Servicing and installing an air conditioner is not something most people should attempt. It requires a knowledge of multiple disciplines, any one of which could turn in to huge problems if they are glossed over.


When an AC is running properly, it is removing 2 kinds of heat, sensible, which is the temperature you see on your thermostat, and latent, which is the moisture in the air. When that moisture hits the cold indoor coil, it turns into from a vapor into water. That water needs to be carried away from the unit, and a good HVAC guy has to know how plumbing works to make that happen safely. He also has to know about safety switches that will cut the electricity off in case something goes wrong because water and electricity don’t mix.


Knowing when a place in the attic is will not support the weight of a system, or how much can be removed from a joist or a stud before structural problems arise is another thing a seasoned professional HVAC installer / service tech will know. Sometimes things have to be cut / removed to make way for pipes and or wires. This is something most folks should not do. Very bad things can happen when you “just start cutting”.

Low Voltage

Low voltage is an area that can is very complex in an air conditioning system, and every year, manufacturers are making it more complex. The sheer number of service manuals a competent tech reads in a year would shock most people. We have to keep up because every year things are new. If you are an electrical engineer, you may give her a go, but unlike computers, our control systems are almost always next to deadly and exposed high voltage wires and contact points.

High Voltage

Unlike most electricians, an HVAC tech is almost always working with the system panels removed and live high voltage inches away from our fingers / head / arms / etc. We have to in most cases because it is very difficult, and sometimes impossible to find a problem without being able to trace a voltage or amps around the system. If you do not know a LOT about high voltage, you should definitely NOT work on an air conditioner. IT WILL KILL YOU.


An air conditioning mechanic must know quite a bit about physics. Thermodynamics in particular. Thirty years ago, the industry was using a refrigerant called R22. It was has some of the best properties for cooling a building for people to be in. It is a very forgiving refrigerant, and would allow people to make quite a few mistakes and still work. People used to use all kinds of “rules of thumb” when working with air conditioners like “Beer can cold” for the large copper line coming out of the house. “60 or 70” for the pressure on that line. Now that won’t fly. Equipment is much more expensive and much more delicate. The metal is thinner and not the same quality it used to be. The same refrigerant that keeps you cool keeps the equipment cool. If you get the charge wrong, you will destroy an air conditioner.


In the old days, the oil used to lubricate the compressor was called “Mineral Oil”. Todays oil is called “Poly Oil” and it attracts moisture at an extremely rapid rate compared to the old style of oil. If you don’t know how to test, remove moisture from the system, that moisture will mix with the other things in your system and form acid. That acid will eat the varnish off the motor windings in your compressor and your system will be non-functional and the fix is very expensive.


Sheet metal is a large part of installing an air conditioner. Even the most competent of installers has dozens of battle scars from an install gone wrong. Stitches and tetanus shots are pretty common for us. (for those of us that play guitar it can be awful). I cringe at the thought of a typical home owner working with sheet metal. If you decided to work with it, use gloves and know it can be just as bad or worse than shards of glass. People lose fingers often.

Just Hire A Pro

Please, for your safety, and the benefit of your unit, if not us, hire someone that knows what they are doing. There are plenty of things I would encourage a home owner to tackle, this is not one of them.