Glossary of Terms

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Desuperheater: A device for recovering superheat from the compressor discharge gas of a geothermal heat pump for use in heating or preheating water.

DOE: The Department of Energy is a federal agency responsible for setting industry efficiency standards and monitoring the consumption of energy sources.

Downflow: A type of furnace or fan coil that draws cool air from the top and blows the warm air out the bottom into the ductwork. This type of furnace is usually installed in closets and modular homes.

Dual fuel: A system that pairs an electric heat pump with a gas or oil furnace. The heat pump is a first stage heat with the gas or oil furnace providing second stage heat. This is an energy efficient alternative to the conventional gas/oil furnace/ air conditioner combination.

Ductless Split: An A/C or heat pump system that consists of an indoor evaporator blower unit and an exterior condensing unit. The indoor units are usually wall or ceiling based and connect to the outdoor condensing unit via insulated refrigerant lines. These units do not require any duct work and simply free-blow into a room, making them ideal for areas that are impossible to install ductwork. Many ductless split systems are modulating and have very high energy ratings.

Ductwork: Round, rectangular, or spiral hollow pipes that are used to transfer air from an air handler or furnace to the vents throughout a home or building. Ductwork is usually galvanized metal duct and should be insulated on the exterior in unconditioned spaces. Ductwork is one of the most important components of a home heating and cooling system. It is strongly recommended to seal the duct with mastic, as well as insulating, for optimum system performance.

EER: Energy Efficiency Ratio measure the efficiency with which a product uses energy to function. It is calculated by dividing a product’s BTU output by it’s input power in wattage at a particular outdoor condition and single point in time.

Electronic Air Cleaner (EAC): An electronic filtering device on a central system that filters out large particles and bioaerosols in indoor air.

Energy Star: An EPA (Environmental Protection Agency) designation attached to HVAC products that meet or exceed EPA guidelines for high-efficiency performance above the standard government regulations. Products with Energy Star ratings will be efficient and save cost on energy bills.