Different quantities of air always travel through pipelines and water heating appliances. It remains in the lines when the system is filled, penetrates through the walls of the polymer pipes and is released from the coolant (water contains oxygen in dissolved form). Removing the resulting bubbles is a task that solves an important element of the circuit - the air vent. Further we will consider the types of valves for venting and explain where they need to be installed.
Varieties of air valves
Air bubbles contained in the coolant tend to accumulate in certain places of the heating network and inside radiators. The resulting bubble continues to be fueled by new portions of oxygen and grows into an air plug that blocks the movement of heated water in this area. As a result, nearby batteries or radiator sections cool down.
For the descent of air from the heating system, 2 types of valves are used:
- Mayevsky manual crane;
- automatic float type air vent.
History reference. In the days of the USSR, such air separators were not used. In private houses, open-type circuits were used, where air escaped through an expansion tank. The centralized heating networks of apartment buildings were equipped with air collectors and drain cranes installed at the highest points, and sometimes in batteries.
How the drain cock works
The device of the Maevsky valve shown in the drawing is not difficult to understand. At the end of the brass body with an external threaded connection ½ ”(DN 15) or ¾” (DN 20), a hole of Ø2 mm was made, whose cross section overlaps a screw with a conical tip. A small diameter hole was made in the side of the case for air exhaust.
Note. The upgraded air outlet valve is equipped with a rotary plastic insert, inside of which a bypass channel is made. Convenience is that the position of the discharge opening can be adjusted by turning the plastic washer.
Mechanical "air vent" works as follows:
- In heating operation mode, the locking screw is tightened and the cone seals the hole.
- When you need to release the air plug, the screw is unscrewed by 1-2 turns. Under the pressure of the coolant, air passes through an opening with a diameter of 2 mm, enters the exhaust channel and moves outward through it.
- First, clean air escapes from the hole, then mixed with water. The screw is tightened after a dense stream of coolant flows from the channel.
A manual Maevsky air cock is a trouble-free tool for venting gases from pipelines and heating radiators. The secret of reliability is the absence of moving parts that could become clogged, worn or rusted. As a rule, the valve is used as a radiator air vent.
Manual heating air valves are divided into varieties according to the method of unscrewing the screw:
- using a plastic or metal handle;
- the traditional option is a slot for a flat screwdriver;
- hexagon screw to use special wrench.
What is the Majewski tap and how it functions is clearly shown in the video from the master - plumbing:
The principle of operation of an automatic air vent
It is easy to guess that this type of air vent valve operates without human intervention. The element is a vertical brass barrel with a threaded connection G ½ “(DN 15), where the plastic float is placed.The latter is connected by a lever with a spring-loaded valve for venting, mounted in the cover.
For reference. Automated air vents (in common parlance - auto air vents, air vents or vents) are available with two types of connecting external threads - ½ “and 3/8“. But in the post-Soviet space, products with a half-inch thread are usually used, 3/8 is extremely rare.
The principle of operation of an automatic air vent is as follows:
- In operating mode, the chamber inside the housing is filled with water, pressing the float up. The spring-loaded air valve is closed.
- As air accumulates in the upper zone of the chamber, the coolant level decreases and the float begins to sink.
- When the level drops to a critical value, the weight of the float will overcome the spring's elasticity and the valve will open, and air will bleed out.
- Due to the excess pressure in the heating system, water will displace all air from the device’s chamber, take its place and again raise the float. The valve will close.
When the pipeline network is filled with coolant, air is removed continuously while the float lies at the bottom of the tank. As soon as water fills the chamber, the spring will close the valve and bleeding will stop. Note that part of the air mixture will remain inside the housing under the cover itself, which will not affect normal heating operation.
By design, air vents are automatic with direct and angular connections. Some manufacturers take the discharge vertically upward, others - to the side, from the side "nose" with a jet. From the point of view of the ordinary homeowner, these differences do not matter much, but the master plumber will say a lot.
Example. Practice shows that an automatic valve with a side outlet works more reliably than with a vertical outlet. Conversely, a product with an angled fitting collects air bubbles worse than a design with a lower direct connection.
The device of automatic air vents is constantly being improved. Leading manufacturers of parts for heating systems give their products additional functions:
- Protection against water hammer using a reflective plate (placed at the entrance to the chamber).
- Efficient capture of small bubbles is achieved in a flow-through design with two horizontal fittings for connecting to the network. The lower zone of the increased tank volume is occupied by a special filler, which stops the moving air bubbles and collects them in the chamber.
