The correct choice of air ducts is essential for efficient operation of the kitchen hood. With the advent of plastic pipes on the construction market, it has become cheaper and easier to install ventilation communications. Plastic ventilation pipes have become an affordable alternative to galvanized exhaust ducts.
Specifications and properties
For the manufacture of plastic air ducts, 4 types of polymers are used: polyethylene, polypropylene, polyvinyl chloride (PVC), fluoroplastic (PVDF). Consider the characteristics of each type.
Polyethylene plastic air ducts are used mainly in country houses with seasonal residence. They are UV protected and antistatic. Polyethylene is resistant to temperature extremes, it can be used both outside and indoors. Safe operation of polyethylene pipes is guaranteed in the range from — 45C to + 75C.
Polypropylene ducts are used to connect the hood due to their low cost and ease of installation. Polypropylene is a good dielectric, resistant to aggressive environments, but does not withstand low temperatures, therefore it is used only in a warm room.
Important! If the temperature norm + 85С is exceeded, the material is combustible and melts easily. You can find varieties with fire-resistant components.
The main qualities of their PVC ventilation ducts are lightness, structural strength and inexpensive price. The temperature range for efficient operation is from 0C to 80C, temperatures below zero are not tolerated. Heating above +120C is hazardous to health, the product will begin to release chlorine. PVC pipes are actively used when installing the hood, if the temperature during use does not exceed the recommended threshold.
PTFE ventilation ducts are durable and resistant to aggressive environments. They are able to withstand acid-base vapors, therefore they are mainly used for ventilating aggressive air flow in production. Safe operation temperature from ‑40С to +140С. Due to the high cost and increased gas permeability of the material, they are rarely used in an apartment.
Advantages and disadvantages of plastic ventilation pipes
Plastic air ducts have the following advantages:
- light weight;
- complete tightness;
- low noise level;
- finished appearance that does not require painting;
- ease of installation;
- resistance to corrosion;
- toxic safety;
- produce minimal static resistance to airflow;
- easily dismantled for installation in another version;
- antistatic treatment prevents dust from settling inside the system.
- brittleness in comparison with metal;
- low fire resistance.
The main types of plastic air ducts
According to the type of section, plastic ventilation ducts are:
Round ducts are suitable for installation of long ventilation ducts. They are not very convenient for small kitchens — they take up a lot of space and stand out strongly in the interior. However, their throughput is better, they are almost silent and easy to install.
The diameter of the round ventilation pipe is 80 mm — 150 mm. The length is 500mm, 1000mm, 1500mm. The larger the diameter of the duct, the more air it can pass through itself. For example, a pipe with a cross section of 100 mm has a capacity of 300 m3 /hour. The capacity of the air ducts is indicated in the table.
Rectangular or square plastic air ducts are more compact in size. The flat ventilation route is easily attached to the walls and ceiling with special holders. Flat and square boxes can be hidden in a closet or under a false ceiling. The assembly of elements does not require the presence of specialists. Tees and flanges are required for mounting the ventilation duct.
On sale there are the following sizes of ventilation rectangular plastic pipes for exhaust equipment:
- product width — 110 mm, 122 mm, 204 mm;
- flat ventilation pipe height — 55 mm, 60 mm;
- length — 350 mm, 500 mm, 1000 mm, 1500 mm, 2000 mm and 2500 mm;
- wall thickness from 2 to 8 mm.
The thickness of the walls depends on the size of the section — the larger the section, the thicker the walls.
Round and rectangular exhaust pipes are:
Rigid ones have thick walls, so over time they will not lose their shape.
Rigid pipes have a smooth inner surface, there are no drops and bulges. The air flow moves through them quickly and silently. Soot will not accumulate on the smooth walls inside — this will facilitate the maintenance of the exhaust system.
Flexible plastic pipes are corrugated, which during installation can stretch, bend at any angle.
Corrugated pipe is used where there is no technical possibility to lay rigid boxes. The length of one such air duct is up to 2.5 meters. Their installation does not require a large number of fasteners. The disadvantages are the same as those of flat plastic ones — instability to high temperatures.
A plastic corrugated pipe for exhaust is rarely used, mainly a similar smooth metal construction is preferred. Channels made of corrugated pipes emit increased noise during ventilation.
Calculation of the section of plastic air ducts
Each hood model has a branch pipe with a certain cross section, so round ducts must be selected for this size. When installing flat ducts, it is necessary to calculate the cross-sectional area of a round pipe.
If the diameter on the hood is 110 mm, the area is calculated using the formula:
S=πD²/4= 3.14 x 0.11²: 4 = 0.01 m²
The area of a flat pipe with sides 125mm * 80mm will be equal to 0.01 m2. It turns out the replacement of a round duct with a diameter of 110 mm. You can set a larger size, but not a smaller one. This will degrade the performance of the entire system.
The diameter of the outlet of the hood serves as the initial size when choosing ventilation plastic pipes. Also take into account the power of the hood and the length of the duct. The longer and more winding the track, the lower the performance of the entire system. The best option is one turn when moving from the hood to the horizontal section.
The correct calculation of the section of plastic air ducts for the hood will ensure the efficiency of the equipment and optimal air exchange in the room.
Attention! If there is no confidence in the correctness of independent calculations, you need to turn to professionals. Payment for the services of an engineer is sometimes cheaper than the cost of correcting the defects that have arisen.
After the calculation, it is necessary to double-check the result and only after that make a purchase decision and proceed with installation.
What equipment is used for installation
To connect ventilation from plastic pipes to the hood with your own hands, you will need:
- pipes of rectangular or round section;
- clamps of the same diameter with an exhaust outlet;
- couplings, fittings of the appropriate diameter;
- ventilation grille;
- silicone sealant.
Corrugated ducts are the most convenient to install. Insertion of such is carried out without the use of fittings, with any bends. The corrugated pipe stretches well, so one piece can be enough for the entire route.
The corrugation is attached to the exhaust pipe with a plastic clamp. No more fasteners are needed. In the same way, the other end is attached to the sides of the ventilation grill. The grate is screwed onto the screws to the exhaust hole in the wall.
PVC air ducts are cut with a hacksaw into sections of the desired size.
Round and flat plastic ducts require additional elements for connection between each other and when turning the network. For their connection, double-sided couplings of round or rectangular section are used. The diameter of the coupling is slightly larger than the diameter of the pipe, so it can be easily inserted into it. For tightness of the structure, the joints are treated with silicone sealant.
A fitting is also attached to the flat ventilation ducts. Since the branch pipe in the hood is round, it is impossible to immediately install a rectangular box into it. A special adapter is used here, on one side of which there is a round hole for landing, and on the other, a rectangular one. The size of the fitting is selected according to the size of the duct.
In certain cases, to connect the ventilation pipes to the hood, it is required to dismantle it. Then the entire assembly is installed in place.
Recommendations from experienced craftsmen
For efficient operation of air ducts during installation, the following rules must be observed:
- observe the diameters of the pipe and the ventilation hole;
- do not exceed the length of the structure — 3 meters;
- do not make more than three bends and knees;
- try to avoid 90 degree angles;
- take into account the direction of movement of the air flow — from the socket to the thin end of the pipe.
Air ducts made of polymers are gaining popularity, gradually replacing steel counterparts. For the efficient operation of the ventilation system in the kitchen, it is necessary to choose the appropriate option. Proper installation of pipes will ensure long-term operation of the equipment.