The non-return valve on the ventilation grill serves to prevent odors from entering the room from the general air purification system, as well as air from the street through the hood.
Its function is to pass air in one direction. If you save on its purchase and installation, ventilation can work both for supply and exhaust, depending on the difference in temperature and pressure in the room and on the street or in adjacent rooms. It may turn out that the residents will know for sure that the neighbors have dinner today, and this is far from the worst option - bathrooms also go into the ventilation system.
The principle of operation of the ventilation grill with a valve
The check valve grille consists of three main parts: the fixed part, the moving part and the flange to which the duct is connected.
Fixed part It is a grille that plays a decorative and protective role, partially hiding the valve and protecting it from mechanical damage. It is made of plastic, as a rule, has a rectangular shape and, in addition to the ventilation shaft, covers part of the wall.
Moving part It looks like a rectangular or round petal, opening in one direction. Sometimes there is a form of "butterfly". Since the system is operated in conditions of high humidity, the check valve is made of plastic, which is not afraid of the aggressive effects of moisture. Metal structures are of artisan origin, and are not particularly reliable.
Flange represents a section with a circle with a diameter of 110-150 mm and is intended for connection of the valve in an air duct.
Types of check valve designs
There are four main options for preventing back draft in the ventilation system. Each option has strengths and weaknesses, the choice of a particular option depends on specific conditions:
Single-leaf valve of gravitational action
The principle of operation is based on the use of the law of gravity, the sash closes under the action of gravity in the absence of traction from the room. It is carried out in two versions for horizontal and vertical installation - opening occurs either due to the displacement of the axis on which the sash is mounted relative to the center of the duct channel, or due to the counterweight located in the device (or outside the device).
Important! It is mandatory to install a check valve of this type strictly in level. If this is not done, it may not close completely, or it can only act on a large air pressure. The installation of the valve strictly according to the level in systems with natural ventilation is especially relevant.
Double-leaf valve using springs
It is also called the "butterfly" due to the similarity of the flap petals with wings, folding at excess air pressure and expanding in the absence of traction. It does not depend on gravity and is placed in the ventilation system at any angle. By tensioning and loosening the springs, the sensitivity of the valve to pressure drops is regulated. Most butterfly valves are installed in forced draft ventilation systems.
Ventilation Blinds
The principle of operation of the device is gravitational, placed outside the system and looks like a grill that closes the air duct from the street. There are valve options for the entire grill and the size of a lockable duct opening. Due to the small size and weight of the petals, it is suitable for natural ventilation.
Flexible membrane
The design is very sensitive to air flow, therefore it is used both in natural and forced ventilation. The membrane bends when air moves in one direction, allowing air to circulate freely, and when the air direction changes, the membrane bends and closes the duct.
Important! With a strong current of air, the membrane can bend in the opposite direction. As a result, the membrane can deform against the walls of the duct and partially allow air to pass in the opposite direction. In such cases, stiffening ribs, in which the membrane abuts, are additionally installed in the duct.
Rules for the placement and installation of a ventilation grill with a valve
The basic rule is that the installation of the system should be carried out in such a way that when the fans and hoods are turned on or off, there is no back draft.
If the system has only one point of air intake, from which it is directed to the street through the air duct, then installing one valve will be enough. In the case of a more complex ventilation topology, the following rules are followed:
- At each point of air intake, a valve is installed to avoid backward thrust at this point.
- At the exit point of the duct into the street, another valve is placed; for prevention, there will be no reverse thrust without it only when the duct is completely tight.
Mount the check valves so that they can be easily reached, care for them - remove dirt and grease so that they do not jam.
Before mounting the valve, make sure that the manufacturer has not installed his device in the ductif it already exists - there is no need to install it.
In the ventilation shafts of apartment buildings, in addition to extraneous odors from neighboring apartments, birds, rats, and insects live. The products of their livelihoods do not differ in special sanitation, therefore the use of forced ventilation is mandatory in such systems. Access of air from the duct back into the room should be excluded. It is not worth counting on the good faith of management companies in the performance of treatment works.
Operational Features
In frosty weather, ice crusts may form on louvres equipped with shutters and the following problems occur:
- The flaps cease to completely block the outlet of the duct, the return air flow to the apartment begins, although insignificant, but in the cold it is very noticeable.
- The hole cross section decreases due to frozen ice, the overall exhaust performance drops, the fans are overloaded.
The ice is removed mechanically, but the main thing here is not to overdo it and not to remove the grate with the ice. It makes sense to put on the street a metal structure instead of a plastic one.
Finally we can conclude that by investing a relatively small amount in the installation of a grill with a check valve, it will become much easier to breathe, and in the literal sense of the word. A person can do without food for a month, without water for three days, and without air one and a half - two minutes. Do not neglect the most necessary, necessary as air.
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