Pressure in the expansion tank of the two-door boiler
The expansion tank in the heating boiler is designed to compensate for pressure drops when heating and cooled coolant (water or antifreeze). At the same time, the physically the tank itself is divided into two parts of the membrane. For one side there is water falling from the general system. On the other. the air that creates the necessary pressure.
If the expansion tank is periodically not punctured, it ceases to work properly. As a result, it may be observed, for example, the following picture:
Turn on water to fill the bath. The boiler from the heating regime passes to the DHW mode, water in the heating circuit gradually cools. The bath is closed for a long time, the expansion tank does not work, as a result, the pressure in the system is suddenly (!) Falls. In the end you still close the crane, and then the most interesting thing begins. In theory, the boiler must start to warm the battery again. But it was not there. The pressure fell below the critical, and the automation blocked everything.
Unpleasant situation. Although actually decides quite simply.
First you need to understand that we pump out the expansion tank, and not inject air into the system. Therefore, the pressure gauge installed on the boiler is not the main indicator in this procedure. We use a pressure gauge on the pump. Yes, the usual car pump is suitable for work. Masters from serving organizations come with compressors. But in this case the difference is not significant. You need to pump up pressure in one atmosphere in a fairly small volume. Pump more than enough.
In a good way, the whole system does not need to touch. If your boiler competently installed, then the cranes installed next to it (except one). The location of the pipes under the boiler may differ, but there are always five of them: the supply and reverse of heating, the inlet of cold water to feed the boiler and for the GWS system, the exit of the DHW, gas supply.
You close the feed and reverse of the heating system. this will help not merge water from the entire system and engage only with a boiler. Close Cold Water Feed Crane. Crane hot water (the one that leaves the boiler) leave open. Additionally open the hot water valve on the nearest mixer. From here and will merge the water contained in the boiler.
In principle, you can merge and through the special nozzle installed below. But this is an extra break with buckets and basins. With sink somehow all clearer.
Why all these manipulations? To make sure that they really give the expansion tank, and not create the appearance of this work due to the fact that water remained in the tank.
Open the boiler feeding fauce (located below a small valve). Through an outdoor mixer flows water contained in the boiler. Pressure on the pressure gauge, which is located on the housing, should fall to zero!
There is nipple on the tank to which the pump is connected.
Usually the expansion is located so that you can get to Nipple without removing the boiler lid. often for this you need to brush the top. as in the picture. Sometimes the same thing is done, but below.
Pressure in the tank is recommended to do about 80% of the operating pressure in the system. It turns out about 1.2 atmosphere. (Important moment: if you throw more stronger, the tank will not work). Swing, focusing on pump pressure gauge. In the process of the mixer can continue to flow water.
When expansion is finished, you need to return the system again to the working condition.
Open the crane of the supply of cold water. Naturally, all this will immediately go to an outdoor mixer.
When all dirt and all air bubbles are merged, close the mixer. After that open the feeding tap and re-fill the boiler to the operating pressure. focusing on the gauge on the case.
In the final open the cranes of the feed and returns. Most likely the pressure will fall slightly, then you can still add water. Or wait, pull the air from all batteries and here to navigate the terrain.
Latest Barcode. Remove air from the pump. When the boiler is running on the end of the pump, a plug is twisted with a flat screwdriver. The principle here is the same as with the cranes of Maevsky.
That’s all. For new boilers, it is recommended to pump the expansion tank every two years. For the rest. every season.
The advantages of the circulation pump
The inclusion in the heating system of such an instrument has the following advantages:
- The role of the coolant is allowed to use both water and antifreeze. In this case, it is guaranteed not to freeze the entire system.
- Due to the fact that the circulating fluid moves with increased speed, it does not have time to cool. At the same time, the water boiler will work on average gentle mode.
- Such a heating system does not cease to function and in the offseason period when the temperature of the coolant decreases.
Circulation pump model UPS 25-60, material. Cast iron, manufacturer. “Grundfos”, Denmark.
Leakage in the heating system
The first thing to check with a slow pressure decrease is the leakage of the coolant from the pipes or the proceedable radiators. And as a coolant most often that? That’s right, water!