- The ability to remove the air vent for maintenance purposes without emptying the pipes. This is achieved by installing an automatic shut-off valve with a spring on the inlet fitting. When the plumber unscrews the element, the spring straightens and the washer with the o-ring closes the passage, as shown above in the diagram.
- Embedding the mini valve in the radiator plug (see photo).
Lyrical digression. Homeowners and some “experts” unknowingly call a float air vent with an automatic Mayevsky tap, which is fundamentally wrong. In the 30s of the last century, the inventor Mayevsky proposed the construction of a manual crane, but he has nothing to do with the “machine”.
Where are the air release valves placed
In any water heating system, there are places where the installation of air vents is mandatory. If we talk about Maevsky cranes, then they need to be put on all batteries in order to bleed the collecting air. The exact place is in the traffic jam of the upper corner, distant from the point of connection of the supply line to the device. An air bubble forms there.
The automatic air valve must be installed strictly vertically at the following points in the heating network:
- in the safety group of the boiler connected to the closed type system;
- on both collectors of a heat-insulated floor;
- if the highest point is the pipeline, and not the radiator, then a float air vent crashes into it;
- in the buffer tank and indirect heating boiler, if this is provided by the design;
- on a heated towel rail coil;
- into a common distribution comb of a complex and branched system (on both collectors);
- to the hydraulic circuit separator (hydraulic arrow).
In addition to these points, air vents are installed in problem areas of the heating network, where, due to the difficult conditions for laying the pipes, they form U-shaped loops turned upward. For example, a highway bypasses a doorway or a flight of stairs on top, and then again goes down. In such compensators, air jams are formed with a probability of 100%, so an air vent is needed there, better automatic.
Tip. Never cut the Majewski tap directly into the pipeline, as the bubbles will pass by it along with the flow of coolant and the valve will be useless. For proper operation, the manual "descent" needs a camera to collect air (the "machine" has its own). Make a tie-in to the trunk with a vertical pipe that will serve as an air collector, and install a crane on top.
If you do not want to run between radiators with a screwdriver when filling the heating network with water, install automatic angular air vents instead of Mayevsky valves. This option is also suitable for residents of apartments that are heated centrally: air ducts often occur in cast-iron batteries, and there is no way to remove them from there.
Another tip. To prevent the angled air vent bulb from sticking out and clinging to the curtains, take the mini-model of the valve integrated into the radiator cap.
Instead of a conclusion - tips for choosing
The first and main recommendation is not to buy automatic “air vents” made in China. The consequences of such savings are well known to heating masters:
- together with air, the product passes the coolant, causing leaks on the body and floor, and the pressure in the system drops;
- poor air vent may jam and not work;
- the inside of the element quickly deteriorates under the influence of the coolant.
With the Mayevsky cranes, the situation is not so deplorable for one reason - there is nothing to break. On the other hand, the product does not belong to sophisticated heating equipment and its price is quite affordable even for eminent brands. For example, manufacturers Icma, Caleffi and Valtec offer decent products of the middle price category. Reliability is also known for the "machines" from the Spirotech brand, shown in the picture.
Now we give some tips on choosing valves for venting:
- It is better to take a Mayevsky crane with a handle, so as not to mess with screwdrivers and keys. It is convenient to twist it in hard-to-reach places when the radiator is hiding in a niche.
- If small children live in an apartment or in a private house, put a manual crane under the screwdriver. The child can reach the handle, open the valve and scald with coolant.
- If possible, take an automatic valve with a shut-off valve. It will allow you to remove the part at any time for repair or replacement.
- The anodized coating of the case does not play a special role in operation. It protects the metal from oxidation.
- The presence of additional functions that improve the operation of heating is welcome. If your budget allows, take an air vent to catch the bubbles.
Note. On sale there is a combination of valves and equipment equipped with a relief valve. These include circulation pumps, balancing valves and a variety of taps. It is not worth focusing on such products; it is better to buy and install each part of the circuit separately.
Float models of air vents are designed for a specific pressure and temperature of the coolant.As an example, we propose to consider the table of technical specifications from the Italian brand Caleffi and make sure that for installation in a private house 2 options will fit - the MINICAL and VALCAL product line (effective response pressure - 2.5 and 4 Bar, respectively).
For installation in an apartment connected to district heating, you should take the ROBOCAL model, designed for operation at a pressure of 6 Bar. Other bona fide manufacturers provide similar tables with characteristics by which you can pick up an automatic “air vent”.