An Introduction to Central and Local Heating and Cooling Systems

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Heating, ventilation and air conditioning (HVAC) in the home has a few principal functions. These principles include controlling the temperature, the humidity, and maintaining the atmosphere quality. Heating and cooling systems are classified into two groups: Central and local systems.

 Central System

The central system is the most standard method for controlling the temperature in the home. It produces warm or cool air in one central area and then distributes it throughout the house. They may be either radiant or forced air. It is most commonly a central AC unit, as well. Some examples of central HVAC schemes include heat pumps, gas and oil furnaces, evaporator coils, and air conditioners.

Heating Using Central System

Heating units provide welcomed warmth to the home especially in cold climates. They are either radiant or forced air heating systems.

Radiant systems work by transferring heat from heated water or steam that is circulated through an arrangement of radiators or exchangers. The radiators transfer heat to the area or room by convection and not radiation.

Forced air central heating operates by heating an exchanger (usually a furnace) either by hot water, gas, electricity or oil. Air is forced to pass over or through the exchanger that warms the atmosphere. The hot ventilation circulates through sheet metal ducts which run into each room or area by registered vents.

Some typical warming products include heat pumps, gas and oil furnaces, fan coils, and broilers.

Cooling Using Central System

The central system used for AC relies on ducts to deliver the cooled ventilation throughout the home. The AC provides cooling, ventilation, humidity control, and even heat (if using a heat pump). Typical AC uses refrigerants such as Puron or Freon to distribute the cool breeze into the duct work.

The AC unit is placed outside the structure in the proximity of the furnace or boiler since the cool breeze circulates through the same ducts as the warm breeze. This sends a large amount of heat to the outside atmosphere.

The cooling unit helps control the humidity in the home by dehumidifying the atmosphere. This is important since mold is a major health concern in homes. The warm breeze that passes over the indoor evaporator coils does not hold as much moisture as when carried at higher temperatures. The extra moisture condenses on outside of the coils, and it is taken away through a drain. The process takes away the extra moisture relieving the area from mold.

AC homes often have sealed windows because the open window disturbs the control scheme from keeping a constant temperature in the structure

Some central cooling units are central AC, heat pumps, and evaporator coils.

Local Heating and Cooling

Local heating and cooling schemes produce hot and cool air at the location where it's needed and serves small spaces well. It gives immediate results to the area. It doesn't circulate throughout the entire structure.

Some examples of local units include window air conditioning units, wood or pellet stoves, space heaters, and sometimes baseboard heat if installed in a room or area which uses its own thermostat.

The Author is a marketing agent of Arundel Cooling and Heating. The HVAC contractor provides heating and air conditioning throughout Maryland. For more information on their HVAC Contractor please visit their website.