What is the need for an expansion tank
The expansion tank in the boiler serves as an additional reservoir and compensates for the expansion that occurs during heating. In order to avoid a strong increase in pressure, and so that the fuse valve installed in boilers for three atmospheres does not trip, this expansion tank is necessary.
Also, this tank is needed to compensate for the pressure itself when the system cools down, so that it remains in a certain range suitable for the stable operation of the boiler. So that it does not fall into the red zone and the boiler is not blocked. Excessive warmed up liquid gets exactly there, and after cooling down, the pressure comes back to a stable level, and the liquid gets back to the system through the pipes.
How to reduce the pressure in the heating boiler?
Central heating systems of multi-storey municipal buildings and individual houses have not only significant design differences, but also different physical characteristics of the used coolant. When designing in-house heating systems the main design criterion is the pressure in the heating system, the parameters of which have a significant impact on the correct operation of all heating.
In individual houses for the heating are used autonomous systems, which includes a variety of equipment, with independent filling of the circuit heat carrier is important to maintain the correct parameters of the pressure. Control and regulation of pressure in a given framework in the operation of the heating system will ensure the longevity of its operation, optimize the consumption of thermal resources, increase the efficiency of heat exchangers.
- What pressure is needed in the heating system
- Classification of pressures
- Individual House
- Multistory houses
- How to reduce and increase the pressure
- Installation recommendations
How to release the pressure in a gas boiler?
Standard operating pressure in closed heating systems with forced circulation is the value in the range of 1.5-2 bar. If the pressure in the gas boiler drops, the work as a heating circuit, and DHW circuit heavily 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 look at all the possible causes, in descending order of likelihood, and identify 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
First, 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 created 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 circuit (by pump or by expansion of the heated coolant), depends on the parameters of the pump, the coolant temperature and tightness of the system.
- working. the real pressure (static dynamic), it is measured by control and measuring instruments, the normal values are 1.5 or 2 bar;
- maximum. the maximum allowable for the operation of the system, even its 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 boiler heat exchanger).
How it is measured
In most models of wall and floor gas boilers is built-in manometer that measures the working pressure of water in the heating circuit. But even if you have one, we recommend installing an additional one: as part of the safety group (pressure gauge/thermometer, safety valve, bleeder valve).
The fact is that even an arrow factory pressure gauge can fail over time and measure the pressure incorrectly or show its jumps, not to mention the electronic sensors. Additional control instrument installed on the boiler feed, will quickly check and compare the readings to immediately eliminate the problem with the main pressure gauge.
Faulty make-up valve (fill)
Location of make-up valve in wall mounted gas boilers. For the exact location of the valve in your model, refer to the instruction manual.
The most common, known to many owners of two-circuit models, especially with plastic, unreliable make-up valve. It may be loose or faulty.
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 you open the hot water tap, the pressure drops quickly.
Decrease observed only with DHW, this is a sign of the fault, as soon as the hot water tap is closed, the pressure sharply recovers to previous values.
Combi Boiler Too Much Pressure. How to reduce the water pressure. Central Heating
Failure of the make-up valve is not only dangerous in terms of possible malfunctioning of the system, but also leads to increased oxidation of the inner surface of the pipes, rapid deposition of salts inside the pipes and boiler coil heat exchanger coil, subsequently leading to complete clogging.
Leakage of the heating medium
Check the fittings most carefully.
Leaks can be not only through the make-up faucet, but also in the joints of pipes and spigots, heating radiators, the expansion tank. Therefore, if the low pressure during operation of the boiler is constantly observed, not only when using DHW, it is necessary to check the entire system for leakage. It is also necessary to remove the front cover of the boiler, check all the 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 the operation of heating system.
Presence of air s
The cause of blowing air in the system can be a number of factors: sucking air through the leaky areas, improper filling of the circuit coolant and putting it into operation, high water temperature (above 85-90 ° C), which leads to increased release of air. A characteristic feature of air lock is often an interruption of heat transfer in any part of the system (after the air lock).
However, the problem is easily solved. It is sufficient to bleed air through the drain valve safety group or Mevsky 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 operate normally 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, to set the membrane in the proper position and to 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 air can escape from the expansion tank chamber, due to which the pressure on the diaphragm is not provided, the tank does not hold an optimal pressure.
