How to reduce the pressure in the boiler Baxi

What should be the pressure in the expansion tank of a two-circuit boiler Baxi?

If you open the instructions. there is a pressure in the expansion tank 0.5 bar, but it is the minimum value, right. the pressure should be about 20% less than the pressure in the heating circuit at room temperature coolant.

Based on the fact that for most systems, the recommended pressure at filling is within 1.2 to 1.5 bar, we obtain the necessary pressure in the air cavity of the expansion tank equal to 0.8-1 bar. Experts usually recommend setting the pressure in the expansion tank Baxi equal to 1 bar.

Boiler Baksi depressurize

Today I wanted to add water to the DHW system of the gas boiler Arderia 2.16 according to the instructions, but it did not work as it was on one, and remains so.

On one forum wrote that “the pressure of cold water in the boiler is less than the heating pressure in the heating system”.

How to depressurize the heating system?

And the heating systems are different and the reasons for that same excess pressure and methods of pressure relief may be different.

That is, in the beginning it is necessary to determine what causes the rise in pressure (the cause).

If it is a closed heating system, you may be too powerful circulating pump, install a less powerful, the pressure will be fine.

Perhaps the problems in the expansion tank, for example the membrane broke down, or the volume of the expansion tank is not large, when installing the heating system errors were made in the calculations.

The cause of overpressure. there may also be air in the heating circuit.

May be the failure of cocks Maevsky (if yes, then they must be changed completely), if not, open them and bleed,

The problem with make-up cocks, the solution is the same, replace them with a new one and the pressure is normalized.

Problems with the boiler automation, the heat exchanger is damaged and.т.п.

This is the whole, but there are individual moments (you need to look at the place), if you find the reason for the pressure increase, you can normalize it.

This situation may be due to a variety of reasons and your description does not tell at once what is the matter. You need to analyze the behavior of the system. In well-constructed systems pressure gauges are installed at the inlet and outlet of the boiler, and especially prudent people cut into the system pressure gauges in the lower and upper segments of the system at the inlet and outlet pump. Thus, we get the maximum control of the system, there is food for thought and analysis of the situation.

Let’s go from simple to more complex. The pressure in the system could have increased due to e.g:

  • mechanical clogging of the system. The quality of the thermal fluid plays a crucial role in the operation of the entire system. Hard water with m salts and minerals when heated will form a scale and sediment use special desalinated water,
  • air cork (can help to use faucet Maevsky, which helps to bleed excess air or water directly from the radiator),
  • Maybe there is a valve screwed in some area (say, children were playing),
  • Because of a loosely closed faucet in the system slowly but surely comes the extra water from outside,
  • The temperature of the heat carrier has increased and it has expanded,
  • mistakes were made during installation (e.g. pipe diameters larger at the outlet and smaller at the inlet to the heat exchanger),
  • Mistakes in the operation of the pump (for example, excessive power or some failure).

Let’s talk about the situation, someone has a sore point.

namely. Boiler Baxi constantly stops on error no pressure in the system, that is, on the display blinks error E10.

The arrow of a pressure gauge is on zero. You feed, that is, add water to the heating system, and after some time, from a few hours to a few days, the gauge arrow is again at zero, and the boiler display again shows error E10.

And you start calling us and ask to solve the problem. Come and deal with the boiler, to fix Baxi boiler.

And the variant that the matter may not be in the boiler Baxi, and the boiler has nothing to do with the problem. Customers, as a rule, do not think.


For example, the main/bithermal heat exchanger is leaking, like in the photo below.

Leak in the boiler can be anything, more precisely, any hydraulic element: the main / bithermal heat exchanger, bleeder pump, overgrown with scale alarm, copper tubes, gaskets, three-way valve on the rod (especially true for boilers Baxi Fourtech/Eco-5 Compact). We will not talk about the causes of leaks in the boiler.

Therefore, the first thing the master does is to remove all the panels of the boiler Baxi and combustion chamber cover and examine, visually and by hand, for leaks.


