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Cooling and Ventilation Equipment

Air Conditioners – Common Terms

Here are some common terms you will come across when considering the purchase of an air conditioner:

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 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 and circulating 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 immediately above the heat exchanger.

Other terms

  • Btu/h (British thermal unit per hour): a measure of the output of a heating or cooling system, the amount of heat required to raise or lower the temperature of a pound of water by a single degree fahrenheit. One Btu is the amount of heat energy given off by a typical birthday candle. The heat energy released by a candle over the course of one hour is the equivalent of one Btu/h.
  • Watt (W): the standard unit of power; one kilowatt (kW) equals 1000 watts. This is the amount of power required by ten 100-watt light bulbs.
  • Ton: a measure of cooling capacity. It is equivalent to 3.5 kW or 12 000 Btu/h.
  • Cooling capacity of an air conditioner (expressed in Btu/h): indicates the quantity of heat a room air conditioner can remove in one hour.
  • Cooling load (expressed in Btu/h): the maximum amount of heat, under design conditions, that builds up in a space without a cooling system operating. It is calculated to determine the capacity of air conditioner required.
  • Heat gain: a term applied to various components of the heat load, such as appliance heat gain and solar heat gain. All heat gain components are summed to calculate the cooling load.
  • Oversizing: the selection of an air conditioner with a cooling capacity greater than the cooling load.
  • Undersizing: the selection of an air conditioner with a cooling capacity smaller than the cooling load.
  • Energy efficiency ratio (EER): a comparative measure of cooling provided by an air conditioner for each unit of electrical energy it consumes under standard operation. A unit's EER is calculated by dividing its cooling capacity by its electrical power input at a specific temperature. In general, the higher the EER, the more efficient the unit.
  • Seasonal energy efficiency ratio (SEER): measures the cooling efficiency of an air conditioner over an entire cooling season. It is determined by dividing the total cooling provided over the cooling season, in Btu/h, 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.
  • Bel (B): 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 is approximately 6.5 B.