How Your A/C Works
conditioning includes both the cooling and heating of air. It also cleans the
air and controls the moisture level.
An air conditioner is able to cool a building because it removes heat
from the indoor air and transfers it outdoors. A chemical refrigerant in the
system absorbs the unwanted heat and pumps it through a system of piping to the
outside coil. The
fan, located in the outside unit, blows outside air over the hot coil,
transferring heat from the refrigerant to the outdoor air.
Most air conditioning systems have
five mechanical components:
- a compressor
- an expansion valve or
- an evaporator coil and blower
- a chemical
Most central air conditioning units operate by means of a split
system. That is, they consist of a "hot" side, or the condensing unitincluding
the condensing coil, the compressor and the fanwhich is situated outside
your home, and a "cold" side that is located inside your home. The
cold side consists of an expansion valve and a cold coil, and it is usually part
of your furnace or some type of air handler. The furnace blows air through an
evaporator coil, which cools the air. Then this cool air is routed throughout
your home by means of a series of air ducts. A window unit operates on the same
principal, the only difference being that both the hot side and the cold side
are located within the same housing unit.
The compressor (which is
controlled by the thermostat) is the "heart" of the system. The
compressor acts as the pump, causing the refrigerant to flow through the system.
Its job is to draw in a low-pressure, low-temperature, refrigerant in a gaseous
state and by compressing this gas, raise the pressure and temperature of the
refrigerant. This high-pressure, high-temperature gas then flows to the
The condenser coil is a series of piping with a fan that draws outside
air across the coil. As the refrigerant passes through the condenser coil and
the cooler outside air passes across the coil, the air absorbs heat from the
refrigerant which causes the refrigerant to condense from a gas to a liquid
state. The high-pressure, high-temperature liquid then reaches the expansion
The expansion valve is the "brain" of the system. By sensing
the temperature of the evaporator, or cooling coil, it allows liquid to pass
through a very small orifice, which causes the refrigerant to expand to a
low-pressure, low-temperature gas. This "cold" refrigerant flows to
the evaporator coil.
The evaporator coil is a series of piping connected to a furnace or
air handler that blows indoor air across it, causing the coil to absorb heat
from the air. The cooled air is then delivered to the house through ducting. The
refrigerant then flows back to the compressor where the cycle starts over again.