Glossary of Maintenance Terms
A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, and Z

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A

Access Control. The process of granting or denying connectivity to system resources. Security safeguards allow different types of access to authorized individuals (e.g., read, write, administrative, etc.). 12

Actuator. A device that converts an electrical control signal to the physical movement of a damper. 10

Advanced Metering Infrastructure (AMI). An integrated system of smart meters, communications networks, and data- management systems that enables two-way communication between utilities and customers.

Advanced Metering System. A system that collects time-differentiated energy or water usage data from advanced meters via a network system on either an on-request or defined schedule basis. The system is capable of providing usage information on at least a daily basis and can support desired features and functionality related to energy-use management, procurement, and operations. 7

Advanced Meters. Advanced meters are those that have the capability to measure and record interval data (at least hourly for electricity) and communicate the data to a remote location in a format that can be easily integrated into an advanced metering system. EPAct 2005 Section 103 requires at least daily data-collection capability. 7

Air Change Rate. Airflow in volume units per hour divided by the building space volume in identical volume units - normally expressed in air changes per hour (ACH or ACPH). 11

Air Conditioning. The process of treating air to control its temperature, humidity, and cleanliness while distributing it to cool building space. 7

Air Infiltration. Uncontrolled inward leakage of air, that which may contain entrained water vapor, through cracks and interstices in any building element and around windows and doors of a building, caused by the pressure effects of wind or the effect of differences in the indoor and outdoor air density. 11

Air-Handling Unit (AHU). Equipment used to distribute the conditioned air to a space; includes heating and cooling coils, fans, ducts, and filters. 10

Air-Side Economizer. An opening in the supply-air ductwork with an operable damper, a filter, and a fan. It operates by substituting some outside air for building return air. The outside air is then used either directly, for cooling, or to supplement a conventional cooling system.  Often just called an economizer when used with rooftop units. 10

Annual Fuel Utilization Efficiency (AFUE). A measure of the efficiency of heating equipment that accounts for fuel-burning losses, flue losses, off-cycle losses, and equipment-jacket losses. 10

Application Service Provider (ASP). Third-party entities that manage and distribute software-based services and solutions to customers across a wide-area network from a central data center. 7

Apprentice. A tradesperson (or craftsperson) in training. 3

Asset Management. The systematic planning and control of a physical resource throughout its life. This may include the specification, design, and construction of the asset, its operation, maintenance, and modification while in use, and its disposal when no longer required. 3

Asset. Maintenance term commonly taken to be any item of physical plant or equipment. 3

Authentication. The ability to verify the identity of a user or device before allowing access to an information system. 12

Automated Fault Detection and Diagnostics (AFDD). Software products that can automatically identify (detect) deviations from normal or expected operation (faults), and resolve (diagnose) the type of problem or its location. 9

Automated Meter Reading (AMR). A form of advanced (or enhanced) metering that uses communications devices to communicate data from the meter to the meter data-management provider. AMR may be used to transmit simple energy-use data from the meter, or to transmit more complex measures of energy recorded in the meter, or and to implement advanced functionality, such as outage detection or remote programming. 7

Availability. The proportion of total time that an item of equipment is capable of performing its specified functions, normally expressed as a percentage. It can be calculated by dividing the equipment's available hours by the total number of hours in any given period or its scheduled run time. 3

Available Hours. The total number of hours that an item of equipment is capable of performing its specified functions. It is equal to the total hours in any given period, less the downtime hours. 3

Average Demand. The demand on, or the power output of, an electric system or any of its parts over an interval of time, is determined by dividing the number of kilowatt hours by the number of hours in the interval. 7

Average Life. How long, on average, a component will last before it suffers a failure. This is commonly measured by Mean Time Between Failures. 3

Avoided Cost. The total economic costs consisting of the capital and operating costs to provide generation capacity and fuel, transmission, storage, distribution, and customer service to serve end-use energy requirements using a given set of resources. These costs are referred to as “avoided” when an alternative set of resources is used to serve requirements. A better term for these costs would be “avoidable cost.” Avoided The avoided cost must be determined to assess the cost-effectiveness of potential supply-side and demand-side resources. 7

Axial Fan. A type of fan that consists of a cylindrical housing with the impeller mounted inside along the axis. The impeller consists of blades mounted around a central hub similar to an airplane propeller. 10

B

Backlog. Work that has not been completed by the nominated 'required-by date.' The period for which each work order is overdue is defined as the difference between the current date and the 'required-by date. 3

Balancing. Process of measuring and adjusting equipment to obtain desired flows. Applies to both air‑side and water-side systems. 10

Base Load. The minimum average electric load over a given period of time. 7

Baseline. An initial performance level established to track improvements over time. 10

Basis of Design. A document that records the design criteria and assumptions upon which the design is based. 8

Baud Rate. The rate of speed at which information is transmitted over communications lines; expressed in bits per second. 7

Bathtub Curve. A graphical representation of maintenance failure probability whereby the probability begins higher, reduces to a low point, remains constant, and then increases as the component nears the end of its useful life. 3

Benchmarking (buildings/systems). Comparing building energy performance to that of similar buildings (cross-sectional benchmarking) or its own historic performance (longitudinal benchmarking). Benchmarking may be performed at the system or component level. 4

Best Practice. A practice that leads to superior performance in a specific process. 6

Billing Demand. The demand for which a customer is billed. Since billing demand is based on the provisions of a rate schedule or contract, it does not necessarily equal the actual measured demand of the billing period. 7

Blowdown. The discharge of water from a system to remove precipitated solids. 10

Boiler. A pressure vessel designed to transfer heat produced by combustion or electric resistance to a fluid. In most boilers, the fluid is water in the form of liquid or steam. 10

Breakdown. A specific type of failure, where an item of plant or equipment is completely unable to function. 3

Breakdown Maintenance. Maintenance performed in response to a breakdown; typically costs between two and four times as much compared to the same maintenance performed in a planned mode. 6

British Thermal Unit (Btu). A commonly used unit of energy, especially for fuels or heat and defined as the quantity of heat required to raise one pound of water by one degree Fahrenheit. 7

Building Automation System (BAS). A system of digital controllers, communication architecture, and user interface that monitors and controls a building’s mechanical and electrical equipment such as heating, ventilation, and air conditioning (HVAC); lighting; fire protection; vertical transport systems; and irrigation systems. The system can be used to optimize facility operation and reduce energy consumption. Also known as a Building Control System (BCS), Energy Management System (EMS), and Building Management System (BMS). 4

Building Commissioning. The systematic process for achieving, verifying, and documenting that the performance of facilities and its equipment meet the design intent. The process extends through all phases of a project and culminates with occupancy and operation. The process includes the testing and accepting of new or repaired building, system, or component parts to verify proper installation. 8

Building Envelope. The exterior surfaces of a building, such as the roof, walls, windows, doors, etc., that are exposed to climatic conditions. 7

Building Re-Tuning™. Defined as a systematic process to identify operation problems by leveraging data collected from the BAS and correcting those problems at no-cost or low-cost. 13

C

Calibration. A scheduled maintenance task characterized by the measurement of output values or system performance in comparison to a standard to known accuracy. 9

Capacity (electrical). The maximum quantity of electrical output for which a supply system or component is rated. 7

Carbon Dioxide (CO₂). Colorless, odorless, incombustible gas formed during respiration, combustion, and organic decomposition. Increasing levels of CO₂ in the atmosphere contribute to the global warming phenomenon. 10

Carbon Monoxide (CO). Colorless, odorless, poisonous gas formed during incomplete combustion of fuel. 10

Central HVAC System. An entire HVAC system that serves a whole building, such as a chiller or boiler. 10

Central Plant. Centrally located equipment that satisfies a building’s cooling and heating loads. 10

Centrifugal Fan. A type of fan consisting of a rotating wheel, or impeller, mounted inside around housing. The impeller is driven by a motor, which is usually connected via a belt drive. 10

Chilled-Water Reset. The practice of increasing chilled water temperature to raise chiller efficiency. 10

Chiller. A mechanical device that generates cold liquid that is circulated through cooling coils to cool the air supplied to a building. 10

Coefficient of Performance (COP). A measure of either full- or part-load efficiency for heating or cooling equipment, where a higher value designates a more efficient system. For heating systems, it is the ratio of the rate of heat output to the energy input. For cooling systems, it is the ratio of the rate of heat removal to the energy input.

