§ 431.172 Definitions. *Air circulating axial panel fan* means an axial housed air circulating fan head without a cylindrical housing or box housing that is mounted on a panel, orifice plate or ring.
*Air circulating fan* means a fan that has no provision for connection to ducting or separation of the fan inlet from its outlet using a pressure boundary, operates against zero external static pressure loss, and is not a jet fan.
*Air circulating fan discharge area* means the area of a circle having a diameter equal to the blade tip diameter.
*Air circulating fan outlet area* means the gross inside area measured at the plane of the outlet opening.
*Air-cooled steam condenser* means a device for rejecting heat to the atmosphere through the indirect condensing of steam inside air-cooled finned tubes.
*Axial inline fan* means a fan with an axial impeller and a cylindrical housing with or without turning vanes.
*Axial panel fans* means an axial fan, without cylindrical housing, that includes a panel, orifice plate, or ring with brackets for mounting through a wall, ceiling, or other structure that separates the fan's inlet from its outlet.
*Basic model,* with respect to fans and blowers, means all units of fans and blowers manufactured by one manufacturer, having the same primary energy source, and having essentially identical electrical, physical, and functional (*e.g.,* aerodynamic) characteristics that affect energy consumption. In addition: ( 1 ) All variations of blade pitches of an adjustable-pitch axial fan may be considered a single basic model; and
( 2 ) All variations of impeller widths and impeller diameters of a given full-width impeller and full-diameter impeller centrifugal fan may be considered a single basic model.
*Box fan* means an axial housed air circulating fan head without a cylindrical housing that is mounted on a panel, orifice plate or ring and is mounted in a box housing.
*Centrifugal housed fan* means a fan with a centrifugal or mixed flow impeller in which airflow exits into a housing that is generally scroll-shaped to direct the air through a single fan outlet. A centrifugal housed fan does not include a radial impeller.
*Centrifugal inline fan* means a fan with a centrifugal or mixed flow impeller in which airflow enters axially at the fan inlet and the housing redirects radial airflow from the impeller to exit the fan in an axial direction.
*Centrifugal unhoused fan* means a fan with a centrifugal or mixed flow impeller in which airflow enters through a panel and discharges into free space. Inlets and outlets are not ducted. This fan type also includes fans designed for use in fan arrays that have partition walls separating the fan from other fans in the array.
*Cross-flow fan* means a fan or blower with a housing that creates an airflow path through the impeller in a direction at right angles to its axis of rotation and with airflow both entering and exiting the impeller at its periphery. Inlets and outlets can optionally be ducted.
*Cylindrical air circulating fan* means an axial housed air circulating fan head with a cylindrical housing that is not a Positive Pressure Ventilator as defined in AMCA 240-15 (incorporated by reference, see § 431.173).
*Evaporative field erected closed-circuit cooling tower* means a structure which rejects heat to the atmosphere through the indirect cooling of a process fluid stream to a lower temperature by partial evaporation of an external recirculating water flow.
*Evaporative field erected open-circuit cooling tower* means a structure which rejects heat to the atmosphere through the direct cooling of a water stream to a lower temperature by partial evaporation.
Fan or blower means a rotary bladed machine used to convert electrical or mechanical power to air power, with an energy output limited to 25 kilojoule (kJ)/kilogram (kg) of air. It consists of an impeller, a shaft and bearings and/or driver to support the impeller, as well as a structure or housing. A fan or blower may include a transmission, driver, and/or motor controller.
*Fan static air power* means the static power delivered to air by the fan or blower; it is proportional to the product of the fan airflow rate, the fan static pressure and the compressibility coefficient and is calculated in accordance with section 7.8.1 of AMCA 210-16 (incorporated by reference, see § 431.173), using fan static pressure instead of fan total pressure.
*Fan total air power* means the total power delivered to air by the fan or blower; it is proportional to the product of the fan airflow rate, the fan total pressure and the compressibility coefficient and is calculated in accordance with section 7.8.1 of AMCA 210-16 (incorporated by reference, see § 431.173).
*Field erected air-cooled (dry) cooler* means a structure which rejects heat to the atmosphere from a fluid, either liquid, gas or a mixture thereof, flowing through an air-cooled internal coil.
*Field erected evaporative condenser* means a structure which rejects heat to the atmosphere through the indirect condensing of a refrigerant in an internal coil by partial evaporation of an external recirculating water flow.
*Full-diameter impeller* means maximum impeller diameter with which a given fan or blower basic model is distributed in commerce.
*Full-width impeller* means the maximum impeller width with which a given fan or blower basic model is distributed in commerce.
*Housed air circulating fan head means* an air circulating fan with an axial or centrifugal impeller, and a housing.
*Housed centrifugal air circulating fan* means a housed air circulating fan head with a centrifugal or radial impeller in which airflow exits into a housing that is generally scroll shaped to direct the air through a single, narrow fan outlet.
*Induced flow fan* means a type of laboratory exhaust fan with a nozzle and windband; the fan's outlet airflow is greater than the inlet airflow due to induced airflow. All airflow entering the inlet exits through the nozzle. Airflow exiting the windband includes the nozzle airflow plus the induced airflow.
*Jet fan* means a fan designed and marketed specifically for producing a high velocity air jet in a space to increase its air momentum. Jet fans are rated using thrust. Inlets and outlets are not ducted but may include acoustic silencers.
*Packaged air-cooled (dry) cooler* means a device which rejects heat to the atmosphere from a fluid, either liquid, gas or a mixture thereof, flowing through an air-cooled internal coil.
*Packaged evaporative closed-circuit cooling tower* means a device which rejects heat to the atmosphere through the indirect cooling of a process fluid stream in an internal coil to a lower temperature by partial evaporation of an external recirculating water flow.
*Packaged evaporative condenser* means a device which rejects heat to the atmosphere through the indirect condensing of a refrigerant in an internal coil by partial evaporation of an external recirculating water flow.
*Packaged evaporative open-circuit cooling tower* means a device which rejects heat to the atmosphere through the direct cooling of a water stream to a lower temperature by partial evaporation.
*Power roof ventilator* means a fan with an internal driver and a housing to prevent precipitation from entering the building. It has a base designed to fit over a roof or wall opening, usually by means of a roof curb.
*Radial-housed fan* means a fan with a radial impeller in which airflow exits into a housing that is generally scroll-shaped to direct the air through a single fan outlet. Inlets and outlets can optionally be ducted.
*Safety Fan* means: ( 1 ) A reversible axial fan in cylindrical housing that is designed and marketed for use in ducted tunnel ventilation that will reverse operation under emergency ventilation conditions;
( 2 ) A fan for use in explosive atmospheres tested and marked according to the English version of ISO 80079-36:2016 (incorporated by reference, see § 431.173);
( 3 ) An electric-motor-driven-Positive Pressure Ventilator as defined in AMCA 240-15 (incorporated by reference, see § 431.173);
( 4 ) A fan bearing a listing for “Power Ventilators for Smoke Control Systems” in compliance with UL 705 (incorporated by reference, see § 431.173); or
( 5 ) A laboratory exhaust fan designed and marketed specifically for exhausting contaminated air vertically away from a building using a high-velocity discharge.
*Unhoused air circulating fan head* means an air circulating fan without a housing, having an axial impeller with a ratio of fan-blade span (in inches) to maximum rate of rotation (in revolutions per minute) less than or equal to 0.06. The impeller may or may not be guarded.
[88 FR 27389, May 1, 2023, as amended at 88 FR 53375, Aug. 8, 2023]