Air in the heating system: causes, valves – vents, air vents

Normally working heating in winter is a vital necessity. It is impossible to survive without heating in our climate. But periodically, a previously normally working system starts to fail – the radiators do not heat up or heat up poorly, extraneous noise (gurgling) appears. All these are signs that air has appeared in the heating system. The situation is far from rare, but bringing discomfort. 

What threatens the air in the heating system

Everyone, probably, has repeatedly met with the fact that the heating is turned on, and some kind of radiator or a whole group does not heat up well or even stay cold. The reason for this is the air in the heating system. It usually accumulates at the highest point, displacing the coolant from this place. If it accumulates a lot, the circulation of the coolant may stop altogether. Then they say that an air lock has formed in the heating system. Professionals in this case say that the system is airborne.

To resume normal operation of the heating, the accumulated air must be removed. There are two options for this. The first is more often used in central heating systems. Cranes are installed on the extreme radiators in the branch. They are called descenders. This is a normal faucet. After filling the system with coolant, it is opened, kept open until an even stream of water flows without air bubbles (then the water flows in jerks). If we talk about multi-storey buildings, then during the launch of the system, the air vents on the risers should first open, and the rest can already be taken out to the apartments.

In private systems or after replacing radiators in apartments, not ordinary taps are installed to bleed air, but special air valves. They are manual and automatic. They are placed in the upper free collector on each radiator (preferably) and / or at the highest point of the system.

What else threatens the air in the heating system? It contributes to the faster destruction of the components of the heating system. Although polymers are used more and more today, there are still enough metal parts. The presence of oxygen contributes to the activation of oxidation (ferrous metal rusts).

Causes of appearance

Air in the heating system can appear for various reasons. If this is a one-time problem, you can simply delete it and not look for the source. If airing is required several times per season, you will have to look for the cause. Here are the most common:

• Repair, modernization of the heating system. During repair work, air almost always enters the pipeline. It `s naturally.
• Filling the system with coolant. If you pour water into the system slowly, it carries a little air with it, simultaneously displacing the one that is in the pipes and radiators. This is also an understandable process, it does not require special measures either.
• Depressurization of joints and welds. This defect requires elimination, since airing will occur constantly. In individual heating systems, this phenomenon (leaky connections) is also accompanied by a pressure drop. And this is another reason to look for faults. The most likely place is the connection of pipes and radiators. They may not be sealed. It is very difficult to look for them, since outwardly they do not always appear. If you notice that one of the compounds “digs” everything much easier – eliminate the drops. But if outwardly everything is fine, and air accumulates all the time, you have to coat the joints and seams with soapy foam and observe whether new bubbles appear. After finding each “suspicious” connection, they are tightened, coated with sealant or repacked (the method depends on the type of connections).
  

• If there are already air vents (air vent valves) in the heating system and plugs have begun to appear in it, it is necessary to check the serviceability of the valves, as well as the tightness of the connections.
• The appearance of air in the heating system may be due to a rupture of the expansion tank membrane. In this case, you will have to change the membrane, and for this you need to stop the entire system.

These are the most common places and ways in which air enters radiators and batteries. It is necessary to expel him from there from time to time, but during the autumn start-up of heating – it is necessary.

Installing air bleed valves

To remove air from heating, air vents are installed on radiators – manual and automatic air valves. They are called differently: a bleeder, an air vent, a bleed or air valve, an air vent, etc. The essence of this does not change.

Mayevsky air valve

This is a small device for manually bleeding air from radiators. It is installed in the upper free radiator manifold. There are different diameters for different sections of the collector.

It is a metal disc with a conical through hole. This hole is closed with a cone-shaped screw. By unscrewing the screw a few turns, we allow air to escape from the radiator.

To facilitate the exit of air, an additional hole is made perpendicular to the main channel. Through it, in fact, the air exits. During de-airing with the Mayevsky crane, direct this hole upwards. After that, you can unscrew the screw. Loosen a few turns, don’t over tighten. After the hissing stops, return the screw to its original position, move on to the next radiator.

When starting the system, it may be necessary to bypass all the air collectors several times – until the air stops coming out at all. After that, the radiators should heat up evenly.

Automatic air release valve

These small devices are placed both on radiators and at other points in the system. They differ in that they allow you to bleed air in the heating system in automatic mode. To understand the principle of operation, consider the structure of one of the automatic air valves.

The principle of operation of the automatic descent is as follows:

• In the normal state, the coolant fills the chamber by 70 percent. The float is at the top, it presses the rod.
• When air enters the chamber, the coolant is forced out of the housing, the float drops.
• He presses the protrusion-flag on the jet, wringing it out.
  

• The pressed jet opens a small gap, which is enough to release the air that has accumulated in the upper part of the chamber.
• As the water exits, the air vent housing is filled with water.
• The float rises, releasing the stem. It springs back into place.

Different designs of automatic air valves work according to this principle. They can be straight, angular. They are placed at the highest points of the system, present in the security group. They can be installed in identified problem areas – where the pipeline has the wrong slope, which causes air to accumulate there.

Instead of Mayevsky’s manual taps, you can put an automatic drain for radiators. It is only slightly larger in size, but it works in automatic mode.

Salt cleaning

The main trouble with automatic valves for venting air from a heating system is that the air outlet is often overgrown with salt crystals. In this case, either the air does not come out or the valve starts to “cry”. In any case, it needs to be removed and cleaned.

So that this can be done without stopping the heating, automatic air valves are installed paired with reverse valves. The check valve is mounted first, an air valve is mounted on it. If necessary, the automatic air collector for the heating system is simply unscrewed, disassembled (unscrew the cover), cleaned and assembled again. After that, the device is again ready to bleed air from the heating system.

How to get rid of an airlock

Unfortunately, the airlock is not always in an easily accessible place. With design or installation errors, air can accumulate in the pipes. It’s very hard to get him out of there. First, we determine the location of the plug. In the place of the cork, the pipes are cold and a murmur is heard. If there are no obvious signs, they check the pipes by sound – they tap on the pipes. In a place where air accumulates, the sound will be more sonorous and loud.

The found air plug must be expelled. If we are talking about the heating system of a private house, for this they raise the temperature and / or pressure. Let’s start with pressure. Open the nearest drain valve (in the direction of movement of the coolant) and the make-up valve. Water begins to flow into the system, raising the pressure. It forces the cork to move forward. When air enters the bleeder, it exits. Stop feeding after all the air is out – the drain valve stops hissing.

Not all airlocks give up so easily. For especially persistent it is necessary to simultaneously raise the temperature and pressure. These parameters are brought to values ​​close to the maximum. It is impossible to exceed them – it is too dangerous. If after that the plug has not gone away, you can try to open the drain valve (to drain the system) and the make-up valve at the same time. Maybe in this way it will be possible to move the air plug or even get rid of it.

If a similar problem occurs constantly in one place, there is an error in the design or wiring. In order not to suffer every heating season, a valve is installed in the problem area to vent air. A tee can be inserted into the line and an air vent can be installed on the free entrance. In this case, the problem will be solved simply.