Glossary of Terms

     Let's start at the beginning: HVAC stands for Heating, Ventilating and Air Conditioning and are the initials often used to describe the industry that produces the equipment that brings comfort to your home.

Efficiencies

AFUE - This is a percentage measurement of a furnace's heating efficiency. The U.S. Government's minimum efficiency level is 78%. The higher the AFUE, the more efficient the furnace. The initials stand for Annual Fuel Utilization Efficiency.

ENERGY STAR - Products/Homes/Buildings that earn the ENERGY STAR prevent greenhouse gas emissions by meeting strict energy efficiency guidelines set by the U.S. Environmental Protection Agency and the U.S. Department of Energy. To learn more, please visit www.energystar.gov.

EER - The EER is the efficiency rating for the equipment at a particular pair of external and internal temperatures. SEER rating more accurately reflects overall system efficiency on a seasonal basis and EER reflects the system’s energy efficiency at peak day operations.

SEER - This is a measurement of the efficiency of cooling products. The U.S. Government's minimum efficiency level is 13 SEER for split systems and packaged units. The higher the SEER, the more efficient the cooling product. SEER stands for Seasonal Energy Efficiency Rating.

HSPF - This is a measurement of a heat pump's heating efficiency. There is no governmental minimum rating. The higher the HSPF, the more efficient the heat pump's heating performance. HSPF stands for Heating Seasonal Performance Factor.

COP - Coefficient Of Performance. A ratio that compares a heat pump system's heating efficiency to that of electric resistance heat. For example, a heat pump system with a COP of 3.0 provides heat at 3 times the efficiency of electric resistance heat. A heat pump's system COP will decrease as outdoor temperatures drop, eventually providing little or no efficiency advantage over electric resistance heat - and that's when your auxiliary heat strips start to heat your home.

A Note About Efficiencies: When you're getting ready to replace an older heating or cooling system, it's very important for you to get a Load Calculation done by your dealer/contractor. The greater the difference between the efficiency of your old system to the new system, the more likelihood that the dealer will recommend a smaller sized unit. This should not cause alarm, as the dealer, by running a Load Calculation, will be able to accurately size the system to the load in your home. It can be quite detrimental to equipment if the units are too large for the load in your home - they can start to "short cycle" (they run often but for very short periods of time, because they are pumping out too much heat/cooling and reach the thermostat's setting too quickly), which can shorten the life of the unit dramatically.

Capacities & Ratings

BTU - British Thermal Unit. This is the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. You'll see this measurement when you look at heating and cooling capacities - for example, your dealer may recommend a 75,000 Btu furnace and a 24,000 Btu air conditioner for your home.

A Note About Capacities: Gas furnaces are generally rated by "input" in Btus per hour (Btuh). A furnace rated at 100,000 Btuh that is 80% efficient (80% AFUE) will have an output of 80,000 Btuh. In other words, 80% of the total heat produced by burning the gas will be in the form of usable heat to warm your home. The other 20% is exhausted from your house along with the flue products.

By the same token, a 100,000 Btuh furnace that is 90% efficient only sends 10% of the total heat out the chimney - thus burning less gas to get the same results and reducing your gas heating costs.

GPH - Gallons Per Hour. You might see this rating if you are looking at an oil furnace. In addition to input and output, an oil furnace also has a rating of gallons per hour, the volume of oil a furnace is capable of burning in 60 minutes.

A Note About Oil Furnaces: Many oil furnaces are dual rated. That is, they are listed with two different heating capacities. For example, your oil furnace might be rated as:

This means that at the lower rating, the furnace is capable of producing 113,000 Btus of usable heat per hour to heat your home. And, if it ran constantly for one hour, it would consume .85 gallons of oil. If, however, your dealer sets up your oil furnace to operate at the higher rating, it would produce 125,000 Btus of usable heat per hour, and use 1.00 gallons of oil. Whether your oil furnace is set up by your dealer to operate at the higher or lower rating depends on that all important Load Calculation. By properly sizing the furnace to your home, you will be assured of maximum comfort, energy savings and extended equipment life.

Ton - You'll often see this as a measurement of the capacity of an air conditioning system. Don't panic, it doesn't measure weight! Just like gas and oil furnaces, air conditioners and heat pumps are rated in Btus. One ton of air conditioning is 12,000 Btus per hour. This means that a "one ton" air conditioning system has the capability of removing 12,000 Btus of heat per hour from your home.