Leaks, drips, spots, stains, damp, puddles of water are all signs of a leak in the boiler.

If you find a leak in the boiler, be prepared for the fact that it will be necessary to replace current parts, in the example in the photo. the main/bithermal heat exchanger!


This is when the boiler and heating system are filled with water, leave the boiler unattended, for example, in a house under construction, then the boiler for some reason does not work or goes into error, for example, shut off the electricity or gas WATER AT MINUS TEMPERATURES turns into ice!

Even if the room is warm, an inoperative boiler can defrost through the coaxial chimney!

Consequences are replacement of something expensive in a boiler Baxi.

It should be noted that on a new, newly installed boiler Baxi-leakage or no leakage at all, or their appearance is unlikely. Unless, of course, you have defrosted the boiler!

All boilers Baxi pressed at the factory, and the boiler is normally packed, damage during transportation is impossible.

If no leaks are detected, the master proceeds to the second stage of the check.

Perhaps the air pressure in the boiler expansion tank is missing or vice versa, set too high (the tank is “over-pumped”)

Pressure gauge too high BAXI Duo-Tec

Then both pressure drops and pressure surges are possible.

The expansion tank acts as a compensator. When the liquid heats up, it expands in volume, and this extra volume must go somewhere. it goes into the tank. When the liquid cools down, its volume decreases and the pressure drops, and in this case the lack is also compensated from the tank.

Therefore, the second thing that the master will do after the examination of the boiler is to check and, if necessary, adjust the air pressure in the expansion tank.


And you no longer have any reason to call us and tell us the same thing about how the pressure drops over and over again, how you are feeding, and that you can not find the leak, you do not believe in the leak and still think that the boiler is to blame.

I understand that you really want to think that the problem is in the boiler, because then you do not have to press the system to fix the leak. No and no.



How often do we have to hear. I went everywhere, I checked everywhere, there’s no leakage.

First, a leak does not mean that the water flows by the stream and somewhere must be a big puddle! Not at all!

A slightly leaking nut or a gasket between radiator sections is enough to cause a pressure drop. It can get wet and then dry out!

How often do customers say that there is no leak, while paying no attention to the fact that has long leaked stop tap, they believe that this is normal or not important.

As for “I went to all the floors and checked.”.

In every house there are impenetrable places, such as pipes under the threshold, pipes in the basement, pipes, immured in the wall, as well as underfloor heating, poured concrete. Yes, they have leaks, too, for example, because of a self-tapping screw.

Occasionally, some part of the pipe defrosts in the winter and the pipe bursts.

Secondly. The only sure way to find a leak when you can’t see it

That is, you come to you plumbers, preferably those who did this system, with a magic device called a presser. They close the boiler (it is not designed for pressure over 3 atmospheres) and pressurize the system with water or air. Pumped pressure of about six atmospheres and went to look for places where water or air comes out of the system (in places of leaks air will come out with a whistle)

It is not our task to tell you how the pressure test is carried out. Carrying out pressure testing should be entrusted to professional plumbers.

At the end of pressure testing is logical to issue an act of pressure testing of the system. This is an official document confirming that there is no leakage, or saying that you could not find a leak.

If you call us again and again and categorically say that, say, no leak in your system, you personally all went through and checked, and the fault is the boiler, come to me and do the boiler, but pressurization you while or not doing, or it did semi-literate persons posing as plumbers. if the act of pressure testing you do not have, then talk to you we will not!

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It happens so. The house has old steel or iron pipes, 30 years in the house was an open heating system, ie WITHOUT PRESSURE, and boiler AOGV. Changed the boiler to Baxi, and the pipes are left the old. and immediately E10.Because the old pipes under pressure immediately ran!And in all places. What were you waiting for??

On the assumption of whether the pressure from the heating system through the DHW system in the boiler. (That is, again the fault of the boiler:)))

reduce, pressure, boiler, baxi

Theoretically, yes, it’s possible. Practically-usually not.

