How to reduce the pressure in the gas boiler

How to set the optimal pressure?

There are pressure gauges on the heating system to control the pressure in the circuit. On the expansion tank itself there is no connection for the installation of a gauge. But there is a nipple or spool for releasing and pumping air or gas. The nipple is the same as on the wheels of cars. You can therefore check the pressure and adjust it using a normal car pump with a manometer.

Before releasing excess pressure or pumping air into the expansion tank of the domestic gas boiler, it is necessary to prepare the system. Pressure gauge in a car shows the value in MPa, the data received should be converted into atmosphere or bar: 1 Bar (1 atm) = 0,1 MPa.

• Stop the gas boiler. Wait until water does not circulate in the system.
• In the hydrographic tank section shut off all shut-off valves and drain the medium through the drain fitting. For boilers with a built-in tank, the return flow as well as the water supply is shut off.
• Connect the pump to the tank nipple.
• Inflate to 1.5 bar. Wait a little longer for the remaining water to run out and vent the system.
• Stop valves and use compressor to increase pressure to the values shown in the certificate or to the level of pressure in the system minus 0.2 bar. If the tank is overflowing, bleed off excess air.
• Remove the pump from the nipple, screw the cap on and close the drain connection. Pour water into the system.

You can check the correctness of the air head adjustment when the boiler reaches operating parameters.

Improper adjustment of the air head in the expansion tank can cause malfunction of the entire heating system. If the expansomate is over-pumped, the compensating properties will not work. As the air will push the excess of hot water from the tank, increasing the pressure in the pipes of the heating system.

And with an underestimated pressure compensating tank, the water will simply push the membrane and fill the entire tank. As a result, when the temperature of the coolant rises, the safety valve will work.

Sometimes in two-circuit gas boilers, fuses are triggered and if the pressure of the built-in expansion tank is properly adjusted. This indicates that the tank volume is too small for this heating system. In this situation it is recommended to install an additional hydraulic tank.

High pressure in the gas boiler. what to do to reduce it

What is the reason and what can be done if the pressure gauge shows high pressure?

The problem may lie in the expansion tank.

Damage of the diaphragm. When heated to the maximum set temperature in the heating system, the liquid increases in volume by about 4%. This excess volume flows into the expansion device, compensating the pressure in the system.

If the diaphragm is damaged, the fluid will completely fill the volume and the pressure in the system will initially drop. When you open the make-up valve and add water to the system with an increase in temperature, the pressure will be higher than the nominal.

Pump until you see no water flowing. It is then necessary to deflate and pump again to the value indicated in the boiler manual.

Unfortunately, not all manufacturers indicate in the instructions the pressure of the expansion tank of their products, for example, in the manual to the Immergaz heat generator it is not specified.

How you can reduce the impact of the pump and remove excess pressure. expansion tank is mounted on a pipe back, and the pump is installed in series after the tank, before the boiler.

Working pressure of compensation tank of some models of 24 kW are given in the table.

Pressure in closed heating systems

By means of the circulation pump in the heating system is created diminishing pressure.

Due to this, the closed system has the following advantages:

• the length of the heating circuit increases directly in proportion to the pump capacity;
• batteries can be connected either in series or in parallel, when connected in parallel the heat is distributed more evenly;
• the possibility of installing pipes with a small diameter;
• Gas saving, since the coolant has a higher speed than in open systems, it does not cool down as much;
• to reset the excess pressure, you can reduce the capacity of the circulation pump;
• the possibility of choosing the pump capacity to overcome hydraulic pressure and depending on the length of the circuit and the diameter of pipes.

Air lock as a cause of increased pressure

Another possible reason why the pressure rises by itself is the presence of air in the heating circuit.

• When the heating circuit is filled with fluid too quickly. the system needs to be filled slowly with open valves to release air. Valves open until liquid flows from the highest point of the system;
• Maevsky cocks are broken, replace the cocks;
• Pump impeller loose, air could be sucked in, adjust the impeller.

