HVAC Glossary Of Terms

AIR FLOW:
The amount of air that a blower system circulates through your home, expressed in cubic feet per minute (CFM). A typical system requires 400 CFM per ton of cooling.

AFUE:
The Annual Fuel Utilization Efficiency (AFUE) number compares the percentage of heat delivered to your home vs. the amount exhausted from the home. Mid-efficiency furnaces deliver approximately 80% AFUE and high-efficiency furnaces deliver approximately 90% or more. The difference between a high- and a mid-efficiency furnace is that the high-efficiency furnace is a "condensing" furnace, which means that the combustion gases, including steam, are cooled from about 350°F to about 100°F. This makes the steam condense back into water, allowing more heat to be recovered and less to escape into the outside environment. A high-efficiency furnace offers you a higher AFUE or energy efficiency rating, which saves you fuel costs.

BEL:
The bel (B) is a unit of sound measurement equivalent to 10 dB (decibels). It is used for rating the sound made by the outdoor unit of an air conditioner. The lower the number, the quieter the unit. The industry standard maximum sound for new air conditioning equipment is 7.6 Bels. For every .3 Bels lower, on a sliding scale, the sound is reduced. 7.3 would be one half of the standard.

BTU:
A British Thermal Unit, is the amount of energy required to change the temperature of one pound of water one degree Fahrenheit. For your home, it represents the measure of heat given off when fuel is burned. 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.

COIL:
A coil is a system of tubing loops through which refrigerant flows where heat transfer takes place. The tubing has fins to increase the surface area available for heat exchange. It removes heat and moisture as refrigerant changes from liquid to gas.

CONDENSER:
The condenser is a coil that allows the refrigerant gas to give off heat to its surroundings and become a liquid. An expansion device releases the pressure created by the compressor. This causes the temperature to drop and the refrigerant to becomes a low-temperature vapor/liquid mixture.

EVAPORATOR:
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 vapor. The compressor squeezes the molecules of the refrigerant gas together, increasing the pressure and temperature of the refrigerant.

HVAC:
A common industry short-form for heating, ventilation, and air conditioning. Pronounced h-vac.

MERV:
The Minimum Efficiency Reporting Value is the standard comparison of the efficiency of an air filter. The MERV scale ranges from 1 (least efficient) to 16 (most efficient), and measures a filter's ability remove particles from 3 to 10 microns in size.

PLENUM:
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.

REFRIGERANT:
A fluid that changes from liquid to gas at low temperatures that circulates through the air conditioner, alternately absorbing, transporting, and releasing heat and humidity out of the air. Common refrigerants include Puron and Freon.

SEER:
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 28oC. The higher the SEER, the more energy-efficient the unit. The Ontario government's minimum standard is 10 SEER. An increase in SEER value from 10 to 11 represents an increase in efficiency of approximately 10% and a decrease in operating costs of approximately 10%.

TON:
The term "ton" was originally based on the amount of ice it would take to achieve a desired level of cooling. Now it is more typically used as a measure for an air conditioning system's capacity. It is equivalent to 3.5 kW or 12 000 Btu/h. A kW, or kilowatt, is equal to 1000 watts. This is the amount of power required by ten 100-watt light bulbs. 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 test 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. One ton is equivalent to 12,000 BTUs per hour of cooling. Residential air conditioners usually range from one to five tons. For a smaller home, you would typically need 18,000 BTUs or 1.5 tons of energy to cool the home effectively.

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