Believe me! Such a leak, in the heating season, to find not easy, and the fact is that you will not see on the floor puddle, well, of course if only it is not a serious leakage, but in this case the pressure will fall instantly. Most often the leakage will be in the form of droplets and these droplets you will not see, because they quickly evaporate from heated pipes.
As a result, slowly, but the pressure will fall correctly. Once again, let’s pour water and continue to kill radiators. Because the oxygen allocated from the received, fresh water, does not benefit them. In addition, most of the models of boilers have protection and with insufficient pressure are simply disconnected, well, if you are at home and respond to the problem, and if there is no one for a long time. Then it can turn around much more difficulties.
How and where to seek leakage
You need to pay attention to the tubes of radiators, connectivity or pipes and fittings. Often you can see traces from water flutters in the form of rusty or salt divorces. But it depends on the composition of water in your area.
Not rarely modern radiators, aluminum or bimetallic, also come into disrepair, sometimes in extremely inconspicuous places, between the ribs or the bottom begin to pour out due to metal corrosion. Not rust of course, but different chemical processes also damage them. Radiators need to carefully examine while searching for leakage.
It will be easier to detect a different kind of leakage, if you turn off the heating for a while, give cool radiators and add pressure to about 2.5 Bara. After that, you can see drops or puddle on the floor. Carefully inspect the floors under the radiators, the locations of the pipes, the place of soldering.
The boiler can also be the cause of leakage. For example, the primary heat exchanger itself or its connection is proceeded. But while these are small droplets, you will not notice anything, during the boiler work they evaporate. How starts to proceed more active, notice “drops” from the boiler.
Not depending on, burner is burning or no, pipe feeding taps or emergency discharge valve will be well noticeable.
So, the first reason for the pressure drop in the system. leakage of the coolant.
Installation of expansion tank
Boilers are originally designed for functioning at a certain heat transfer head. This means that for proper operation, the pressure in the expansion tank of the heating system should have a specific amount. To maintain it use nitrogen or air to be filled. In the container they are pumped in the factory.
When the installation of the device is running, you need to prevent the release of air, otherwise the device will not be able to perform its purpose. adjust the pressure in the expansion tank of heating.
This indicator is tracked by a manometer. The fact that the air left the extender is evidenced by running device. This situation is not a problem, since the air can be accepted by nipple.
The fluid pressure in the tank is 1,5 atmospheres, but it may not come up for a specific heat supply system. The indicators of how pressure should be in the expansion tank, regulate independently.
Normal value is always less than 0.2 atmospheres than this indicator in the system. If in the expansion instrument the pressure is higher compared to the fact that in the network, then the increased water in the volume will not fall into the housing. The device is connected to the pipeline by connecting size.
How To Recharge and Check an Expansion Vessel. Combi Boiler. Plumbing
Not only the correct connection of the device is of great importance, but also the competent selection of its installation. Despite the fact that modern Bachkov models are allowed to install anywhere, experts recommend that to do on the return on the pump and boiler equipment.
To be able to repair the connecting size by which the container is connected, the ball valve is used. If the equipment can be broken, thanks to the shut-off valve, you can remove the tank, without pumping out the coolant.
During the design of the design, the crane holds open, otherwise the pressure in the expansion tank of the heating of a closed type begins to grow sharply and flowing in the weakest place.
If an open system with a natural circulation of the coolant is operated, the device of another type is mounted. Capacity in this case is open. It is made of sheet steel. Place the tank in the highest point of the heating network.
The principle of operation of this device is simple. Liquid in the process of increasing volume is displaced from pipes and rises along with air. When the coolant is cooled, it returns to the pipeline, due to the action of gravitational forces and as a result of natural air pressure.
Expansion Tank Problems
Pressure indicators in it and in the entire system are identical and depend on the modification of the boiler. Normated data: 1.5 and 2 bar. Models with modest power enough and 1-1.2 bar.
Insulated expansion tanks inside have two departments: with air and with heat carrier. They are separated by a special membrane. And when the coolant increases in the amount, it is bent, and thus the parameters of the second department are reduced.
