HVAC - Heating, ventilating and air conditioning refers to the indoor comfort industry.

Watt (W) - a Watt is a unit of electricity.

DOE - The Department of Energy is a federal agency in charge of setting industry efficiency standards and monitoring the consumption of energy sources.

Kilowatt (kW) - a kilowatt equals 1,000 Watts. A kilowatt hour (kWh) is the amount of kilowatts of electricity used in one hour of operation of any equipment.

Sensible Heat -  Heat, that when added or removed, causes a change in temperature but not in state.

Latent Heat - Heat, that when added or removed, causes a change in state - but no change in temperature.

Superheated Vapor - Refrigerant vapor which is heated above its saturation temperature.  If a refrigerant is superheated, there is no liquid present.

Saturation Temperature -  Also referred to as the boiling point or the condensing temperature.  This is the temperature at which a refrigerant will change state from a liquid to a vapor or visa versa.

Sub cooled Liquid - Liquid refrigerant which is cooled below its saturation temperature.

BTU - British thermal unit is the amount of heat that will raise or lower one pound of water by one degree Fahrenheit. A Btuh is how many BTUs are used per hour.

Ton - Heat pumps and air conditioners are generally sized in tons. Typical sizes for single family residences are between two and five tons. Each ton equals 12,000 Btuh.

It is important to note that actual capacity is not constant and will change based on outdoor or indoor temperatures. The published capacity rating of air conditioners and heat pumps is based on performance at the ARI standard temperature levels of 95 F outside, 80 F inside.

SEER - Seasonal energy efficiency ratio is the amount of cooling your equipment delivers per every dollar spent on electricity. SEER applies to air conditioners and heat pumps. In the past, a unit with a SEER of 8.00 was considered standard efficiency, and a unit with a 10.00 SEER was considered high efficiency. After January 1, 1992, the minimum SEER required by the DOE is 10.00 and 15.00+ SEER is considered high efficiency.

Efficiency -A rating on comfort equipment is similar to the miles per gallon rating on your car. The higher the rating number, the more efficient the system and the lower your fuel consumption will be. You can save a lot of money with a high efficiency unit, as shown in the chart below. Depending on your local climate, lifestyle and electricity rates, savings will vary.

HSPF - Heating seasonal performance factor is similar to SEER, but it measures the efficiency of the heating portion of your heat pump. Like SEER, industry minimums have been raised recently, and the minimum is now 6.80 HSPF.

COP - Coefficient of performance compares the heating capacity of a heat pump to the amount of electricity required to operate the heat pump in the heating mode. COPs vary with the outside temperature: as the temperature falls, the COP falls also, since the heat pump is less efficient at lower temperatures. ARI standards compare equipment at two temperatures, 47 F and 17 F, to give you an idea of the COP in both mild and colder temperatures.

Sound Rating Number (SRN) - sound is measured in bels (a bel equals 10 decibels). The SRN of a unit is based on ARI test, performed at ARI standard rating conditions. Average sound rating range from 7.0 to 8.0 decibels. The lower the SRN rating, the quieter the unit.

Decibel (db) - a decibel describes the relative loudness of a sound. Some common sounds are fairly close to a typical air conditioner or heat pump's sound level: human voice, 7.0 decibels; blender, 8.8 decibels.

Indoor Coils - A homes comfort system consist of two components: the outdoor unit (air conditioner or heat pump) and the indoor unit (coil or blower coil). Combinations of various units will result in vastly different efficiency ratings.

Unreasonably high efficiency ratings can be created by using unrealistic indoor and out door equipment combinations. The term "most popular coil" indicates the actual tested combinations; other ratings may be simulated and unrealistic. Be sure that the efficiency ratings you are comparing are for "most popular coil." You'll know the ratings are attainable and close to reality.

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