Consider where the boiler heating system is directly connected to the DHW system.

-Make-up valve, aka filling valve of the system. It can really leak, wear out. And sometimes you forget to close it.)

-Secondary heat exchanger DHW. I met several times that it formed a “hole” that connects the heating and DHW systems, which are usually not connected in it.

-“Hole” in the bithermal heat exchanger, which is a “tube-in-tube” design, somewhere between the heating circuit and the DHW circuit.

BUT. According to the principle of communicating vessels, the pressure will go from MORE to LESS.

In heating, the average pressure is 1.5 atmospheres.

In the water supply- 2.5-3 if you have a well and have a pressure switch, and differently if you have a central water supply. As a rule, it’s also high pressure, more than 1.5, although there may be periods of low pressure.

IMPORTANT! People who have the problem described above usually complain of a constant ROSS of pressure, not a drop in pressure!

Theoretically, if the feed really worn out or there was a “hole” in the secondary heat exchanger (this is hardly possible in a relatively new boiler), and the pressure in the water supply is very low, that is, from a cold tap water runs in a thin trickle. if these factors ONE time. Which is negligibly unlikely, the cause of the pressure drop will be this.

If you insist that you have it this way, be prepared for the fact that you will need to buy a make-up valve and a secondary heat exchanger, or worse bithermal.

Sometimes it is impossible to find and repair the leak. For example, the pipes are walled up, they’re covered in garnish, the floors are poured. Please do not tell us about it over and over again, because we did not do your system! We can not make the boiler work without pressure!

By the way, if you have to recharge constantly, and you do not find the leak and do not fix it, then be prepared for the fact that in a short time will fail, FALL OUT OF THE SYSTEM / BATTERMIC HEAT REFRIGERANT!


If there is a leak in your system, it is in your best interest to find it and fix it as quickly as possible!

So. Again. Algorithm. If you have error E10.

-If the error occurs for the first time, to start with you can just feed it and forget about it. It is possible that the error is normal and does not mean there is a problem. For example, there was no electricity all day, the boiler did not work, the system went cold, the pressure dropped. Or did you change the radiator and drain the system yourself.

-Walk around the house and look at the pipes and radiators. If you find a leak, you need to fix it.

If you walked around the house and did not find anything:

-Call a specialist to check the boiler. The handyman will inspect the boiler visually and pump up the expansion tank.


Even if the master finds out that it is not in the boiler, and the problem of falling pressure you still pay money!


We only work with systems that we did, we don’t work with “other people’s” systems.

-Pressurize the heating system.Find leaks under pressure and fix them.

-If you can’t fix the leak, for example, the floor is already filled don’t have to ask us what to do. And start saving money for the main heat exchanger.

In some cases, the air coming out of the system is to blame for the pressure drop. For example, some work was carried out, the system was drained or part of it, along with the coolant air got into the system. Also, under certain circumstances, hydrogen can form in some systems. Or the system was very airtight because it was originally filled with rainwater of unknown composition.In this case it helps to change the coolant, release air from the system.

Important note. It is necessary to remove people with mental problems, behavioral disorders and senile dementia, who do not understand what they are doing, from the balancing of the system. For example, they want and “deflate” everywhere and where there is no air, which causes the pressure drop, open taps, turn the nuts.

We had this example. An elderly grandfather lived in the house together with his son. During the regular maintenance of the boiler, he was at home, talked to the craftsmen, remembered what they do, he liked it all very much. Then, in the absence of his son, he began to walk and,

imitating the masters, flush the “air” from the radiators) Of course, nonexistent “air”, he flushed with the pressure) When his son returned from work, he saw the error E10 on the boiler and the lack of pressure in the system. He attributed it to the recently performed maintenance and believed that the problem was the fault of the masters. Masters came twice, checked everything and found nothing) Son refuel the system through the boiler, in his presence the pressure did not drop. But when he came home from work, he had another error E10. The problem was suddenly solved when the grandfather went to the hospital for a checkup))) “Leaks” immediately stopped) Grandfather gave himself away by asking his son to perform an important mission in his absence.of draining “air” from the radiators)

That’s probably all we wanted to tell you about this problem.

