration in which characteristic convection currents arise. Placing the boiler at the top point promotes an accelerated rise of the heated coolant with subsequent movement by gravity into the heating devices through the pipes. In addition, the upper location ensures unhindered rise of the resulting air bubbles;
• for closed heating, the optimal area for installing the tank is the straight section located in front of the pump that provides forced circulation. The absence of turbulence in a straight section of the pipeline and a constant fluid flow rate create favorable conditions that allow the tank to compensate for hydraulic shocks and dampen the thermal expansion of the medium. In this case, the air formed when the liquid is heated can be easily removed using the existing air valves.

When deciding where to install the expander, pay attention to the following points:

• the proximity of the tank location to the boiler room or furnace room, facilitating control over the operation of the device;
• free access to the damper tank, allowing for maintenance of the unit;
• the presence of a gap between the body and the wall, facilitating visual inspection;
• reliability of fixation of the container with coolant, which must be fixed independently without transferring the load to the supply lines.

Proper placement of the expansion tank will ensure proper functioning and facilitate maintenance.

What types of expansion tanks are there depending on the heating system?

The design of the damper tank depends on the type of heating circuit:

• in a system with natural circulation, open-type expansion devices are used, allowing liquid to be filled if necessary. Open tanks do not require shut-off valves, a sealed lid or a rubber membrane. Adding liquid is carried out by opening the supply tap of the water main or manually using a bucket;
• In a closed heating circuit with forced circulation, expanders of a closed design are used. They are made in the form of a sealed tank, divided into two parts by a rubber membrane. One contains inert gas or air. In the other there is a coolant, which, with an increase in volume, deforms the rubber, reducing the volume of the chamber with air, and thus compensates for load differences.

The following types of tanks are used in closed systems:

• flanged, equipped with a replaceable balloon-type membrane;
• flangeless with a stationary diaphragm membrane.

More modern closed-type designs are gradually replacing open heating systems, which are more susceptible to corrosion and require constant monitoring of the liquid level and regular topping up. The final decision on choosing the type of damper unit is dictated by the design of the heating system being installed.

Open type expansion tank

For decades, heating circuit damping tanks have been widely used in natural circulation systems. They made it possible to replenish the water supply in case of small leaks or evaporation of the coolant, and also ensured the removal of air bubbles from the heating circuit.

Design

Structurally, an open expander is a welded vessel connected to the atmosphere, made in the form of:

• cylinder;
• parallelepiped.

The following materials are used for manufacturing:

• Sheet steel;
• polymer materials.

The tank is equipped with the following elements:

• a cover that allows you to protect the thermal fluid from dirt and provides access for maintenance;
• a durable bracket that allows you to securely fix the case to the wall of the room;
• pipes necessary for connecting the heating circuit lines, as well as water supply and overflow pipes;
• a drain valve that allows you to drain the coolant during maintenance and repair work.

Due to the simplicity of the design, an open type expander is easy to make yourself.

Advantages and disadvantages

The main advantages of an open type damper tank:

• possibility of self-production;
• simplicity of design;
• low cost;
• air removal efficiency;
• accelerated pressure release.

Along with the advantages, the open design has a number of serious disadvantages:

• the need for thermal insulation of an expander located in an unheated room;
• contact of the coolant with the atmosphere, which causes corrosion of metal elements;
• the need to regularly add liquid to the container due to its constant evaporation;
• special installation requirements that require the installation of additional lines.

Design weaknesses limit the widespread use of open tanks.

Installing an expansion tank in an open heating system

When deciding how to connect an expansion tank to an open-type heating system, you should be guided by the recommendations of a previously developed project and instructions. In this case, it is necessary to pay special attention to compliance with the following requirements:

• installation of a damper on the highest possible section of the heating main;
• ensuring reliable fastening of the tank, the mass of which increases when filled with water;
• thorough insulation of the body surface, reducing heat loss and protecting the liquid from freezing;
• maintaining the operating parameters of the circuit by adding water, the level of which must be regularly monitored.

Installation activities include the following operations:

• installation of a control pipe at the level of the minimum coolant volume;
• installation of an overflow line that drains at the maximum level;
• connecting a supply line to make up for losses.

Activities for connecting the tank do not require special training and can be carried out independently.

Closed expansion tank

Damper tanks of a closed design, equipped with an elastic diaphragm or water chamber, are used in heating circuits with forced circulation. They provide reliable compensation for pressure surges and dampen the increase in coolant volume. Thanks to a set of advantages, sealed expanders compare favorably with similar open-type units.

Membraneless

Expansion tanks, the design of which does not contain a membrane, were widely used before the advent of high-quality rubber membranes with increased service life and strength. They functioned without a membrane, but required the connection of a compressed air cylinder or a compressor that supplied air in the required quantity.