Other problems

In addition to the above causes, there are other moments when the pressure in the heat generator rises above normal:

• Closed or insufficiently open shutoff valves. Pressure on the flow increases, the unit is blocked. In order to decrease the pressure open the valves to the stop, check if the stop cocks are leaking.
• The Strainer Dirt Trap is clogged. To reduce the pressure will help rinse the filter, if it is in a very bad condition, replace it with a new one.
• Faulty make-up valve when water is dripping from it. The liquid from the water mains, where the pressure is about 2.5-3.5 bars, flows into the heating circuit, where the pressure is less.

As a consequence the pressure in the heating circuit increases. To turn it down, replace the valve, but more often the gasket needs to be replaced, it wears out quickly, especially if the water is very hard.

Preventive maintenance

Watch for serviceability manometer, air vent and safety valve, these devices serve to protect your unit from excessive pressure.

A safety group for the heating system

Adding antifreeze to the coolant in models where it is not prohibited by the manufacturer, will reduce filter clogging, sticking elements of the safety valve, reduction of scale formation on the air vents.

Flush the heat exchanger regularly, it will prolong its life, prevent the formation of fistulas and scaling.

We suggest you watch a video with answers to questions about increasing the pressure in the heating system:

The pressure in the heating system, its normalization, the reasons for changes

The pressure in the heating system should be in the norm. 1.5. 2.0 atmospheres for private houses with a height of up to 2 floors. If the pressure differs from the specified limits, the system must be “treated”.

In this article we will analyze the nuances of the heating system and boiler room equipment. Let’s define what pressure should be maintained, how to set it, what it depends on Probably the material above will help the readers in questions related to the efficiency of the heating system and the use of equipment.

What pressure in the heating system should be

In low-rise private homes working pressure of the heating system is about 2 atmospheres. often 1.5 to 2.0 atm. The maximum pressure rise is allowed up to 3 atmospheres, and above. should trigger an emergency valve.

In high-rise buildings, the standard pressure is between 5 and 10 atm. Most often 5 to 8 atm. The maximum that heating radiators in apartments of high-rise buildings are designed for is 12 atm.

The same pressure. 12 atm, can be in the main pipes of heating systems.

In high-rise buildings, hydraulic pressure reducers are installed on heating risers to reduce pressure.

Why does the pressure rise

According to the laws of physics, when a liquid or gas is heated their volume increases. Therefore, if the liquid is in a closed heating system, its pressure will increase with increasing temperature.

Fluid cannot compress as much as gas. If the space is closed, there may be a large pressure surge and the shell will burst.

In a “wrong” closed heating system this is what happens. the weakest link, such as a heat exchanger of the boiler breaks down and the liquid finds its way out.

In open heating systems. with gravity-flow fluid (which have an open expansion tank) pressure during heating does not increase. It is set there by the height of the water column. usually at 1. 2 floors. respectively up to 1 atm. “Excess” liquid simply goes into the tank or escapes into the sewer. But in closed systems other special equipment is used.

How to normalize the situation

To avoid a dangerous increase in pressure when heating the coolant, in closed systems (with forced circulation of liquid), include mandatory elements:

• The expansion tank is a closed vessel, partially filled with air, which is able to compress significantly when the pressure rises, freeing up volume for “incompressible” liquid.
• Safety valve. a device that opens the discharge of fluid from the system, if the pressure in it has reached a predetermined maximum pressure. usually 3atm.
• A pressure gauge is a device that measures and indicates the pressure of a liquid or gas. Its readings are also guided when filling, pumping the system, controlling the work.

The same equipment should be installed on the hot water system in private homes, which includes a boiler of indirect heating.

What is the volume of the expansion tank

It is unacceptable to use the expansion vessel of smaller volume than 1/10 of the total heating system. However, for a professional calculation of the expansion tank volume there is a special method. But at the domestic level is solved as follows. not less than 1:10 of the coolant poured into the heating system. Then the expansion tank can compensate for the increase in fluid volume from its heating without problems.

How to know how much coolant is in the system?The only thing to do is to arm oneself with geometric formulas and reference data on the applied equipment. But in practice, when creating heating with your own hands, without a project, the volume is just counted in buckets during the initial pouring. Then a suitable expansion tank is to be installed.