Service maintenance of boilers Baxi in Chelyabinsk

Safety valves for boilers Baxi, as the name suggests, protect equipment and people from an emergency situation.

Their principle of operation may be somewhat different, but usually this device, if there is excess pressure in the heating system, some of the steam or liquid is removed from it, normalizing the state of the equipment.

This page contains different models for different boilers, so that any visitor can find the right one for his case. All are of high quality and made in accordance with accepted standards.

How to relieve pressure in a Baksi boiler?

Gas boilers are used for heating and hot water supply in private homes by transferring heat from the combustion of gas through a system of pipes and radiators.

To provide warm water for all plumbing, heating walls and “warm floors” is enough for a two-circuit device.

To perform its functions, the boiler must maintain operating pressure in the circuit. only under these conditions, the coolant will circulate normally and keep a comfortable temperature. If it decreases, precious heat is lost, and the unit itself may shut down and even break down.

Pressure standards in a gas boiler

There is no common pressure standard for all domestic gas boilers. It is calculated based on the technical characteristics of the equipment and pipes that make up the heating system. However, there is a rule of thumb: the average operating figure must not exceed the minimum figures for the lowest-powered components of the circuit.

Important! The necessary requirement for the working circulation of water inside the boiler is also the difference between the pressures of forward and reverse flow of the coolant, which must be at least 0.3 atmospheres.

There is also a static pressure on the pipe system due to the differences in the positioning of the components of the heat circuit (each meter of height adds 0.1 bar).

On average, when fully heated, the pressure level in the system should be kept at around 1.8 bar, and in the cold 1.5 bar.

Data on each specific model, including the maximum and minimum allowable values, are given in the manuals from manufacturers. The pressure at the lower limit is allowed only during the filling phase of the circuit with the coolant.

To control the pressure level home gas boiler equipment is equipped with manometers.

The main causes of pressure drop in the gas boiler

Normal pressure is necessary for the operation of boilers, otherwise the water supply to the unit will shut off and it will shut down automatically. Therefore, when you see the first signs of a drop in pressure in the circuit to avoid emergency shutdown (especially unpleasant in winter), you should call a service technician or find out yourself why the pressure in the gas boiler drops.

The most common causes of faults are as follows.

Turning on the hot water

When the gas boiler is first started, air is squeezed out of the system, starting with the boiler itself, which it leaves through automatic air vent valves. Experts explain this situation by the peculiarities of construction of two-circuit boilers and believe that the pressure in fact does not go down.

To prevent air from accumulating in the radiators, the Mayevsky cocks should be installed on them. When unscrewing them, first the air comes out with a hiss, then the water starts to drip a little bit.

Wall-mounted boilers are equipped with a screw that allows the air to escape from the pump. It is also necessary to unscrew and slightly clamp, such manipulation helps to increase the water pressure, after which the unit operates in normal mode.

Often face this problem owners of warm floors, and it is many meters of pipes, which receives the coolant from the boiler. Therefore, at first start-up and a couple of weeks after that may hiss and air coming out of the system through the automatic air vents, and the pressure in the system will be below normal.


The most frequent reason to call a master because of the drop in pressure in the boiler. leaks. It is good if it is in a visible place, it can be quickly detected by puddles of hot water and eliminate. But sometimes it’s very difficult to visualize, for example inside a floor heating system. In the implicit cases, the refilled coolant “flies out” of the circuit and the pressure in the system does not rise.

