Glossary

Absolute Zero

The temperature at which molecular activity theoretically ceases.

Accumulator

A device installed in the suction line of a HVAC system to prevent liquids from entering the compressor

Air Balance

Distributing air through duct system to precisely match the required amount

Air Cleaning

To remove various airborne particulates and/or gases from the air. The three most common types of air cleaning are particulate filtration, electrostatic precipitation, and gas sorption

Air Conditioning

The control of the quality, quantity, humidity, and temperature of the air in an interior space

British Thermal Unit (BTU)

The amount of heat required to raise the temperature of one degree Fahrenheit, equal to 252 calories

Air Exchange Rate

The rate at which outside air replaces indoor air in a space. Expressed in two ways; the number of changes of air per unit of time- air changes per hour (ACH); or the rate at which a volume of outside air enters per unit of time- cubic feet per minute (CFM)

Carbon Monoxide (CO)

A colorless, odorless but poisonous combustible gas produced in the incomplete combustion of carbon and carbon compounds such as fossil fuels (i.e. coal, petroleum) and their products (e.g. liquefied petroleum gas, gasoline)

Combustion Air

Air that provides the necessary oxygen for complete and clean combustion and maximum heating value

Dampers

Controls that vary airflow through an air outlet, inlet, or duct. A damper position may be immovable, manually adjustable or part of an automated control system

Condensing Unit

The component of a central air conditioner that is designed to remove heat absorbed by the refrigerant and transfer it outside the conditioned space

Flue

The structure into which combustion gases flow and are contained until they are emitted into the atmosphere

Diffusers and Grilles

Components of the ventilation system that distributes and returns air to promote air circulation in the occupied space. Supply air enters through a diffuser and return air leaves through a grille

HEPA

Acronym for high efficiency particulate arrestance (filters)

HVAC

Acronym for heating, ventilation, and air conditioning system

Plenum

Air compartment connected to duct

IAQ

Acronym for indoor air quality

Negative Pressure

Condition that exists when less air is supplied to a space than is exhausted from the space, so the air pressure within that space is less than that in surrounding areas

R-Value

A measure of the capacity of a material to resist heat transfer. The larger the R-value of a material the greater its insulating properties

Preventative Maintenance

Regular and systematic inspection, cleaning, and replacement of worn parts, materials, and systems. Helps to prevent system failure

Relative Humidity

A measure of the percent of moisture actually in the air compared with what it would be if it were fully saturated, its relative humidity is 100%

Refrigerant

The fluid used in air conditioners, heat pumps, and refrigerators to transfer heat into or out of a space. This fluid boils at a very low temperature enabling it to evaporate and absorb heat

Seasonal Energy Efficiency Ratio (SEER)

Measurement of the annual or seasonal efficiency of an air conditioner or heat pump. It is the average number of BTU of cooling delivered for every watt-hour of electricity used

Ton

A unit of air conditioning capacity; 12,000 BTU per hour

Ventilation

The process of moving air (changing) into and out of an interior space either by natural or mechanically induced (forced) means

Variable Air Volume System (VAV)

Air handling system that conditions the air to a constant temperature and varies the outside airflow to ensure thermal comfort

Weatherezation

Caulking and filling of gaps around windows and exterior doors to reduce air infiltration and exfiltration into/out of a building

Zoning

The combination of rooms in a structure according to similar heating and cooling patterns. Zoning requires using more than one thermostat to control the temperature in separate areas