Terminology

I want to buy a furnace or air conditioner but what do all those ratings mean?
WE’RE GLAD YOU ASKED!

When purchasing furnaces, air conditioners or heat pumps, consumers will find a lot of abbreviations, acronyms and efficiency ratings used to describe the products. Listed below are some common terms used in our industry and a “plain talk“ explanation of each.

General Terms

HVAC
Heating, Ventilating and Air Conditioning

AHRI
Air-Conditioning, Heating, and Refrigeration Institute is a nonprofit, voluntary organization comprised of manufacturers of air conditioning, refrigeration and heating products. It publishes standards for testing and rating heat pumps and air conditioners in order to provide the consumer with a standardized unit of comparison between equipment of various manufacturers.

GAMA
Gas Appliance Manufacturers Association

DOE
Department of Energy is the federal agency in charge of monitoring the consumption of energy sources.

Watt (W)
A Watt is unit of electricity.

Kilowatt (kW)
A kilowatt is 1000 watts.

Kilowatt hour (kWh)
A kilowatt hour is the amount of kilowatts of electricity used in one hour of operation.

Therm
A therm is a unit of measure for natural gas. You will find this term used on your gas bill.

Btu
A British Thermal Unit is the amount of heat required to raise the temperature of one pound of water (about one pint) by one degree Fahrenheit.

Btuh
Btu’s per hour.

Ton
A ton is a unit of measure for the cooling capacity of an air conditioner or a heat pump. To determine the number of tons of cooling you must take the Btu’s per hour and divide by 12,000 (Btuh/12,000). Typical sizes for single family residences are between 2 and 5 tons. For example, a 3 ton air conditioner will remove 36,000 Btuh ( 3 X 12,000). The actual capacity of a unit will change based on indoor and outdoor conditions. The published rating of a unit is based on its performance at the ARI standard temperature levels: 95°F outside, 80°F inside.

Efficiency Terms

SEER
Seasonal Energy Efficiency Ratio applies to air conditioners and heat pumps and describes the relationship between the Btuh, or cooling capacity of a unit, and the amount of electricity required to run the unit. This ratio is based on normal annual usage. Units with higher SEER ratings require less electricity to cool a home and are therefore more efficient.

AFUE
Annual Fuel Utilization Efficiency. This rating applies to gas furnaces and is based on average usage and includes fuel usage during on and off cycling. The higher the AFUE rating, the less fuel a furnace or boiler will use.

COP
The Coefficient of Performance is a ratio used in rating the heating efficiency of heat pumps. It is determined by dividing the total heating capacity (excluding supplementary resistance heat) by the total electric input.

Sound Ratings

Decibel
A decibel describes the relative loudness of a sound.

Bel
A bel is a decibel divided by 10.

SR
Sound Rating is measured in bels. The SR of a unit (heat pump or air conditioner) is based on tests performed at ARI standard rating conditions. Although no energy consumption is tied to the SR, it can directly affect the consumer’s comfort (as well as that of a neighbor!). Average sound ratings range from 7.2 to 8.2. Lower numbers indicate quieter units.

Equipment Components

Compressor The compressor is the major component located in your outdoor unit (heat pump or air conditioner). New units are sold with a 5 year or 10 year limited warranty form the manufacturer on this part. When the compressor fails after the warranty has expired it usually means the replacement of the entire unit due to the high cost of the compressor alone.

Condenser
The condenser is a term referring to the outdoor unit (air conditioner). It is called the condenser because it is where the refrigerant goes from a gas to a liquid (condenses) in the refrigeration cycle.

Evaporator
The evaporator is the indoor coil used in air conditioning. It is called the evaporator because it is where the refrigerant goes from a liquid to a gas (evaporates) in the refrigeration cycle.

Heat Exchangers
This term refers to the components in a gas furnace in which the actual combustion takes place. Typically the manufacturers place a 20 year limited warranty on the heat exchangers. On the highest efficiency furnaces the heat exchangers are warranted for as long as you own your home.

Inducer Fan
The inducer fan helps send the products of combustion up the chimney or through the appropriate exhaust vent. This component is only found on the newer generation of furnaces with efficiencies of 78% AFUE and higher.

Hot Surface Ignition
This component replaces the traditional pilot on a gas furnace. A hot surface ignition will “turn on“ when the furnace is starting and “turns off“ once the burners are lit. Because this is only in use when the furnace is starting there is no wasted energy from continuous pilot operation.

Variable Speed Blower
A common upgrade for higher efficiency is the variable speed blower motor available air handlers and furnaces. These are systems that have a higher efficiency rating than the HVAC equipment that has the typical electric blower or condenser fan motor. The ECM (Electronically Commutated Motor) uses less energy than the standard PSC motor. The ECM motor also offers more control also which has good benefits in HVAC applications.

The ECM motor is preprogrammed to run at certain speeds as determined by the HVAC manufacture. The first stage in the program is usually a lower speed in the cooling cycle to remove humidity. A slower rate of airflow across the evaporator coil allows the cold evaporator coil to remove the humidity in the air. The second stage of the ECM motor is usually 100% peak speed as designed for CFM’s and tonnage of the system. From low to high speed the ECM (Electronically Commutated Motor) maintains a good efficiency range between 60% and 80% between all speeds versus the PSC motor with multiple windings getting between 10% efficiency at lower speeds to nearly 50% efficiency at higher speeds. As you can see the no matter the speed of the ECM it maintains efficiency and reduces the amount of electricity consumed to do the same thing the PSC motor does to move air. Another bonus for the ECM motor especially in cooling mode is the fact that temperature of the motor is constant and typically at or near ambient temperature whereas the operating temperatures of the PSC motor is 90 degrees F. to 170 degrees F. This means the air conditioner that uses the PSC motor must also overcome the heat generated and added to the system by the PSC motor while the heat added to the system with the ECM motor is nil to none.

ECM motors are here and they offer a higher efficiency because they use less energy and provide benefits that the typical PSC motor cannot offer. ECM blower motors have been around for a while have proven their reliability in HVAC applications. By purchasing the air handler or gas furnace and condenser with an ECM motor you will consume less energy when your air conditioner or heating system is running. This means lower utility bills and more money in your pocket in the long run.