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.
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.
SEER - This is a measurement of the efficiency of cooling products. 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.
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.
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:
|Input 140,000 Btuh||Input 154,000 Btuh|
|Output 113,000 Btuh||Output 125,000 Btuh|
|.85 gph||1.00 gph|
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.
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.
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.