Determine the location of the breakdown can be determined by passing a dry cloth over the entire accessible surface of the pipes, including joints, inspect the walls for leaks. You should first disconnect the heating from the boiler and drain the coolant. You can use a compressor to pump air through the system and listen for leaks. In the most difficult cases a thermal imaging camera can help.

reduce, pressure, boiler, baxi

Air locks

A possible reason why the pressure in the gas boiler is dropping, even without leaks, is the formation of airlocks. They are formed due to:

  • Incorrect filling of the heating system. there was a lot of air in the water. Experts recommend treating coolant with a special device before pumping into the circuit, otherwise air locks can not be avoided;
  • Poor sealing of joints in pipes and other elements of the system;
  • Failure of air release valves.
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Additional information. Air plugs cause noise and vibration of the system, which provokes violations of the tightness of connections, leading to leaks. Coolant circulates inefficiently: gas consumption will increase markedly, while the batteries will be slightly warm.

The problem with the expansion tank

Usually they begin a couple of months after the start of the heating circuit: no leaks are not observed, but the coolant escapes, and the pressure in the faucets is discharged. The problem is that the pressure in the expansion vessel of a two-circuit boiler, separated from the other part of the boiler by an elastic membrane, decreases due to bleeding of air through the nipple on top of the unit. As a result the entire expansion tank is filled with water from the circuit under the pressure of the coolant. At further increase in pressure, there is nothing to bleed, so a safety valve reset the coolant.

Pay attention! If the problem is not eliminated the membrane of the expansion tank can rupture completely, which will require replacing it.

Malfunction of measuring equipment

In cases where there is no visible or detectable with the equipment leaks, tightness in the system is not broken, the expansion tank is intact, and the pressure in the boiler must be constantly increased, you should call specialists and check the performance of the boiler automation or manometer. This equipment can also fail and give incorrect readings. In such a case, there is nothing else but to replace the pressure gauge with a new one.

Cracks on the heat exchanger in the boiler

With long-term operation of the gas boiler, constant flushing with caustic reagents, poor quality of parts manufacturing, as well as periodic emergency water hammer, microscopic cracks appear on the heat exchangers. Through them the coolant leaks from the circuit. When the gas is turned on, such cracks can drain and evaporate all the moisture from the heat exchanger and combustion chamber.

It is possible to determine the localization of the problem by the presence of scale. Microcracks in a conventional heat exchanger can be soldered, and the bi-thermal ones need to be replaced.

The coolant drain valve is not closed tightly

One of the easiest and most trivial causes, due to which the pressure in the heating circuit can gradually drop. a loose screwed valve.

Other possible reasons

There are also a number of other nuances, leading to inadequate pressure in the heating system. These are:

  • Leaks of heat carrier at the joints of pipelines;
  • The metal of the components of the heating system is affected by rust;
  • low-quality heating installation;
  • Incorrect functioning of boiler automatics.

Ways to raise the pressure in the boiler

There are different solutions to this problem depending on what caused the drop in temperature.

If leaks are detected visually or by means of a thermal imaging camera, the problem can be eliminated by tightening or sealing the connection or by replacing the unit completely.

Please note! Before pumping pressure in case of a rupture in the boiler expansion tank or a nipple injury, this element must be replaced with a new one. In difficult situations you have to replace the tank itself.

Cracks in the heat exchange elements of the boiler are visualized by long-term observation or with the help of specialists, after which the damaged part of the circuit must be sealed.

To eliminate air s in the system you need to turn off the heater, open the valve on the cork Meyevsky and bleed all the air, then you should add coolant until the pressure in the system is normalized. All bubbling noises must disappear.

If the valve on the heating medium outlet is not closed, turn it back until it is completely closed after checking that it is tightly closed.

A difficult situation occurs when the pressure drops in the heating circuit, located inside the walls, the pipes are firmly embedded in the frame of the building. Therefore it is better to choose durable and reliable materials for such constructions.

Further information. When carrying out repair work should objectively assess their technical knowledge and in difficult situations to contact professionals.

