2. Air Conditioning Terminology
Here are some common terms you will come across when comparing and determining
the best choice for air conditioners:
COMPONENTS OF AN AIR CONDITIONER
The refrigerant is a substance that circulates through the
air conditioner, alternately absorbing, transporting and releasing heat.
A coil is a system of tubing loops through which refrigerant
flows and where heat transfer takes place. The tubing may have fins to increase
the surface area available for heat exchange.
The evaporator is a coil that allows the refrigerant to absorb
heat from its surroundings, causing the refrigerant to boil and become a low-temperature
vapour.
The compressor squeezes the molecules of the refrigerant gas
together, increasing the pressure and temperature of the refrigerant.
The condenser is a coil that allows the refrigerant gas to
give off heat to its surroundings and become a liquid.
The expansion device releases the pressure created by the
compressor. This causes the temperature to drop and the refrigerant to become
a low-temperature vapour/liquid mixture.
The plenum is an air compartment that forms part of the system
for distributing warmed or cooled air through the house. It is generally a large
compartment immediately above the heat exchanger.
OTHER TERMS
A Btu/h or British thermal unit per hour, is a measure of
the heat output of a heating system. One Btu is the amount of heat energy given
off by a typical birthday candle. If this heat energy were released over the
course of one hour, it would be the equivalent of 1 Btu/h.
A kW or kilowatt, is equal to 1000 watts. This is the amount
of power required by ten 100-watt light bulbs. A ton is a measure of cooling
capacity. It is equivalent to 3.5 kW or 12 000 Btu/h.
The capacity of an air conditioner is a measure of the maximum
rate at which it can remove heat from the conditioned space. Capacity is expressed
in British thermal units per hour or tons and is determined under a specific
set of best conditions.
The cooling load also stated in British thermal units per
hour, is the maximum amount of heat that builds up in a space without a cooling
system operating. It is calculated to determine the capacity of air conditioner
required.
Heat gain is a term applied to various components of the heat
load, such as appliance heat gain and solar heat gain. All of the heat gain
components are summed to calculate the cooling load.
Over sizing is the practice of selecting an air conditioner
with a cooling capacity greater than the cooling load.
Under sizing is the practice of selecting an air conditioner
with a cooling capacity smaller than the cooling load.
The energy efficiency ratio (EER) is a measure of how much
cooling effect is provided by the air conditioner for each unit of electrical
energy that it consumes under steady-state operation. It is determined by dividing
the cooling output of the unit, in British thermal units per hour, by the electrical
power input, in watts, at a specific temperature. The higher the EER, the more
efficient the unit.
The seasonal energy efficiency ratio (SEER) is a measurement
of the cooling efficiency of the air conditioner over the entire cooling season.
It is determined by dividing the total cooling provided over the cooling season,
in British thermal units per hour, by the total energy used by the air conditioner
during that time, in watt/hours. The SEER is based on a climate with an average
summer temperature of 28°C.
The bel (B) is a unit of sound measurement equivalent to 10
dB (decibels). One bel is the threshold of human audibility. The sound level
in a busy typing and accounting office would be approximately 6.5 B.
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Source: Natural Resources Canada (NRCan)
- Office of Energy Efficiency
