Why is the pressure in the heating system rises

It’s critical to comprehend the causes of rising heating system pressure if you want to keep your house safe and efficient. An abrupt rise in pressure may be a sign of underlying problems that require medical attention right away. Let’s examine a few typical causes for this to occur.

A malfunctioning pressure relief valve is one of the most frequent causes of increased pressure in heating systems. This valve’s purpose is to relieve excess pressure in order to shield the system from harm. On the other hand, if it breaks down or becomes stuck, pressure may build up inside the system.

Air trapped in the system is another possible cause. With time, air pockets may appear, particularly in older or improperly maintained systems. Pressure rises as a result of the expanding air brought on by heat. One way to help release trapped air and reduce pressure is to bleed the radiators.

Pressure can also rise as a result of system leaks. A build-up of pressure can result from any loss of water in the system, no matter how minor or large. Regularly check your radiators, valves, and pipes for leaks by looking for corrosion or wetness.

Rising pressure can also be caused by an expansion tank that isn’t working properly. When water expands as a result of heating, the expansion tank is in charge of absorbing extra water. Pressure may increase if the tank is malfunctioning or is too small for the system to handle the expansion.

Finally, an excessive amount of water pressure coming from the mains into the system may raise the pressure inside the heating system. To control water pressure and keep it from rising above safe limits, install a pressure-reducing valve.

Reason Explanation
Thermal Expansion As water heats up in the heating system, it expands, causing pressure to rise.
Blocked Pipes If there"s a blockage in the pipes, water flow is restricted, leading to pressure buildup.

What air pressure should be in the expansion tank of the heating system

A temperature-dependent indicator of the empty air chamber capacity. It ought to be equivalent to a static value in the water-filled tank. In this state, the membrane is in equilibrium and the liquid is compensating for the gas pressure. Procedure calls for one atm of pressure for every ten meters of pressure. Nevertheless, creating the indicator listed in the device passport is sufficient for the system’s regular operation as a whole.

Picture 1: The closed heating system expansion tank device diagram. Parts of the product are indicated by the arrows.

Most expansion tanks are sufficient for 0.9 atm of favorable work. This is because the membrane is created during operation by pressure. It is 1.2 atm on average. There is a tiny variation between the two values, with a maximum deviation of 0.1.

Separate calculations are made for her if the heating system is not constructed in accordance with traditional schemes. These calculations determine the coolant volume, tank capacity, coefficient of benefit, and initial loading pressure. You should invite an expert who will consider other minor details to accomplish this.

How to check the indicators

Attaching a pressure gauge is the most straightforward method of taking a measurement. Since most tanks don’t have space for fastening, the issue starts during the preparation phase. The device should be nipple at the same time, allowing for easy connection of the compressor and sensor.

Citation. Translating the value dimension is not difficult: 1 MPa = 1 atm ÷ 1 bar.

How to adjust the pressure of hot water in the system

Water pressure is a parameter that can be easily customized. This will require:

  1. Calculate. Having completed it, they take away from the obtained value 0.2 atm.
  2. Before starting installation Lower (or pump) from the system air to the desired indicator.
  3. Attach the capacity to the pipeline and fill in the liquid. The process is done slowly, so as not to miss the moment of installing normal pressure.
  4. Connect the pump and upload liquid before receiving operational pressure.
  5. The first inclusion of the device occurs after maximum water heating. In this case, the volume of the liquid will grow to the value taking into account the specific increment.

In order to adjust an automobile manometer, you will need:

  1. Disconnect the heater and wait 7-10 minutes to the stop of the system.
  2. Tighten the locking elements, drain the working water. If the membrane is built into the boiler, close the feed and return.
  3. Attach the pump to the nipple.
  4. Pour one and a half atmosphere, Lower the remaining liquid, then air.
  5. Close all the valves, Create the necessary pressure.
  6. Remove the pump, Open the valve, pour water.

Selection of a tank

It will be necessary for all to rationally select and install such a tank when building a trustworthy heating system. The functions utilized and the installed design type will determine the device’s characteristics. There are just three viable options on the market.

Closed-type format. Depending on the needed volume, the price of these units in the domestic market can range from 2500 to 75,000 rubles. Air is poured into a standard sealed tank. A rise in system pressure causes the air to compress, filling the tank’s capacity. The interior of the container is fitted with a unique membrane. After mixing with oxygen to increase the corrosion activity of water, the aggregate must be protected from rust.

An open tank lacks a sealed cover. In the home market, the average price is roughly 3,000 rubles. These devices are employed not only to offset system expansion but also to remove air traffic congestion. Through the use of a tank like this, coolant can be added to the design to offset its slow evaporation.

A tank with an upper outlet can be used in the design of the house’s water heating system. This is a valve-equipped sealed container. You can stir the water in your home heating system the fastest by using a tank like this one.

We adjust the tank for working in the heating system.

We will set up the expansomate according to the advice provided by Reflex, a well-known German producer of similar apparatus.

We’ll go over the fundamentals of tank settings here.

As we set up the tank, we are interacting with various pressure levels that require mutual consent:

PArt: the system’s static pressure, which is equal to the water column’s height as a result of the heating system’s height from the tank’s connection point to the top of the last upper element;

P0: air pressure within the chamber of air;

Beginning: the recharge’s starting pressure;

Pdedication: the pressure that the expanding water volume causes to be created in the system;

Pcon is the pressure that is produced when the heating system is removed to the upper operating mode in accordance with temperature, as a result of additional feeding. (In cases where the system is subject to expansion pressure);

PCl: safety valve pressure (three bars for private residences);

PMax: The maximum working pressure, determined by the system’s most delicate component (often the boiler heat exchanger).

Increased pressure due to expansion tank

The following are the causes of the expansion tank issues that are causing the pressure in the heating circuit to increase:

  1. Small volume of expansion tank. Water when heated to 85-90 ° C adds about 4% in a volume. If a small tank is selected, then the coolant when heated expands and fills the capacity. The air is full of air through the valve. With further heating, the tank can no longer compensate the thermal increase in the volume of water, as a result, pressure rises in the system. The volume of the expansion tank should be at least 10% of the total volume of the coolant in the circuit if the gas boiler is installed, and at least 20% if the boiler is solid fuel. The volume of the tank can be taken approximately – by the power of the boiler: 1 kW accounts for approximately 15 liters of water. But it is better to calculate the volume of a single contour (on the surfaces of heating);
  2. Damage to the rubber membrane of the tank. In this case, the water will fully fill the container, and the pressure gauge will show the drop in the system. But, if you open the feed valve and add water, then when the coolant is heated, the pressure in the heating circuit will become much higher. To solve the problem, you will need to replace the tank if the membrane of the diaphragm type, or replacement of the membrane, if it is a cylinder type;
  3. Too high or too low pressure in the expansion tank. Non -varnishes in the operation of the expansion tank are one of the main reasons for increasing pressure in the closed system. Check the pressure and pump it if necessary, you can an ordinary car pump. Before checking, you need to drain the water from the heating system – the arrow of the system manometer should be at the zero mark. If there is a locking reinforcement and drainage plum on the water pipeline to the expansion tank, then it is enough to drain the water only from the tank. Then, through the nipple, which is located from the opposite water supply, air descends. If the boiler works at a pressure of 2 bar, then the pressure gauge on the pump should show 1.6 bar. It is necessary to open the shut -off valve through the water and add the volume of water drained from the expansion tank through the feed tap. This adjustment method works both for tanks with lower and upper water supply;
  4. The tank stands immediately after the circulation pump. This leads to the fact that the pressure rises sharply, and it is discharged almost immediately, while pressure surges are observed. This situation can provoke hydraulic shots in the circuit. To solve this problem in a closed heating circuit, the expansion tank is installed on the return pipe – in the laminar current zone with a minimum coolant temperature. The pump is cut into the return after the tank, in front of the boiler.

Tank tuning.

To begin, set pArt to 4/10, or 0.4 bar.

The next step is to generate pressure p 0 by pumping air into the expansion tank’s matching camera.

What pressure (p0) must be pumped up? We’ll apply Reflex’s formula:

As per the guidelines, Reflex p0 > or = 1 bar.

Choose p0 = 1 bar because the house is not very tall and the sum of pArt and p0 is less than 1 bar.

Use the locking reinforcement to open or set the tank in the system.

Next, we initiate the system’s initial pressure by opening the firmware valve.

To what extent? We can benefit from the following suggestions in this regard:

Pbeginning = 1 + 0.3 = 1.3 bar, or Pbeginning > or = p0 + 0.3 bar.

We now switch on the boiler, heat the system to the predicted temperature—let’ssay80 degrees Celsius—and drain the air from the system while monitoring the manometer to see how new pressure—the pressure of expansion—is produced. which will eventually acquire some significance.

And lastly. we reactivate the feed and raise the system pressure to pcon, which is determined by the following formula:

Everything is operational, including the expansion tank!

A few important comments:

It’s not always necessary to open a recharge twice. The manometer needs to be navigated. You don’t need to open the feeding again if your system has a 3-bar safety valve and the manometer indicates that the preheated system has 2.5 bar of pressure.

When recharging a preheated system, it’s important to keep in mind the risk of thermal shock to the boiler. Вогда стенки котла, разогретые до высокой температуры, получают холодную воду, происходит внутренние напряжения в самом металле. Їто может привести к трещинам и соответственно к порче котла. When the system has cooled to 40 °C or when the feed is severed at a considerable distance from the boiler, hot water must be fed.

When increasing the system’s pressure, even slightly, you must consider the components of the installed heating system. Under no circumstances should the system’s operating pressure be greater than the maximum allowable for the most sensitive component (refer to the manufacturer’s passport).

When we compare the factory settings for expansion tanks with the advice provided here, we can see that most residential heating systems can operate well with this configuration.

