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Common Heating and Air Conditioning Terms

AFUE:     Annual Fuel Utilization Efficiency (AFUE) is the measurement of how efficiently a gas furnace or boiler will operate over an entire heating season. It's like a miles per gallon rating for a car. The AFUE is expressed as a percentage of the amount of energy consumed by the system that is actually converted to useful heat. For instance, a 90% AFUE means that for every BTU worth of gas used over the heating season, the system will provide .9 BTU of heat. The higher the AFUE, the more efficient the system.


Blower:     The blower, or fan, is what draws the air from the return duct and blows it through the heat exchanger and evaporator. There are three types of blowers: single-speed, three-speed and variable speed. Variable is the most efficient. The size of the blower determines how much air will be delivered to the home and how efficient the air conditioner will perform.


BTU:     The British Thermal Unit (BTU) is a measurement of heat. It is used to determine how much heat is needed to warm the home or how much heat we need to remove to cool the home. it takes one BTU of heat to warm one pound of water by 1 degree Fahrenheit. Heating and air conditioning equipment is rated with the BTU capacity needed to heat or cool the home. 

For air conditioning every 12,000 BTUs = 1ton. Air conditioning sizing is as follows: 
24,000 BTUs = 2.0 ton

30,000 BTUs = 2.5 ton

36,000 BTUs = 3.0 ton

42,000 BTUs = 3.5 ton

48,000 BTUs = 4.0 ton

60,000 BTUs = 5.0 ton

Our furnace equipment pricing is determined by the blower size needed for air conditioning and is rate in tons. Furnace sizes range from 40,000 BTUs to 150,000 BTUs.


Burners:     The burner is where combustion of the fuel takes place. Some o the causes of carbon monoxide are dirty burners and too little air for combustion at the burner. This can also be a fire hazard. 


Certification:      The awarding of a credential acknowledging that an individual has demonstrated proof of a minimum level of knowledge or competence, as defined by a professional standards organization. Professional certification can be used as a screening tool and as verification of an individual's skills or knowledge. 


Compressor:     The compressor is the heart of an air conditioning or heat pump system. It pumps the coolant through the system. There are two types of compressors: piston-type and scroll-type. The scroll-type is the most efficient and reliable compressor. 


Condensing Coil:     The condensing coil is what cools the coolant as it is pumped out of the compressor. The bigger the condensing coil, the more efficient the system will be. There are coils made of copper or aluminum. The copper type can be easily repaired if it develops a leak. A leaking aluminum condensing coil would need to be replaced. 


COP:     Coefficient of performance (COP) is the measurement of how efficiently a heating or cooling system will operate at a single outdoor temperature condition. When applied to the heating modes of heat pumps, that temperature condition is usually 47 degrees Fahrenheit. The higher the COP, the more efficient the system. COP can be calculated by two different methods. 

In the first method, you divide the BTU of heat produced by the heat pump by the BTU equivalent of electricity that is required to produce that heat. This formula is stated:

BTU of heat produced at 47 degrees Fahrenheit COP = _______ BTU worth of electricity used at 47 degrees.

The second formula is most frequently used to determine chiller efficiency. Using this calculation method, yo would divide 3.516 by the number of kilowatts (kW) per ton used by the system. We do not have a lot of chillers in the Omaha Metro area. 


EER:     Energy Efficiency Ratio (EER) is a measure of how efficiently a cooling system will operate when the outdoor temperature is at a specific level (usually 95 degrees Fahrenheit). A higher EER means the system is more efficient. The term EER is most commonly used when referring to window and unitary air conditioners and heat pumps, as well as water-source and geothermal heat pumps. 


EPA:     Environmental Protection Agency


Evaporator Coil:     The evaporator is where the coolant flows through. The blower blows air through the evaporator and it cools or heats the air. 


