ASHRAE

Term	Term Definition	Options	Unit of Measure
Built up	Customized assemblies built to suit a specific application	View	None
Centrifugal	A non-positive displacement compressor that depends, in part, on centrifugal forces for pressure rise. A turbocompressor. Centrifugal compressors supply the compression in water chillers cycles.	View	None
Centrifugal	A non-positive displacement compressor that depends, in part, on centrifugal forces for pressure rise. A turbocompressor. Centrifugal compressors supply the compression in water chillers cycles.	View	None
Cooling degree days	Cooling degree days are calculated as the sum of the differences between daily average temperatures and the base temperature, calculated at the ASHRAE base temperature of 65F. Use the Interval Frequency term to characterize whether the HDD calculation is for annual or monthly intervals	View	None
Dual	Configuration in which conditioned air at two temperatures and humidity levels are supplied through two independent duct systems to the points of usage where mixing may be carried out.	View	None
Evaporator pressure regulators	Automatic valve or control device used to maintain the pressure, and thereby the temperature, in an evaporator above a predetermined minimum. For instance, when mechanical or electronic regulators are used to maintain the suction temperature in the individual cases.	View	None
Gross	The sum of the floor areas of all the spaces within the premises with no deductions for floor penetrations other than atria. it is measured from the exterior faces of exterior walls or from the centerline of walls separating buildings but it excludes covered walkways, open-roofed over areas, porches and similar spaces, pipe trenches, exterior terraces or steps, roof overhangs, parking garages, surface parking, and similar features.	View	None
Heating degree days	Heating degree days are calculated as the sum of the differences between daily average temperatures and the base temperature, calculated at the ASHRAE base temperature of 50F. Use the Interval Frequency term to characterize whether the HDD calculation is for annual or monthly intervals	View	None
Induction units	Uses nozzles or the velocity of the primary air source to induce a flow of secondary air to be mixed with the primary air.	View	None
Occupant Activity Level	The activity level that drives the amount of internal gains due to occupants.	View	None
Parking	Enclosed, partially enclosed, or open parking premises including attached garage, underground parking, uncovered driveways or lots, and covered carports.	View	None
Photovoltaic	Photovoltaic (PV) systems derive energy from incoming solar radiation that is dependent on time, quality of sunlight, and the mounted pitch. PV arrays can exists as facade systems and roofing systems. Facade systems include curtain wall products, spandrel panels, and glazings. Roofing systems include tiles, shingles, standing seam products, and skylights with option for fixed-tilt (non-adjustable) or sun-tracking (adjustable). PV systems can also exist on a premises off of the building envelope such as on the ground, awnings or carports. Types of applications include thin-film or PV modules. This DC power can be used, stored in a battery system, or transformed into AC electricity.	View	None
R Value	The R-value, also known as thermal insulance, is the temperature difference per unit heat flux, at steady state, between two defined surfaces of a material or construction that induces one unit of heat flux between the surfaces. The R-value is used for comparing insulating values of different materials, for the specific thickness of the material. The higher the R-value, the greater a material's insulating properties and the slower heat flows through it. The R-value does not include the interior and exterior air film coefficients. The R-value is the reciprocal of the U-factor.	View	hr-ft2-F/Btu
Screw	A positive displacement rotary compressor that produces compression with two intermeshing helical rotors. A compressor that is a component of a vapor-compression refrigerating machine and is used to draw the refrigerant vapor from the evaporator and deliver it to the condenser.	View	None
Screw	A positive displacement rotary compressor that produces compression with two intermeshing helical rotors. A compressor that is a component of a vapor-compression refrigerating machine and is used to draw the refrigerant vapor from the evaporator and deliver it to the condenser.	View	None
Scroll	Positive displacement compressor in which the reduction in internal volume of the compression chamber is accomplished by an orbiting scroll (involute spiral) within a mating stationary scroll. A device for compressing air or refrigerant.	View	None
Scroll	Positive displacement compressor in which the reduction in internal volume of the compression chamber is accomplished by an orbiting scroll (involute spiral) within a mating stationary scroll. A device for compressing air or refrigerant.	View	None
Single	Configuration in which the air, having been conditioned, is distributed to various zones through a single duct.	View	None
Split	System consisting of equipment provided in more than one assembly or enclosure, usually with supply air-distribution equipment housed separately from refrigerant-condensing equipment.	View	None
Split condenser	Condenser comprising several heat-exchanging components operating on one or several refrigeration systems. For instance, valve is used to split the condenser loop to better control head pressure.	View	None
Thermal Conductance	A measure of a material's ability to conduct heat, defined as the heat flux through the material induced by a unit temperature difference between the surfaces of the material.	View	Btu/(hr-F)
Thermal Conductivity	A measure of a material's ability to conduct heat, defined as the amount of heat transferred per unit time, given a unit area of the material and a unit temperature gradient through the thickness of the material.	View	Btu/(hr-ft-F)
Three	Configuration in which hot, cold, and tempered conditioned air are supplied through independent duct systems to the points of usage where mixing may be carried out.	View	None
Unitary	Factory-made assemblies that normally include an evaporator or cooling coil and a compressor and condenser combination	View	None