You might wonder, "So why are all these calculations?" "Why make things more complicated?" We respond. The following computations are required in order to comprehend how the expansion tank is set up:

  • when the pressure in the air chamber falls or is completely absent;
  • when a decision is made to change the tank membrane;
  • когда нужно настроить расширительный бак для нетипового объекта.

We also mention the existence of an effective useful volume of expansion tank, which is the volume of water the tank can hold before replenishing the system. Only with correct tank tuning can this indicator be used to its full potential.

What features does this indicator possess?

Put simply, this means that the amount of water in the expansion tank (also known as the tank’s "reserve") determines the amount of water the tank can return to the system.

When is it required?

Water in the system decreases due to evaporation or tiny leaks (dropped). Additionally, the pressure does not decrease when he adds water to the system while the tank is still filled with it. However, as soon as this supply is cut off, the coolant loss process will resume. This results in a drop in boiler automation pressure and operation. Because there is not enough water in the system, it either shuts down or cannot function at all.

Recognize that there is a difference between your tank’s capacity to hold 100 g of water (if it is mistuned) and its ability to make up for the lost liters, which helps the heating system run until the leak is fixed and the system is never filled up again.

This is particularly true for rural homes whose owners do not reside there frequently, as there is a risk of the heating system being turned off too soon and its components defrosting.

When the boiler temperature drops, either automatically or manually, the tank must have the same capacity to adjust for the coolant volume. In addition to cooling to a lower temperature, the coolant’s volume decreases. And this is where expansomate saves the day.

Make the right expansion tank selection and setup! Wishing you luck!

Systems in the system and setting

In the event that every choice is made accurately, the system will be the same. Consequently, now that you’ve run into this issue, you need to determine why:

  • incorrectly selected volume;
  • Breakthrough of the membrane;
  • Nippel malfunction;
  • Incorrect installation.

All repair work is carried out only after the tank is removed from the circuit. Settings can be carried out if there is no liquid in the tank. Therefore, it needs to be removed from there. To do this, you need to pump it. When there is no liquid, the air must be struck. After that, using a pump with a pressure gauge, pump air into the tank to the required level. If there is no pump with a manometer, you can use a manual pressure gauge. Since you can’t check the pressure in the expansion heating tank without it, you still have to purchase. Having made sure of the correct settings, you can install the tank back on the outline.

Red tanks are all made to be heated. Apart from them, there are still blue ones. These are cold water accumulators; their operation is based on a different principle than expansion.

The following heating issues will arise if the setting is done incorrectly:

  • increasing pressure in the heating system and expansion tank;
  • emergency emissions of the coolant and, accordingly, the need for constant feeding;
  • The decline in the manometer readings to a critically low level, at which the boiler cannot turn on.

There are a lot of models available that can’t control how much gas is in the tank’s air chamber. While it’s generally preferable to avoid purchasing such items, their low cost frequently makes a big difference. Network users claim that there are situations in which there are just no other options available, only cheap options without nipples, and they do not want to decline it.

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We offer expert turnkey heating systems in addition to prompt and excellent heating pipe repair. You can view and familiarize yourself with samples of our work on our heating theme page at Resant.Ru/Otoplenie-Doma.html. More precisely, though, it is preferable to get clarification from the engineer regarding the cost of work and equipment.

To initiate communication, please use LLC Design Prestige’s phone number, 8 (495) 744-67-74, which is available 24/7.

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In understanding why the pressure in your heating system might rise, it"s crucial to consider several factors. One common reason is trapped air within the system, which can cause pressure to build up as the air can"t escape. Another possibility is a faulty pressure relief valve, which is designed to release excess pressure but may fail to do so properly. Additionally, a malfunctioning expansion tank can lead to pressure spikes as it struggles to accommodate the expanding water volume in the system. Leaks in the system can also contribute to pressure increases by allowing more water into the closed system than it can handle. Regular maintenance and prompt repairs can help prevent these issues and keep your heating system running smoothly.

We select the volume of the tank.

Selecting the right expansion tank will be aided by knowledge of its primary duties.

The primary function of the expansomate, also known by the English term "Expanse" (which means to expand), is to absorb the excess coolant volume that is created due to thermal expansion.

How much does heating cause the volume of water, the primary coolant, to increase?

The volume of water increases by roughly 4% when it is heated from 10 °C to 80 °C. It is important to remember that the closed expansion tank is made up of two sections: gas or air under jam pressure, and one section receiving an excess of expanding coolant.

Considering the expansion tank’s device, it is advised to set its volume to between 10 and 12 percent of the total water volume in the home’s heating system:

  • in pipes;
  • in heating devices;
  • in the heat exchanger of the boiler;
  • The small initial volume of water, which with the initial temperature under pressure enters the tank itself (static pressure in the system is usually higher than the air pressure in the expansomat).

Setting indicators in a new expansion tank before starting the system

A membrane divides the diaphragm-style tank. Air or nitrogen is pumped into one of the halves, which is under pressure. Looking through the documents on the tank will help you understand this parameter. For operating the contour, preliminary (factory) pressure may not always be the best option. It is simple to change this parameter. This was supplied by the manufacturers, who left the spool in the corps of its "air" part so that you could change the pressure.