To replace the nipple is usually impossible separately, so you need to replace the entire tank. Before that it is necessary to make sure that the rest of the system is airtight and the air is bled through the expansion tank nipple. Price of a question: 1 500-6 000
Cracks on the heat exchanger
Microcracks on the heat exchanger are difficult to see, the more so the water seeping out quickly evaporates and dries out due to the high temperature of the element. In many models of wall boilers, the heat exchanger is in a closed combustion chamber, it can be accessed by removing its front cover.
If the water pressure drops in a dual-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 bi-thermal heat exchanger which represents the single element. Minor depressurization can be solved by caulking or welding damages, in case of a serious leak the heat exchanger will have to be replaced.
Defective dump valve
Principle of operation of the spring loaded safety valve for individual heating systems.
Resetting (safety) valve is part of the group security or installed separately, it is necessary to bleed excessive pressure in the heating system.
The principle is as follows: the spring presses on the valve, which blocks the flow of coolant, 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. With this there is a constant leakage.
Do not disassemble and repair the dump valve yourself, it is better to replace the mechanism. The price is only 500-900
Malfunction of control and measuring instruments
If all the previous possible causes cannot be detected, it may be the pressure gauge. Sometimes a malfunction can be detected when the pressure according to the instrument has dropped to 0, which is rarely the case due to at least the 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 was not done, it is difficult to diagnose the problem yourself, it is necessary to call a master.
The pressure constantly jumps in a new gas boiler after the initial start
If the pressure is constantly changing when you first start the equipment. it is normal, there may be a sufficient volume of air masses in the circuit, which, with the proper drain valves will soon be released and the values normalize.
Diaphragm tank failure
If you find that the pressure in the boiler is dropping because of the membrane tank, but you can not pump it, it may be out of order.
A sure sign that the membrane tank needs to be replaced is the appearance of liquid droplets on the fitting when you try to pump up the pressure in it with a pump. Most likely, it has a ruptured membrane. This can happen due to the fact that it has worked out its resource or because at some point in the system there was too much pressure.
But, whatever the cause of failure of the membrane expansion tank, it will have to be replaced. They can not be repaired.
For the replacement of the tank it is better to call a specialist. As it is located inside the boiler and to carry out the work will have to disconnect the device from the gas, water and electricity. If it is a wall mounted boiler, it must be removed from the wall.
This work is serious and requires some skills and abilities. But, there are those jack-of-all-trades who manage to do the replacement of the membrane tank on their own. over, it often happens that the original tank is expensive, or even difficult to find on sale. In this case, people go to all sorts of tricks, finding budget options for repair.
Why the pressure in a closed heating system falls or rises
The main condition for the operation of modern gas heating equipment. Stable operating pressure in the heating system (1 bar). 2 bar). Boiler will not start if system pressure is less than 0.6 bar. At more than 3 bar there is an emergency release of water to the equilibrium state of the system. These conditions are related to the safe operation of the equipment. If you notice that the pressure in a closed heating system jumps when the temperature of the coolant changes, it means that the heating system is faulty and must be repaired immediately.
Causes of increased pressure
What pressure for the boiler can be considered as normal? If the manometer readings exceed 1,5-2,5 bars (normal boiler pressure), this is a serious cause for concern. It means that there is a breakdown (or malfunction), and it must be eliminated immediately. The most common causes are as follows:
- The body of the heat exchanger is cracked or has latent defects. In this case, water from the hot water circuit flows into the heating circuit. This causes a significant increase in pressure in the system. The heat exchanger cannot be repaired. It only needs to be replaced;
- Makeup valve problem. An open or broken valve can also cause an increase in operating pressure. This is due to the fact that the water from the water supply system flows into the heating circuit;
- Failure or malfunction of the three-way valve. This failure is similar to the one described above;
- Defective diaphragm of the expansion vessel. Inside the tank manufacturers place an elastic membrane. It changes its position when the volume of liquid in the system increases. If it breaks, normal operation of the system is impaired. In some models it is replaced separately from the tank. Other manufacturers offer to buy the assembly.
- Insufficient volume of the expansion tank. This defect appears at the design stage;
Let’s analyze each cause separately and see how it can be eliminated.
A defect in the heat exchanger. Another cause of pressure growth in the wall mounted boiler
Cracks on the body can be a factory defect. Sometimes the defect is hidden: the walls are not strong enough. A bubble is hiding inside the metal, or an inconspicuous crack has begun to appear from inside the case. Being subjected to stress during operation, this defect causes the heat exchanger to depressurize.
The second reason is a defect that appeared during operation. It is a consequence of either long operation or water hammer. In the first case, timely replacement of the equipment will help to avoid breakdown. In the second. The cause of frequent water hammer can be the wrong location of the pump. If it is installed directly in front of the tank, the sharp increase in pressure at the time of startup is transmitted to the walls. Because the metal of the body is not designed to withstand such stresses, cracks may appear in it.