How to reduce the pressure in the boiler

There may also be a question, how to release excess pressure in the gas boiler, because the constant increase provokes emergency shutdowns, and this can lead to failure of the boiler. The pressure can be reduced through the Mayevsky valve. It is also necessary to check and fix the make-up valve or the secondary heat exchanger.

Prevent an increase in pressure in the circuit can install a brass safety group for 3-4 bar. We recommend adding corrosion inhibitors to the heaters to remove clogged filters.

Preventing the formation of air s

It is necessary to comply with the mandatory rules:

  • Properly install the piping and connect the boilers,
  • Check the equipment before the final start-up;
  • Treat the coolant before loading into the system.


This manufacturer has a bypass element, which allows you to solve the problem of how to raise the pressure in the boiler Ariston in case of power outage.

It allows you to reduce unnecessary heating of the heat exchanger due to insufficient water flow. The flow of the coolant in the system is started bypassing the circulation pump.


The minimum pressure at these boilers is half a bar, in case of its insufficiency on the screen of the boiler appear errors E40 and E41. It can be regulated by the tire pump, because the valve on Baksi boilers is a common car nipple.

Please note! At the first start-up of the heating medium in the system, the boiler may display error E10, this is passed automatically.


These Korean boilers are structurally designed for a pressure drop to 0.1 bar, which minimizes emergency blockages. These units are ideal for high rise buildings. Boiler is equipped with a system of nozzles, safety systems and delivery devices that allow it to operate at a reduced pressure of up to 4 mbar. You can regulate the pressure by remote control.

Tips and recommendations for adjusting the pressure in the gas boiler

Be sure to make sure the system is airtight before raising the pressure in gas boilers. All heating appliances, pipes, fittings, circulating pumps are inspected.

Experts also advise to carefully monitor the upper limit of pressure in the system. it should not exceed three atmospheres.

Addition of pressure to the tank is possible with ordinary air by means of an autopump with a manometer.

Pay attention to! To prevent the formation of air s is necessary to correctly select the boiler model for the premises, coordinating the possible areas for heating and capacity of the unit.

Any private home must be heated and supplied with hot water. In modern construction gas boilers are used for this purpose. For their normal operation requires optimal pressure, which for a number of reasons can drop, leading to a stoppage of the boiler. A competent owner should know how to raise it, or turn to professionals.

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

With the help of a circulating pump in the heating system creates dinamic pressure.

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

  • The length of the heating circuit increases in direct proportion to the power of the pump;
  • Batteries can be connected both in series and in parallel, when connected in parallel, the heat is distributed more evenly;
  • the possibility of installing pipes with a small diameter;
  • Saving gas, because the coolant has a higher velocity than in open systems, it does not cool down as much;
  • To relieve excessive head, you can reduce the capacity of the circulation pump;
  • the possibility of selecting the pump capacity to overcome the hydraulic pressure and depending on the length of the circuit and the diameter of the 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 fills too quickly. the system must be filled slowly, with open venting valves. The valves are open until liquid flows from the highest point of the system;
  • Mayowsky cocks broken, change the cocks;
  • The circulation pump’s impeller is loose, air can escape because of this, adjust the impeller.

Other problems

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

  • Closed or insufficiently open shutoff valves. Pressure on the supply stream increases, the unit is blocked. To release the pressure, open the valves to the stop, check if the stop cocks are leaking.
  • Dirt filter in the dirt separator. To reduce the pressure will help rinse the filter, if it is in bad condition, replace it with a new one.
  • Faulty make-up valve when water is dripping from it. Liquid from the water main, where the pressure is about 2.5-3.5 Bar, flows into the heating circuit, there the pressure is less.

It causes increase of pressure in the heating circuit. To turn down the pressure, replace the valve, but more often you need to replace the gasket, it quickly wears out, especially if the water is very hard.

Preventive maintenance

Watch for the good condition of the pressure gauge, bleeder and safety valve, these devices serve to protect your boiler from high pressure.

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, reducing the formation of scale on the air vents.

Regularly flush the heat exchanger, this will prolong its life, preventing the formation of fistulas and scaling.

