Air Handling Unit: A factory made encased assembly or flat-packaged unit that consists of a fan or fans and other necessary equipment to perform one or more of the following functions: circulating, filtration, heating, cooling, heat recovery, humidifying, dehumidifying and mixing of air. The unit should be suitable to be used with ductwork.
Range: A family of Air Handling Units of different sizes grouped under the same designation and using the same selection procedure.
Model Box: Construction envelope built according to specifications presented in manufacturer’s literature, used to establish mechanical, thermal and acoustical performance according to the relevant EN standards.
Real Unit: Unit from the range of a specific size, used to establish complete performance for all the available functions of the Air Handing Unit range, according to the relevant EN standards.
Sub-range: Part of a range using the same Model Box(es) and grouped under the same designation.
Deflection [mm/m]: The largest deformation of the sides of the unit under pressure, positive or negative, given as a difference in distance from a reference plane outside the unit to the external unit surface with and without test pressure. The deflection, related to the span, defines the casing strength.
Air leakage factor [l.s-1.m-2]: The air leakage in volume per unit of time, related to the external casing area.
Thermal transmittance [W.m-2.K-1]: The heat flow per area and temperature difference through the casing of the air handling unit.
Thermal bridging factor [-]: The ratio between the lowest temperature difference between any point on the external surface and the mean internal air temperature and the mean air-to-air temperature difference.
Filter bypass leakage [%]: Air bypass around filter cells as a percentage of rated air volume flow.
Acoustical insulation [dB]: Sound insertion loss value of the Air Handling Unit.
Heating capacity [kW]: Thermal energy supplied into the air per unit of time.
Cooling capacity [kW]: Thermal energy removed from the air per unit of time.
Heat recovery [%]: Heat transferred from exhaust air into supply air or reverse.
In-duct sound power level [dB]: Sound power level per octave band, radiated in the duct.
Airborne sound power level [dB(A)]: Sound power level radiated through the envelope of the Air Handling Unit.