Find a comprehensive list of terms and concepts that are essential for understanding the topics we cover. Use this glossary for clarifying terminology and enhancing your familiarity with key concepts.
A
- ACH (Air Changes per Hour)
- The number of times per hour that the air in a defined space is completely replaced with outside air.
- AHU (Air Handling Unit)
- Equipment that conditions air through heating, cooling, ventilation, and sometimes relative humidity that is often part of a larger, integrated heating, ventilating, and air–conditioning (HVAC) system.
B
- BAS (Building Automation System)
- A computer-based system that provides centralized automation and control access of building systems, typically for HVAC and lighting systems.
- BMS (Building Management System)
- See BAS.
- BTU (British Thermal Unit) (Btu)
- Btu, or British Thermal Unit is the measure of the heat content of fuels or energy sources. One Btu is the quantity of heat required to raise the temperature of one pound of liquid water by 1° Fahrenheit at the temperature that water has its greatest density (approximately 39° F).
- BTU/H (British Thermal Unit / Hour)
- Units for thermal power.
C
- CAV (Constant Air Volume)
- A constant air flow rate, which is characteristic of some air handling units.
- CCV (Cooling Coil Valve)
- A valve that controls how much chilled water passes through a cooling coil in an air handling unit.
- CFM (Cubic Feet per Minute)
- Air flow unit of measurement.
- ChW (Chilled Water)
- The water that is cooled by a chiller and supplied to cooling coils in air handling units used for space cooling.
- ChWLDP (Chilled Water Loop Differential Pressure)
- The difference in pressure between the supply and return piping of a chilled water loop.
- ChWLDP-SP (Chilled Water Loop Differential Pressure Set Point)
- The target differential pressure for the ChWLDP to achieve.
- CHWRT (Chilled Water Return Temperature)
- The temperature of the chilled water that returns to the chilled plant after traversing through the chilled water piping, air handling units, and other terminal devices.
- CHWST (Chilled Water Supply Temperature)
- The tempearture of the water that leaves from the chiller and supplied to the zones.
- COP (Coefficient of Performance)
- Efficiency of chillers (= power generated / power draw)
- CT (Current Transformer)
- Often used as "CT Sensor". Measures current (amps).
- CUNY BPL (City University of New York Building Performance Lab)
- City University of New York Building Performance Lab is this guide's author and non profit organization that works to advance high-performance building operations and practices in existing commercial and public buildings. Learn more.
- CW (Condenser Water)
- The water that is warmed by the condenser, pumped to heat rejection equipment such as cooling towers, and delivered back to the chiller plant.
- CWRT (Condenser Water Return Temperature)
- The temperature of the water exiting a chiller's condenser and pumped to heat rejection equipment, such as a cooling tower.
- CWST (Condenser Water Supply Temperature)
- The water supplied to a chiller's condenser.
- CWST-SP (Condenser Water Supply Temperature Set Point)
- The target temperature at which the condenser water is to be supplied to the chiller's condenser.
D
- DA RH (Discharge Air Relative Humidity)
- The relative humidity of the air that is supplied to ductwork flowing to zones after it has been conditioned by an air handling unit.
- DA RH-SP (Discharge Air Relative Humidity Set Point)
- The target relative humidity of the DA RH.
- DAT (Discharge Air Temperature)
- The temperature of the air that is supplied to ductwork flowing to zones after it has been conditioned by an air handling unit.
- DAT-SP (Discharge Air Temperature Set Point)
- The target temperature of the DAT.
- DCAS DEM (NYC Department of Citywide Administrative Services Division of Energy Management)
- The NYC Department of Citywide Administrative Services Division of Energy Management is the hub for energy management in City buildings. DCAS plays a critical role in supporting City agency partners' progress towards the City's major emissions reduction and energy objectives. Learn more.
- DCV (Demand Controlled Ventilation)
- A method ventilation control based on carbon dioxide (CO2) concentration.
- DOAS (Dedicated Outdoor Air System)
- An HVAC system designed to condition 100% outdoor air and deliver the air to other systems or spaces.
- DP (Dew Point Temperature)
- The temperature of a gas or liquid at which condensation or evaporation occurs.
- DSP (Duct Static Pressure)
- The pressure created in the air supply ductwork that varies primarily with supply fan speed and VAV damper positions. Duct static pressure is often measured about 2/3rds the distance from the air handling unit to the end of the ductwork.
E
- ECM (Energy Conservation Measure)
- Specifies measures that are expected to provide energy usage reductions, emissions reductions, and energy cost savings.
- EER (Energy Efficiency Report)
- A report that captures energy audit and retro-commissioning study findings and outlines recommended energy conservation measures (ECMs) for a specific building.
- ERO (Emissions Reduction Opportunities)
- A metric used by the LL97 IAP.
- ERV (Energy Recovery Ventilation)
- A ventilator that exchanges (recovers) the energy contained in exhaust air and uses it to treat (precondition) incoming outdoor air.
- EUI (Energy Use Intensity)
- The energy use per unit area per year for a given building.
H
- HCV (Heating Coil Valve)
- A valve that controls how much water passes through a heating coil in an air handling unit.
- HOBO (Onset HOBOware)
- Not an acronym, just the name of the product. BPL used various types of HOBOWare loggers.