Coefficient of Utilization (lighting). The ratio of lumens on the work surface to total lumens emitted by the lamps. 9

Coil. A heat exchanger element typically coupled with a fan is used to transfer heat to or from a heating or cooling system. 10

Coincident Demand. Two or more demands that occur during the same time interval. Often used to express the demand level of subgroups of customers that occurs at the time of the electric system’s overall maximum peak demand. 7

Collateral Equipment. Encompasses building-type equipment, built-in equipment, and large, substantially affixed equipment/property and is normally acquired and installed as part of a facility project. 8

Color Rendering Index (CRI). The color appearance of an object under a light source as compared to a reference source. 9

Combustion Air. Air that supplies the oxygen required to burn fuel. 10

Commissioning. A systematic process of ensuring, using appropriate verification and documentation, during the period beginning on the initial day of the design phase of the facility and ending not earlier than 1 year after the date of completion of construction of the facility, that all facility systems perform interactively in accordance with the design documentation and intent of the facility and the operational needs of the owner of the facility, including preparation of operation personnel; and the primary goal of which is to ensure fully functional systems that can be properly operated and maintained during the useful life of the facility. 16

Commissioning Plan. A document that outlines the organization, scheduling allocation of resources, and documentation pertaining to the overall commissioning process. 8

Component. A subassembly of a device or system, usually removable in one piece and interchangeable with other, standard components. 3

Computerized Maintenance Management System. A computerized system to assist with the effective and efficient management of maintenance activities through the application of computer technology. It generally includes elements such as a computerized work order system, capabilities for scheduling routine maintenance tasks, recording and storing standard jobs, bills of materials, applications parts lists, and equipment manuals. 2

Condensate. Water obtained by changing the state of water vapor (i.e., steam or moisture in the air) from a gas to a liquid usually by cooling. 9

Condenser. A heat exchanger which removes heat from vapor, changing it to its liquid state. In refrigeration systems, this is the component that rejects heat. 9

Condenser Coil. A heat exchange element in the form of a pipe or tube that is used to condense refrigerant from a gas to a liquid. 10

Condenser-Water Reset. The practice of decreasing condenser water temperature to obtain higher chiller efficiency. 10

Condition-Based Maintenance. An equipment maintenance strategy based on measuring the condition of equipment to assess whether it will fail during some future period, and then taking appropriate action to avoid the consequences of that failure. The condition of equipment could be monitored using Condition Monitoring, Statistical Process Control techniques, monitoring equipment performance, or using Human Senses. The terms Condition-Based Maintenance, On‑Condition Maintenance, and Predictive Maintenance can be used interchangeably. 3

Condition Monitoring. The use of specialist equipment to measure the condition of equipment. Vibration Analysis, Oil analysis and Thermography are all examples of Condition Monitoring techniques. 3

Conditional Probability of Failure. The probability that an item will fail during a particular age interval, given that it survives to enter that age. 3

Conduction. Heat flow through a material from hot to cold. 10

Connected Lighting Systems. A lighting system that is connected to a network for the transmission of data and the control of devices. 12

Constant volume (CV). A type of air-distribution system that circulates a CV of air to the conditioned space regardless of the demands of the space. 10

Constant-Volume, Variable-Temperature (CVVT). A type of air-handling system that adjusts or resets the temperature of the supply air. 10

Continuous Improvement. A process of constantly making a system, process, or organization better. 9

Convection. Transferring heat by moving air or by means of the upward motion of particles of liquid or gas. 10

Cooling Coil. A heat exchange element in the form of a pipe or tube with warm air on the outside and refrigerant on the inside that is used to cool air under forced convection with or without dehumidification. May consist of a single coil section or several coil sections assembled into a bank. 10

Cooling Load. The amount of heat a cooling system must remove per unit of time to maintain the indoor design temperature and humidity level, typically measured in Btu/hour or tons. 10

Cooling Tower. A device in water-cooled systems that transfers heat from warm water to the outside air through evaporation. 10

Cooling Tower Fan. A fan that is used to draw air through the cooling tower to carry away water vapor. 10

Component. A subassembly of an asset, usually removable in one piece and interchangeable with other, standard components. 9

Condition Assessment. Condition assessment is the inspection and documentation of the material condition of facilities and equipment, as measured against the applicable maintenance standard. It provides the basis for long-range maintenance planning as well as annual work plans and budgets. 8

Condition-Based Maintenance (CBM). Facility and equipment maintenance scheduled only when the condition of the facility or equipment requires it. CBM replaces maintenance scheduled at arbitrary time or usage intervals. It usually involves the application of advanced technology to detect and assess the actual condition. 8

Condition Monitoring (also known as Predictive Maintenance). The continuous or periodic monitoring and diagnosis of systems and equipment in order to forecast failure. 8

Constant Dollars. Monetary value based on the purchasing power within the base year—inflationary impacts are not reflected in the value of the constant dollars. 7

Continuity of Operations (COOP). An effort to ensure primary mission-essential functions continue to be performed during a wide range of emergencies, including localized acts of nature, accidents, and technological or attack-related emergencies. 1

Control. Any manual or automatic device designed to regulate the operation of a system or system component. 7

Cooling Loads. The energy required to achieve the desired (space cooling) temperature level. 7

Corrective Maintenance. Any maintenance activity which is required to correct a failure that has occurred or is in the process of occurring. This activity may consist of repair, restoration, or replacement of components. 3

Cost Avoidance. In reference to energy efficiency, the implementation of energy saving measures will result in a dollar savings which will offset any fuel price increase. 7

Cost-Effective. The present value (PV) of the benefits of the potential resource under consideration over the planning period are greater than the PV of its costs. Cost-effectiveness is always measured relative to an alternative. Cost-effectiveness can be measured from a variety of perspectives, which vary in terms of the specific costs and benefits included in the calculation. 7

Criticality. A relative-importance measure of the consequences of failure of a function or asset. 1

Critical Failure. A failure involving a loss of function or secondary damage that could have a direct adverse effect on operating safety, on mission, or have significant economic impact. 8

Critical Failure Mode. A failure mode that has significant mission, safety or maintenance effects that warrant the selection of maintenance tasks to prevent the critical failure mode from occurring. 8

Critical Functions. The operations and activities required to enable a critical mission (e.g., a data center’s critical function is to process data for scientific analysis). Critical functions are enabled by assets (e.g., a chiller is an asset that provides cooling to allow the data center to meet its critical function). 1

Critical Infrastructure. Systems and assets so vital to an organization that the incapacity or destruction of such may have a debilitating impact on security, economy, public health or safety, environment, or any combination of these matters. 12

Critical Mission. A mission of such high importance that its incapacitation or destruction would have a severely degrading effort on the ability of the agency to execute the tasks or mission-essential tasks it supports in all operating environments. A critical mission is supported by critical functions, which are enabled by assets (e.g., facilities, systems, equipment, and resources). 1

Critical Spares. Spare parts that have especially high value and/or long lead times and usually carried in stock to prevent excessive downtime in case of a breakdown. 6

Craftsperson. A skilled maintenance worker who has typically been formally trained through an apprenticeship program. 3

Cubic Feet per Minute (CFM). Usually refers to the volume of air being moved through an air duct. 9

Current Replacement Value (CRV). Approximate cost to replace an existing facility in its present form. The CRV is calculated by escalating facility and its equipment acquisition cost, and any incremental book value changes of $5,000 or more, to present-year dollars. 8

Cybersecurity. The activity or process of protecting electronic information and communication systems from unauthorized use or modification, or exploitation. 12

Cybersecurity Framework. A risk-based approach to managing cybersecurity risk. Typically developed for an entire organization, individual buildings, or critical assets. 12

Cycling. The non-continuous operation of equipment. 10

D

Dampers. Single- or multiple-blade devices that open or close either manually or automatically to control the flow of air through an HVAC system. 10

Defect. A potential failure or other condition that will require maintenance attention at some time in the future, but which is not currently preventing the equipment from fulfilling its functions. 3

Deferred Maintenance (DM). Maintenance that was not performed when it should have been or was scheduled to be and which, therefore, is put off or delayed for a future period. 8

Degree Day. A measure of the heating or cooling load on a building relative to a “base” outdoor air temperature (e.g., 65°F). It is commonly calculated as the difference between the mean daily temperature and the “base” temperature. 7

Degree-Days (cooling). The difference between the average temperature of any given day and a base temperature when the median temperature of the given day is higher than the base temperature. 7

Degree-Days (heating). The difference between the average temperature on any given day and a base temperature when the median temperature of the given day is less than the base temperature. Often the base temperature selected is 65°F. 7

Dehumidification. The process of removing moisture usually from an air stream. 7

Demand. The rate at which electricity is delivered by a system to a set of loads. It is measured in kilowatts, kilovolt amperes, or other suitable unit at a given instant or averaged over a designated timeframe. 7

Demand-Controlled Ventilation (DCV). An HVAC control system that varies the amount of outside air introduced to a building based on the internal concentration of CO₂ (an indication of building occupancy) to reduce the energy necessary to heat, cool, and dehumidify ventilation air. 10

Desiccant. A material that absorbs moisture from another material. In HVAC systems, desiccants absorb moisture from the air. 10

Design Intent. A narrative description of systems equipment and their intended modes and sequences of operation. 8

Dew Point Temperature. The temperature level in which the moisture in the air begins to condense. 7

Digitally Addressable Lighting Interface (DALI). A protocol that enables a computer to communicate with individual lighting fixtures that are equipped with DALI-compatible ballasts.

Dimmer. A device used to control the intensity of a lamp’s emitted light by controlling the voltage or current available to power the lamp. 10

Discount Rate.  The interest rate used to adjust a future cash flow to its PV. 10

Distributed Control System (DCS). Part of a control system; refers to control achieved by intelligence that is distributed through the process to be controlled, rather than through a centrally located single unit. A DCS includes both software and hardware components. 12

Domestic Hot Water System (DHW). A system designed to provide hot water for domestic and commercial purposes other than space heating and process application requirements. The energy required for a DHW system will vary according to building size, design, and human needs. 7

Dominant Failure Mode. A single failure mode that accounts for a significant portion of the failures of a complex item. 8

Downtime.  The time that an item of equipment is out of service, as a result of equipment failure. The time that an item of equipment is available, but not utilized is generally not included in the calculation of downtime. 3

Dry Bulb Temperature. The temperature level as measured on a standard thermometer. 7

Dual-Duct System. A constant-volume system that consists of two independent systems, one warm and one cool, which circulate air through all sections of the building via a parallel set of ducts. 10

Ductwork. A series of ducts for distribution and extraction of air. 7

E

Economic Life. The total length of time that an asset is expected to remain actively in service before it would be less expensive to replace the equipment rather than continuing to maintain it. 3

Economizer Cycle. A method of operating a ventilation system to reduce cooling load. Whenever the outside air conditions are more favorable (lower heat content) than return air conditions, outdoor air quantity is increased. 9

Effective Maintenance. The application of the maintenance approach that will produce the required availability, at the lowest cost, without compromising human safety or health, the environment, or any other conditions the organization specifies. 8

Efficacy (lighting). Ratio of total luminous flux emitted by a lamp divided by the total lamp power input, expressed in lumens per watt. 10

Efficiency. The ratio of power output to power input. 10

Emergency Maintenance Task. A maintenance task carried out to avert an immediate safety or environmental hazard, or to correct a failure with significant economic impact. 3

Emergency Maintenance. A maintenance task carried out to avert an immediate safety or environmental hazard, or to correct a failure with significant economic impact. 3

Emergency. A type of equipment problem where a breakdown has occurred, and immediate attention is required and usually involves safety, health, or critical process integrity. 6

Emission Factor. The ratio of emissions to energy produced or fuel consumed, denominated in units of tons of emissions per unit of energy. 7

End Use. A stand-alone energy using system or device. 7

End-Use (energy). Useful work, such as light, heat, and cooling, which is produced by electricity or other forms of energy. 7

Energy Audit. Analysis of a facility’s electricity and other energy usage, often including recommendations to alter the customer’s electric demand or reduce energy usage. An audit usually is based on a visit by an energy analyst or engineer to the home, building, or manufacturing or agricultural facility. 7

Energy Information System (EIS). Software, data acquisition hardware, and communication systems used to store, analyze, and display building energy data. 4

Energy Management and Information System (EMIS). Comprise a broad family of tools and services to manage building energy use. These technologies offer a mix of capabilities to store, analyze, and display energy use and system data, and in some cases, provide control. EMIS is an umbrella term that covers both meter-level and system-level function. 4

Energy Management System (EMS). A control system that monitors the environment and energy usage in a building and alters equipment operation to conserve energy while providing occupant comfort. 10

Energy Savings. A reduction in energy use from a specific action or set of actions, often quantified by accounting for key normalization factors such as weather or hours of operation. 4

Energy Savings Performance Contract (ESPC). An investment tool that allows organizations to procure energy savings and facility improvements with no up-front capital costs or special appropriations. An ESPC is a partnership between an organization/agency and an energy service company. 1

Energy Service Company (ESCO). A company that develops, designs, builds, and funds projects that save energy, reduce energy costs, and decrease operations and maintenance costs at their customers' facilities. In general, ESCOs act as project developers for a comprehensive range of energy conservation measures and assume the technical and performance risks associated with a project. 1

Energy Use Intensity (EUI). A metric of annual energy use per floor area that is commonly used in benchmarking energy-use data. 4

Energy. The capacity for doing work as measured by the capability of doing work (potential energy) or the conversion of this capability to motion (kinetic energy). 7

Energy-Efficiency Ratio (EER). A measure of full-load efficiency at 95°F outside air temperature in units of Btu/watt-hour. 10

Engineering Work Order. The prime document used to initiate an engineering investigation, engineering design activity, or engineering modifications to an item of equipment. 3

Estimated Plant Replacement Value. The estimated cost of capital works required to replace all the existing assets with new assets capable of producing the same quantity and quality of output. This is a key value often used in benchmarking activities. 3

Evaporator. Heat exchanger in a refrigeration system that absorbs heat from chilled water or building air, thus reducing the supply temperature. 10

Exhaust Air. Air removed from a space and discharged outside (i.e., not reused again) the building by ventilation systems. 11

Existing Building Commissioning (EBCx). A systematic process for investigating, analyzing, and optimizing the performance of building systems through the identification and implementation of low-/no-cost and capital-intensive facility improvement measures and ensuring their continued performance. The goal of EBCx is to make building systems perform interactively to meet the current facility requirements and provide the tools to support the continuous improvement of system performance over time. The term EBCx is intended to be a comprehensive term defining a process that encompasses the more narrowly focused process variations such as retro-commissioning, re‑commissioning and ongoing commissioning that are commonly used in the industry. 14

Expert System.  A software-based system which makes or evaluates decisions based on rules established within the software. Typically used for fault diagnosis. 3

F

Facilities Condition Index (FCI).  A unitless-less number which or percentage which expresses the amount of DM divided by the CRV of the facility being evaluated. A FCI can exist for a single property or a collection of properties. FCI can be expressed on a scale of 1 to 5 (where 5 is excellent, no DM) as reported by NASA to the opposite where 1 is excellent. Other agencies and organizations report FCI on a scale of 0 to 100 percent. 8

Facilities Maintenance. The recurring day-to-day work required to preserve facilities (buildings, structures, grounds, utility systems, and installed equipment) in such a condition that they may be used for their designated purpose over an intended service life. It includes the cost of labor, materials, and parts. 8

Fail-Safe. An item is fail-safe if, when the item itself incurs a failure, that failure becomes apparent to the operating workforce in the normal course of events. 2

Failure Code. A code typically entered against a Work Order which indicates the cause of failure (e.g., lack of lubrication, metal fatigue, etc.). 2

Failure Consequences. The implications of all failures can be classified as being either: Hidden, Safety, Environmental, Operational, or Non-Operational. 3

Failure Effect. A description of the events that occur after a failure has occurred because of a specific action or anomaly. 3

Failure Mode and Effects Analysis (FMEA). Analysis used to determine what parts fail, why they usually fail, and what effect their failure has on the systems in total. 8

Failure Mode, Effects, and Criticality Analysis (FMECA). An extension of FMEA. In addition to the basic FMEA, it includes a criticality analysis, which is used to chart the probability of failure modes against the severity of their consequences. The result highlights failure modes with relatively high probability and severity of consequences, allowing remedial effort to be directed where it will produce the greatest value. 8

Failure Mode. Any event which causes a failure. 3

Failure Rate. The number of failures divided by an interval such as time or cycles. The failure rate will change over time and can be greater than one (but will never be less than zero). 8

Failure. A cessation of proper function or performance, or an inability to meet a standard, or a nonperformance of what is requested or expected. 8

Fan Coil. A device that combines a heat exchanger and a fan in a single unit that conditions air by forced convection. 10

Fault Detection and Diagnostics (FDD).  Software products that can automatically identify (detect) deviations from normal or expected operation (faults), and resolve (diagnose) the type of problem or its location. 4

Fault. A lack in the functioning of an item due to failure or human operation. 3

Firewall. A system designed to prevent unauthorized access to or from a private network. Firewalls can be implemented in both hardware and software, or a combination of both. 7

Foot Candle. The illumination at a distance of one foot from a standard candle, or one lumen per square foot. 9

Function. Defined performance standard. Usually quantitative in nature (e.g., flow rate, cooling capacity). 8

Functional Failure. The inability of an item of equipment to fulfill one or more of its functions. Interchangeably used with Failure. 3

Functional Performance Test. A full range of checks and tests carried out to determine whether all systems, subsystems, and components function in accordance with the design intent. 8

G

Gateway. In Local Area Networks (LANs), a computer system and its associated software that permit two networks using different protocols to communicate with each other. A gateway translates all protocol levels from physical layer up through applications layer and can be used to interconnect networks that differ in every detail. 7

H

Hazard. A natural or accident-based driver of potential disruption of a site’s mission(s). Examples of the former include earthquakes, storms, and wildfires. Examples of the latter include dam failures, train derailments, and industrial accidents. Sometimes the hazard refers to the probability of a hazard being realized. 1

Healthy Building. There is no consensus on the definition of a healthy building. The World Health Organization defines health as “…a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity.” A healthy building is one that does not inflict or provoke medical issues such as Sick Building Syndrome allergies, asthma, or heat exhaustion and goes beyond that to promote and optimize occupants’ productivity, performance, and satisfaction.

Heat Exchanger. A device that transfers heat from one fluid to another. 10

Heat Pump. A device that uses the vapor compression refrigeration cycle to move heat from one area to another. It can deliver cooling or heating to a space by reversing the flow of refrigerant. 10

Heating Coil. Heat exchanger that heats air under forced convection. May consist of a single coil section or several coil sections assembled into a bank. 10

Heating Load. The amount of heat a heating system must provide per unit of time to maintain the indoor design temperature level, typically measured in Btu/hour. 10

HEPA Filter. High Efficiency Particle Air (HEPA) filter with an efficiency of 99.97 percent% removal of particulates larger than 0.30 microns. 11

High Potential (Hi Pot) Testing. The process of applying high voltage to electrical components (typically motors) to verify a lack of leakage current and unsafe conditions. 9

Hourly Metering.  A type of interval metering where the measurement or recording of customer use is collected in 6-minute intervals. The competitive metering model is based upon the implementation of hourly metering of customers or the application of load profiles, which average customer use over hourly periods. 7

I

Incremental Cost. The difference in costs between two alternatives, for example, between that of an efficient technology or measure and the standard technology. 7

Indoor Environmental Quality (IEQ). The conditions inside the building. It includes air quality, but also access to daylight and views, pleasant acoustic conditions, and occupant control over lighting and thermal comfort. It may also include the functional aspects of space such as whether the layout provides easy access to tools and people when needed and whether there is sufficient space for occupants. 15

Industrial Control System (ICS). An information system used to control industrial processes such as manufacturing, product handling, production, and distribution or to control infrastructure assets. 12

Infant Mortality Rate. The first stage of the product life cycle in use, characterized by high but declining failure rate. 8

Infant Mortality. Refers to the relatively high conditional probability of failure during the period immediately after an item begins first operation or returns to service. 3

Infectious Aerosol. A system of liquid or solid particles uniformly distributed in a finely divided state through a gas, usually air, where the particles are small and buoyant enough to behave much like a gas, yet they can be filtered out of the gas. 11

Infiltration. Air that leaks into a building through the building shell. 10

Information Technology (IT). Any equipment or interconnected system or subsystem of equipment that transmits, receives, processes, stores, or interchanges data or information electronically. IT includes computers, software, firmware, networks, services (including support services), and related resources. 12

Infrared Thermography. A predictive maintenance and inspection technique that uses infrared imaging to identify defects in electrical and electro-mechanical devices such as fuse boxes, circuit breakers, and switchgear. It also can be used effectively in a non-predictive manner to detect thermal cavities and leaks in walls, ceilings, and rooftops, the correction of which can result in sizeable reductions in heating and air conditioning expenses. Thermal imaging is extremely sensitive, and since it evaluates the heat an object emits, emittance and reflective factors of the object and environment must be considered. 8

Inherent Reliability. A measure of the reliability of an item, in its present operating context, assuming adherence to ideal equipment maintenance strategies. 3

Insider Threat. The threat that an entity will use his/her authorized access, wittingly or unwittingly, to do harm to the security of an organization. 12

Inspection. Any task undertaken to determine the condition of equipment, and/or to determine the tools, labor, materials, and equipment required to repair the item. 3

Instantaneous Peak Demand. The electrical demand at the instant of greatest load, usually determined from the readings of indicating meters or graphic meters. 7

Interconnection. The physical connection of the customer’s generation source to a utility’s distribution network. Implicit in this are the requirements and protocols for code compliance and safety standards. 7

Interface. A device that allows communication between systems or ports of systems. 7  

Internal Rate of Return (IRR). A percentage figure that describes the yield or return on an investment over a multiyear period; the discount rate that results in a Net Present Value (NPV) of zero. 10

Internet of Things (IoT). The interconnection via a network of computing devices embedded in everyday objects, enabling them to send and receive data. 12

Interval Data. Measurements taken and collected at regular periods for the purposes of future analysis of pattern and use. 7

Interval Metering. The measurement of customer energy use by fixed time periods or intervals. Typically, the interval is 15 minutes, but can vary according to the customer or transmission and distribution system needs. 7

Intrusion. A set of actions that constitutes a security incident in which an intruder gains or attempts to gain access to a system or resource without having authorization to do so. 12

Inventory. Spare parts or equipment components kept in case of equipment breakdown or from replacement when the original part or equipment component wears out. 6

Islanding. The condition in which on-site power is still being generated while the grid is down. This situation creates a variety of safety and equipment concerns and is usually a stipulated code issue. Many modern on-site power systems have (as are required) anti-islanding mechanisms that cease to energize upon detection of line voltage/frequency anomalies. 7

J

Just In Time. An operating philosophy that focuses on reducing lead times and work in process in manufacturing operations. 6

K

Key Performance Indicators (KPIs). A select number of key measures that enable performance against targets to be monitored. These indicators generally fall into one of two categories:

• Leading KPIs: A measure of performance prior to change or degradation and used to track future performance.
• Lagging KPIs: A measure of performance of what has already happened and how it impacts the system, process, or business and used to track past performance. 5

Kilowatt (kW). Unit of power equal to 1,000 watts. 10

Kilowatt-hour (kWh). A standard unit of electric consumption equal to the work done by 1 kilowatt acting for 1 hour. 10

L

Latent Load.  The portion of the cooling load necessitated by water vapor in the air. 10

Levelized Cost.  The uniform annual cost that results in the same NPV over the planning horizon as the stream of actual annual average costs. 7

Life Cycle Cost Analysis. A standard form of benefit-cost analysis used to evaluate cost-effectiveness by comparing incremental system costs to the cost savings over the life of the project. The difference between the life cycle cost of the baseline and each alternative is a NPV or the net savings offered by that alternative. 1

Life Cycle Costing. A process of estimating and assessing the total costs of ownership, operation, and maintenance of an item of equipment during its projected equipment life. Typically used in comparing alternative equipment design or purchase options to select the most appropriate option. 2

Life Cycle. The successive stages of development that a facility passes through during its lifetime until it is disposed of or the process begins over again in its next generation. Typically, facilities pass through the following stages in their lifetime: planning, design, construction, commissioning, occupancy, operation and maintenance, renewal/revitalization, and disposal. 8

Line Losses. Kilowatt-hours and kilowatts lost in the transmission and distribution lines under specified conditions. 7

Load Aggregation. Aggregation of energy consumption from facilities that are geographically separate from each other for purposes of acquiring and billing utility services. 7

Load Duration Curve. A graph showing a utility’s hourly demand, sorted by size, as well as by the amount of time a given level of demand is exceeded during the year. 7

Load Factor. The ratio of the average load in kilowatts supplied during a given period to the peak or maximum load in kilowatts occurring during that period. Load factor may be calculated for a customer, customer class, or the entire electric system. 7

Load Leveling. A process in which the energy demand can be temporarily reduced during certain periods. Typical examples include the intermittent operation of certain electrical equipment and shutting off equipment when rooms or buildings are not in use. 7

Load Management. The controlling, by rescheduling or direct curtailment, of the power demands of customers or groups of customers in order to reduce the total load that a utility must meet at times of peak demand. Load management strategies are designed to either reduce or shift demand from on-peak to off-peak, while conservation strategies reduce usage over larger multi-hour periods. Load management may take the form of normal or emergency procedures. Utilities often encourage load management by offering customers a choice of service options with varying price incentives. 7

Load. The amount of electric power (or gas) consumed at any specified point or points on a system. Load originates primarily in the power consuming equipment of the customers. 7

Local Area Network (LAN). Computer network that spans a relatively small area. 7

M

Maintainability. The ability to retain or restore function within a specified period, when provided with an identified level of tools, training, and procedures. Maintainability factors include machine and systems access, visibility, simplicity, ease of monitoring or testing, special training requirements, special tools, and the capability of the local work force. 8

Maintenance Approach. The plan to prevent failure and, when failure occurs, perform repair. 8

Maintenance Schedule. A list of planned maintenance tasks to be performed during a given time period, together with the expected start times and durations of each of these tasks. Schedules can apply to different time periods (i.e., Daily Schedule, Weekly Schedule, etc.). 2

Maintenance Strategy. A long-term plan covering all aspects of maintenance management, which sets the direction for maintenance management and contains firm action plans for achieving a desired future state for the maintenance function. 2

Maintenance. Any activity carried out on an asset to ensure the asset continues to perform its intended functions, or to repair the equipment. 2

Makeup Air. Any combination of outdoor and transfer air intended to replace exhaust air and air leakage. 11

Mean Time Between Failures (MTBF). A measure of equipment reliability equal to the number of failures in a given time period, divided by the total equipment uptime in that period. 2

Mean Time To Repair (MTTR). A measure of maintainability equal to the total equipment downtime in a given time period, divided by the number of failures in that period. 2

Measurement and Verification (M&V). A formal documentation process that establishes the energy savings generated by an energy-efficiency project. Energy savings in a building can be very difficult to measure given the effects of weather, occupant behavior, and activity volume in addition to the performance efficiency of the building and its systems. 10

Megawatt (MW). Unit of power equal to one million watts. 7

Megger. An electronic tool that generates high voltage used in testing insulation integrity. 9

MERV. Minimum Efficiency Reporting Value (MERV) system used to evaluate the efficiency of an air filter based on how effective it is at catching particles of varying sizes. The higher the MERV rating, the higher the air filtration capabilities of a particular filter.  11

Mission Critical. A building, area, or system that is critical to the site’s mission or is essential for the site’s performance to meet its goals. Also see Mission Support and Site Support. 8

Modification. Any activity carried out on an asset which increases the capability of that asset to perform its required functions. 2

Modular (energy source). A system arrangement whereby the demand for energy (heating, cooling) is met by a series of units sized to meet a portion of the load. 9

Motor Analysis. A predictive maintenance technology focused on faults within, and intrinsic to, electric motors resulting from winding short circuits, open coils, or improper torque settings. 9

Motor Circuit Analysis (MCA). A maintenance technique whereby the static characteristics (i.e., impedance, capacitance to ground, and inductance) of a motor or generator are measured as indicators of equipment condition. 8

Motor Current Spectrum Analysis (MCSA). A maintenance technique whereby motor current signatures provide information on the electro-mechanical condition of AC induction motors. It detects faults such as broken rotor bars, high resistance joints, and cracked rotor end rings by collecting motor current spectrums with clamp-on sensors and analyzing the data. 8

Multi-Zone System. A type of air-distribution system that is similar to a dual-duct system in that two streams of air, hot and cold, are mixed to produce a desired temperature. But whereas dual-duct systems mix the air in individual boxes located at each area or room, multi-zone systems mix air with dampers near the fans, then feed the conditioned air to each zone based on its load.

N

NEMA Standards. Property characteristics adopted as standard by the National Electrical Manufacturers Association. 7

Net Metering. A utility procedure for crediting customers for electricity generated on-site and in excess of their own needs. In its simplest form, this allows for the flow of electricity both to and from a customer’s location through a single bi-directional meter. 7

Net Present Value (NPV). A measure of investment worth, computed as the sum of the present values of an investment’s cash flows. 10

Network. A group of computing devices that are connected to each other by communications lines to share information and resources. 7

Non-Destructive Testing. The testing of equipment, which does not destroy the equipment, to detect abnormalities in physical, chemical, or electrical characteristics. 2

Normalize. A statistical method of massaging data to account for differences in circumstances, such as weather, occupancy levels, or tasks that affect energy use. Normalizing creates a level playing field that avoids apples-to-oranges comparisons. 10

No-Scheduled Maintenance. An equipment maintenance strategy, where no routine maintenance tasks are performed on the equipment. The only maintenance performed on the equipment is Corrective Maintenance, and then only after the equipment has suffered a failure. Also described as a Run-to-Failure strategy. 2

O

Off-Peak Energy. Electricity supplied during periods of relatively low system demand. 7

Oil Analysis. A predictive maintenance technology (also known as tribology) focused on the lubrication system, fluid, and wear-elements, all within the lubrication medium (e.g., oil). 9

Ongoing Commissioning. A process that includes planning, point monitoring, system testing, performance verification, corrective action response, ongoing measurement, and documentation to proactively address operating problems in the systems being commissioned. Also known as monitoring-based commissioning (MBCx).

Operating Context. The operational situation within which an asset operates. For example, is it a stand-alone piece of plant, or is it one of a duty-standby pair? Is it part of a batch manufacturing process or a continuous production process? What is the impact of failure of this item of equipment on the remainder of the production process? The operating context has enormous influence over the choice of appropriate equipment maintenance strategies for any asset. 2

Operating Hours. The length of time that an item of equipment is actually operating. 2

Operational Consequences. A failure has operational consequences if it has a direct adverse impact on operational capability (lost production, increased production costs, loss of product quality, or reduced customer service). 2

Operational Efficiency. The life-cycle, cost-effective mix of preventive, predictive, and reliability-centered maintenance technologies, coupled with equipment calibration, tracking, and computerized maintenance management capabilities all targeting reliability, safety, occupant comfort, and system efficiency. 9

Operational Technology (OT). The hardware and software dedicated to detecting or causing changes in physical processes through direct monitoring and/or control of physical devices. 12

Operations and Maintenance (O&M). Decisions and actions regarding the control and upkeep of property and equipment. 8

Optimal Start. A machine learning algorithm that provides an air-handler with a custom start-up time every morning in response to the outdoor air temperatures, zone temperatures, and time remaining prior to occupancy.  

Outage. A term used in some industries (notably power generation) which is equivalent to a shutdown. 2

Outdoor Air. Air outside a building or taken from the outdoors and not previously circulated through the system including ambient air that enters a building through a ventilation system, through intentional openings for natural ventilation, or by infiltration. 11

Overhaul.  A comprehensive examination and restoration of an asset to an acceptable condition. 2

P

Packaged Unit. A self-contained HVAC unit that provides heating and/or cooling to a building space. 10

Pareto Analysis. A problem-solving tool that breaks data down into manageable groups and identifies the greatest opportunity for return on investment. The analysis is based on the Pareto Principle, also known as the 80:20 Rule. Simply stated, the principle says that 20 percent of a population will cause 80 percent of the problems associated with the population. 8

Part Load. Condition in which equipment operates at less than design load to meet the demand placed upon it; this is often the majority of the time the equipment is operating. 10

Payback Period. The time required for an investment’s cumulative cash flow (including the initial outlay) to reach zero. 10

Peak Demand. The maximum rate of electricity consumption, expressed in gigawatts or kilowatts during a specified period. May be expressed for groups of electricity users or the whole system, and by season (summer or winter) or annually. 7

Peak Load. The maximum anticipated electrical demand for any given system during a specified period. 7

Percent Planned Work. The percentage of total work (in labor hours) performed in a given time period which has been planned in advance. 2

Performance Contract. An agreement in which the success of an energy-efficiency project plays a role in determining how the contractor is compensated for managing the project. Performance contracts generally shield the project owner from losses due to a failed project, thereby reducing or eliminating risk. A successful project may reward the contractor with above-market returns as compensation for taking on the risk of failure. 10

Performance Standards. Standards that an item is required to meet in order to maintain its required function. The performance standard defines functional failure for the item. 8

Performance Trending. A maintenance activity centered on capturing, tending, and tracking key indicators on a component or system. 9

Personal Protective Equipment (PPE). Equipment worn to minimize exposure to hazards that cause serious workplace injuries and illnesses.

Phishing. Tricking individuals into disclosing sensitive personal information by claiming to be a trustworthy entity in an electronic communication. 12

Planned Maintenance. Any maintenance activity for which a pre-determined job procedure has been documented, for which all labor, materials, tools, and equipment required to carry out the task have been estimated, and their availability assured before commencement of the task. 2

Pneumatic Control. A control that utilizes air pressure to vary equipment operation. 10

Potential Failure (P-F) Interval. The time from when a Potential Failure can first be detected on an asset or component using a selected Predictive Maintenance task, until the asset or component has failed. 2

Potential Failure.  An identifiable condition which indicates that a functional failure is either about to occur, or in the process of occurring. 2

Power Factor. The cosine of the phase angle between the current and voltage waveforms in an electrical system. Electrical loads such as motors have a property called inductance, which causes changes in the flow of current to be delayed relative to the changing AC voltage. Power factor is a measure of the degree to which current lags voltage. 10

Power Line Carrier (PLC). A communication system that transmits data between devices over power lines. 7

Power Purchase Agreement (PPA). A legal contract between an electricity generator (provider) and a power purchaser (buyer, typically a utility or large power buyer/trader). 1

Predictive Maintenance. An equipment maintenance strategy based on measuring the condition of equipment to assess whether it will fail during some future period, and then taking appropriate action to avoid the consequences of that failure. 8, 9

Predictive Testing & Inspection (PT&I). The use of advanced technology to assess machinery condition. The PT&I data obtained allows for planning and scheduling preventive maintenance or repairs in advance of failure. Also see Condition Monitoring and Condition-Based Maintenance. 8

Present Value. The value of a cost or stream of yearly costs that have been discounted to reflect the fact that future benefits or expenditures are worth less than current benefits or expenditures. Also called present worth. 7

Pressure Drop. The loss in pressure experienced by flowing water or air due to friction and obstructions. 10

Pressure Reset. A method of reducing duct pressure that can yield additional energy savings in systems that have VSDs installed. Reducing the pressure supplied by fans also reduces the flow supplied, which in turn reduces the power required. 10

Preventive Maintenance. An equipment maintenance strategy based on replacing, overhauling, or remanufacturing an item at a fixed interval, regardless of its condition at the time. Scheduled Restoration tasks and Scheduled Discard tasks are both examples of Preventive Maintenance tasks. 2

Principle of Least Privilege. The idea that a person should be authorized with the minimum level of access necessary to complete their work. 12

Priority. The relative importance of a task in relation to other tasks. Used in scheduling work orders. 2

Proactive Maintenance. The collection of efforts to identify, monitor and control future failure with an emphasis on the understanding and elimination of the cause of failure. Proactive maintenance activities include the development of design specifications to incorporated maintenance lessons learned and to ensure future maintainability and supportability, the development of repair specifications to eliminate underlining causes of failure, and performing root cause failure analyses to understand why in-service systems failed. 8

Probabalistic Risk Assessment. A "top-down" approach used to apportion risk to individual areas of plant and equipment, and possibly to individual assets to achieve an overall target level of risk for a plant, site, or organization. 2

Process Load. A cooling or heating load not related to maintaining occupant comfort, such as file server rooms and specialized diagnostic equipment in the health-care sector. The loads may be intermittent or continuous. 9

Programmable Logic Controller (PLC). A solid-state control system that has a user- programmable memory for storage instruction to implement specific functions such as input/output (I/O) control logic, timing, counting, arithmetic, and data manipulation. 7

Programmed Maintenance (PGM). Those maintenance tasks whose cycle exceeds one year, such as painting a building every fifth year. (This category is different from proactive maintenance since if a planned cycle is missed, the original planned work remains to be accomplished, whereas in proactive maintenance only the next planned cycle is accomplished instead of doing the work twice, such as two lubrications, two adjustments, or two inspections.) Reactive Maintenance: See repair. 8

Protective Device. Devices and assets intended to eliminate or reduce the consequences of equipment failure. Some examples include standby plant and equipment, emergency systems, safety valves, alarms, trip devices, and guards. 2

Purchase Order. The prime document raised by an organization, and issued to an external supplier, ordering specific materials, parts, supplies, equipment, or services. 2

Purchase Requisition. The prime document raised by user departments authorizing the purchase of specific materials, parts, supplies, equipment, or services from external suppliers. 2

Q

Quality Rate. Used in the calculation of Overall Equipment Effectiveness. The proportion of the output from a machine or process which meets required product quality standards. Normally specified as a percentage. 2

R

Radiator. A device that provides warmth to a space through radiant or convective heat provided by either steam or hot water.

Reactive Maintenance. The work required to restore a component to a condition substantially equivalent to its originally intended and designed capacity, efficiency, or capability. Reactive maintenance is also known as corrective maintenance, and a reactive maintenance strategy is also known as run-to-failure. No actions or efforts are taken to maintain the equipment as the designer originally intended to ensure design life is reached. 8, 9

Reactive Power. Portion of power in a circuit or system that results in a bi-directional net transfer of energy. 7

Real (active) Power. Portion of power in a circuit or system that results in a single directional net transfer of energy. 7

Real-Time Metering. Metering that records consumer use in the same time frame as pricing changes in the market, typically hourly or more frequently. 7

Real-Time Pricing (RTP). The instantaneous pricing of electricity based on the cost of electricity available for use at the time the electricity is demanded by the customer. 7

Recirculated Air. Air removed from a space and reused as supply air. 11

Recommissioning. A process of commissioning a facility or system beyond the project development and warranty phases of the facility or system and the primary goal of which is to ensure optimum performance of a facility, in accordance with design or current operating needs, over the useful life of the facility, while meeting building occupancy requirements. 16

Redundancy. Provision for more than one component installed in a system aimed at increasing reliability, or in the case of failure, to ensure that the redundant component takes over the function. 3

Regression Analysis. A statistical method for finding a mathematical relationship among two or more variables. 10

Reheat. The heating of air that has been previously cooled (by cooling equipment or an economizer) by a heating device, such as a hot water or electric coil, and controlled via a zone thermostat. 10

Relative Humidity (RH). The percentage of moisture contained in the air compared to saturation. 7

Reliability. The duration or probability of failure-free performance under stated conditions with the probability that an item can perform its intended function for a specified interval under stated conditions. 8

Reliability-Centered Maintenance (RCM). The process used to determine the most effective approach to maintenance. It involves identifying actions that, when taken, will reduce the probability of failure and which are the most cost effective. It seeks the optimal mix of condition-based actions, other time- or cycle-based actions, or run-to-failure approach. 8

Repair. The work required to restore a facility or component thereof, including installed equipment, to a condition substantially equivalent to its originally intended and designed capacity, efficiency, or capability. 8

Request for Proposal (RFP). A document that solicits proposals, often made through a bidding process, by an agency or company interested in procurement of a commodity, service, or valuable asset, to potential suppliers to submit business proposals. 1

Reset. The process of increasing or decreasing the temperature of an HVAC element to raise efficiency. 10

Resilience Gap. A resilience gap exists where risk—as a function of threats and hazards, vulnerabilities, and impact—exceeds a defined acceptable threshold or where conditions do not meet specific established resilience goals or standards. 1

Resilience Planning. Resilience planning seeks to reduce potential impacts to operations from planned or unplanned disruptions via integrated and diverse solution sets. It is an iterative process that needs to be regularly revisited as a part of an organization’s operations. 1

Resilience. Energy and water resilience is the ability for optimized operations to withstand, adapt, and recover from disruption as required. 1

Resource Use Intensity. The key performance indicator relating a resource use (e.g., electricity, natural gas, or water) with another building metric (e.g., total square footage or occupancy) and a time metric. Most commonly listed as an EUI in kWh/ft²/year or kBtu/ft²/year. 7

Retrocommissioning. A process of commissioning a facility or system that was not commissioned at the time of construction of the facility or system. 16

Return On Investment (ROI). The discount rate which, when used to discount all present and future project costs and savings, brings the NPV to zero. 7

Risk. The potential for an unwanted outcome resulting from an event or sequence of events and is quantified in terms of the event likelihood and associated consequences. 1

Root Cause Failure Analysis (RCFA). The process of exploring, in increasing detail, all possible causes related to a machine failure. Failure causes are grouped into general categories for further analysis. For example, causes can be related to machinery, people, methods, materials, policies, environment, and measurement error. 8

Root-Cause Analysis. A structured approach to identifying and characterizing failures and identifying the processes and actions needed to prevent them. 9

Routine Maintenance Task. Any maintenance task that is performed at a regular, predefined interval. 2

Run-to-Failure. An equipment maintenance strategy where no routine maintenance tasks are performed on the equipment. The only maintenance performed on the equipment is corrective and then only after the equipment has suffered a failure. Candidate systems or machines for Run-to-Failure are usually low-cost, easily repaired, and non-critical. 2, 8

R-Value. A measure of thermal resistance of insulation; higher R-values mean better insulation. 10

S

Safety Consequences.  A failure has safety consequences if it causes a loss of function or other damage that could hurt or kill someone. 2

Schedule Compliance.  One of the KPIs often used to monitor and control maintenance. It is defined as the number of scheduled work orders completed in a given time period (normally one week), divided by the total number of scheduled work orders that should have been completed during that period, according to the approved maintenance schedule for that period. 2

Scheduled Maintenance. Any maintenance work that has been planned and included on an approved Maintenance Schedule. 2

Scheduled Operating Time. The time during which an asset is scheduled to be operating, according to a long-term production schedule. 2

Scheduled Work Order. A Work Order that has been planned and included on an approved Maintenance Schedule. 2

Seasonal Efficiency. Ratio of useful output to energy input for a piece of equipment over an entire heating or cooling season. It can be derived by integrating part- load efficiencies against time. 9

Seasonal Energy-Efficiency Ratio (SEER). A seasonally adjusted measure of efficiency at 82°F outside air temperature in units of Btu/watt-hour. 10

Secondary Damage. Any additional damage to equipment, above and beyond the initial failure mode, that occurs as a direct consequence of the initial failure mode. 2

Secondary Function. A term used in RCM. The secondary functionality required of an asset—generally not associated with the reason for acquiring the asset, but now that the asset has been acquired, the asset is now required to provide this functionality. For example, a secondary function of a pump may be to ensure that all the liquid that is pumped is contained within the pump (i.e., the pump does not leak). An asset may have tens or hundreds of secondary functions associated with it. 2

Sensible Heat. The form of heat that results in a temperature change, but no change in state. 9

Sensible Load. The portion of the cooling load contributed by dry air. Sensible loads change the temperature of the air. 10

Setpoint. Desired temperature, humidity, or pressure in an area, space, or duct. 10

Shadow Metering. The process to quantify and verify the system generation and assure proper “net metering” credit. 7

Shutdown Maintenance. Maintenance that can only be performed while equipment is shutdown. 2

Shutdown. That period of time when equipment is out of service. 2

Simple Payback. The measurement of the elapsed time between an initial investment and the point at which accumulated savings are sufficient to offset the initial investment. 10

Smart Meter. Resource metering devices that allow data capture, storage, and communication typically used for monitoring and billing purposes.

Standard Job. A Work Order stored in the computerized maintenance management system (CMMS) which contains all the necessary information required to perform a maintenance task. 2

Standing Work Order. A work order that is left open either indefinitely or for a pre-determined period for the purpose of collecting labor hours costs and/or history for tasks for which it has been decided that individual work orders should not be raised.

Static Pressure (SP)/Static Pressure Reset. The pressure downstream of the supply fan; typically measures 2/3 of the way down the duct, with respect to the zone (building pressure).

Statistical Process Control. A statistical method used to determine whether a process is being controlled within the required band of variance where the mean and standard deviation are used to express the distribution of outcomes and their conformance to goal(s). 8

Steam Trap. A device that separates air and condensed water from steam. 10

Submeter. A meter that records energy or water usage by a specific process, a specific part of a building, or a building within a larger facility or complex. 9

Submetering. A method of using multiple meters to collect real-time energy data from any energy consumption related source in a building (electricity, water, gas, or other uses such as district steam and chilled water). Submeters capture information that is downstream of the main utility meter, and can be used to disaggregate building loads and provide more granular visibility into energy consumption. 4

Supervisory Control and Data Acquisition (SCADA). A computerized system that can gather and process data and apply operational controls to geographically dispersed assets. 12

Supply Air. Air delivered by mechanical or natural ventilation to a space that is composed of any combination of outdoor air, recirculated air, or transfer air. 11

Sustainability. Meeting the needs of the present without compromising the ability of future generations to meet their own needs. 8

System Condition Index (SCI). A unitless number which or percentage which expresses the amount of Deferred Maintenance divided by the CRV of a system being evaluated. SCI can be expressed on a scale of 1 to 5 (where 5 is excellent, no DM) as reported by NASA to the opposite where 1 is excellent. Other agencies and organizations report SCI on a scale of 0 to 100 percent. 8

T

Temperature Reset. A strategy for saving energy that adjusts the temperature of either the air or water supplied by an HVAC system based on measurements of the actual load or a proxy for the actual load, such as outdoor air temperature. 10

Testing, Adjusting, and Balancing (TAB). The process of adjusting HVAC system components to supply air and water flows at desired values. 10

Therm. A unit of gas fuel containing 100,000 Btus. 9

Thermostat. A device that maintains a temperature setpoint by controlling equipment in response to temperature changes. 10

Threat. A hazard associated with malicious intent to create adverse consequences. Sometimes the term threat refers to the likelihood of that threat being realized as an event. 1

Time of Use. The pricing of electricity based on the estimated cost of electricity during a particular time block. 7

Time- or Cycle-Based Actions. Maintenance activities performed from time-to-time that have proven to be effective in preventing failure. Items such as lubrication and restoration of wear fit this description. 8

Tons of Refrigeration. A standard for identifying cooling capacity. One ton of refrigeration is equal to 12,000 Btu/hour of cooling. 7

Total Asset Management. An integrated approach (yet to be developed!) to Asset Management which incorporates elements such as RCM, Total Productive Maintenance, Design for Maintainability, Design for Reliability, Value Engineering, Life Cycle Costing, Probabilistic Risk Assessment, and others, to arrive at the optimum Cost-Benefit-Risk asset solution to meet any given production requirements. 2

Total Productive Maintenance. A company-wide equipment management program, with its origins in Japan, emphasizing production operator involvement in equipment maintenance, and continuous improvement approaches. 2

Trend Log. A record of data that may be stored at regular, equal time intervals or upon change of value and that is often used in analyses of use and/or performance over time.

