Chapter 2

2.4.3 Embedded rectangular ducts made of hard plastic

(Meant for embedding in the concrete floor) Material quality

Plastic is used more and more for ventilation ducts.
Plastic air distribution systems are increasingly seen as an extension of the existing steel ducts for residential construction. PE or polyethylene is used to manufacture these air ducts. It is possible that the ducts are fitted at the factory with antistatic and antibacterial additives. The ducts are suitable for temperatures between -20 °C to +60 °C. Wall thickness

Depending on the type, the average wall thickness is approximately 5 mm. Connections

Connections to the main/sub distribution boxes and valve collectors are made by a click connection with rubber seal. This creates a watertight connection so that cement water cannot penetrate the duct. Normally no connections are made to connect duct sections to each other, the ducts are expected to be directly connected to distribution boxes and valve collectors. Dimensions

Plastic distribution systems are made in various shapes and dimensions. The most common form is a round duct with the possible dimensions: ø50, ø63, ø75 or ø90 mm. Length of duct

Ducts are delivered on a roll. Main (sub) distribution box

All the valve collectors on the same floor are connected to the main distribution box, and there is also a connection for the spiral flanged ducts. Connecting collectors and connection sleeve

For the connection of valves there are valve connection collectors. Depending on the air volume, these are equipped with 1, 2 or 3 ducts, which run to the main (sub)distribution boxes. Airtightness

Properly connected ducts on the collectors/distribution boxes comply with airtightness class C as a minimum. This also makes it possible to use the ducts in, for example, suspended ceilings in renovation  projects. Bends

There are basically no bends available for the flexible ducts. Bends and obstacles are avoided by leading the flexible hose along them. Vertical bends must always be guided. Seal

The unused openings on the distribution boxes and collectors are sealed with the plastic caps supplied. The unused openings in the distribution boxes at the top/bottom are sealed with the supplied mortar caps. Mounting

The embedded ducts must be fixed to the concrete floor or formwork in such a way that the duct parts cannot float during the pouring of the concrete. This is done by means of special brackets suitable for these plastic ducts, which are attached to both sides of the duct with anchor plugs to the concrete or formwork. There are several methods of adequately fixing the duct, but the duct must be fixed at most every 1 metre. (See picture below).

The various collectors and distribution boxes must be secured separately using the fitting points provided on these items. Damaged parts may not be assembled and must be replaced. All openings should be closed by plastic caps/covers. The manufacturer's instructions should always be followed for correct assembly and fixing.

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