Key Terms and General Information for HVAC


We all have to start somewhere when gaining knowledge on a complex subject; we have all been there before. There is no need to stress about sounding like you know what you are talking about in the heating and air conditioning world, use this blog as your guide.

Heating, Ventilation and Air Conditioning (HVAC)  has the goal of creating a comfortable and acceptable indoor air quality. 



Air Changes Per Hour is a measure of the air volume added to or removed from a space in one hour.


Annual Fuel Efficiency Ratio is all heating and cooling units manufactured in the U.S. are governed by the Department of Energy. It measures the percent of heat produced for every dollar of fuel consumed.

Condenser Coil 

A component that removes the heat from the system. The condenser is the hot side of an air conditioner or heat pump. 


The diffuser causes the air to spread out in multiple, even directions.


This is not the type of grill you cook your burgers on; Grilles pull air out of a room, ensuring energy efficiency and relative comfort while also providing circulation back to the central heating and air conditioning unit.

Heat Pump 

An outdoor installment that redistributes heat from the air and ground then circulates it between the indoor fan and outdoor compressor to transfer heat.


Outside Air Temperature

Packaged Unit or RTU (Rooftop Unit) 

Allows all of the components needed to provide conditioned air into one unit.

Plenum Space 

An indoor space used for airflow.

SEER (Seasonal Energy Efficiency Ratio) 

“A mathematically determined ratio of the total cooling capacity during normal periods of operation (not to exceed 12 months) divided by the total electric energy input during the same time period.”


This is the process of lowering the temperature of the liquid refrigerant in the condenser coil.

VAV (Variable Air Volume) 

Allow energy-efficient HVAC system distribution through the optimization of the temperature and amount in the air.


If you have any questions or comments, please reach Doug’s Heating and Air Conditioning at 309-764-2500 or send an email to