HVAC DESIGN BASICS
Understanding SEER and EER Ratings and Other Hvac Terms
Hvac Efficiency Terms
AFUE (Annual Fuel Usage Estimate). This term applies to gas fired appliances. An 80% AFUE furnace means that 80% of the fuel consumed by the appliance goes to heating your home. 20% goes out your vent and heats the outside. By increasing your furnace AFUE rating to 94%, now 94% of the fuel consumed goes to heating your home, and only 6% is wasted out your furnace vent. The higher your AFUE, the more efficient the furnace.
SEER (Seasonal Energy Efficiency Ratio). This is the most commonly used term to rate the efficiency of a central air conditioner. SEER measures the efficiency of a cooling system over the entire cooling season. The higher the SEER, the more efficient the air condiioner. SEER ratings can be deceiving. Many equipment model numbers, such as XC16 lead one to believe that the equipment is 16 SEER, when it is actually means up to 16 SEER. Plus different sizes of the same model may be a different SEER (ex: an XC16-024 may be 15.4 SEER while an XC16-048 may be only 14.6 SEER). True SEER ratings can be searched on the AHRI site.
EER (Energy Efficiency Ratio). This is a measure of how efficiently a cooling system will operate at peak load, or a specific outdoor temperature (95*). The higher the EER, the more efficient the air conditioner.
HSPF (Heating Seasonal Performance Factor) An equipment efficiency rating, usually used to rate a heat pump. Similar to car MPG, the higher the rating the more fuel efficient the equipment is.
Glossary of Hvac terms
13 SEER This is the new minimum efficiency standard (effective January 2006) for an air conditioner or heat pump. All new units must now meet this standard. Previously manufactured equipment may be used, sold, and installed.
ACCA (The Air Conditioning Contractors of America). A national trade association that represents heating, ventilation, air conditioning, and refrigeration contractors.
AHU (air handling unit or fan coil unit). Equipment with a heating element and/or cooling coil and other components in a cabinet or casing.
AHRI (Air-Conditioning, Heating and Refrigeration Institute). A non-profit, voluntary organization composed of heating, air conditioning and refrigeration manufacturers. AHRI publishes standards for testing and rating heat pumps and air conditioners.
AIR BALANCING Adjustment of a heating or an air conditioning system so that the desired amount of air is delivered to the areas in your home in order to achieve the correct heating or cooling effect.
BTU (British Thermal Unit). The measurement of heating and air conditioning capacity. A BTU is the amount of heat that must be added to one pound of water to raise its temperature one degree Fahrenheit.
CFC (Chlorofluorocarbons). A refrigerant in air conditioners and heat pumps, linked to the depletion of the ozone layer.
COP (Coefficient of performance). An efficiency ratio that compares the amount of heat delivered to the amount of energy used. The higher the ratio the more energy efficient the equipment.
COIL A heating or cooling element made of pipe or tubing, usually with plates or fins. Located in or near an AHU or furnace, or part of the outdoor condensing unit.
COMMISSIONING (Start-up). The final step in installing a heating or air conditioning system. Components should be checked and tested for compliance with codes, manufacturer requirements, and occupant needs. After commissioning, the technician will provide documentation of testing, provide equipment manuals, and show the homeowner how to operate the system.
CONDENSER The outside unit of an air conditioning system or a heat pump system. Here the refrigerant condenses from a gas to a liquid and hot or cold air from the building is released to the outside.
DEHUMIDIFIER Equipment that removes excess moisture from the air. Crucial for indoor residential swimming pool areas.
DOE (The U.S. Department of Energy). Federal agency that sets industry efficiency standards.
DUCT or Ductwork Conduits used to carry air. They can be round or rectangular, sheet metal or fiberglass or vinyl tubes. Air channels created for both return and supply delivery of conditioned air.
ERV (Energy Recovery Ventilator). Equipment that draws fresh air into the home and exhausts stale air to the outside.
ENERGY STAR® A government supported branding used as a recommendation of energy efficient products. This branding was developed by the US Department of Energy in cooperation with the US Environmental Protection Agency.
EPA The U.S. Environmental Protection Agency.
FAN COIL See AIR HANDLING UNIT
FURNACE Self-contained heating equipment designed to deliver heated air to a home.
