AIR-SOURCE HEAT PUMP REVERSE MOTION
A heat pump is basically an air conditioner that works in reverse to provide heat. The heat pump captures and concentrates heat from one area, then releases it to another.
In heating mode the heat pump takes heat from the outdoor air and delivers it to the home’s distribution system. In cooling mode it reverses direction to work like an air conditioner, extracting heat from inside the house and blowing it outside. In cooling mode, this waste heat can also be used for water heating. The most common type is the split system, which uses separate indoor and outdoor units, but you can also get packaged systems that place everything in a self-contained outdoor unit. While air-source heat pumps can offer efficiencies of 200%–300%, they’re most efficient in the southern part of the country. A backup electric or gas heater may be needed when the outside air drops below a certain temperature. Although different versions are made for forced air and hydronic distribution, the forced air type is the most common. Heat pumps don’t get air as hot as a furnace or boiler, so may require more airflow to maintain the same temperature.
AIR-SOURCE HEAT PUMP -
VIRTUES
> Can provide heating and cooling
> No need for a chimney or exhaust flue
> More fuel-efficient than a fossil fuel furnace or boiler
CAVEATS
> Not practical in very cold climates
> Does not get air as hot as a furnace
GLOSSARY OF TERMS KNOW THE LINGO
> Annual Fuel Utilization Efficiency (AFUE)
The percentage of a fuel’s potential energy that a furnace or boiler converts to usable heat. Government standards that take effect in 2015 require AFUE levels of 82% for gas boilers, 83% for oil boilers, 80% for gas furnaces, and 82% for oil furnaces.
> Air Handler
In a forced air heating or cooling system, the air handler unit moves heated or cooled air through the home’s ductwork.
> British Thermal Unit (BTU)
The unit of measurement for heat, whether it’s the heat given off by burning fuel or extracted from a home for cooling. Technically, one BTU is the energy required to raise one pound of water one degree Fahrenheit.
> Combustion Chamber
The part of a furnace or boiler where the fuel is burned.
> Compressor
That part of the air conditioner or heat pump that compresses and pumps refrigerant.
> Condenser Coil
That part of an air conditioner or heat pump that releases heat from the surrounding air in cooling mode and collects it in heating mode.
> Distribution System
The network of air ducts or hot water pipes that delivers heat from a furnace, boiler, or heat pump to the home’s rooms.
> Evaporator Coil
That part of an air conditioner or heat pump that exchanges heat with the air in the home.
> Heat Exchanger
Located in the furnace or boiler, it transfers heat from the combustion chamber to the air or water in the heat distribution system.
> Heating Seasonal Performance Factor (HSPF)
The heating efficiency of a heat pump. It’s a ratio of the heat it generates over the heating season, in BTUs, to the Watt-hours of electricity it consumes. Heat pumps manufactured after 2006 have to have an HSPF of at least 7.7, but the best units have ratings as high as 10.
> Seasonal Energy Efficiency Ratio (SEER)
The cooling efficiency of an air conditioner or heat pump. It’s the ratio of cooling output to electricity used. The minimum SEER requirement for units manufactured beginning in 2006 is 13.
> Zoning
A method of partitioning a home’s hydronic or forced-air distribution system into independently controlled comfort zones.
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