Device Features:

• lack of mechanical separation of the tank capacity, resulting in direct contact of the coolant with the gas;
• the need to maintain operating pressure using a gas cylinder or compressor;
• the ability to operate a membraneless tank only with automatic control of operation and continuous gas supply.

Membraneless tanks are significantly inferior in performance characteristics to membrane devices.

Membrane

The design features of the membrane expander provide for the separation of the coolant and the gaseous medium by an elastic membrane of different shapes:

• hemispherical (disc-shaped). The membrane is a stationary element and, under the influence of pressure, takes on a spherical shape;
• balloon (pear-shaped). The removable membrane is attached to the flange on the vessel body and, under load, tends to repeat its shape.

A device with a disc diaphragm is characterized by the presence of the following elements:

• a vertically located steel case, representing a sealed capsule consisting of two parts;
• a rubber membrane permanently fixed between the components of the steel capsule;
• a pipe located in the lower part of the container and intended for connection to the heating lines;
• nipple located at the top of the tank and allowing air to be pumped into the tank.

As the temperature increases, excess coolant enters the container between the membrane and the housing, compressing the air. As the temperature generated by the boiler decreases, the volume of water decreases. It is squeezed out by compressed air located at the top of the tank. The sealed design of the damping reservoir allows, if necessary, to change the air pressure by opening the nipple or pumping.

Tanks equipped with a pear-shaped balloon membrane are manufactured for closed systems in vertical and horizontal versions. By design, the device consists of the following parts:

• a stamped container with a flange for attaching a balloon membrane;
• a rubber chamber for water, inserted into the housing and tightly connected to the flange;
• connecting pipe required to connect the damper device to the pipes;
• bottom valve designed to maintain air pressure.

The design feature of the tank is that the coolant does not come into contact with the metal surface, but fills a rubber balloon. This allows you to protect the steel case from corrosion processes and extend its service life. Unlike diaphragm tanks, the ability to replace the rubber balloon is a great convenience.

Advantages and disadvantages

Advantages of membrane devices:

• compact dimensions;
• minimum heat losses;
• no need for external thermal insulation;
• possibility of functioning without recharge;
• complete tightness;
• work at increased pressure;
• increased reliability;
• operational safety;
• no air pockets.

Disadvantages include:

• the need to control working pressure;
• the need for periodic air pumping;
• increased cost.

The devices are widely used due to their numerous advantages.

Installing an expansion tank in a closed heating system

Installation of a damper tank installed in a closed heating circuit is a responsible operation that requires special training. However, if you have the skills to perform plumbing work, you can install the device yourself, following the following recommendations:

• install the expander only in the return circuit (from the water supply side to the boiler), choosing any convenient location;
• check the pressure in the tank, which should be 0.2 atmospheres less than the liquid pressure;
• install the tank in a room with a positive temperature, placing it close to the boiler;
• securely attach the container to the wall surface, since its mass will increase when filled with liquid;
• provide access to the air nipple to adjust the pressure in the chamber;
• secure the device so that it does not take the load from the mass of the pipes with liquid;
• connect the tee and shut-off valves that allow you to disconnect the tank from the heating pipes;
• perform an upper pipe connection, which ensures the operation of the device if the integrity of the membrane is damaged.

How to use extenders correctly

Activities for the operation of the damper tank provide for the following maintenance rules:

• visual inspection of external damage associated with corrosion and mechanical stress;
• control of the pressure of the air space of the container, which must correspond to the passport data;
• checking the integrity of the rubber membrane, which must be replaced if damaged;
• draining water from the damper tank when preserving heating for a long period.

The frequency of inspection is at least twice a year.

Conclusion

The recommendations given in the article will help you choose the right damper tank and calculate its volume. Knowing how to install an expansion tank for heating, you can ensure the safety, reliability and durability of a heating structure with natural or forced circulation of coolant.

Every year, at the end of the heating season, the autonomous water circuits, which diligently supplied the owners with heat, are freed of water or the antifreeze that replaces it. With the onset of the first cool days, the heating system is again filled with the coolant necessary for its operation.

It is worth familiarizing yourself with the procedure for performing this difficult work and the necessary equipment in order to avoid mistakes. In this material we will talk about how to correctly fill the system with water and non-freezing coolant, the rules that should be followed during the work process, as well as how to correctly calculate the amount of coolant.

Due to its fluidity and high heat capacity, water is used to transfer heat from the boiler to consumers, among which water ranks first.

It is used to fill even the most capacious heating systems. It is publicly available and inexpensive, which determines the widest range of applications.

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