Direct current electricity. This type of electricity (as opposed to Alternating Current, or AC) flows in one direction only, without reversing polarity.
Glossary of Terms
To melt frost; as in from an air conditioner or heat pump coil.
A computation that gauges the amount of heating or cooling needed for a building. A degreeday is equal to 65 degrees Fahrenheit minus the mean outdoor temperature.
An air cooler that removes moisture from the air.
A grille over an air supply duct having vanes to distribute the discharging air in a specific pattern or direction.
Department of Energy
A furnace that intakes air at its top and discharges air at its bottom.
Also referred to as a condensate pan. This is a pan used to catch and collect condensate (in residential systems vapor is liquefied on the indoor coil, collected in the drain pan and removed through a drain line).
Heat intensity, measured by a dry bulb thermometer.
An instrument that measures air temperature independently of humidity.
A pipe or conduit through which air is delivered. Ducts are typically made of metal, fiberboard or a flexible material. In a home comfort system, the size and application of ductwork is critical to performance and is as important as the equipment.
Direct expansion. A system in which heat is transferred by the direct expansion of refrigerant.
Energy Efficiency Ratio (steady state)
Environmental Protection Agency
The other half of an air conditioning system, located inside your home in the indoor unit. This is a tubing coil in which a volatile liquid evaporates and absorbs heat. This is where the refrigerant evaporates as it absorbs heat from the indoor air that passes over the coil.
A refrigerant metering valve with a pressure or temperature controlled orifice.
The temperature scale on which water freezes at 32 degrees and boils at 212 degrees; designated by the letter F. To convert Fahrenheit to Celsius, subtract 32 from the Fahrenheit number, multiply by 5 and divide by 9 (77 32 equals 45, times 5 equals 225, divided by 9 equals 25 degrees Celsius).
Any device that creates air currents.
Any device that removes impurities through a straining process.
Any vent or passageway that carries the products of combustion from a furnace.
That part of the heating system in which the combustion of fossil fuel and transfer of heat occurs.
A metal strip in an electrical circuit that melts and breaks the circuit when excessive current flows through it. The fuse is designed to break in order to save more expensive electrical components.
Gas Appliance Manufacturers Association.
Located in the furnace, the heat exchanger transfers heat to the surrounding air, which is then pumped throughout your home.
An area, box or coil where heat flows from the warmer to the colder fluid or surface.
Heat added to the conditioned space by infiltration, solar radiation, occupant respiration and lighting.
The rate of heat transfer from a heated space to the outdoors.
A mechanical compression cycle refrigeration system that can be reversed to either heat or cool the controlled space.
The movement of heat energy from one point to another. The means for such movement are conduction, convection, and radiation.
Any coil that serves as a heat source.