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Purpose and Function of a Manifold

A manifold (or distribution box) is the central hub in modern radial MVHR (Mechanical Ventilation with Heat Recovery) systems. Its main purpose is to take a large volume of air from the main duct coming from the heat recovery unit and efficiently divide it into several equal, smaller streams. These streams are then directed through individual flexible ducts to different rooms, forming a radial layout.

The choice of galvanized steel as the material for distribution manifolds is driven by high requirements for mechanical strength, fire safety, and system longevity. Unlike polymer alternatives, a steel body possesses absolute rigidity, which is critically important for installation in a concrete screed—it does not deform under load and guarantees the preservation of the factory-sealed connections for decades. Furthermore, steel is a non-combustible material, which ensures compliance with strict building codes. This makes a galvanized manifold the professional standard, ensuring the reliability and stability of the entire radial ventilation system's operation.

The Role of the Manifold in System Efficiency and Hygiene

The quality of the manifold directly impacts the overall performance, energy consumption, and hygiene of the entire ventilation system. Professional galvanized steel manifolds address three key objectives:

• Maximum Energy Efficiency: Like all system components, manifolds must meet Airtightness Class D. Any leak in the central distribution hub is a direct loss of heat and energy, as the fan has to work harder to compensate for the losses. The manifold's airtightness is the key to a low SFP value for the entire system.
• Foundation for Hydraulic Balance: The manifold's design is engineered to ensure the most uniform pressure distribution across all outgoing spigots. This creates a "level playing field" for each branch of the system, which significantly simplifies the final, precise balancing at the endpoints using dampers in the plenum boxes.
• Hygiene and No Cross-Contamination: A radial system built around a manifold is inherently more hygienic than a traditional trunk-and-branch system. Since each room has its own dedicated duct, the risk of transferring stale air, odors, or microorganisms from one room to another through the duct network is completely eliminated.
• Strength and Reliability: The use of galvanized steel provides high mechanical strength, which is especially important for models designed for installation in a floor screed. The body can withstand the weight of concrete, does not deform, and maintains its airtightness for its entire service life.

Explanation of Airtightness Classes (EN 12237 standard)

The airtightness class is a key indicator that defines the quality of the entire ductwork system. It specifies the volume of air lost due to leaks in the connections. The standard establishes four main classes:

• Class A: A basic level with high permissible leakage. It is not used in modern energy-efficient buildings.
• Class B: An improved class, formerly the standard for general ventilation. It is insufficient for heat recovery systems due to significant losses.
• Class C: A high class of airtightness. It is considered the mandatory minimum for quality ventilation systems aiming to meet energy efficiency standards.
• Class D: The highest possible class, with maximum airtightness. Air leakage is practically reduced to zero. This is the "gold standard" for passive and nearly zero-energy buildings (NZEB), guaranteeing that no energy spent on air treatment is wasted.

Comparison of Radial and Trunk-and-Branch Ventilation Systems

Manifold Types and Selection

Manifolds vary by the number of spigots for connecting flexible ducts and by the installation method. The correct choice depends on the scale of the ventilation system and the building's construction.

1. By Number of Outlets

The main parameter is the number of outgoing spigots (usually for ø75 or ø90 mm ducts). It must correspond to the number of branches in your system. Manifolds are available with 6, 10, 12, 15, or more outlets. It is always a good practice to have a small reserve when designing the system.

2. By Installation Type

• For Floor Installation: Flat and low-profile models that are convenient to place in the insulation layer or to cast into the floor screed.
• For Ceiling/Wall Installation: Compact models that are easy to mount under the ceiling or on a wall, taking up minimal space.

Manifold Selection Criteria

When choosing a distribution manifold, the following key aspects should be considered:

• Certified Airtightness Class (D): Ensure that the manufacturer guarantees compliance with Class D.
• Gasket Quality: All spigots (both the main inlet and the outlets) must be equipped with reliable EPDM gaskets.
• Material and Strength: A body made of sufficiently thick galvanized steel ensures that the manifold will not deform during installation.
• Low Hydraulic Resistance: Check with the manufacturer for pressure loss data to ensure low energy consumption for the system.

Choosing a quality manifold is the foundation for building a reliable, quiet, and energy-efficient ventilation system.

Main Steps for Manifold Installation

Proper installation of the manifold ensures the airtightness and correct operation of the entire radial system. The process includes the following steps:

• Connecting the Main Duct: The spiral-wound duct from the heat recovery unit is securely connected to the main spigot of the manifold. The factory gasket ensures Class D airtightness.
• Securing the Body: The manifold is firmly fixed to the sub-floor, wall, or ceiling structure. It is important to ensure the body is stationary to avoid vibrations and noise.
• Connecting the Flexible Ducts: Each branch of the system is connected one by one to the outgoing spigots. Thanks to the mechanical locking system, the ducts snap into place quickly and create an airtight seal.
• Insulation (if necessary): If the manifold is installed in a cold zone, it is recommended to add thermal insulation to prevent condensation.

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