Remember that every manometer reads only elevated pressure. That is, you must always add one atmosphere (bar) to the manometer’s testimony if you must utilize the concept of absolute pressure in calculations.

The expansion tank’s starting pressure is set to be 0.2 atm higher than the coolant system’s pressure, which is equivalent to the contour’s static pressure. The height difference between the expansion tank’s middle and the circuit’s upper point is what defines this pressure. For example, the statistical pressure will be the same if the heating system is 8 m (2 stories) high.

If ∆P = 0.8 atm (10 m = 1 atm), the membrane tank pressure can be computed as follows:

∆P + 0.2 is equivalent to 0.8 + 0.2 atm (bar).

The following are the results of incorrectly applied pressure:

  • Tank of the pump. For example, an indicator of 3 bar with static pressure of 1.5 bar was originally set in the air cavity. When the pump is launched, the pressure of the coolant will change, but not much – within 1 atm. It turns out that when the manometer at the boiler shows a maximum of 2.5 bar, in the air of the membrane tank there are still 3 bar. Such a setting is negligent for the entire compensatory ability of a membrane device – the air will strive to push the coolant from the tank.
  • The indicators inside the expansion tank are underestimated. In this case, when filling the closed system, water or antifreeze will easily be paved up with a membrane and fill the entire container. At every increase in temperature, and with it and the pressure, the safety valve will work. In this case, the expansion hydraulic tank also becomes useless.

Counseling! The heating system’s safety valves are still in operation even though the initial air pressure setting was done correctly. The expansion tank’s chosen volume may have been too small. Installing a tank with a volume of at least 10% of the coolant’s total volume is advised to prevent this.

Installation of an expansion tank in a closed heating system

Since forced coolant circulation is a common feature of closed heating systems, a circulation pump is included. Since closed expansion tanks for heating serve a completely different purpose—to compensate for temperature expansion—and because proper installation is crucial to the stability of the entire system, they are far more difficult to select and install.

It makes the most sense to install it on the straight portion of the pipeline before the circulation pump since it is situated in an area free from turbulence during the water flow. When putting the system together, there are a few crucial guidelines that need to be followed for installation and selection:

  • An important requirement is the right choice of the volume of the tank. It is a tenth of the entire coolant circulating in the system.

You can select a larger or smaller volume at the same time, but that is not feasible. This computation is only appropriate in the case of water being used as a coolant. It expands slightly at temperature, so if ethylene glycol is used instead, the tank needs to be bigger.

A safety valve needs to be installed in the expansion tank. Although he is typically included in the factory package, it is preferable to add him to the list of available options.

If there isn’t one, you’ll need to buy one and install one more. The safety valve will keep the system’s pressure from building up too much.

If the calculation was carried out incorrectly, and the volume of the tank was insufficient, it is enough to connect the second tank in parallel. The main feature of an incorrectly selected volume is a frequent increase in pressure in the system, it can be checked using a pressure gauge, which should also be installed in the system.
The height of the tank installation from the floor does not play any role: it will be sealed, and the air in the system will be removed through special air taps. At the same time, the best option for receiving the coolant – on top, this must be taken into account when installing. This allows you to get rid of the air that can enter the fluid department.

For closed heating, an expressive tank does not always need to be purchased separately. A contemporary dual-circuit gas or electric boiler may come pre-configured with all the accessories you could possibly need.

One benefit of purchasing double-circuit equipment is that it will come pre-assembled and ready to use, saving you the trouble of making additional purchases. Since a circulation pump is frequently already included in the kit, installing the heating system is feasible even in very large homes.

What is the ideal water level for the heating system? Both the house’s size and the boiler’s power are factors. The calculation is done in the standard system at a rate of 14 liters per kilowatt of power. This quantity will be sufficient to guarantee appropriate heat exchange and circulation.

Possible problems

Uploading an expansion tank to the required number of atmospheres is not always feasible. People rarely run into issues when they closely monitor the technology’s serviceability, of course.

However, carelessness or an irresponsible attitude can lead to a variety of issues. Frequently, the pressure is steadily dropping, and the tank bursts after several boiler ticks.

It even gets to the point where a spool deforms the membrane as a result of pressing against the wall.

In this situation, repair is not possible; the expander can only be replaced entirely. On the other hand, the tank was not filled and was left without pressure, and the heating circuit’s pressure was at the highest level allowed. The liquid clenches as soon as the heating system shuts off and starts to cool; this prevents the pressure from changing. The boiler thus becomes involved in the "accident". Such issues may arise from prolonged use of the water heater for hot water supply or from mains interruptions.

Serving fresh water consistently and without obvious motives is another likely scenario. For instance, when the boiler cuts off and the hot water supply circuit is operational, the pressure gauge indicates a drop in pressure. Because there is no compensation for thermal expansion, heating the coolant causes its excess to be released via safety valves. You may be in for a lot of trouble if you fail to recognize this situation in time. As a result, it’s important to regularly check the pressure inside the tank and pay close attention to how the expansion is going.