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

How to reduce the pressure in the boiler Baxi?

Standard operating pressure in closed heating systems with forced circulation is a value within the range of 1.5-2 bar. If the pressure in the gas boiler drops, the work of both the heating circuit, and the DHW circuit is severely hampered or becomes impossible, automation of some models suspend the boiler.

There are many reasons why it happens, but to diagnose them yourself is not difficult. In this article we will consider all the possible causes, in descending order of probability, and indicate what should or should not be done in each case and how to raise the pressure in the gas boiler.

Standards and methods of control

To begin, let us 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

As in the single-circuit and two-circuit heating systems, the pressure is:

  • Static. natural pressure created by gravity acting on the coolant (each meter of height riser system creates about 0.1 bar);
  • Dynamic. forced artificial pressure created in a closed loop (by the pump or the expansion of the coolant heated), depending on the parameters of the pump, the coolant temperature and tightness of the system.
  • working. the real pressure (static dynamic), it is it is measured by control and measuring instruments, the normal values are considered 1.5 or 2 bar;
  • maximum. the maximum allowable for the operation of 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 heat exchanger of the boiler).
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How it’s measured

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

The fact that even an arrow factory pressure gauge over time can fail and measure the pressure incorrectly or show spikes, not to mention the electronic sensors. Additional control and measuring device installed on the boiler supply will allow to quickly check and compare the readings to immediately exclude the failure of the main pressure gauge.

Faulty make-up tap (fill)

Location of make-up valve in wall mounted gas boilers. Consult your model’s instruction manual for the exact location of the valve.

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

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

Decrease is observed only for DHW, this is the sign that you can determine the malfunction, as soon as the hot water tap is closed, the pressure is rapidly restored to its previous values.

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

Coolant leakage

Check the fittings carefully.

Leaks can be not only through the make-up valve, but also in the joints of pipes and fittings, radiators, expansion tank. Therefore, if low pressure during operation of the boiler is constantly 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 and check all components 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 you can not exclude the wear of gaskets and seals, possible metal corrosion, looseness of connecting fittings, etc.д. During operation of the heating system.

The presence of air s

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

However, the problem can easily be solved. It is sufficient to bleed air through the bleed valve of the safety group or Maevsky cock on the radiators.

Problems with the expansion tank

The pressure in the expansion vessel 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 values of 1.5-2 bar. Some models operate normally at 1-1.2 bar.

Inside the closed expansion vessels are divided into two compartments: the 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 diaphragm in the proper position and adjust the pressure in the system, air is pumped into the tank through the nipple from above.

Over time, it can leak and during the expansion of the coolant to bleed air from the chamber of the expansion tank, so the pressure on the diaphragm is not given, the tank does not hold an optimal pressure.

It is usually impossible to replace the nipple separately, that’s why the entire tank must be replaced. Before that you should make sure that the rest of the system is tight and the air is bled through the nipple of the expansion tank. Price of the question: 1 500-6 000

Cracks on the heat exchanger

Microcracks on the coil is difficult to see, the more so that 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 located in a closed combustion chamber, it can be accessed 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 have a bi-thermal heat exchanger which is a single element. Minor depressurization can be solved by caulking or welding damages, serious leaks will need to replace the heat exchanger.

Defective bleeding valve

Principle of operation of the spring loaded safety valve for the individual heating system.

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

The principle of its work is the following: the spring presses on the valve, which blocks the coolant flow, but as soon as the pressure exceeds the allowable 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 declines. At the same time there is a constant flow.

Do not disassemble and repair the relief valve yourself, it is better to simply replace the mechanism. Price of the question is only 500-900

Improper functioning of control and measuring devices

If all the previous possible causes could not be detected, the matter may be in the pressure gauge. Sometimes the malfunction can be determined when the pressure according to the device has dropped to 0, which is rarely the case due to at least static pressure of the coolant. The best way out, as we wrote earlier, is to install an additional pressure gauge on the boiler supply. 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 the new gas boiler after the initial start

If the pressure is constantly changing at the first start of the equipment. it is normal, there may be a sufficient amount of air masses in the circuit, which, with the appropriate drain valves will soon come out and the indicators will normalize.

