Ducted comfort cooling and mechanical ventilation systems incorporate many different components including fire-rated steel, insulated ductwork, plenums, regulators, dampers and access panels, as well as various bends, saddles and reducers. A well-designed air management ductwork installation is instrumental in balancing the comfort cooling and ventilation air supply to provide the required supply and extraction volumes to each location while maintaining fire safety levels.
Ductwork is the method by which mechanical systems convey air throughout the building. For Fire Safety design considerations, steel ductwork is typically used in large housing projects, and this is available with a non-fire or fire-rated specification. However, even the non-fire rated products are confirmed within Approved Document B Fire Safety to have the ability to withstand temperatures up to 800 °C without deforming or rupturing and are therefore suitable for various fire-resistant applications. Pre-insulated high density mineral wool ductwork is a good choice for a fire-rated, sound absorbent, low environmental impact solution.
Plenums are ‘boxes’ installed within the supply and return ventilation ductwork system and act as airflow distribution points to either distribute the supply air into ductwork and on to the ventilation diffusers, or collect the extract air before exhausting it externally. In addition, plenums may be installed to transition between standard distribution ductwork and linear bar grilles or diffusers. Plenums, in particular for the return air path, can be a good location to install the air filters for a ventilation or air-conditioning system.
Volume control dampers or regulators are available in various options.
Manual Air Volume (MAV) regulators require no power and are manually adjusted at commissioning stage to ensure that target air volumes for correct supply and return levels are being met for each room. Constant Air Volume (CAV) regulators also require no power, these are calibrated to the project specifications before installation and open and close automatically subject to changes in air pressure and flow rates. Variable Air Volume (VAV) regulators are controlled with an electronic motor and sensors, and designed to provide a constant airflow at variable temperatures.
Fire dampers are designed for installation into metal air conditioning and mechanical ventilation ducted systems to prevent the spread of fire through the system and from one fire compartment to another. The damper blade remains open under normal operating conditions and automatically self-closes in the event of a fire. Typical installation of dampers is the point where ductwork passes through a fire compartment wall, for example mechanical risers or protected staircases, and when closed provide an equivalent fire performance to the compartment itself.
Fusible Link Fire Dampers are inexpensive and may be mounted horizontally or vertically within a duct; these automatically close dependent on temperature, once the fusible link releases itself at a temperature typically around 72°C.
Motorised Fire Dampers use power open/spring close actuators which remain open during normal mode and close in the event of system power loss or fire signal.
Intumescent dampers have no moving parts and are often installed into ductwork or apertures; these expand to block the opening upon exposure to heat. These require no maintenance, but because they expand to block the opening upon exposure to heat from a fire they will obstruct the free area after operating.
Access panels are easily openable or removable doors or panels that facilitate access to climate control equipment requiring regular maintenance or replacement. These can be integrated into the building fabric flush with the wall, with hidden hinges and locks to minimise negative aesthetic effects but at the same time provide easy access to fan coil units and filters. They can also be installed into the ductwork itself to access fire and smoke dampers and volume control regulators.
Control and monitoring systems provide overall control of the mechanical equipment through intelligent user interface.Find out more
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