HVAC Repair – Understanding the Basics for Beginners

HVAC systems are vital to keeping homes and businesses cool in summer and warm and comfortable in winter. They have a lot of components that work together to function, and knowing how these systems function is essential for anyone interested in becoming an HVAC technician.

Getting familiar with the basics of an HVAC unit will make it easier to diagnose problems and communicate with professionals about what may be needed for repairs.


Thermostats control the heating and cooling of HVAC systems. They’re typically situated on a wall at the main level of your home and can be either mechanical or digital. Many modern thermostats are programmable, which allows homeowners to fine-tune their energy bills while saving time and money by automatically turning on and off at specific times.

While being an HVAC technician requires mechanical skills, it also demands a solid grasp of electronics and math. New technicians must understand how a thermostat works before beginning their career training to become adept at using one before working on actual HVAC repair. This means learning the terminology, as well as gaining an understanding of basic tools like hand and piping tools for cutting and bending and cordless and sheet metal tools. It’s also important to know how to use HVAC cleaning equipment and schedule regular maintenance with a professional. This can help keep the warranty valid and prevent future issues with the unit.


The compressor and condenser are the heart of any HVAC system. They use a non-combustible liquid called refrigerant to pressurize the air. Refrigerant flows from the compressor through the condenser coils, which are cooled and turned back into a liquid. It then travels to the evaporator, where it becomes cool air. A faulty condenser can lead to lukewarm or even hot air.

The coils are copper tubing with aluminum fins designed to increase surface area and speed up heat transfer. They should be kept free of debris to keep airflow at maximum.

The condenser also contains a capacitor that stores electricity during compressor and fan startup to give them an extra jolt of power and smooth out voltage fluctuations to protect them from damage. The compressor and condenser fan motor are the two most likely parts to fail. If yours does, check for blown fuses in the disconnect box with a multimeter set to the lowest Ohms scale and touching opposite leads (red and black). Then, call a pro.


The evaporator coil is an indoor air conditioning unit that absorbs heat from the air passing over it. It is located near the furnace and circulates cool air through ducts in your home when the system is running. The blower fan draws heat-laden indoor air into the evaporator coil. Then, it forces it over the fins and coils to surrender its warmth to the refrigerant, which then pries the moisture from the perspective in the form of water vapor.

A clogged or dirty evaporator coil prevents your air conditioner from working properly. You can take care of simple cleaning tasks, such as brushing away dust from the evaporator coil and replacing the air filter. Still, more advanced issues, such as a frost-covered coil that doesn’t thaw, are best left to a professional HVAC technician.

The evaporator coil looks like an upright structure in the shape of an “A” made from panels and coiled tubes lined with aluminum or copper to maximize heat absorption. It is a direct expansion type that does not depend on a specific liquid refrigerant level.


When a home’s air is heated or cooled, it must be circulated throughout the house. This is the job of the ductwork.

Air ducts are a network of metal tubes and vents that carry conditioned air to rooms in the house. They are often located inside walls, floors, and ceilings. A duct system can be divided into return and supply ducts. The return ducts connect to the furnace’s trunk line, while the supply ducts carry conditioned air to other rooms.

Ducts can be made of a variety of materials. Metal ducts are commonly used because they are durable and can be lined with fiberglass to limit heat loss. They can also be fitted with smoke dampers and rubberized vibration isolators.

Dirty ductwork can reduce indoor air quality and make you and your family sick. Mold, pollen, dust, mildew, and pet dander can build up and circulate in your home’s ductwork. These contaminants cause your HVAC system to work harder to clean the air.