Filter:     There are basically three types of filters. The basic equipment protector catches the larger dust. The other two types help control indoor air pollution. The polarizing media type is 600 times more efficient than common filters and cleans the air of dust, pollen, and spores. The HEPA type filters remove microscopic particles and are similar to the filters used in hospitals, clean rooms, and microchip plants. HEPA filters are 12,000 times more efficient than common filters. 


Flue:     The poisonous fumes that come from the flames are vented out of the home through the flue. The most efficient furnaces use plastic pipes that go through the wall. If the flue is incorrect, it can be a fire hazard or cause carbon monoxide poisoning. 


Heat Exchanger:     Heat exchangers are steel chambers that transfer heat from the flames to the air. If the system is oversized or the ducts are too small, the heat exchanger will overheat and stress will occur.This can cause the heat exchanger to crack, which can allow carbon monoxide to enter the home. 


Heat Pump:      A heat pump operates like an air conditioner is the summer. In the winter, a heat pump reverses the process. It blows the cold air outside and the warm air inside. All heat pumps must have a back-up source of heat for very cold weather. When you pair your heat pump with a gas or oil furnace, it is referred to as a dual fuel application and is one of the most efficient ways to heat or cool your home. 


HSPF:     Heating Seasonal Performance Factor (HSPF) is the measurement of how efficiently all residential and some commercial heat pumps will operate in their heating mode over an entire normal heating season. The higher the HSPF, the more efficient the system. HSPF is determined by dividing the total number of BTUs of heat produced over the heating season by the total number of watt-hours of electricity that is required to produce that heat. You must have the exact match to get the manufacturer's listed HSPF rating. The formula is written: 

BTU of heat produced over the heating season HSPF = ______ watt-hours of electricity used over the heating season


Humidifier:     Years ago people placed pans of water on radiators or stoves to add moisture to the air. Whole-house evaporative humidifiers precisely control the humidity in the home without creating the mold and mildew problems that can occur with the reservoir type. Reservoir humidifiers do no drain the water that doesn't evaporate. It sits in the bottom, where slime and mold can grow. 


Metering Device:     The metering device controls the amount of coolant that flows through the evaporator. There are two types of metering devices: fixed opening and modulating, with modulating being the most efficient type. If the metering device is not the right match, too much coolant could flow through the evaporator and damage the compressor. 


OxyQuantum:     This is a high intensity, medical grade germicidal ultra-violet air purifier that will eliminate airborne germs such as bacteria and viruses. This product has been used in hospitals for more than 50 years to kill airborne diseases such as measles, tuberculosis and influenza. This product can dramatically reduce mold, fungus, odors, such as smoke, gases, and toxic agents such as formaldehyde, xylene, and other hydrocarbons.


Refrigerant Lines:     The refrigerant lines must be clean and be the correct size, or increased operating costs and reduced compressor life will result. 


Return Air Duct:     The return air duct is the duct on the suction side of the blower. If the return air duct is undersized, it can increase operating costs as much as 30%. Improper airflow will reduce heat exchanger and compressor life. 


SEER:     Seasonal Energy Efficiency Ratio (SEER) measures how efficiently a residential central cooling system (air conditioner or heat pump) will operate over an entire cooling season, as opposed to a single outdoor temperature. As with EER, a higher SEER reflects a more efficient cooling system. SEER is calculated based on the total amount of cooling (in BTU) the system will provide over the entire season divided by the total number of watt-hours it will consume. By federal law, every central split cooling system manufactured in the US today must have a SEER of at least 13.0.


Supply Duct:     The supply duct distributes the air to the home. Undersized supply ducts will create airflow problems and hot and cold spots in the home. If the supply duct is undersized, it can increase operating costs as much as 30%. Improper airflow will reduce heat exchanger and compressor life. 


Thermostat:     There are three types of thermostats: mechanical, digital, and digital-programmable. Digital is the most accurate. 


U-WIN:     A consumer advocacy organization that provides consumers with access to reputable home service companies that implement an extensive best practice list. For additional information, refer to the U-WIN website: