HVAC GLOSSARY - E

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Economizer, Air: A ducting arrangement and automatic control system that allows a heating, ventilation, and air conditioning (HVAC) system to supply up to 100 percent outside air to satisfy cooling demands, even if additional mechanical cooling is required.

Economizer, Water: A system which uses either direct evaporative cooling, or a secondary evaporatively cooled water loop and cooling coil to satisfy cooling loads, even if additional mechanical cooling is required.

EER: (Energy Efficiency Ratio) A ratio calculated by dividing the cooling capacity in Btu's per hour (Btuh) by the power input in watts at any given set of rating conditions, expressed in Btuh per watt (Btuh/watt). EER & SEER cannot be compared equally. Air source equipment is rated by SEER and geothermal equipment is rated by EER. EER changes with the inside and outside conditions, falling as the temperature difference between inside and outside gets larger.

Effective area: (of an air terminal device) The smallest net area of an air terminal device used by the air stream in passing through the air terminal device.

Efficiency: A rating on comfort equipment is similar to the miles per gallon rating on your car. The higher the rating number, the more efficient the system and the lower your fuel consumption will be. You can save a lot of money with a high efficiency unit. Depending on your local climate, lifestyle and electricity rates, savings will vary. For furnaces, it is the rate at which a furnace maximizes fuel use. This rate is numerically described as a ratio called AFUE (see AFUE). As of January 1991, no furnaces can be manufactured with efficiencies lower than 78% afue. High efficiency furnaces will be rated 85 to 95% afue.

Electric Radiant Heating: A heating system in which electric resistance is used to produce heat which radiates to nearby surfaces. There is no fan component to a radiant heating system.

Electric Rate Schedule: A statement of the electric rate and the terms and conditions governing its application, including attendant contract terms and conditions that have been accepted by a regulatory body with appropriate oversight authority.

Electric Resistance Heater: A device that produces heat through electric resistance. For example, an electric current is run through a wire coil with a relatively high electric resistance, thereby converting the electric energy into heat which can be transferred to the space by fans.

Electrostatic air cleaner:A device that uses an electrical charge to trap particles traveling in the

air stream.

Emergency Heat:(Supplementary Electric Heat) The back up electric heat built into a heat pump system. The same as an auxiliary heater, except it is used exclusively as the heat source when the heat pump needs repair.

Emission Standard: A voluntary guideline or government regulation that specifies the maximum rate at which a contaminant can be released from a source.

Encapsulate: A mitigation technique that reduces or eliminates emissions from a source by sealing with an impenetrable barrier.

Endotoxin: A biological agent that is part of the outer membrane of some bacteria. Endotoxins are highly toxic, capable of causing fever, malaise, respiratory distress, even death.

Energy: Broadly defined, is the capability of doing work. More specifically, it is 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). Forms of energy include thermal, mechanical, electrical, and chemical. Energy may be transformed from one form into another form useful for work. Most of the world¹s convertible energy comes from fossil fuels that are burned to produce heat that is then used as a transfer medium to mechanical or other means to accomplish tasks. Electrical energy is usually measured in kilowatt-hours, while heat energy may be measured in British thermal units or other traditional non-metric specialized units in addition to metric units. In the electric power industry, energy is more narrowly defined as electricity supplied over time, expressed in kilowatts.

Energy Efficiency: Refers to programs that are aimed at reducing the energy used by specific end-use devices and systems, typically without affecting the services provided. These programs reduce overall electricity consumption (reported in megawatt hours), often without explicit consideration for the timing of program-induced savings. Such savings are generally achieved by substituting technically more advanced equipment to produce the same level of end-use services (e.g., lighting, heating, motor drive) with less electricity. Examples include high-efficiency appliances, efficient lighting programs, high-efficiency heating, ventilating and air conditioning (HVAC) systems or control modifications, efficient building design, advanced electric motor drives, and heat recovery systems.

Energy Management System: A control system (often computerized) designed to regulate the energy consumption of a building by controlling the operation of energy consuming systems, such as the heating, ventilation, and air conditioning (HVAC), lighting and water heating systems.

