Types of Heating and Air Conditioning Systems...

There are two basic methods of conditioning a room or building.  The first type is a radiant system, the second type is a forced air system.

Radiant Systems usually involve running hot or chilled water through pipes that loop around the structure and radiate into the conditioned space via a floor surface or radiator pipe.

Forced air systems use a fan to push air through a duct system where it is conditioned by a coil on a furnace or air handler before being returned to the space.  Most systems in the Fredericksburg Virginia area are forced air systems fueled by either gas (LP, or CNG) or electricity (Heat Pump / Air Conditioner).

The Heat Pump

A heat pump, comprised of an outdoor condenser and indoor air handler, uses electricity to move heat from one location to another.  In the summer a heat pump acts just like an air conditioner removing heat from inside your home and exhausting it to the outside.  In the winter, a heat pump runs backwards removing heat from the outside and exhausting it indoors.  As the outside temperature falls, eventually there is not enough heat outside to meet the requirements of the indoor occupants.  At this point, a heat pump system will use supplemental electrical resistance heaters (sometimes called aux heat or emergency heat) to warm the air and satisfy the thermostat.

Heat pumps have two ratings for efficiency.  In cooling mode a heat pump is rated in SEER (Seasonal Energy Efficiency Rating) just like an air conditioner.  Common SEER values range from 10 to 18+ SEER.  In heating mode, heat pumps are rated in HSPF (Heating Season Performance Factor) with values ranging from 6.5 to 9+.  The efficiency numbers are usually related to each other in that high SEER equipment also has a high HSPF rating.

The Air Conditioner & Gas Furnace

An air conditioner and coil are coupled to a gas furnace to make a complete heating and air conditioning system.  The gas furnace provides heat by combusting natural gas or propane and contains a fan which forces air over a cooling coil when the system is air conditioning.  Gas furnaces are rated in AFUE which corresponds to the percent of fuel energy that warms the air versus going up the flue pipe.  For example, an 80 AFUE furnace suggests that for every dollar of fuel purchased 80 cents is used the warm the air and 20 cents goes up the flue pipe.  Air conditioners are rated in SEER similar to heat pumps.

The Dual Fuel System