Why the pressure in the heating system is decreasing

The pressure in the heating system decreases constantly from the initial set point. This drop may be very small and not noticeable on the gauges (manometers). Or it can drop significantly.

A large decrease in pressure can occur for two reasons:

• There is air in the heating system after the fluid has been filled. It will be gradually blown out through automatic air bleeders (must be present). The drop in pressure must be compensated by the addition of a new coolant.
• There is a leak in the heating system, the coolant escapes. But there can also be a leakage of air from the closed expansion tank.

It is not allowed to make an automatic refill of the heating system with water if the pressure drops. If there is a leak, then the water in the system will be constantly renewed, which will lead to a significant precipitation and failure of the entire system.

How to Find a Leak in a Heating System

Usually there is a leakage of the coolant at the joints because of poor installation. It is enough to carefully inspect the system and pay attention to leaks and red marks (sediment from water). Repair by “diagnosis”.

But sometimes it is difficult to detect visually. Then the search is done by ear. the system is drained and filled with air under pressure. A characteristic whistling sound will indicate where the “hole” is located.

It is also possible to use special equipment. the scanner of excessive humidity.

Do not forget about the boiler. Having a leak in a heat exchanger, through small cracks is not uncommon. There is no way to detect it “on the run”. the coolant immediately evaporates and escapes together with the gases. To be checked when the boiler is at a standstill.

It is not desirable to locate joints in places inaccessible for inspection and repair. Read. The problem of installation of polypropylene pipelines. how to properly solder pipes.

How to set the pressure in the heating system

Initial pressure in the heating system is set by pumping the expansion tank with air, when the coolant. The expansion vessel is filled with air to a pressure of 1.3 to 1.5 bar. Accordingly, during heating, if the volume of the tank is selected correctly, the pressure can reach. 2.0 atm.

The expansion tank is equipped with a normal air spool, as in the car, and can be inflated by the car pump or compressor.

We have considered the main issues related to pressure in the heating system for a private home. Also recommended reading How a pressure accumulator and expansion tank work

How to release the pressure in the gas boiler?

Standard operating pressures for closed heating systems with pressurised circulation are between 1.5 and 2 bar. If the pressure in the gas boiler drops, the work of both the heating circuit and DHW circuit becomes very difficult or impossible, automation of some models suspend the boiler.

The reasons why it happens quite a lot, but to diagnose them yourself is not difficult. In this article we will consider all the possible causes in descending order of probability, as well as designate what should or should not be done in each case and how to raise the pressure in the gas boiler.

Norms and ways to control

To begin, let’s briefly consider the types of pressure and how to measure it, which will help you better understand how it is formed in the heating circuit and the circuit of hot water (DHW).

Types of pressure and its norms in the gas boiler

In both single-circuit and two-circuit heating systems the pressure is:

• Static. natural pressure generated by gravity acting on the coolant (each meter of height riser system creates about 0.1 bar);
• Dynamic. artificial pressure created by force in a closed loop (by the pump or the expansion of the coolant), depending on the parameters of the pump, the coolant temperature and tightness of the system.
• Operating. the actual pressure (static dynamic), it is measured by control and measuring instruments, the normal value is 1.5 or 2 bar;
• maximum. the maximum allowable for the system, even a short-term excess (water hammer) with a high probability can lead to emergency depressurization of the system (in other words, rupture of pipes, radiators or the boiler heat exchanger).

How it is measured

Most models of wall and floor gas boilers have a built-in pressure gauge that measures the working pressure of the water in the heating circuit. But even if it exists, it is recommended to install additional: as part of the safety group (pressure gauge / thermometer, safety valve, bleeder valve).

The fact that even the pointer factory pressure gauge can fail over time and measure the pressure incorrectly or show pressure jumps, not to mention the electronic sensors. An additional control gauge installed on the boiler supply will allow you to quickly check and compare readings to immediately rule out a problem with the main pressure gauge.

Faulty make-up valve

Location of the make-up tap in wall mounted gas boilers. Consult your model oil makeup valve manual for the exact position of the valve.

