A fan box must be selected at the airflow and pressure required by the connected system. A free-air capacity describes a different condition from operation through ducts, filters, grilles and other resistance.
Build the air path into the selection
Identify intake and discharge arrangements, duct losses and the relevant filter condition. Compare offers at the same duty point and air conditions. If the system has several operating modes, provide the expected range rather than only a maximum airflow.
Inlet or discharge obstructions and abrupt transitions can affect installed performance. Reserve suitable connection space and coordinate vibration isolation with the supporting structure. Do not use the fan casing as an unintended support for connected ductwork.
Supply and exhaust duties differ
State what the air contains and where it goes. General supply air and contaminated exhaust may require different materials, motor arrangements and maintenance controls. An ordinary ventilation fan box should not be assigned explosive, corrosive or high-temperature process duties without suitable assessment and evidence.
Eurovent's AHU overview describes fans as part of a connected air-treatment system. The same selection principle applies to a fan box: the surrounding equipment and controls determine the required operating point.
Include controls and service in the price comparison
Identify speed control, electrical supply, isolation and the signals needed by the building system. A speed command is not automatically an airflow measurement. Where performance indication is required, define it explicitly.
Provide access to the motor, impeller and any filters or belts present in the selected construction. Check the withdrawal route and the space to remove service panels. Include noise data at the relevant operating condition and distinguish sound power from sound pressure at a particular location.
shengtongJH can coordinate supply and exhaust fan-box configurations. Send the airflow, resistance schedule and installation layout to compare complete selections.