- HumV (Humidification Valve)
- A control valve that responds to fluctuating humidification demand.
- HW (Hot Water)
- Water that is heated by a boiler or heat exchanger and pumped to any combination of heating equipment such as heating coils, fan coil units, zone reheats, and fin and tube perimeter systems.
- HWLDP (Hot Water Loop Differential Pressure)
- The difference in pressure between the supply and return piping of a hot water loop.
- HWLDP-SP (Hot Water Loop Differential Pressure Set Point)
- The target that is set for the HWLDP to achieve.
- HWRT (Hot Water Return Temperature)
- The temperature of the water that returns to the boiler or heat exchanger after being pumped to the various heating elements around the building.
- HWST (Hot Water Supply Temperature)
- The temperature of the water that leaves the boilder or heat exchanger and is supplied to the various heating elements in the building.
- HWST-SP (Hot Water Supply Temperature Set Point)
- The target temperature for the HWST to achieve.
K
- kW (Kilowatt)
- A Kilowatt is the measure of electrical power equivalent to 1,000 watts.
- kWh (Kilowatt Hour)
- A Kilowatt Hour is the measure of electrical energy delivered by one kilowatt for one hour.
L
- LDP (Loop Differential Pressure)
- The difference in pressure between the supply and return pressures in the piping of a chilled or hot water loop.
- LDP-SP (Loop Differential Pressure Set Point)
- The target differential pressure for the LDP to achieve.
- LM (Load Management)
- Helps City agencies optimize building energy usage during regular operating periods, not just periods of peak demand, through ongoing operational improvements. Reducing energy consumption with low cost implementations (e.g. changing the controls of a boiler to turn on only at 55 degrees instead 60).
M
- MAT (Mixed Air Temperature)
- The temperature of the air that results from the mixture of outside air and return air in an air handler or rooftop unit.
- MEP (Mechanical, Electrical, Plumbing)
- Contruction drwaings that include HVAC, electrical, and plumbing systems and their relevant schedules.
- MTCO2e (Metric Ton of Carbon Dioxide Emissions)
- Unit used to characterize carbon emissions and greenhouse gases.
- M&V (Measurement and Verification)
- M&V stands for Measurement and Verification. It is the process of quantifying the resulting energy savings from the implementation of energy conservation measures within an individual property.
- MW (Megawatt)
- A Megawatt is the measure of electrical power equivalent to 1,000 kilowatts or 1,000,000 watts.
O
- OAD (Outdoor Air Damper)
- A damper that controls the amount of outside air that enters the building.
- OAF (Outdoor Air Fraction)
- The percentage of outside air in mixed and discharge air. Calculated through this formula: Percentage of fresh air intake = (MAT - RAT) / (OAT - RAT).
- OAT (Outdoor Air temperature)
- Temperature of the air outside the building. Per ASHRAE Terminology, Outdoor air is "(1) air outside a building or taken from the external atmosphere and, therefore, not previously circulated through the system. (2) ambient air that enters a building through a mechanical ventilation system, through intentional openings for natural ventilation, or by infiltration."
P
- PTAC (Packaged Terminal Air Conditioner)
- A unit that provides both heating (by hot water, steam, or electricity) and cooling to a single room or zone.
- PV (Photovoltaic)
- Photovoltaic.
R
- RA RH (Return Air Relative Humidity)
- The relative humidity of the air that returns to the air handling unit or rooftop unit after it has passed through the zones.
- RA RH-SP (Return Air Relative Humidity Set Point)
- The target relative humidity of the RAT.
- RAT (Return Air Temperature)
- The temperature of the air that returns to the air handling unit or rooftop unit after it has passed through the zones.
- RAT-SP (Return Air Temperature Set Point)
- The target temperature of the RAT.
- RFM (Refrigeration Machine)
- Chillers are sometimes abbreviated at a RFM
- RH (Relative Humidity)
- Ratio of the actual water vapor density to the saturation water vapor density.
- RTM (Real Time Metering)
- Monitoring technology that captures power usage information in near real–time intervals and transmits that data to be displayed via a web–based EIS platform. Helps City agencies gain access to near real–time energy data.
- RTU (Roof Top Unit)
- A packaged air conditioner installed on the roof of a building that provides heating and cooling, usually using gas burners and a direct expansion system (vapor compression refrigeration cycle).
S
- SAT (Supply Air Temperature)
- Supply Air Temperature (see DAT).
- SOO (Sequence of Operations)
- The control sequence of any system (e.g. at 50 degrees, turn on).
T
- True Power (True RMS Power)
- The true root-mean-square power or heating potential of an applied voltage.
V
- VAV (Variable Air Volume)
- A terminal unit that supplies variable airflow, typically using a modulating damper.
- VFD (Variable Frequency Drive)
- Makes a constant speed motor variable. Very common ECM.
Z
- ZT (Zone Temperature)
- The space temperature observed by the thermostat of a particular zone in a building.
- ZT-SP (Zone Temperature Set Point)
- The target temperature of the zone.
- ZT-SP(A) (Zone Temperature Set Point - Air)
- The zone temperature setpoint that controls the air system in a room that is also served by a perimeter system.
- ZT-SP(P) (Zone Temperature Set Point - Perimeter)
- The zone temperature setpoint that controls the perimeter system in a room that is also served by an air system.