Whatever the cause of the leak, the bottom line is the same. Water from the heat exchanger, going at high pressure, begins to enter the system through the crack. As a consequence. High pressure in the boiler. To fix the damage the heat exchanger will have to be replaced.
Make up valve and three way valve
The first thing to do is to check if the valve is closed. The pressure in the water system is higher than in the boiler, consequently, the excess heat transfer fluid flows into the system, causing the pressure gauge reading to increase. Once the safety valve is triggered, they are reset and the situation repeats itself.
Valve may appear to be closed. But a factory defect or component wear and tear can lead to loss of tightness. In this case, the valve must be replaced immediately. Otherwise, due to a constant increase in pressure inside the heating system, there will be other problems.
The reason for the increased pressure can be debris from the water supply system. This dirt accumulates on the three-way valve and causes its breakage. As a result, more fluid is getting into the circuit. If the valve is already broken. it only needs to be replaced. It needs to be cleaned periodically for prevention. It is better to simply install an angle filter so that less debris enters the system.
Excess fluid gets into it, which can not fit into the system because of the increase in volume. If the membrane of the tank does not work properly, there is increased pressure in the system. There are several causes of failure.
If pressure gauge shows frequent pressure jumps. The diaphragm may have burst. Then it is necessary to replace either the valve itself, or the entire tank, if the design does not provide for the replacement of an individual part. In the case where the pressure rises smoothly, the cause may be different.
For example, the volume and type of the expansion tank was originally chosen incorrectly by the engineer. It is necessary to know what pressure is in it now. It must be below the pressure in the circuit by 0.2 bar.
If the heating system is connected to the underfloor heating, or simply increases the load on the boiler (eg in winter), the volume of the tank may be small. The pressure inside will gradually become equal to that of the boiler. Consequently, there will simply be no outflow of water.
How to reduce pressure in such a case? It will be necessary to install an additional expansion tank, so that it would take on the excess fluid.
Causes of pressure drop in the gas boiler
The company produces dozens of varieties of gas boilers: floor-standing and wall-mounted, single-circuit and double-circuit, with open and closed combustion chambers. Particularly popular were two-circuit wall mounted gas boilers Protherm, which this article is dedicated to.
Setting the boiler Proterm Jaguar
All the user settings for the boiler are set on the front boiler control panel. There, too, is an LCD display for displaying the required information.
- Rotary switch to set the boiler operating mode and heat carrier temperature in the heating system.
- D.H.W. temperature setting and boiler on/off rotary switch
- Button to reset and switch modes. economy / comfort
- LCD display for displaying information
When the boiler is connected to the mains, the LCD display shows the current pressure. With the boiler switched on, to read the current pressure, press and hold the “eco/comfort” button for two seconds.
Setting the temperature on the boiler Protherm Jaguar
Rotary switches Change the temperature of the heating medium by turning the right knob on the control panel. When using radiators as the main source of heating, the temperature can be from 38 ° C to 85 ° C. In case of under floor heating, the temperature of the heating medium is in the range from 30 ° C to 50 ° C. Maximum and minimum temperature settings are set by the technician depending on the type of system.
To change the DHW temperature, use the rotary switch located to the left of the LCD display. The temperature range can be from 35 ° C to 64 ° C.
Changing the boiler operation mode. economy and comfort mode
To switch from ECO to Comfort mode, or vice versa, press once the “eco/comfort” button. After pressing it, the display shows the selected mode. the symbol “C” if you selected comfort mode or “E” if you selected economy mode.
Changing the operation mode. Comfort or ECO
When switching to economy mode, the boiler will shut down every time the water in the heating circuit is heated to the desired temperature. In comfort mode, when reaching or exceeding the set temperature, the boiler does not turn off, and produces a modulation of the flame.
The norm and control
The operation process after some time can cause failures in the boiler. This occurs under the influence of the negative impact on the heating system. Such a negative impact can be called both excessively high and low pressure, measured in atmospheres. The normal level is 1.5-2 atmospheres. And why the pressure in the gas boiler falls?
If we talk about private households, then here, as a rule, are used autonomous heating systems with power from single-circuit and two-circuit boilers. Two-circuit boilers are especially widespread. In addition to heating, such units provide water heating. One circuit in them heats the coolant circulating in the pipes, and the other provides the operation of the hot water system.