PVC duct for ventilation is used to provide residential and industrial premises with a stream of fresh air, eliminate unpleasant odors and remove harmful fumes. Nowadays, plastic channels have become especially popular due to their practicality, strength, ease of installation, and relatively low cost. The article discusses in detail the issues of calculation, selection, and installation of ventilation ducts.
PVC duct for ventilation: types, sizes, and classification
A wide variety of use of air ducts in ventilation systems determines a wide range of their types and options. There are several parameters that form the basis of the classification:
- section shape: elliptical, rectangular, round;
- execution material: plastic, metal-plastic, steel;
- the size or diameter of the section;
- method and type of connection;
- structural performance.
In order to satisfy broad consumer needs and provide possible design options, manufacturers offer a wide range of plastic ventilation ducts. So, for rectangular flat air ducts, typical dimensions are in the range from 100×55 to 204×60 mm, the diameter of round ones are 100-200 mm.
The most commonly used section types are round and rectangular. In some cases, when the design imposes strict restrictions on the size and shape of the channel, an elliptical version is used. This section is achieved by processing around products on special machines.
For the manufacture of round plastic air ducts, less material is required, and the technology for their production is simpler. In the case of a rectangular design, costs increase by an average of 20-30% when switching from a circular section. The complication of the manufacturing process is due to the fact that such ducts are assembled together from several separate parts.
The main arguments in favor of choosing a round shape are the best tightness (which is ensured by a one-piece design and no welds), high air flow rate, reduced noise level, lighter weight, and ease of installation.
As an advantage of rectangular channels, optimal placement in space should be highlighted. This form takes up less space, it is easier to adapt to the features of the layout, for example, when combined with suspended ceilings.
Helpful advice! If the location of the intended location of the ventilation system imposes restrictions on the lateral dimensions of the ducts, transition elements can be used to change the cross-sectional shape. In this case, the transverse area of the combined parts must be the same.
Is metal duct better than flex duct?
The material used for the manufacture of different types of air ducts depends on their area of application and possible restrictions imposed by the existing ventilation system.
The plastic or PVC type has become widespread both in the conditions of the transfer of aggressive air flows and for use in all types of residential premises. Plastic is light and smooth material, resistant to moisture, acids, and alkalis. Due to its tightness, various connecting elements (elbows, tees, bends) are made from it. 4.
Galvanized steel air ducts are used in ventilation systems that operate in a non-aggressive environment (temperatures up to 80 ° C). The protective coating has anti-corrosion properties and significantly increases the service life of products, but increases the cost of installing ventilation ducts per m2.
The metal-plastic type of air ducts is produced using two metal layers (often made of corrugated aluminum) and a foam plastic interlayer. This type has high strength with low weight. The products have an aesthetic appearance and do not need additional thermal insulation. The disadvantage is the increased cost.
Helpful advice! In residential environments (especially when organizing ventilation in the kitchen of an apartment), it is preferable to use plastic wires due to less noise, weight, ease of installation and lower cost.
Other types of air ducts include polyethylene, vinyl plastic, and fiberglass. These types are characterized by high corrosion resistance, low weight, the ability to bend in all planes at an unlimited angle.
Since today the most common are rigid air ducts – the bulk of all ventilation equipment on the market is focused on this type. Rigid boxes are often circular or rectangular in cross-section. The sheet material is used for manufacturing. Basalt wool can be used as external thermal insulation.
Flexible air ducts for ventilation are presented in the form of corrugation (corrugated sleeve), which is made of polyvinyl chloride (PVC). The excellent ease of transport and installation should be noted here. Before buying a flexible duct, you should consider the disadvantages of this type. Thin walls have a low level of sound insulation. Also, the embossed surface of the corrugation negatively affects the speed of air flow through the wire.
The last type is semi-rigid. It is an intermediate link between flexible and rigid products, combining high strength and elasticity. The disadvantages of such air ducts include a reduced air velocity, which imposes restrictions on their use in branched systems.
Helpful advice! Do not limit your choice to only one type of duct. The wide range of fittings makes it easy to combine rigid and flexible channels. This combination does not in any way affect the performance of the ventilation system as a whole.
Plastic air ducts for ventilation: methods and types of connection
The most common methods for joining duct sections are flanged and wafer joints. The basis of the first is the installation of flanges, which are attached to the ventilation duct sections with rivets or self-tapping screws. Tightness at the joints is achieved using rubber and other seals.
The flangeless connection is made using a band of thin sheet steel and metal rails.
The main types of air duct connections are:
- tees (at the points of interface or branching of the system);
- knees and bends (at the bends of the channel);
- adapters (for switching from around to rectangular duct or, conversely, connecting parts of different sections);
- confusers and diffusers (in places of transition to another size). The first ones narrow the channel, and the second ones widen it.
Advantages and Disadvantages of PVC duct for Hoods
Undoubtedly, flat plastic air ducts are very popular for non-industrial residential use. The following positive properties of such products should be highlighted here:
- due to the absence of elements subject to oxidation in them, plastic wires do not suffer from corrosion. This feature has greatly simplified the work of designers, eliminating the need to provide additional protection systems. Oxidation resistance makes the structure itself and the process of its installation simpler;
- cost reduction: PVC ventilation pipes are much (sometimes 2-3 times) cheaper than their metal counterparts;
- smooth inner surface for maximum airflow and does not require periodic cleaning;
- the ability to cut parts of the wire at the installation site and a wide range of different fittings greatly simplify the assembly and installation of the structure;
- non-toxicity and complete safety for both humans and the environment. 8.
Along with all the listed advantages, flexible PVC air ducts have one significant drawback: low fire resistance.
Installation of PVC duct for hoods in the kitchen
After selecting plastic rectangular ducts for ventilation in the catalog and purchasing all the necessary elements, you can proceed to installation. Trial assemblies are carried out on the floor or on a table, which is then suspended from the ceiling or attached to the wall. The connection of straight sections is carried out with couplings. Shaped elements are joined by nipples, which, in turn, are obtained by cutting parts of the required length from a straight section.
Connecting elements in ventilation systems are manufactured with larger diameter nozzles for tight entry of straight ducts. Therefore, for example, a tee with a branch must be joined using a straight short pipe (nipple). After connection, this section is completely hidden by the pipes.
Leaks and gaps arising at the joints of the elements can cause air leaks, so they are covered with a sealant before joining. It is worth remembering that the use of self-tapping screws also leads to depressurization.
Some contractors use self-tapping screws to screw plastic exhaust ducts to a hanger or bracket. With this method of installing air ducts, the price is reduced, and the process itself is significantly accelerated. It is correct to install the channel on clamps that tightly cover the pipe. This mount has a rubber gasket and is specially made for fixing to a wall bracket or hanging rod.
Studs of the required length are attached to the floor slabs with anchors or other hardware. Also on sale are plastic brackets and clamps in the form of latches. Such elements greatly simplify and speed up the installation process.
The organization of the ventilation system is a relatively simple process. The described simple calculation method allows you to easily select the necessary elements, and a wide range of ventilation ducts and connecting elements simplifies the placement and installation of plastic air ducts in the limited space of ordinary residential premises.