The most common cause known to many owners of two circuit models, especially those with a plastic, unreliable make-up valve. It may be loose or defective.

Then the heating circuit communicates with the water system where the pressure is usually higher, there is a pressure equalization between the two systems. However, as soon as the hot water tap is opened, the pressure drops quickly.

Combi Boiler Too Much Pressure. How to reduce the water pressure. Central Heating

Decrease is observed only during DHW, precisely on this sign you can determine the fault, as soon as the hot water tap is closed, the pressure sharply restores to its previous values.

Failure of make-up valve is not only dangerous in terms of possible malfunctioning of the system but also leads to increased oxidation of the internal surface of pipes, rapid deposition of salts inside pipes and boiler coil heat exchanger leading to complete clogging.

Coolant leakage

Check the fittings most carefully.

Not only the make-up valve can leak, but also connections of pipes and fittings, radiators, expansion tank. Therefore, if the low pressure during operation of the boiler is always observed, not only when using DHW, it is necessary to check the entire system for leaks. It is also necessary to remove the front cover of the boiler, check all the nodes inside the boiler, even if there is no water dripping from the closed boiler unit.

Usually the system is checked for leaks before the heating season, but one can’t rule out the degradation of gaskets and seals, possible metal corrosion, loosening of fittings, etc.д. During the operation of the heating system.

The presence of air s

Many factors can be the reason of blowing air in the system: sucking air through the leaky areas, improper filling of the circuit with the coolant and putting it into operation, high water temperature (above 85-90 ° C), which leads to increased air emissions. A characteristic feature of clogged air is often an interruption of heat transfer in any part of the system (after the air lock).

Nevertheless, the problem is easily solved. It is sufficient to bleed the air from the bleeding and venting valve of the safety group or Maevsky cock on the radiators.

Problems with the expansion tank

The pressure in the expansion tank of the gas boiler corresponds to the pressure in the whole system and depends on the boiler model. Normal operating values, as we said earlier, are 1.5-2 bar. Some models normally work at 1-1,2 bar.

Inside the closed expansion tanks are divided into 2 compartments: coolant and air. They are separated by a special membrane, which bends when the coolant expands, increasing the volume of the chamber for the coolant and reducing the volume of the chamber for air. But in order to initially, when starting the system, set the membrane in the correct position and adjust the pressure in the system, the air is pumped into the tank through the nipple from above.

Over time it can leak and when the coolant expands air can escape from the expansion tank chamber, due to which the membrane is not pressurized, the tank does not hold an optimal pressure.

Replace the nipple is usually impossible separately, so you need to replace the entire tank. Before this, it is worth making sure that the rest of the system is tight and the air is bled through the nipple of the expansion tank. The price of a question: 1 500-6 000

Cracks in the heat exchanger

Microcracks on the heat exchanger are difficult to see, especially the water seeping out quickly evaporates and dries out due to the high temperature of the element. In many models of wall hung boilers, the heat exchanger is in a closed combustion chamber, you can access it by removing its front cover.

If the water pressure drops in a two-circuit gas boiler, do not forget to pay attention to the secondary heat exchanger, it is located next to the primary. Some models are equipped with a bi-thermal heat exchanger which is a single element. Minor leaks can be repaired or welded, serious leaks will require exchanger replacement.

Defective dump valve

Function of the spring loaded safety relief valve for individual heating systems.

The pressure relief valve (safety valve) is part of the safety group or is installed separately, it is necessary to bleed excessive pressure in the heating system.

The principle of its operation is as follows: the spring presses on the valve, which closes the coolant flow, but as soon as the pressure exceeds the permissible limits, the spring compresses, opening the valve and releases the excess air or coolant.

After 7-10 cycles spring reset valves fail due to wear of the spring, which no longer holds the same pressure: it jumps or drops. There is a persistent leakage.

It is strongly not recommended to disassemble and repair dump valve by yourself, it is better to replace the mechanism. Price of the issue is only 500-900

Improper operation of instrumentation

If all the previous possible causes are not detected, it may be the pressure gauge. Sometimes the fault can be determined when the pressure according to the device has dropped to 0, which is rarely the case in view of at least the static pressure of the coolant. The best way out, as we wrote earlier, is to install an additional manometer on the boiler feed. If this has not been done, it is difficult to diagnose the problem yourself, it is necessary to call a master.