Trend Logging. Recording system variables (e.g., temperature, volume, pressure, power) at time intervals to monitor equipment operation and help identify or diagnose problems. Logging is often accomplished using portable data loggers, electrical meters, or the resident Direct Digital Control (DDC) system. 9

Tribology (also known as Oil Analysis). The process of monitoring the condition of equipment through the analysis of properties of its lubricating and other oils. Typically conducted through the measurement of particulates in the oil, or the measurement of the chemical composition of the oil (Spectographic Oil Analysis). Commonly used for monitoring the condition of large gearboxes, engines, and transformers, amongst other applications. 2

U

U Value (or U-Factor). A coefficient expressing the thermal conductance of a composite structure in Btus per (square foot) (hour) (degree Fahrenheit difference). 9

Ultrasonic Analysis. A predictive maintenance technology focused on the sound waves emitted at frequencies above 20 kilohertz and, the changes in which, can be indicative of equipment performance and/or degradation. 9  

Unplanned Maintenance. Any maintenance activity for which a pre-determined job procedure has not been documented, or for which all labor, materials, tools, and equipment required to carry out the task have not been estimated and their availability assured before commencement of the task. 2

Unscheduled Maintenance. Any maintenance work that has not been included on an approved Maintenance Schedule prior to its commencement. 2

Uptime. Defined as being the time that an item of equipment is in service and operating. 2

Useful Life. The maximum length of time that a component can be left in service before it will start to experience a rapidly increasing probability of failure. 9

Utility Energy Service Contract (UESC). A limited-source contract between a federal agency and its serving utility for energy and water efficiency improvements and demand reduction. 1

Utilization. The proportion of available time that an item of equipment is operating. Calculated by dividing equipment operating hours by equipment available hours. Generally expressed as a percentage. 2

V

Value Engineering. A systematic approach to assessing and analyzing the user's requirements of a new asset, and ensuring that those requirements are met, but not exceeded. Consists primarily of eliminating perceived "non-value-adding" features of new equipment. 2

Variable Air Volume (VAV). A type of air-handling system that provides air at a constant temperature and varies the air quantity to each zone to match the variation in room load.

Variable Operating and Maintenance (O&M) Costs. The additional cost per kWh of electricity produced that goes toward operation and maintenance of the plant. These costs vary with the output of the plant and are expressed in cents per kWh of electricity produced. 7

Variable-Volume, Variable-Temperature (VVVT). A type of air-handling system that can change supply- air temperature in addition to air volume.

Variable-Speed Drive (VSD). An electronic device that adjusts a motor’s speed to match load requirements by changing the frequency of the voltage applied to motor terminals.

Ventilation. A process of supplying air to or removing air from a space for the purpose of controlling air contaminant levels, humidity, or temperature within the space. 11

Verification. The full range of checks and tests carried out to determine whether all components, subsystems, systems, and interfaces between systems operate in accordance with the contract documents. In this context, operate includes all modes and sequences of control operation, interlocks, and conditional control responses, and specified responses to abnormal or emergency conditions. 8

Vibration Analysis. The process of monitoring the condition of equipment, and the diagnosis of faults in equipment through the measurement and analysis of vibration within that equipment. Typically conducted through handheld or permanently positioned accelerometers placed on key measurement points on the equipment. Commonly used on most large items of rotating equipment, such as turbines, centrifugal pumps, motors, gearboxes, etc. 2, 9

Vulnerability. The probability of a consequence occurring given that the hazard or threat has been realized. It is the probability that safeguards, or protections intended to mitigate the hazard or threat fail. (Note: Within the TRN, consequence and impact are used interchangeably.) 1

Vulnerability Assessment. Evaluates the potential vulnerability of the critical assets against a broad range of identified threats and hazards. Determines the sensitivity of a system’s infrastructure to the realization of specific threats or hazards and the potential disruption or loss of that system. 1

W

Water-Side Economizer. A heat exchanger that transfers heat from an HVAC system’s chilled water to its cooling-tower water. 10

Watt. The electrical unit of power. The rate of energy transfer equivalent to 1 ampere flowing under a pressure of 1 volt at unity power factor. 7

Watt-Hour. The total amount of energy used in one hour by a device that requires one watt of power for continuous operation. Electric energy is commonly sold by the kWh (1,000 Watt-hour). 7

Wear Particle Analysis. A type of lubricant analysis that examines the wear particles suspended in a lubricant allowing wear patterns to be identified before a failure occurs. 6 

Weibull Analysis. An equipment life distribution widely used in reliability engineering life cycle analysis. 8

Work Order. The prime document used by the maintenance function to manage maintenance tasks. It may include such information as a description of the work required, the task priority, the job procedure to be followed, the parts, materials, tools, and equipment required to complete the job, the labor hours, costs, and materials consumed in completing the task, as well as key information on failure causes, what work was performed, etc. 2

Work Request. The prime document raised by user departments requesting the initiation of a maintenance task. This is usually converted to a work order after the work request has been authorized for completion. 2

Workload. The amount of labor hours required to carry out specified maintenance tasks. 2

Z

Zone. A space (or group of spaces) that has its heating and cooling controlled by a single thermostat. 10

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References

1. FEMP. n.d. Technical Resilience Navigator Glossary. https://femp.energy.gov/resilience/technical-resilience-navigator-glossary
2. NE-SpinTech 2018. Glossary of Maintenance Terms. New England SpinTech: Reliability and Maintenance Solutions. Spencer, MA. https://www.ne-spintech.com/wp-content/uploads/2018/04/Glossary-of-Maintenance-Terms.pdf
3. United Nations Industrial Development Organization. 1994. Maintenance Management Manual. Vienna, Switzerland.
4. LBNL – Lawrence Berkeley National Laboratory. 2017. Using EMIS to Identify Top Opportunities for Commercial Building Efficiency. LBNL-1007250, Lawrence Berkeley National Laboratory, Berkeley, CA.
5. KPI Issues Paper – not sure how best to reference this document.
6. Wireman, T. Developing Performance Indicators for Managing Maintenance.1998. Industrial Press, Inc. New York, New York.
7. FEMP – Federal Energy Management Program. 2011. Metering Best Practices: A Guide to Achieving Utility Resource Efficiency. U.S. Department of Energy, Federal Energy Management Program, Washington D.C.
8. NASA – National Aeronautics and Space Administration. Reliability-Centered Maintenance Guide for Facilities and Collateral Equipment. National Aeronautics and Space Administration, Washington, D.C.
9. FEMP ─ Federal Energy Management Program. 2010. Operations & Maintenance Best Practices: A Guide to Achieving Operational Efficiency. Release 3.0. Prepared by Pacific Northwest National Laboratory for FEMP, Richland, WA. https://www.wbdg.org/FFC/DOE/DOECRIT/femp_omguide.pdf.
10. EPA – Environmental Protection Agency. Energy Star Building Upgrade Manual. 2008. U.S. Environmental Protection Agency, Washington D.C.
11. ASHRAE -  American Society of Heating, Refrigerating and Air-Conditioning Engineers. Standard 90.1 Energy Standard for Buildings Except Low-Rise Residential Buildings. (2019)  
12. National Institute of Standards and Technology and National Initiative for Cybersecurity Careers and Studies.
13. PNNL 2018. Large Building Re-Tuning Resources. https://buildingretuning.pnnl.gov/resources.stm
14. BCA - Building Commissioning Association. 2008. Best Practices in Commissioning Existing Buildings Building Commissioning Association. https://cdn2.hubspot.net/hubfs/416421/pdf/bca-ebcx-best-practices.pdf
15. GSA ─ General Services Administration Sustainable Facilities Tool. 2018. https://sftool.gov/learn/about/1/indoor-environmental-quality-ieq.
16. Energy Act of 2020. 42 USC 8253: https://www.govinfo.gov/content/pkg/USCODE-2010-title42/html/USCODE-2010-title42-chap91-subchapIII-partB-sec8253.htm

Last update: 9/30/2022