A Note About Air Conditioning: You've heard the saying "It's not the heat, it's the humidity." Air conditioning systems do more that just cool your home - they remove moisture. The more humid it is outside, the harder an air conditioner has to work. But does that mean that if you get a bigger unit, it will work better? NO. An air conditioning system that is too large will neither cool nor dehumidify properly, and the result will be an uncomfortable, clammy home.

Ambient Temperature - This is the air temperature (usually the outdoor air temperature) surrounding the equipment.

Equipment Shorthand

Split System - This describes an air conditioning or heat pump system that is split into two sections - an outdoor section and an indoor section. It won't work without the outdoor section plus an indoor section to move the air.

Condensing Unit - This is the outdoor section of a split system air conditioning system. You'll know it best as the air conditioner that sits outside your home.

Air Handler - This is the indoor section of a split system. It can be a dedicated air handler, or could be your furnace. Also known as a fan-coil.

Indoor/Evaporator Coil - If your furnace is the air handler section of your split system, then you'll need an indoor coil added to your furnace to complete the system. The coil transfers heat to give you cool air and also aids in dehumidification. If you do not have a furnace and you have a split system air conditioning system - The Indoor Coil or Evaporator is located in the inside unit.

Outdoor/Condenser Coil - If your furnace is the air handler section of your split system, then you'll need an indoor coil added to your furnace to complete the system. The coil transfers heat to give you cool air and also aids in dehumidification.

Heat Pump - A unit that both cools and heats your home. A heat pump system can be either a split system or a packaged system. A heat pump can be used in conjunction with a gas/oil/LP furnace (using the furnace instead of electric resistance heat when temperatures fall below about 35° F with the addition of a fossil fuel kit These type of heat pumps are known as duel-fuel heat pumps.

Gas-Pack - Short hand for a packaged system that uses gas fuels such as LP or Natural Gas for the heating process.

Geothermal System/Unit - A Geothermal system uses the earth's ground for a heat or cooling source. Thermal conducting lines are installed in the ground to heat or cool a home. Geothermal Systems can save a homeowner anywhere from 30 to 40% on their energy bill. Geothermal Systems can also use ponds or wells for a heating or cooling source.

Packaged System - Packaged units provide both heating and cooling from one unit that is placed outside the home - on the ground, on the roof, or sometimes mounted through the walls of the building. Packaged units come in several combinations of fuel sources - gas heat/electric cooling; heat pump; electric heat/electric cooling; oil heat/electric cooling.

Refrigerants

R-12 - Dichlorodifluoromethane (R-12), usually sold under the Freon-12, is a halomethane (CFC), used as a refrigerant and aerosol spray propellant. Complying with the Montreal Protocol, its manufacture was banned in the United States along with many other countries in 1994 due to concerns about damage to the ozone layer. It is soluble in many organic solvents.

R-22 - (HCFC) It is better known under its code names of HCFC-22, R-22, Genetron 22 or Freon 22, and is commonly used in air conditioning applications, such as residential split systems in the US, rooftop units and window air conditioners. It will soon be phased out due to ozone depletion potential and status as a potent greenhouse gas. All air-conditioning and heating equipment that uses
R-22 will cease production of such by January 1, 2010. The refrigerant supply and production of R-22 will then be slowly cut back and banned by January 1, 2020.

R-134A - also called simply tetrafluoroethane, R-134a, Genetron 134a, Suva 134a or HFC-134a, is a haloalkane refrigerant with thermodynamic properties similar to R-12 (dichlorodifluoromethane), but without its ozone depletion potential.

R-410A - sold under the trademarked names Puron, Genetron R410A, and AZ-20, is a near-azeotropic mixture of difluoromethane (CH2F2, called R-32) and pentafluoroethane (C2HF5, called R-125) which is used as a refrigerant in air conditioning applications. Unlike many haloalkane refrigerants it does not contribute to ozone depletion, and is therefore becoming more widely used as ozone-depleting refrigerants like R-22 are phased out. However, it has a high global warming potential of 1725 (1725 times the effect of carbon dioxide), similar to that of R-22.