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Definitions: (1) ‘specific energy consumption (SEC)’ (expressed in kWh/(m2.a)) means a coefficient to express the energy consumed for ventilation per m2 heated floor area of a dwelling or building, calculated for RVUs in accordance with Annex VIII; (2) ‘sound power level (LWA)’ means the casing-radiated A-weighted sound power level expressed in decibels (dB) with reference to the sound power of one picowatt (1pW), transmitted by the air at reference airflow; (3) ‘multi-speed drive’ means a fan motor that can be operated at three or more fixed speeds plus zero (‘off’); (4) ‘variable speed drive (VSD)’ means an electronic controller, integrated or functioning as one system or as a separate delivery with the motor and the fan, which continuously adapts the electrical power supplied to the motor in order to control the flow rate; (5) ‘heat recovery system (HRS)’ means the part of a bidirectional ventilation unit equipped with a heat exchanger designed to transfer the heat contained in the (contaminated) exhaust air to the (fresh) supply air; (6) ‘thermal efficiency of a residential HRS (ηt)’ means the ratio between supply air temperature gain and exhaust air temperature loss, both relative to the outdoor temperature, measured under dry conditions of the HRS, and standard air conditions, with balanced mass flow, at reference flow rate, an indoor-outdoor temperature difference of 13 K, no correction for thermal heat gain from fan motors; (7) ‘internal leakage rate’ means the fraction of extract air present in the supply air of ventilation units with HRS as a result of leakage between extract and supply airflows inside the casing when the unit is operated at reference air volume flow, measured at the ducts; the test shall be performed for RVUs at 100 Pa, and for NRVUs at 250 Pa; (8) ‘carry over’ means the percentage of the exhaust air which is returned to the supply air for a regenerative heat exchanger according to the reference flow; (9) ‘external leakage rate’ means the leakage fraction of the reference air volume flow to or from the inside of the casing of a unit to or from the surrounding air when it is subjected to a pressure test; the test shall be performed at 250 Pa for RVUs and at 400 Pa for NRVUs, for both under and over pressure; (10) ‘mixing’ means the immediate recirculation or short-circuiting of airflows between discharge and intake ports at both the indoor and outdoor terminals so that they do not contribute to the effective ventilation of a building space, when the unit is operated at reference air volume rate; (11) ‘mixing rate’ means the fraction of extract airflow, as part of the total reference air volume, that recirculates between discharge and intake ports at both the indoor and outdoor terminals and thus does not contribute to the effective ventilation of a building space, when the unit is operated at reference air volume (measured at 1 m distance from the indoor supply duct), less the internal leakage rate; (12) ‘effective power input’ (expressed in W) means the electric power input at reference flow rate and corresponding external total pressure difference and includes the electrical demand for fans, controls (including remote controls) and the heat pump (if integrated); (13) ‘specific power input (SPI)’ (expressed in W/(m3/h)) means the ratio between the effective power input (in W) and the reference flow rate (in m3/h); (14) ‘flow rate/pressure diagram’ means a set of curves for flow rate (horizontal axis) and pressure difference of a unidirectional RVU or the supply side of a bidirectional RVU, where each curve represents one fan speed with at least eight equidistant test-points and the number of curves is given by the number of discrete fan speed options (one, two or three) or, in the case of a variable fan speed drive, includes at least a minimum, maximum and appropriate intermediate curve close to the reference air volume and pressure difference for SPI testing; (15) ‘reference flow rate’ (expressed in m3/s) is the abscissa value to a point on a curve in the flow rate/pressure diagram which is on or closest to a reference point at 70 % at least of the maximum flow rate and 50 Pa for ducted units and at a minimum pressure for non-ducted units. For bidirectional ventilation units, the reference air volume flow rate applies to the air supply outlet; (16) ‘control factor (CTRL)’ means a correction factor for the SEC calculation depending on the type of control that is part of the ventilation unit, according to the description in Annex VIII Table 1; (17) ‘control parameter’ means a measurable parameter or set of measurable parameters that are assumed to be representative of the ventilation demand, e.g. the level of relative humidity (RH), carbon dioxide (CO2), volatile organic compounds (VOC) or other gases, presence, motion or occupancy detection from infrared body heat or from reflection of ultrasonic waves, electrical signals from human operation of lights or equipment; (18) ‘manual control’ means any control type that does not use demand control; (19) ‘demand control’ means a device or set of devices, integrated or as a separate delivery, that measures a control parameter and uses the result to regulate automatically the flow rate of the unit and/or the flow rates of the ducts; (20) ‘clock control’ means a clocked (daytime-controlled) human interface to control the fan speed/flow rate of the ventilation unit, with at least seven weekday manual settings of the adjustable flow rate for at least two setback periods, i.e. periods in which a reduced or no flow rate applies; (21) ‘demand controlled ventilation (DCV)’ means a ventilation unit that uses demand control; (22) ‘ducted unit’ means a ventilation unit intended to ventilate one or more rooms or enclosed space in a building through the use of air ducts, intended to be equipped with duct connections; (23) ‘non-ducted unit’ means a single room ventilation unit intended to ventilate a single room or enclosed space in a building, and not intended to be equipped with duct connections; (24) ‘central demand control’ means a demand control of a ducted ventilation unit that continuously regulates the fan speed(s) and flow rate based on one sensor for the whole ventilated building or part of the building at central level; (25) ‘local demand control’ means a demand control for a ventilation unit that continuously regulates the fan speed(s) and flow rates based on more than one sensor for a ducted ventilation unit or one sensor for a non-ducted unit; (26) ‘static pressure (psf)’ means the total pressure minus the fan dynamic pressure; (27) ‘total pressure (pf)’ means the difference between the stagnation pressure at the fan outlet and that at the fan inlet; (28) ‘stagnation pressure’ means the pressure measured at a point in a flowing gas if it were to be brought to rest by means of an isentropic process; (29) ‘dynamic pressure’ means the pressure calculated from the mass flow rate and the average gas density at the outlet and the unit outlet area; (30) ‘recuperative heat exchanger’ means a heat exchanger intended to transfer thermal energy from one air stream to another without moving parts, such as a plate or tubular heat exchanger with parallel flow, cross flow or counter flow, or a combination of these, or a plate or tubular heat exchanger with vapour diffusion; (31) ‘regenerative heat exchanger’ means a rotary heat exchanger incorporating a rotating wheel for the purpose of transferring thermal energy from one air stream to the other, including material allowing latent heat transfer, a drive mechanism, a casing or frame, and seals to reduce bypassing and leakage of air from one stream or another; such heat exchangers have varying degrees of moisture recovery depending on the material used; (32) ‘airflow sensitivity to pressure variations’ of a non-ducted RVU is the ratio between the maximum deviation from the maximum RVU flow rate at + 20 Pa and that at – 20 Pa external total pressure difference; (33) ‘indoor/outdoor air tightness’ of a non-ducted RVU is the flow rate (expressed in m3/h) between indoors and outdoors when the fan(s) is(are) switched off; (34) ‘dual use unit’ means a ventilation unit designed for ventilation purposes as well as fire or smoke extraction, complying with the basic requirements for construction works with regard to safety in case of fire as set out in Regulation (EU) No 305/2011; (35) ‘thermal by-pass facility’ means any solution that circumvents the heat exchanger or controls automatically or manually its heat recovery performance, without necessarily requiring a physical airflow bypass (for example: summer box, rotor speed control, control of air flow);