But it must be initially installed in the required position. Also, when the system starts, the pressure is adjusted, and the air fills the tank through the top nipple.
Gradually, it is wearing and with an increase in the coolant passes air. Because of this, pressure decay in the tank and the boiler.
Need replacement Nippel. But this item cannot be replaced separately, so you have to change the whole tank. Only before this operation should make sure in the reliable tightness of the rest of the system.
Construction features and principle of operation
All tanks are similar in design. They have a metal case, separated from the inside to two fanned compartments. At the tank on one side there is nipple, and on the second. a neck, intended for connection with pipes.
Inside the case is a diaphragm. When the container is empty, it fills it with most, and the remaining space takes the air. In the process of operation of the network, the coolant is heated, its volume increases, and the excess penetrates the cavity exhibited between the diaphragm and the case.
After declining the temperature, the working environment decreases in the amount, and the previously loaded air squeezes it back into the system.
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How to check and configure pressure in the expansion tank
The expansion tank is embedded in closed heating systems to perform the following tasks:
- Coolant thermal expansion compensation. With increasing temperature for every 100 ° C, the water volume in the system increases by 4.33%. The pressure in the system circuit is growing and acts on the inner surface of pipes and equipment. To prevent the destruction of the heating system, the expansion tank is installed on the reverse of the boiler, it is filled with “excess” coolant;
- Due to the work of the expansion tank, hydrowoods in the heating system, which occur due to air traffic jams or sharp reinstatement of reinforcement. To hydrate not damaged the boiler, the tank put on the return on the heat generator.
You can find two types of hydraulic. balloon and membrane (diaphragm) type. The first is more often used for cold water supply and painted in blue color, the second. red, apply in heating systems.
Setting indicators in a new expansion tank before launching system
The tank of the diaphragm type is divided by the membrane. One of the half is under pressure, air or nitrogen injected into it. You can clarify this parameter by looking at the documents on the tank. Preliminary (factory) pressure will not necessarily be optimal for the operation of the contour. This parameter can be easily reconfigured. Manufacturers have provided it, leaving a spool in the case of its “air” part, with which you can adjust the pressure.
It should be borne in mind that all pressure gauges show only overpressure. That is, if when calculating you need to use the concept of absolute pressure, then one atmosphere (bar) should always be added to the testimony of the pressure gauge.
The initial pressure in the expansion tank is exhibited by 0.2 atm above the pressure of the coolant in a cold system, which is equal to the static outline. This pressure is determined as a distance of height between the upper point of the circuit and the middle of the expansion tank. For example, if the height of the heating system is 8 m (2 floors), then the statistical pressure will be equal to:
Δp = 0.8 atm (10 m = 1 atm), then the pressure in the membrane tank is calculated as follows:
Below are the consequences of erroneously exhibited pressure:
- Tank Perekachan. For example, in an air cavity initially exposed a 3 bar with a static pressure of 1.5 bars. When the pump is launched, the head of the coolant will change, but not much. in the range of 1 atm. It turns out that when the boiler pressure gauge shows a maximum of 2.5 bars, in the air part of the membrane tank there are still 3 bars. Such a setting is reduced to NO, the entire compensating ability of the membrane device. the air will strive to push the coolant from the tank.
- Indicators inside the expansion tank are underestimated. In this case, when filling out a closed system, water or antifreeze with ease will sell the membrane and fill the entire container. With each increase in temperature, and with it and pressure, the safety valve will be triggered. In this case, the expansion tank is also becoming useless.
Advice! Adjusting the initial air pressure was made correctly, but continue to work the safety valves of the heating system. Perhaps too small volume of expansion tank was chosen. To avoid this, it is recommended to install a tank, the volume of which is at least 10% of the total coolant.
How to measure and adjust the pressure in the expansion tank
The pressure in the heating system is controlled by pressure gauges, but in the tank itself there is no fitting under the installation of this device. However, there is nipple, in which a spool for podaching or air release is mounted. It is located on the side opposite to the slaughterhouse of the coolant. Nipple, in fact, is an analogue of automotive, so to check this parameter or adjust it, you can use the ordinary automotive pump with a built-in pressure gauge.