Enforcement: The legal methods used to make polluters obey the CLEAN AIR ACT. Enforcement methods include citations of polluters for violations of the law (citations are much like traffic tickets), fines and even jail terms. EPA and the state and local governments are responsible for enforcement of the Clean Air Act, but if they don't enforce the law, members of the public can sue EPA or the states to get action. Citizens can also sue violating sources, apart from any action EPA or state or local governments have taken. Before the 1990 Clean Air Act, all enforcement actions had to be handled through the courts. The 1990 Clean Air Act gave EPA authority so that, in some cases, EPA can fine violators without going to court first. The purpose of this new authority is to speed up violating sources' compliance with the law and reduce court time and cost.

Envelope: The geometrical surface of the points of an air jet, corresponding to a determined value of the measured air velocity. This velocity is generally called «terminal velocity». Also, the air barrier that separates the conditioned space from the outside and from unconditioned spaces like attics and garages.

Environmental Agents: Conditions other than indoor air contaminants that cause stress, comfort, and/or health problems (e.g., humidity extremes, drafts, lack of air circulation, noise, and over-crowding).

Environmental Tobacco Smoke:(ETS) The combination of sidestream and mainstream smoke that is emitted from a burning cigarette, pipe, or cigar; also called second-hand smoke.

EPA: (Environmental Protection Agency) Environmental Protection Agency - http://www.epa.gov/ A federal agency created in 1970 to permit coordinated governmental action for protection of the environment by systematic abatement and control of pollution through integration of research, monitoring, standards setting and enforcement activities. EPA administers federal environmental policies, enforces environmental laws and regulations, performs research, and provides information on environmental subjects. The agency also acts as chief advisor to the President on U.S. environmental policy and issues.

Epidemiological: Dealing with the scientific study of the incidence, control, and spread of disease in a population.

Ergonomics: The science that investigates the impact of people's physical environment on their health and comfort (e.g., chair design, monitor location, desk configuration or height, etc.)

ERV: (Energy Recovery Ventilator) This device preheats incoming outside air during the winter and pre-cools incoming air during the summer to reduce the impact of heating and or cooling the indoor air. This means that smaller capacity heating and cooling systems can be used in homes, which results in lower installation costs, lower peak demand for energy, and lower operating costs.

Evaporative Cooler: A type of cooling equipment that turns air into moist, cool air by saturating the air with water vapor. It does not cool air by use of a refrigeration unit. This type of equipment is commonly used in warm, dry climates.

Evaporative Cooling: Cooling by exchange of latent heat from water sprays, jets of water, or wet material.

Evaporator Approach Temperature: The temperature difference between the evaporator¹s refrigerant temperature and the leaving chilled water temperature.

Evaporator Coil: (Also see Indoor Coil) The evaporator coil is located inside your house in a split system in the air handler, or above the gas furnace. This will produce cooling in the air conditioning mode and heating in a Heat Pump mode. This coil section in the evaporator is where refrigerant evaporates and absorbs heat from air passed over the coil. This is also very important in removing humidity from your home.

Exfiltration: Uncontrolled air leakage out of a building. Exfiltration Air flow outward through a

wall, building envelope, etc.

Exhaust: Air removed deliberately from a space, by a fan or other means, usually to remove contaminants from a location near their source. The air flow leaving the treated space. Exhaust may be accomplished by one or more of the following methods:

a. Extraction: exhaust in such a manner that the air is discharged into the atmosphere.

b. Relief: exhaust in such a manner that the air is allowed to escape from the treated space if the pressure in that space rises above a specified level. 

c. Recirculation: exhaust in which the air is returned to the air treatment system.

d. Transfer: exhaust in which air passes from the treated space to another treated space.

Exhaust Air Flow Rate:Volume of air leaving an exhaust air terminal device within a time unit.

Exhaust Air Terminal Device: Air terminal device through which air leaves the treated space.

Exhaust Ventilation: Mechanical removal of air from a portion of a building (e.g., piece of equipment, room, or general area).