Why does the pressure increase in the closed boilers

The main reasons why the pressure rises are as follows:

  • The heating circuit is filled from the top;
  • Fast filling of the heating fluid during start-up;
  • loosened pump fan through which air is flowing;
  • air vent breakage;
  • the system was not vented after repair.

The heating circuit must be filled from the bottom and the safety valves must be open. Fill it gradually until the liquid starts to drain from the safety valves. Before starting the filling of the heating circuit all venting parts should be washed with soapy water to check their proper operation.

Important! If the discharge pump is leaking air, this is the cause of the increased pressure.

The air pressure in the expansion tank of the heating system should be 0.2. 0.3 bar (roughly atmospheric pressure) is lower than the working pressure in the system. The working pressure in the cottage or house with a wall or floor standing boiler is 1.5 bar.

Manufacturers of wall hung boilers usually supply expansion tanks from 6 to 8 liters (depends on the model) for heating, and from 2 to 3 liters. for sanitary water (if there is a built-in boiler). Tank volume of 6-8 liters is designed for a heating system with a capacity of 100 to 140 liters.

Is it necessary to have an expansion vessel for a wall hung gas boiler Baxi??

Volume of the built in expansion tank of boiler Baxi is specified in characteristics and for series ECOFOUR makes 6 liters to answer a question of its necessity in separately taken system of heating. it is necessary to know total volume of this system.

To calculate it is not so difficult: the volume of filling of the boiler and radiators is in their characteristics, and the volume of filling of the pipes can be calculated, knowing their diameter and total length. Water after heating to 80 degrees Celsius will increase in volume by about 4-5%, so the recommended volume of the expansion tank is 8% of the total volume of the heating system in case of filling with water and 12% if you use antifreeze as the coolant (coefficient of thermal expansion of antifreeze is greater). The standard expansion vessel is therefore sufficient for a heating system with a capacity of approx. 75 liters for water and up to 50 liters for non-freeze medium.

These figures are notional (with reserve) and when selecting the capacity of the expansion tank should be guided by the design calculations of a particular heating system, or the manufacturer’s recommendations.

In most cases, the built-in boiler tank is quite enough and the decision to use a separate additional tank is taken by specialists at the design stage.

Causes of pressure increase

Only a professional heating engineer can identify the exact malfunction of the boiler. That is yourself to determine and fix the breakage that caused an increase in pressure in the heating system will not work. The main causes of increased pressure, which occurs in external breakdowns of the boiler are the following:

  • Violation of the integrity of the heat exchanger. Taking into consideration the long time of operation the walls of the equipment can crack. Causes of cracks. factory defect, insufficient strength, hydraulic shock or wear and tear. Liquid is added to the circuit every few days. Leakage cannot be detected visually. coolant flows very slowly, moisture begins to evaporate while the burner is operating. It is necessary to change the heat exchanger, it is possible to solder it in very rare cases.
  • Pressure rises due to an open make-up valve. Due to low pressure in the boiler circuit and increased pressure in the pipeline extra fluid begins to pass through the make-up valve into the heating pipe. The pressure increases until it must be vented via a safety valve.
  • If the pressure in the pipeline decreases, the heating medium closes the liquid supply to the boiler, in this case the pressure in the system decreases. The same problem can happen if the make-up valve is broken. It must either be shut off or replaced.
  • Increase because of the three-way valve. During a valve failure, fluid from the expansion tank will start flowing into the circuit. The three-way valve needs to be replaced or periodically cleaned.
  • The pressure gauge stays in the same place. If during the operation of boiler equipment, when the temperature on the pressure gauge rises or falls, the needle does not move. the pressure gauge is broken. It needs to be replaced.
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