Use this reference guide of heating, ventilation and air conditioning (HVAC) terminologies from Airrific to learn more about the industry.

HVAC Alphabet

We know it's hard to understand the different terminologies used in the field of heating, ventilation and air conditioning (HVAC), so here's a handy alphabet to help educate you in this sometimes confusing field.

AIR CONDITIONING (AC)= A system for controlling the temperature, humidity, movement and purity of the air in an enclosed space.

AFUE= Annual Fuel Efficiency Ratio. The ratio of annual output energy to annual input energy which includes non-heating season pilot loss. The ratio is based on 5200 annual average heating degree days and 4600 average non-heating season hours per year for pilot use.

ARI= Air Conditioning and Refrigeration Institute. Sponsors and administers certification programs to help ensure the industry products perform as rated.

ASHRAE= American Society of Heating, Refrigeration and Air Conditioning Engineers.

BTU= British Thermal Unit. A unit of measure for determining the cooling and heating capacity of equipment, or the cooling and heating requirements of a building.

BTUH= The heat transfer rate of HVAC equipment measured in British Thermal Units per Hour.

CAPACITY= Usually measured in BTU's or tons, capacity refers to an air conditioning or heating units ability to cool or heat a space.

COMPRESSOR= The compressor plays an integral role in cooling your home. It is the device responsible for pumping refrigerant through the refrigerant lines and the coil, making the transfer or heat from inside your house to the outdoors possible.

CONDENSER= The coil responsible for dissipating heat to the surrounding,outside air. Also called the condenser coil, or outdoor coil, its role is reversed when a heat pump is used in the heating mode.

COP= The Coefficient of Performance rates a heat pump's ability to efficiently use electricity in its operation. It is determined by dividing the total heating provided by the system (BTUH) by the total electricity used (watt hours) to produce this heat. FPL recommends a minimum of COP of 3.0 at standard rating conditions.

DOE= Department of Federal Energy sets the standards for efficiency throughout the HVAC industry and monitors consumption of energy sources.

DOWNFLOW= A term used to describe the direction of airflow through a furnace. A down-flow furnace takes return air from the top, heats it and then delivers warm air from the bottom.

DUCTWORK= A central air conditioning and heating system uses many components to heat or cool the air. This warm or cool air is then transferred to different vents throughout the house via flexible large diameter pipes or ducts. The system of ducts though out your house is often referred to as duct-work or ducting.

EER= Energy Efficiency Ratio. A ration calculated by dividing the cooling capacity in BTU's per hour (BTUH) by the power inputs in watts at any given set of rating conditions, expressed in BTUH per watt.

EFFICIENCY= A general term used to describe how effectively a heat pump air conditioning system or furnace converts incoming energy to outgoing energy. The higher the number the more efficient the unit and the lower the operating costs.

EVAPORATOR COIL= A integral part of the indoor unit of a heat pump or air conditioning system. It is called this because the warm air passes over a coil filled with liquid refrigerant, the refrigerant itself evaporates and absorbs some of the heat. This gas refrigerant is then pumped to the outdoor coil where it releases heat into the surrounding air and returns to its liquid state.

GSHP= Ground Source Heat Pump. A heat pump that utilizes the ground or ground water as a heat transfer method.

HARD START KIT= These are installed in the condensing units and are devices that utilize a capacitor and a relay, heat sensor or timer, to allow the Compressor to start with minimum efficiency. HSK's reduce light flicker during air conditioning start ups. The relays in HSK's are called "potential" relays.

HEAT EXCHANGER= Responsible for transferring heat from furnace burners to the blower.

HEAT PUMP= Heating and cooling equipment that operates like a central air conditioning in the summer months removing heat and humidity from the inside air and transferring it to the outside. In the winter, heat pumps extract heat from the outside air and circulate it inside the building.

HOR FLOW= A term used to describe the direction of airflow through a furnace. A horizontal flow furnace takes return air from one side, heats it, and then delivers warm air from the other side.

HSPF= Heating Season Performance Factor. A unit of measuring the heating efficiency of a heat pump. It is determined by dividing the amount of heat the pump produces during the year by the total amount of electric power consumed to produce this heat.

INDOOR COILS= Split system home comfort systems use two main components to deliver air for a comfortable living environment. The indoor coil (located in your air handler) is the device responsible for transferring heat from indoors to outdoor (or the reverse in the case of a heat pump in heating mode). Most modern systems are designed to achieve maximum efficiency when the indoor unit (coils and blower) are properly matched with the outdoor unit (air conditioner or heat pump). For best results be sure to replace the both the indoor and outdoor units at the same time.

LATENT HEAT= Heat given off or absorbed in a process other than a change in temperature. It cannot be measured with a thermometer, but affects the feel of the air.

LOAD CALCULATION= Manual "J" residential load calculation. Heat load calculations are used to estimate the heat loss and heat gain for conventional residential structures.

PACKAGE UNIT= An air conditioner in which the condenser, compressor and evaporator coil are contained in a single unit, usually installed outside the home or business.

REFRIGERANT= The liquid used to absorb and transfer heat from one part of the home comfort system to another.

REFRIGERANT LINES= Copper lines used to transfer the refrigerant between the outdoor unit and the indoor unit.

SEER=Seasonal Energy Efficiency Ratio, the total cooling of a central unitary air conditioner or unitary heat pump in BTU's during it's normal annual usage period divided by the total electric energy input watt-hours during the same period. The higher the seer rating, the more efficient the unit. FPL recommends a minimum SEER rating of 14.

SPLIT SYSTEM=The most widely used type of central air conditioning and heat pump system. The compressor/condenser is located outside the residence, and the evaporator or air handler is placed inside. The equipment is connected by copper piping that carries the refrigerant.

SRN= The Air Conditioning and Refrigeration institute performs tests and assigns a Sound Rating Number (SRN) to units. A lower SRN rating indicates a quieter unit.

SUCTION LINE=The larger copper pipe that connects split system air conditioners or heat pumps. It carries vaporized refrigerant back to the outside compressor/condenser from the air handler/evaporator which is inside the home.

STRAIGHT COOL SYSTEM= An air conditioning system that includes cooling equipment only. Strip, gas or oil heating may be included with straight cool systems.

STRIP HEATING= Many conventional central air conditioning systems incorporate strip heating, which is composed of heating coils located in or near the air handler. Air is blown across electricity--heated coils, into the duct-work.

THERMOSTAT= A temperature measuring device used to control the operation of home comfort systems to maintain a comfortable temperature within the house. Programmable thermostats allow you to program different temperature for different times of the day.

TON=A ton of air conditioning equals 12,000 BTU's of cooling per hour (BTHU). Ton and BTUH are used interchangeably to describe the cooling and heating capacity of central air conditioning systems. For example, a three ton systems equals 36,000 BTHU.

UPFLOW= A term used to describe the direction of airflow through a furnace. An up-flow furnace takes return air from the bottom, heats it, and then delivers the warm air from the top.

WSHP= Water Sourced Heat Pump. A heat pump that normally utilizes cooling towers, lakes or waterways as a heat ttransfer method.

ZONE/ZONING= A home may be divided into several different areas or zones, to better control the temperatures throughout the house, The process of dividing your home into different zones is called zoning.