Installation of an expansion element

Equipment for boilers is made to function at a specific pressure. This implies that a specific pressure is also necessary for the expansion tank to function normally. Air or nitrogen, which filled the case, supports it. At the factory, the container is circulated. It’s important to make sure the air doesn’t leak during installation. The gadget won’t be able to operate otherwise.

A pressure gauge is used to keep track of the pressure. The device’s running hand indicates that the expander’s air has been released. Since air can be pumped through the nipple, this condition is generally not a major concern. The tank’s average water pressure is 1.5 atm. However, they might not be appropriate for a particular system. In this situation, the pressure needs to be changed on its own.

Indicators that are normal: 0.2 atm lower than the system. Exceeding the pressure in the expansion capacity in relation to this network indicator is prohibited. Under such circumstances, the increased volume of coolant will not be able to enter the tank. Through the joining size, the tank and pipeline are connected.

It’s crucial to install the expansion tank in the proper location in addition to making the proper connections. Installing this system element on the return between the boiler and the pump is advised by experts, even though contemporary models can be mounted anywhere.

A ball valve is installed on the pipe that connects the extensor capacity to guarantee the structural integrity of the pipe. Shut-off valves will remove malfunctioning equipment without requiring the coolant to be pumped out of the system. The crane needs to be open for the system to function. If not, pressure inside it will build up and it will leak at its most vulnerable point.

Boiler room installation

Other kinds of tanks are installed in open systems where the coolant circulates naturally. An open reservoir of this kind is typically made of sheet steel. It must be installed at the engineering network’s highest point.

Such an element operates on a very basic principle. The liquid rises along the pipes with the air as its volume increases, pushing it out of them. After cooling, the natural air pressure and gravitational forces cause the coolant to return to the pipeline.

Pressure setting

One parameter that can be adjusted in the heating system is the water pressure in the expansion element. Everything can be done on its own, and the setup is fairly straightforward.

The following must be configured in order to set the required parameters:

  • Make a calculation and determine the required indicators – by 0.2 atm. less than in the system.
  • Install these indicators before the installation of the tank in the system by dropping air or pumping it through the nipple.
  • Connect the container to the pipeline and fill the system with water. You need to do this slowly, tracking pressure indicators in pipes and tank. Roll the coolant until the pressure indicators are equal.
  • After that, you need to connect the pumping equipment and continue the rolling of the coolant. You need to pump water until the moment when the operational pressure is reached in the tank, calculated before the installation of the network. This will ensure that the reserve volume of water enters the housing.
  • The first inclusion of the system should be carried out in the maximum temperature mode. In this condition, the volume of the coolant increases by the value of the specific increment. This provides the amount of water equal to its capacity. The pressure in the tank rises to maximum indicators.

Calculation of volume

The volume of the expansion tank for heating can be found using the following very easy method: The calculation is 10% of the system’s coolant volume. It was something you ought to have calculated when creating the project. In the event that this data is incorrect, you can calculate the volume experimentally by pouring in fresh coolant while simultaneously measuring the old one (letting it pass through the counter). Compute is the second route. Calculate the system’s pipe volume and then add the radiator volume. This represents the heating system’s volume. Ten percent of this figure is found here.

The shape may vary.


Using the formula is the second method to figure out the expansion tank’s volume for heating. In this case as well, the system’s volume (represented by the letter C) is necessary, but additional information is also required:

  • maximum PMAX pressure in which the system can operate (usually the maximum boiler pressure is taken);
  • The initial Pinin pressure – from which the system begins work (this is pressure in the expansion tank, is indicated in the passport);
  • The coefficient of expansion of the coolant E (for water 0.04 or 0.05, for antifreeze is indicated on the label, but usually within 0.1-0.13);

With all of these numbers, we use the following formula to determine the precise volume of the heating system’s expansion tank:

Formula for figuring out the heating expansion tank’s volume

Although the calculations are simple, is it really worth messing with them? No, if the open-type system is clear-cut. In addition to being independent, the cost of the container is not significantly influenced by the volume.

For closed heating, expressive tanks need to be computed. Their pricing is heavily volume-dependent. However, in this instance, it is preferable to err on the side of caution because the system will deteriorate or possibly fail quickly due to insufficient volume.

Place the second expansion tank if the boiler has one but its capacitance is insufficient for your system. They should provide the necessary volume overall (the installation is the same).

What will the insufficient volume of the expansion tank lead

The coolant expands when heated, and any excess expands to fill an expansion tank. The excess is drawn through the emergency discharge valve if it does not all fit. In other words, the coolant enters the sewer.

The graphic image’s working principle

Then, when the temperature decreases, the volume of the coolant decreases. But since it is already less in the system than it was, the pressure in the system drops. If the lack of volume is slight, such a decrease can be uncritical, but if it is too small, the boiler may not work. This equipment has a lower pressure limit at which it is efficient. When the lower limit is reached, the equipment is blocked. If you are at home at this time, you can correct the situation by adding a coolant. If you are not, the system may defrost. By the way, work at the limit also does not lead to anything good – the equipment quickly fails. Therefore, it is better to play it back slightly and take a slightly larger volume.

