HVAC-Glossary

  • Acceptable indoor air quality – air in which there are no known contaminants at harmful concentrations
  • ACH – air changes per hour
  • Activated carbon – granular, processed carbon that is used in air filters to trap contaminants in the air.
  • Aerosol – liquid or solid particles suspended in air
  • AFUE – Annual Fuel Utilization Efficiency. AFUE is used to measure the percentage of energy that is converted into heat inside your home or building. For example, if a gas furnace is rated AFUE 95 it means that 95% of the fuel burned is converted into heat!
  • Air balancing – the process of adjusting your HVAC system to deliver the proper airflow to each room.
  • Air handler – the air handler is the term for the blower fan and heat transfer coil, as well as the housing of those components. It is used to move heated or cooled air from the HVAC system into your ducts.
  • Airflow – the distribution and movement of air throughout the house.
  • Attic fan – an attic fan is a fan mounted on your attic wall that exhausts warm attic air to the outside.
  • Attic vent – your attic vent is a mechanical device used to ventilate an attic space, primarily to reduce heat buildup and moisture condensation.
  • Baghouse Filter – a large fabric bag used to eliminate intermediate and large particles; it operates like a vacuum cleaner bag, allowing air and smaller particles to pass through it, while entrapping larger particles
  • Biological contaminants – contaminates derived from or that are living organisms (e.g., viruses, bacteria, fungi and mammal and bird antigens) that can be inhaled and cause many types of health effects including allergic reactions, respiratory disorders, hypersensitivity diseases and infectious diseases
  • Blower fan – the blower fan moves air from the return duct over the coil / heat exchanger. The circulated air is then heated or cooled and sent through the supply duct, past the dampers and into your home.
  • British thermal unit (BTU) – most furnaces and heating systems measure their heating output in terms of BTUs. One BTU is the amount of heat required to raise the temperature of one lb of water by one degree – this is equal to 252 calories.
  • BTUh – BTUs per hour. 12,000 BTUh = one ton of cooling capacity.
  • Carbon monoxide (CO) – a colorless, tasteless, odorless and extremely toxic gas that is produced when fuels that contain carbon are burned. Usually it is vented out of your house, but if your furnace is worn out or not properly maintained it can leak into your home.
  • Central air conditioner – an air conditioner where air is cooled and dehumidified at a central location and delivered throughout the house by an air handler and a network of ducts. This is in contrast to window air conditioners and ductless air conditioners.
  • Chlorinated solvents – organic solvents containing chlorine atoms, including methylene chloride, perchloroethylene and 1,1,1 trichloroethylene, often found in cleaning agents
  • Chronic exposure – long-term exposure to chemicals or pollutants, lasting anywhere from several weeks to a lifetime
  • Chronic toxicity – the ability of a substance to cause long-term poisonous human health effects
  • Coagulation – a joining together of particles that settle out in waste water; lime, alum, and iron salts induce the clumping of particles
  • Coil – the general term used to describe one of the main components of an HVAC system. The coil is made of tubing or pipe and often has fins to allow heat to radiate away.
    • Condenser coil – a network of outdoor tubes filled with refrigerant that removes heat from the heated gas refrigerant and converts the refrigerant into liquid form.
    • Evaporator coil – indoor tubes filled with refrigerant that remove heat and moisture from the air, evaporating the refrigerant into a gas.
  • Combustion– burning or rapid oxidation accompanied by a release of energy
  • Compressor – this is the outdoor unit on a split system air conditioner. The compressor puts pressure on the refrigerant in the air conditioner so that it can flow through the system.
  • Condenser – the condenser is a device in an air conditioner or heat pump where the refrigerant condenses from a gas into a liquid when it is depressurized or cooled.
  • Dampers – devices that change the way air flows through your ducts. Dampers can be usually be controlled, either manually or automatically.
  • Dual fuel – HVAC system that pairs up an electric heat pump and a gas furnace to provide energy-efficient heating and air conditioning as an alternative to a conventional furnace/AC combo.
  • Duct fan – a fan that helps blow air through your ducts. That one was easy.
  • Ducts – round or rectangular tubes, usually made of sheet metal, fiberglass board or a flexible plastic / wire composite. Your ducts carry the conditioned air through your home. Forced air HVAC system – any HVAC system that uses a fan to blow conditioned air through air channels or ducts.
  • Electronic air cleaner – an electronic device that filters out large particles and bioaerosols in the indoor air.
  • Freon – once a very popular refrigerant, it has been phased out in recent years because of a tendency to harm the environment.
  • Fuel efficiency – this refers to the amount of heat produced by your heating system vs. how much fuel you burn.
  • Heat exchanger – furnace component that transfers heat to the surrounding air to be pumped throughout the home.
  • Heat Pump – HVAC unit that heats and cools by moving heat from one area to another – from inside your home to outside in the summer and from outside your home to inside in the winter!
  • HEPA filters – High Efficiency Particulate Arrestance filters. HEPA filters are the most effective air filters available and are commonly found in high-end air cleaners.
  • Heating Seasonal Performance Factor (HSPF) – heating efficiency rating for heat pumps – the higher the rating, the more efficient the heat pump.
  • Humidifier – indoor air quality device that adds moisture to heated air as it moves from the furnace through the ducts.
  • Humidistat – device that allows you to control humidity levels from your humidifier.
  • MERV rating – rating that describes the size of the holes in an air filter. Higher numbers mean smaller holes and more effective filters.
  • Packaged air conditioner – air conditioner that had the evaporator, compressor and condenser all in the same unit.
  • Plenum – any air compartment connected to a duct or ducts.
  • R-22 Refrigerant – type of refrigerant used in many residential air conditioners that started being phased out in 2010 due to environmental concerns.
  • R410-A – chlorine-free refrigerant that meets the EPA’s strict environmental guidelines.
  • Return air – “used” air that is returning to your HVAC system to be reconditioned.
  • Return duct – a duct through which return air goes to be cycled back through your HVAC system.
  • Seasonal energy efficiency ratio (SEER) – a measure of efficiency for air conditioners and heat pumps. Specifically, the average BTUs of cooling delivered for every watt-hour of electricity used.
  • Split system air conditioner – an air conditioner that houses the different components in separate units.
  • Supply duct – duct through which conditioned air flows into your room.
  • Ton (in AC terms) – one unit of cooling capacity or 12,000 BTU per hour.
  • Zone (in AC terms) – an area within your home that is individually heated or cooled. A zone has its own thermostat for individual temperature control.
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