Anatomy Of A Central Air Conditioning System

Categories: Central Air Conditioning 1 Comment
air conditioning system diagram

A Quick Guide To The Parts That Make Up Your Air Conditioner

If you’ve gotten a quote for installing a new central air conditioning unit recently, you might have been a bit confused by the lingo that was used to name the different parts of the system. What does a condenser and coil have to do with anything? You just wanted a quote on a new ac unit right?

Let me shed a little light on the terms that describe each of the components that make up your air conditioning system.


That round’ish piece of equipment that sits outside on the ground that everyone refers to as their air conditioner is technically referred to as a condenser. You’ll also hear it called the ‘outside unit’ as well. Part of your condenser is called a coil, or condenser coil, not to be confused with the evaporator coil that is inside your home attached to the furnace.


This is the piece of your air conditioning system that most people never see. It’s contained in a metal box called a plenum, and sits on top of your furnace. If you have a horizontal furnace in an attic, the evaporator coil will sit on one end of the furnace instead of on top. The ‘inside unit’ or ‘indoor coil’ are other common names that are used when talking about your evaporator coil.


Lineset refers to the copper refrigerant lines that run from your condenser (the outside unit) to your evaporator coil.

ac diagram


It’s very common for people to make the mistake of calling their outside unit the compressor instead of the condenser. A compressor is actually a big component that sits inside the condenser (the outside unit).


The plenum is the metal box that sits on top of your furnace and houses the evaporator coil.


The condensate drain is the white plastic (PVC) pipe that runs from your evaporator coil to the drain in your floor, or to the condensate pump that was installed if you don’t have a floor drain. This pipe allows the condensate (moisture) that the evaporator coil produces to be drained out of the plenum.

I get questions about the names for these air conditioner components all the time, so hopefully this helps clear up any confusion as to what the different parts are called. I’ll post another article explaining what each of these components do for those of you who want to dazzle your friends with your detailed knowledge of how air conditioning actually works.

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