How to control the system and work with it

Verifying the actual pressure in expansion tanks is crucial. Manual manometers are almost always used for this purpose because most air chambers have standard nipples, similar to those found on bicycle or car tires.

The boiler of wall performance could be the source of the issue. The majority of the time, compensating devices are on the back wall, and using them is challenging. The utilization of a small, portable manometer is the result.

The air needs to be appropriately pumped up as soon as a smaller deviation from the indicator is discovered. If everything stays the same, the boiler may experience emergency stops. It is difficult to even determine which situation—such an outcome or excess fluid emissions—is worse. Every gas boiler manufacturer advises customers to check the tank pressure once a year. Of course, doing it twice as often won’t hurt you.

It is important to keep in mind that pumping can only be done with a tank that is completely empty, so make sure to drain the boiler’s water. The most straightforward method involves using a bicycle pump to control the outcome using a manual pressure gauge.

The following is the order of events:

  • the taps of the heating system are twisted;
  • Water descends from the boiler;
  • the tank is pumped to the desired pressure;
  • The drain crane overlaps;
  • The heating circuit is saturated to the desired level through the provided valve;
  • the taps connecting the tank with heating are revealed.

How the system works and works

Large tanks are sound-tightened containers that are split into two halves by rubber bands. This isn’t your average rubber; it needs to transfer a lot of heat while still being elastic and maintaining its fortress.

It’s important to note that the pressure needs to be measured precisely at 20 degrees inside the air cavity that is part of the empty container. It is equivalent to the heating system’s maximum filled static pressure.

You can reach the membrane’s equilibrium state and make up for the coolant’s pressure under this circumstance.

In other words, the tank will be totally empty by the time it is launched into the task and its whole capacity can be utilized to compensate for the thermal expansion of antifreeze or water. The gas boiler sensor sends out a command to turn off the heater if it detects a drop in system pressure to 0.7 bar or less. Additionally, 1.2 bar is the average value that produces normal work. The membrane can increase pressure while transitioning from an out-of-equilibrium state to an equilibrium state, but its starting pressure for a tank that is empty is typically 0.3 bar higher than the heating system’s standard.

In conclusion, the pressure in a closed heating scheme using a gas boiler should range from 0.8 to 1 bar. Any system that deviates from these standards will have its parameters individually calculated, accounting for the following factors:

  • the estimated volume of water or antifreeze;
  • Efficiency of the tank;
  • its required value;
  • initial pressure when starting.

According to the instructions, BAXI double-circuit tanks should operate at 0.5 bar of pressure. In actuality, though, this indicator is very low and ensures that the device will operate normally at a pressure of 0.8 to 1 bar. With 75-liter heating systems (on water), the 6-liter built-in expander is continuously operating. or fifty liters (on antifreeze).

When the project is getting ready, only experts can determine whether an additional expansion tank is needed or if the standard equipment is sufficient.


The matter at hand concerns how these tanks ought to function normally in the event of operational violations or maintenance requirements. Eliminating the effect of expanding heating water is the primary objective of utilizing the tank. The amount of pipes, radiators, and accumulative tanks is final, though it is growing more and more. Since full filling is required in closed heating contours, the excess coolant mass needs to be disposed of. The tank is the only appropriate location.

If all of a sudden there is nowhere to escape, the liquid will undoubtedly find the route where the excess escapes. Supply valves are typically used in this capacity, but they are still primarily emergency gear. Even if everything goes perfectly, the system will still need to be filled (added to) and the poured water removed. The installation of a tank aids in averting such a course of events beforehand. And even in the event that a boiling coolant is needed to maintain order.

Rules for installing an expansion tank in an open heating system

The main purpose of the expansion tank in an open heating system is to eliminate air bubbles. Water moves in an open heating system in accordance with the general laws of physics, but the container itself has a complex shape and multiple convection flows.

Since circulation pumps are typically not installed in these kinds of systems, gravity should be used to move the coolant. The heated water must be delivered to the system’s highest point in order for it to proceed.

In this instance, eliminating air bubbles that may cause pipe traffic jams is essential. The basic guidelines for installing the expansion tank are determined by the air’s rise:

It ought to be installed in the system’s highest point. It is typically positioned at the accelerated collector’s highest point. The tank in a system that has an upper outlet mounted will be situated in the attic. Although it is not as common as it once was, this option still exists today. For him, no locking reinforcement is needed. If a cover is placed over it, it is only there to keep trash out of the pipes; tightness in the system is not necessary. Typically, these tanks are created by welding common metal sheets together; their walls are 3–4 mm thick.

Combining an open expansion tank for heating with a water supply enables the system to adjust for the water level after evaporation. But, you can just add water from a bucket on a regular basis; the homeowner won’t face any difficulties with this task.