On the scale of the car pressure gauge, the values are indicated in MPa, while the pressure in the heating circuit is given in bars or kgf / cm2. Translate easily:
Pressure measurement by automotive pressure gauge:
- It is necessary to turn off the boiler and wait 5-10 minutes to complete the termination of the circulation of the system;
- Block shut-off valves on a plot where the hydraulic. Drain. If the membrane tank is built into the boiler, then the feed and coolant feed is overlap;
- Unscrew the cap nipple and connect the pump to it;
- Build air to 1.5 atm and wait until the heat carrier remains will not be increasing from the membrane tank, after which the air is again;
- Overlap the shut-off valves and bring the pressure in the membrane tank to the recommended in the section above. If the tank is picked, you need to put too much through the spool;
- Remove the pump, screw the cap on the nipple and block the drain fitting. Open the cutting fittings and finish the water heating system through the feeding tap;
- Check, correctly adjusted by the pressure of air or not, easy. When the boiler reaches the operating parameters, the pressure gauge arrow does not jump, the pressure is recruited smoothly without jumps.
This tank is an additional technique. But without it, the heating network works with failures. So that the technique worked properly, you need to competently configure all values.
An important indicator is an internal tank head. It is initiated by nitrogen or air filling the case at the enterprise. To track its level, a pressure gauge is used. If the arrow on this device is twitching, the tank can be filled with air. It uses nipple.
What should be the pressure in the expansion tank of the gas boiler? In many modifications, this is a parameter of 1.5 atm. Ring 0.3 less indicator in the heating network. Its indicator is more network, the heat carrier (TN) will not be able to be in the expansion.
For the possible repair of this technique to the tank mounting pipe, the ball valve is attached.
With technical problems, it is withdrawn. You can repair the equipment without eliminating TN from the contour.
It is important to know the possible causes of pressure drop:
- TT flows. It usually happens in the heating circuit. There is a carrier of antifreeze.
- Decreased pressure in the GK itself. If the decline is insignificant, you can simply restart the boiler. If serious. help professional assistance.
- Calculation of its norm in a specific GK.
- Before connecting the tank to the network, these indicators are exhibited.
- Capacity is connected, filled with liquid. In this process you need to control the pressure. When the pion values are identical, the process is completed.
Then the pump is connected. TN download ends when the parameters are reached in.one
When you first start the system, the limit temperature is set. Since when heated, the volume reaches its limit. Water can be in the tank by filling it up to an extreme point.
Water pressure in the heating network is formed due to the circulation of TN and its heating. This parameter is constantly monitored. After all, it affects the proper operation of the entire system.
Independent heating networks cost without normalized values. Indicators are due to a certain type of technology, cross-section of pipes, Volume of TN
There is a normal pressure criterion in the heating circuit: it is equal to the minimum of the weakest component.
What should be the pressure of water in the gas boiler? It works here and such a norm. 0.3. 0.5 atm. This is the difference in the heads of the original and reverse tube in the GC,
And more scrupulous control occurs only with the installation of auxiliary measuring points. Their positions:
The following are the norms of this parameter on certain models.
What air pressure should be in the expansion tank of the heating system
An indicator of the empty capacity of the air chamber at room temperature. It should be equal to the static value in the tank filled with water. In a similar position of the membrane in equilibrium, and the gas pressure is compensated by liquid. For every 10 meters of pressure, about 1 atm is required. Despite this, for the normal operation of the entire system, it is enough to create an indicator specified in the device passport.
Scheme of an expansion tank device for closed heating systems. Arrows are indicated parts of the product.
Most expansion tanks for favorable work is enough 0.9 atm. This is due to the pressure that creates a membrane during operation. Its average is 1.2 atm. Both values fluctuate in a small gap with a maximum deviation of 0.1.
If the heating system is made not according to classic schemes, individual calculations are performed for it: the volume of the coolant, tank, the benefit rate and the initial charge pressure are determined. To do this, you should invite a specialist who will consider other small factors.