AIR HANDLER:
Indoor unit of an air conditioning system which contains heat exchange coil, filters, and fan. Provides conditioned air into the space.

AIR TO AIR ENERGY RECOVERY VENTILATION EQUIPMENT:
(AAERVE) Energy recovery components and packaged energy recovery ventilation which employ Air-to-Air Heat Exchangers to recover energy from exhaust air for the purpose of pre-conditioning outdoor air prior to supplying the conditioned air to the space, either directly or as part of an air-conditioning (to include air heating, air cooling, air circulating, air cleaning, humidifying and dehumidifying) system.

BTU:
British Thermal Unit. Used to measure cooling or heating capacity.

CAPACITY:
Refrigerating rating system usually measured in BTU ’s per hour (or Btu/h).

CFM:
An IP measure of airflow and volume, “Cubic Feet per Minute” also can be expressed in “Cubic Meters per Hour” - M3/H in SI. 1 CFM=0.58 x M3/H.

COMPRESSOR:
A pump found in a refrigerating or air conditioning system which pumps refrigerant through pipes between an outdoor condensing unit and an indoor evaporating unit, using pressure. Sometimes referred to as the heart of the refrigeration or a/c system.

CONDENSING UNIT:
Outdoor unit of an air conditioning system which contains compressor, propeller fan, circuit board, and heat exchange coil. Pumps refrigerant to evaporator.

EFFECTIVENESS:
The measure of energy recovery effectiveness not adjusted to account for that portion of the psychrometric change in the leaving supply air that is the result of leakage of entering exhaust air rather than the exchange of heat or moisture between the airstreams. (source: ARI-1060)

ENERGY RECOVERY VENTILATOR (ERV):
A ventilator combining a full enthalpic air-to-air heat exchanger which transfers both sensible heat and humidity (latent heat) between air streams with some combination of fans or blowers to provide fresh air into a building and exhaust air out of a building at minimized cost.

ENTHALPY EXCHANGE:
The exchange of both sensible and latent heat energies.

ENTHALPY:
A thermodynamic function of a system, equivalent to the internal energy plus the product of the pressure and the volume.

EXHAUST AIR (EA):
Sstale indoor air leaving a building

EXHAUST AIRFLOW:
Airflow leaving the conditioned space.

FRESH AIR (FA):
Outside ventilation air entering a building.

HEAT PUMP:
An air conditioning system that is capable of reversing the direction of refrigerant flow to provide either cooling or heating to the indoor space.

HEAT RECOVERY VENTILATOR (HRV):
A ventilator combining an air-to-air heat exchanger which transfers sensible heat between air streams with some combination of fans or blowers to provide fresh air into a building and exhaust air out of a building.

HSPF:
Heating Season Performance Factor. A rating of the average efficiency of a heat pump unit when operating in the heating mode.

HUMIDITY RATIO:
The weight of water divided by the weight of air containing the water vapor. This corresponds directly to the dewpoint temperature and does not change with air temperature.

HVAC:
General term and abbreviation for the industry of Heating, Ventilation, and Air Conditioning.

INVERTER:
Some outdoor units use inverter compressor technology (Variable Frequency Drive) to provide exceptional indoor, high-speed cooling and heating. By responding to indoor temperature changes, these systems reduce power consumption by varying the compressor speed for extra energy savings. The system operates only at the levels needed to maintain a constant and comfortable indoor environment.

LATENT ENERGY:
Potential heat energy as water vapor / Humidity.

MICROPROCESSOR:
Electrical component consisting of integrated circuits which may accept, store, control, and output information.

OUTSIDE AIR (OA):
Air outside a building in its natural state – Atmospheric Air.

PRESSURE DROP:
Pressure drop through the heat exchanger shall be expressed as the difference in static pressure between the Entering Supply Airflow and the Leaving Supply Airflow.

REFRIGERANT LINES:
Copper tubing through which refrigerant flows between condenser and evaporator coils. These lines are typically insulated when installed.

RELATIVE HUMIDITY:
The ratio of the amount of water vapor in a volume of air to the greatest amount of water vapor that could be in the same volume of air at the same temperature and pressure expressed as a percent. (source: ASHRAE F97)

RETURN AIR (RA):
Air inside a building returning to an HVAC system or ventilation system.

SEER:
Seasonal Energy Efficiency Ratio. A rating of the average efficiency of an air conditioning unit in cooling mode.

SENSIBLE HEAT:
Temperature

SPLIT-DUCTLESS SYSTEM:
Comprised of a remote outdoor condensing unit connected by refrigerant pipes to a matching, non-ducted indoor air handler. Special cases for introducing fresh air may call for limited ducting to air handler from outside.

STATIC PRESSURE:
Pressure classified as having a small or undetectable change with time. (source: ASHRAE F97)

THERMISTOR:
A resistor having semiconductor properties where resistance varies rapidly and predictably with changes in temperature.

VENTILATION:
The controlled introduction of outside air into a structure, complete with an equal amount of exhaust air.