Pressure constantly jumps in a new gas boiler after the initial start-up

If the pressure is constantly changing when you first start the equipment. it is normal, in the circuit may be present at a sufficient volume of air masses, which in the presence of appropriate bleeding valves will soon come out and indicators are normalized.

Air lock as a cause of increased pressure

Another possible reason why the pressure increases by itself is the presence of air in the heating circuit.

• When the heating circuit fills too quickly with fluid. the system should fill slowly, with the valves open to release air. Valves open until liquid flows from the highest point of the system;
• Maevsky cocks are broken. Change the valves;
• impeller of circulation pump loosened. air can escape because of this, adjust the impeller.

The main causes of pressure drop

Common causes of pressure drop in the heating gas boiler, are:

• Leakage of the heating medium. Damage to the heating line leads to leakage, loss of heating water and reduced head.
• Cracks in the heat exchanger. Leaks in the boiler itself will not only lead to a drop in pressure, but can also cause more serious damage to equipment, damage electronics.
• Diaphragm rupture in the expansion tank. Fluid flows through the rubber seal into the air chamber and the pressure in the circuit is reduced.

To determine the location of leaks in the system, back it up to normal pressure and stop the circulation pump. It is necessary to inspect the pipeline step by step, to identify the problem area and eliminate the faults.

Pressure in the two-circuit boiler drops

This is a fairly common problem. it manifests itself in the fact that the pressure in the heating system slowly decreases and when it falls below normal, some models of boilers shut down.

Most often the cause is elementary leakage of water from pipes or leaking radiators. Such a leak in the heating season is not easy to detect, you will not see a puddle on the floor (of course, unless it is a serious leak). Most often it will be just droplets and you will not see these droplets, because from the heated pipes, they quickly evaporate.

How and where to look for leaks pay attention to plugs radiators, joints or soldered pipes and fittings. Often you can see traces of water leaks in the form of rusty or salt stains. It will be easier to find all sorts of leaks, if you turn off the heating for a while, let the radiators cool down and add pressure to about 2.5 Bar. After that you can see drops or puddles on the floor.

The boiler can also be the cause of the leak. For example the primary heat exchanger itself or joints are leaking. But as long as they are small droplets, you will not notice anything, during the operation of the boiler they evaporate. As it begins to flow more actively, notice the “drips” from the boiler.

Pressure drops in the two circuit boiler when turning on hot water

When you open the hot water tap, the pressure in the heating system drops (about 0.3 atmosphere). The valve has closed the pressure is restored.

Causes of increased pressure due to air lock in an open system

In an open system with a correctly designed slope all air is evacuated through the expansion tank. Air s can occur only if the system is incorrectly filled with water at start-up or after repair of radiators.

In the case of such problems, the air can easily be blown out through the Mayevsky cocks on the radiators. If you can not reduce the pressure, you may need to completely drain the system and restart it.

How to normalize the situation

To avoid a dangerous increase in pressure when heating the coolant, in closed systems (with forced circulation of liquid), include mandatory elements:

• An expansion tank is a closed vessel, partially filled with air, that is capable of compressing significantly when the pressure rises, freeing up volume for the “incompressible” liquid.
• Safety valve. a device that opens the discharge of fluid from the system, if the pressure in it has reached a set maximum pressure. usually 3atm.
• Manometer. a device that measures and indicates the pressure of a liquid or gas. Its readings are also guided when filling, pumping the system, controlling the operation.

The same equipment should be installed on the hot water system in private homes, which includes a boiler of indirect heating.

Safety group for heating system with non-automated boiler. safety valve, air vent, manometer. In wall hung boilers these devices are built-in.

Read more on the site. how to correctly make the strapping of a non-automated boiler

These readings should always be normal The pressure in the heating system in a private home

Owners of private homes have to personally monitor the heating of their homes. The most important indicator that needs to be controlled is the pressure inside the heating system.

It affects the efficiency and durability of the entire heating system of the house.