HVAC Terminology

  • AFUE (Annual Fuel Utilization Efficiency): AFUE is an expression of gas furnace efficiency, and higher AFUE ratings indicate better efficiency. Federal law requires that new residential furnaces (constructed after 1992) operate with an AFUE of 78 percent or better. Furnaces built before 1992 operate, on average, at 60 percent AFUE. In such cases, homeowners should consider the energy and cost savings of installing a newer, high efficiency unit.
  • ARI (Air Conditioning and Refrigeration Institute): ARI is a non-profit HVAC organization that helps to regulate industry quality. ARI publishes ratings standards for testing heating and cooling products.
  • BTU (British Thermal Unit): A BTU is the amount of heat required to raise or lower the temperature of one pound of water by one degree (F).
  • BTUH (British Thermal Units per Hour): The heat transfer rate of heating and cooling systems is measured in BTUHs.
  • Capacity: Typically measured in tons or BTUs, an HVAC unit’s capacity refers to its ability to heat or cool a specified area.
  • CFM (Cubic Feet per Minute): CFM is used to express the movement of air volume. In the case of a blower or fan, it indicates how much air can be moved per minute.
  • Compressor: Compressors are critical to cooling your home or business. A compressor pumps refrigerant through a unit’s coil and refrigerant lines, which allows heat to be transferred outdoors.
  • Condenser: Also called the outdoor coil, a condenser helps dissipate heat to the outside air. When a heat pump is used in heating mode, this role is reversed.
  • COP (Coefficient of Performance): COP, or CP, is used to rate a heat pump’s electrical efficiency. ARI designates the COP at 47 degrees (F) and 17 degrees (F).
  • dB (Decibel): Decibels are the relative loudness of a sound, and can be used to measure the noise level of HVAC equipment.
  • DOE (Department of Energy): The DOE is a federal agency that monitors resource consumption and sets HVAC efficiency standards.
  • Downflow: Describes a direction of furnace airflow. Since heat rises, downflow furnaces take advantage of this. As cool air enters the unit’s top, it is heated and allowed to exit the bottom of the furnace—where it is sent through heating vents and rises to warm up a room.
  • Ducts: Central air conditioning systems rely on many components to cool or heat the air, and that air is then transferred to many rooms via large-diameter ducts or pipes. Your home’s duct system is referred to as ductwork or ducting.
  • EER (Energy Efficiency Ratio): EER represents the ratio of AC cooling capacity in BTUs per hour/wattage. Higher EERs indicate higher efficiency.
  • Efficiency: Generalized term that describes how effectively a heating or cooling system converts incoming to outgoing energy. High-efficiency HVAC units work better—and are less costly to operate.
  • Evaporator Coil/Evaporator: Another critical part of your heat pump or AC system. As warm air passes over a refrigerant-filled coil, the refrigerant evaporates and absorbs heat from the air. The resulting gas refrigerant is then pumped to an outdoor coil, which releases heat into the air and turns refrigerant back into a liquid.
  • Heat Exchanger: Moves heat from furnace burners to your system’s blower.
  • HOR Flow (Horizontal Flow): Describing the airflow direction through a furnace. A HOR flow furnace pulls in air from one side, and after heating it, delivers warm, arid air out the other side.
  • HSPF (Heating Seasonal Performance Factor): Similar to SEER, HSPF measures your heat pump’s heating efficiency. According to the Department of Energy, the minimum HSPF is 6.8.
  • Humidifier: Added as an optional accessory to your HVAC system, a humidifier injects water vapor into dry, heated furnace air. Benefits include increased energy efficiency, improved home comfort and reduced upper respiratory dryness.
  • HVAC (Heating, Ventilating & Air Conditioning): Commonly used to refer to heating and air conditioning manufacturers and contractors—and the industry at large.
  • Indoor Coils: Split-systems utilize two main components for air delivery. The indoor coil transfers heat from inside to outside (or the reverse for heating pump mode). Contemporary systems are designed to be energy efficient when the indoor unit (blower and coils) is properly matched with outdoor equipment (heat pump or air conditioner). For best results, customers should replace indoor/outdoor system units at the same time.
  • kW (Kilowatts): The unit used to express 1,000 Watts. kWh (Kilowatts per Hour): When an HVAC unit uses 1,000 Watts in 1 hour, it is given an energy rating of 1 kWh.
  • Package Unit: Used to denote a cabinet that houses all heating and cooling components in one place. Package units are typically installed on top of or next to a home or commercial facility.
  • Refrigerant: A liquid that absorbs and transfers heat from one area of an HVAC system to another.
  • Refrigerant lines: Copper tubes that transfer refrigerant between indoor and outdoor cooling units.
  • SEER (Seasonal Energy Efficiency Rating): The SEER is used to denote the efficiency of a heat pump (in cooling mode) or air conditioning unit. The Department of Energy SEER minimum is 10. Higher SEER ratings are more efficient and desirable.
  • Split System: Home comfort systems that utilize indoor and outdoor components to delivery climate-controlled air.
  • SRN (Sound Rating Number): The Air Conditioning and Refrigeration Institute performs tests and assigns an SRN to HVAC units. Average SRNs range between 74dB and 80dB, and lower SRNs indicate quieter units.
  • Thermostat: A device that measures and controls the temperature of home comfort systems. Programmable thermostats are an energy-efficient way to manage temperatures throughout the day, and when properly used, can be used to save on household utilities.
  • Ton: Ton ratings do not denote a unit’s weight. Instead, a ton represents 12,000 BTUs. Typical home heating/cooling units use equipment with a capacity of 1.5 to 2 tons.
  • Upflow: Used to describe airflow direction through a furnace. An upflow furnace takes return air from the bottom, heats it, and delivers it from the unit’s top.
  • W (Watt): Expression of electrical power. A 60W globe consumes 60 Watts of electrical power. Watts were named after a person, and therefore the term is uppercased.
  • Zone: Your home or facility may be divided into a number of different heating or cooling areas, which are called zones.

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