GAMA (Gas Appliance Manufacturing Association). A national trade association serving the interests of manufacturers of gas, oil, and electric appliances and equipment, components and related products used in residential, commercial, and industrial applications.
HCFC (Hydrochlorofluorocarbons). Refrigerant in air conditioners and heat pumps. HCFCs were thought to contribute to the depletion of the earth’s ozone layer.
HEAT EXCHANGER The part of a furnace that transfers heat from burning of a fuel to the air used to heat your home. Also, from a boiler to water for hydronic heating.
HEAT PUMP A single refrigeration system designed for mild climates to provide both heating and cooling. Similar to a conventional feon-based central air conditioner.
HRV (Heat Recovery Ventilator). Equipment that provides fresh air into a structure while dispelling stale air to the outside. This unit also recovers some of the heat from the air stream and transfers it back inside, so it has less impact on your utility bill.
HFC (Hydroflorocarbon). A refrigerant used in air conditioners and heat pumps. Reputed to be environmentally friendly.
HUMIDIFIER A device that adds moisture to warm air for your home.
HVAC Heating, ventilating, and air conditioning
HVACR Heating, ventilating, air conditioning, and refrigeration
INFILTRATION Cold or hot air that sneaks into your home through holes, gaps, and cracks.
IAQ Indoor air quality
LATENT HEAT Energy that suspends moisture vapor in the air.
LOAD CALCULATION A mathematical determination of how much cooling, heating (BTUs), and air an HVAC system must deliver for occupant safety and comfort. This calculation looks at a variety of factors: square footage, building orientation, number of occupants, size and placement of rooms, number and size of windows and doors, amount of insulation, number of floors, climate, and historical weather data.
MANUAL D® An ACCA procedure outlining the proper design, sizing, and ductwork installation of a comfort system.
MANUAL J® An ACCA procedure covering the method for calculating heating and cooling requirements of a structure.
MATCHED SYSTEM A comfort system (furnace, coil, air conditioner or heat pump) composed of equipment that has been certified by AHRI to work efficiently together to deliver the specified heating and cooling capacity at a given efficiency rating.
MOLD (ACCA definition) A natural byproduct of the fungi family that thrives when organic substances and water combine under certain circumstances. Mold reproduces via spores that can remain dormant, yet viable, for years. Many molds are beneficial. For example, they are the “bleu” in bleu cheese, and we use them to make wine, penicillin, and antibiotics. However, some molds can cause health problems.
NATE (North American Technician Excellence). A nonprofit organization that certifies HVACR technicians.
PLANNED MAINTENANCE AGREEMENT An agreement reached between an hvac service contractor and a consumer to provide regular maintenance of an HVACR system.
R-22 Rrefrigerant containing chlorine used in air conditioning systems. Harmful to the ozone. Being phased out and replaced with other environmentally friendly refrigerants, such as R410a.
R-410A Environmentally friendly refrigerant that is rapidly taking the place of R-22 in residential applications. This is not a drop-in replacement. Equipment or component changes are required.
REFRIGERANT A fluid which flashes from a liquid to a gas and absorbs heat for transfer to a component which will dispell the heat and turn the gas back into a liquid.
REFRIGERANT CHARGE Amount of refrigerant in a system. This must be adjusted to proper levels by a qualified refrigeration specialist or technician.
RELATIVE HUMIDITY (RH). Percentage of the amount of moisture present in the air compared to the maximum amount of moisture the air can hold at that temperature.
RETURN AIR Air pulled to an air-handling unit or furnace so it can be cooled or heated before distribution back into the conditioned space.
SENSIBLE HEAT A thermometer measurement of the temperature of the air.
SPLIT SYSTEM A two-component comfort system with the two components located apart, such as a conventional furnace and central air conditioner, where the condensing unit is outside and the furnace and evaporator coil are located inside.
SUPPLY The delivery side of an HVAC system that moves conditioned air from the air-handling unit or furnace and distributes to the now conditioned spaces of your home.
ZONED SYSTEM Through use of dampers, a single HVAC system that can deliver different heating and cooling needs in different areas of the home. Each zone would have it's own thermostat for temperature and humidity control.
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