Additional Information

The expander aids in putting out hydraulic blows brought on by air traffic congestion and abrupt reinforcement closure. If you place backs on the coolant’s reverse course right in front of the boiler, they will be able to carry out this task. It is not realistic to expect that the pressure that is set at the plant will be perfect for all applications. It is reconfigured by means of a spool.

Important: Any pressure gauge that measures the expander’s pressure only registers an excess value; add one bar to get an absolute number.

Since the coolant will be forced out by the air, the pumped tank performs poorly. If everything is set up properly but the fuses are still occasionally dumping water, the expander’s excessively small volume is probably the cause of the issue. It is therefore worthwhile to select tanks that hold 10% or even more of the total coolant circulating in the system. Pressure gauges need to be connected to the nipple because the tank does not have stools for them. It is positioned on the side of the coolant opposite to the side.

The pressure in the heating system is expressed in a bar or kgf/sq. cm, so you must compare the readings from automobile and bicycle pressure gauges, which measure pressure in MPa. 100 kPa is equal to one bar. It is advised to wait ten minutes after shutting off the boiler before using a car meter in order to allow the circulation to stop. It is intended for the tank, which is integrated into the boiler, to cross over the coolant supply and reverse path in addition to the locking valves. If you follow these suggestions, your life will become a lot easier.

Watch the following video to learn how to determine whether the expansion tank is still serviceable.

Setting indicators in a new expansion tank of a membrane type

The membrane divides the device into two sections. She applies pressure to one of the halves; this is considered during configuration.

The majority of devices have factory settings that aren’t always appropriate for use under specific circumstances.

A nipple is supplied, to which the plumber attaches a compressor or hand pump in order to alter the indicators.

Take note! Many gauges indicate excess pressure. To find the actual pressure, add 1 atm.

By adding 0.2 atm, the initial indicator is made equal to the value obtained in the cold system. The amount is determined using the static pressure value on 10. For instance, in the eight-meter-tall house:

P is equal to 8/10 plus 0.2 atm.

By passing air through the spool and into the container, the values are obtained.

One of two issues can result from inaccurate computations:

  • Overflow of the tank. Sometimes an indicator is set in the air cavity twice. The inclusion of the pump will lead to a change in the number, but no more than for 1 atm. With a greater difference, the drawback will be obtained, which is why the compensator will begin to push the coolant from the tank. This can lead to a serious accident.

Picture 2 shows the expansion tank’s pressure standards when it’s empty, filled with water, and at its maximum fill level.

  • Obtaining insufficient indicator. In the completed system, the working fluid will be paved with the membrane and fill the entire volume. Each inclusion of the heater or an increase in pressure can lead to a fuse. The expander in such an atmosphere will become useless.

Crucial! To prevent issues, primary setting needs to be done properly. Fuse malfunctions can occur even after a skilled specialist’s work is completed.

Usually, this is the result of the expansion tank’s inadequate capacity.

You’ll need to buy a new gadget in order to solve. At least 10% of the total strapping volume must fit within it.

Why is an expansion tank necessary in the heating system

The pressure in the boiler and heating system circuit rises dramatically when the coolant gets heated. Because the heating system is sealed and the liquid is an almost incompetent medium, this physical phenomenon may cause the boiler or pipelines to burst. If there were one significant factor that prevented the excessive amount of hot coolant from entering the external environment from shaking the installation of a basic valve, the problem might be resolved.

Air will enter the cooling circuit where the coolant was disposed of after the fluid has been compressed during cooling. Any heating system’s worst enemy is air traffic jams, which make network circulation impossible. As a result, the air coming from the heating radiators must be lowered. Heating cold water is far more expensive than heating the heat-unit fluid that traveled via the opposite pipe to reach the boiler, and replacing the coolant in the system on a regular basis is also highly expensive.

Installing the so-called expansion tank, a reservoir with a single pipe connecting it to the system, solves this issue. The expansion heating tank’s volume balances out the excess pressure inside, enabling the contour to operate steadily. The tanks are expanding externally for the heating system; their size and shape vary according to the type of heating circuit and the computation results. There are now tanks available in a variety of shapes, from traditional cylindrical tanks to what are known as "tablets."

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Why is this design needed

It is necessary to address the types and principles of operation of this equipment before discussing the functions and configuration of an expansion tank. Why is a design like this required for the heating system? The device’s primary function is to adjust the network for thermal expansion. It is true that the coolant’s density and volume change with heating and cooling.

Take note! The hot water will increase in volume and damage the walls of the pipes and radiators if this device is not installed in the engineering network. A significant rise in water pressure could easily cause the system to fail.

You can save the boiler in addition to the pipeline by installing the expander. Ultimately, his initial calculations are based on a specific water pressure within the system.

The volume of expansion devices varies. It is important to keep in mind that the volume of this element should be at least 10% of the total volume of coolant circulating in the system when selecting a model appropriate for the technical parameters of a given network. The volume is summed up in the boiler, pipes, and radiators for this computation. Finding the volume is simplest when the system is being pumped. It is best to choose a model with a small margin, but keep in mind that the volume that comprises 10% is a minimum.

