Maintaining And Troubleshooting Cooling Systems

You've probably noticed that degree for degree, cooling consumes far more energy than heating. Why?

The answer lies in the nature of the cooling process. The cooling unit must absorb heat from the air -- a big task in itself. It also has to reduce humidity to a more comfortable level. It does this by overchilling the air, then pushing controlled amounts of warm, humid air through the cooling coil, causing moisture to form on the coil. This moisture is carried away through a condensate drain.

What's more, cool air weighs more than warm air, so , unlike heat, it doesn't tend to rise of it's own accord. The result: First you pay dearly to lower the temperature and humidity of the air, then you need additional energy to move it around.

Any inefficiency in a room air conditioner or a central system just compounds the already heavy electrical loads it needs. To minimize this energy draw, you must keep your home's cooling equipment in top working order.

Begin by familiarizing yourself with the two principle components of a cooling system. One of these is a condensing unit, in which refrigerant is condensed into a liquid. You'll always find this component located outdoors, where it can release heat (and most of the system's noise) to the outdoor air.

The condensing unit then sends the now-cool refrigerant to an evaporator coil inside the house. Here, a blower moves air through the coil to cool and dehumidify it. If yours is a central system, the evaporator coil is located in the furnace plenum, and the blower is the furnace's blower. Room air-conditioners house all their parts in a single, two-compartment cabinet. Heat pumps -- essentially two-way air-conditioners -- have additional components.

Anatomy of a central cooling system

To trace the circuits of heat and cold through a whole-house air-conditioning system, study the drawing above. Outdoors, a compressor and condenser coil "make cold" by pressurizing refrigerant gas, which loses heat as it turns to a liquid. The coil, a network of tubing and fins, transfers the heat to the outdoor air pulled through it by a fan. Cool refrigerant flows through tubing to the evaporator coil, where the refrigerant absorbs heat from air pushed through it by the furnace blower.

Cool, dry air then moves into the plenum. Meanwhile, water that condensed from the air in the plenum runs down a condensate drain. The refrigerant, a hot gas once again, returns through another line to the condensing unit.