It is appropriate to discuss wall gas boiler expansion containers separately. The majority of contemporary wall-mounted models come with an integrated device that is mounted on the side or back wall and has nipples. The nipple aids in increasing pressure.

Pressure in the heating system we pump up an expansion tank

When heating and cooling the coolant (water or antifreeze), pressure drops are intended to be compensated for by the expansion tank in the heating boiler. The membrane is physically split into two sections at the same time as the tank. Water is dripping from the main system on one side. Conversely, the air generates the required pressure.

The expansion tank will eventually stop functioning if it is not regularly pumped up. Consequently, the following image is seen:

To fill the bath, turn on the water. The water in the heating circuit gradually cools as the boiler switches from the heating mode to the DHW mode. The expansion tank stops working while the bath is filling up, which causes the system’s pressure to abruptly (!) drop. Finally, you shut down the crane, and then the most fascinating part. Theoretically, the boiler ought to reheat the batteries once more. However, it was absent. When the pressure dropped below the critical point, the automation failed.

Unpleasant circumstances. However, it’s actually decided enough.

The expansion tank is pumped up.

It is important for you to first realize that we do not pump air into the system—rather, we pump up the expansion tank. As such, the primary indicator in this procedure is not the manometer that is mounted on the boiler. We make use of the pump’s manometer. Yes, you can work with a standard car pump. Compressors are provided by service organization masters. However, the difference is not very noticeable in this instance. It is necessary to pump a relatively small volume at one atmosphere of pressure. There is ample supply of the pump.

1. Close the boiler by turning off the outlet.

2. We remove the water from it.

It is not necessary to touch the entire system in a positive way. Overlap the taps adjacent to the boiler (apart from one) if it is installed correctly. The supply and heating return, the cold water input for the boiler that is fuel and for the DHW system, the gas supply, and the gas supply are the five pipes that are always located beneath the boiler, though their exact locations may vary.

It is theoretically possible to empty a specific fitting located beneath the below. However, this is just one more hassle involving basins and buckets. Something makes everything clearer with the sink.

Why are these manipulations being done so much? To ensure that the expansion tank is genuinely pumped up and that the work is not visible because water is still in the tank.

The boiler fuel tap is a small valve that you can open. The water in the boiler will flow through the open mixer. The pressure on the case-mounted pressure gauge ought to drop to zero!

3. The expansion tank is pumped up.

The pump is connected to a nipple located on the tank.

Typically, the expansion is positioned to allow access to the nipple without having to take off the boiler lid. Usually, to do this, you have to crawl on top, as seen in the image. Occasionally, the identical action is taken, but from below.

It is advised that the tank’s pressure equal about 80% of the system’s working pressure. As it happens, 1.2 atmospheres. Important note: the tank will simply not function if you pump it harder. Grumbling, staring at the pump’s manometer. Water may continue to flow out of the mixer.

Once the expansion is complete, you must put the system back in operating order.

Shut off the boiler recharge crane.

Unlock the cold water supply valve. All of this will, of course, go straight into the open mixer.

Close the mixer once all of the dirt and air bubbles have combined. Next, with an eye toward the pressure gauge on the case, open the fuel tap and refill the boiler to the operating pressure.

Finally, turn on the feed’s taps and come back. You can still add water when the pressure drops a little, which is likely to happen. Alternately, wait, deflate every battery, and use this to find your way around.

The final stroke involves deflating the pump. A flat screwdriver is used to twist a plug at the pump’s end while the boiler is operating. This works on the same principle as the Maevsky cranes.

That’s it. It is advised to fill the expansion tank of new boilers every two years. For everyone else, every season.

Unexpected increases in the pressure within your heating system may be reason for concern. The expansion of water due to heat is one common cause of this phenomenon. Water expands when it gets hot, which raises the pressure in the system. This is a normal occurrence that is usually controlled with expansion tanks, which let the water expand without creating sudden pressure surges.

A broken pressure relief valve is another possible reason for increased pressure in a heating system. In order to avoid damage or safety risks, the pressure relief valve is made to release excess pressure from the system. This valve may malfunction or become clogged, causing pressure to build up above acceptable limits.

In addition, variations in pressure may be caused by trapped air in the system. A heating system’s overall system pressure may rise as a result of air becoming trapped in the pipes or radiators and producing pockets of high pressure. Normal pressure levels can be restored and this problem can be mitigated by properly venting the system and bleeding the radiators.

In order to avoid possible damage and guarantee effective operation, it’s critical to promptly address rising pressure in a heating system. Pressure buildup problems can be avoided with routine maintenance, which includes bleeding radiators, inspecting and maintaining expansion tanks, and checking and servicing pressure relief valves. Homeowners can keep their homes safe and comfortable by being watchful and taking care of problems as soon as they appear.

Video on the topic

Why is the pressure in the dual -circuit boiler jumping and what to do

The pressure in the heating system jumps. Urgent exit to the object. Again an expansion tank!

What type of heating you would like to have in your home?
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