Introduction to HVAC: Basic Terminology Explained

Introduction to HVAC: Basic Terminology Explained

Understanding the HVAC system in your home is more than just knowing it heats and cools. It's a network of components that work together to keep your living space comfortable year-round. But if you're unfamiliar with HVAC terminology, it can be difficult to explain problems or understand what your technician says during a service call.

Whether you're a new homeowner, planning to upgrade your system, or just want to understand the basics, this guide offers a quick yet thorough look at HVAC basic knowledge and the essential terms you should know. Familiarity with air conditioning, ductwork, and furnace terminology can help you make educated decisions and communicate effectively with HVAC professionals.

Let's dive into heating, ventilation, and air conditioning vocabulary.

ACH (Air Changes Per Hour)

ACH stands for air changes per hour and refers to how often the air within a room is replaced with fresh or filtered air every hour. This is a key measure in HVAC vocabulary when evaluating ventilation efficiency. Higher ACH values indicate better air circulation, which is especially important in areas like bathrooms, kitchens, and basements.

When talking to a contractor, understanding ACH helps you assess indoor air quality and recognize ventilation issues.

Air Handler

The air handler is an indoor unit that circulates conditioned air throughout your home. It works with other components, such as the evaporator coil and fan, to push air through the duct system. The air handler is often part of central HVAC systems and plays a substantial role in airflow management.

BTU (British Thermal Unit)

BTU is a standard unit of energy used in HVAC systems, explained in guides to measure the heating or cooling capacity of a system. One BTU equals the amount of energy needed to increase the temperature of one pound of water by one degree Fahrenheit. More BTUs mean greater capacity to cool or heat a space. However, bigger isn't always better—a system that's too powerful for your home may short-cycle and waste energy.

When buying a new system, BTUs help determine the right size for your living space.

Central Air Conditioning

One of the most familiar terms in air conditioning terminology, central AC systems cool the entire house from a single point, distributing air through ducts. These systems often include both an outdoor unit (condenser) and an indoor component (air handler or furnace), forming a split system.

Ductwork

Ductwork terminology is essential when discussing how air is distributed throughout your home. Ducts are channels—usually made of sheet metal or flexible plastic—that transport conditioned air to and from various rooms. Properly sealed and insulated ductwork improves system efficiency and comfort. Leaky or poorly installed ducts can lead to energy loss and inconsistent temperatures.

Diffuser

A diffuser is a component that connects to the end of a duct. It uses directional vanes to help distribute air evenly in a room. You'll often find diffusers in ceilings or high on walls. They contribute to balanced airflow and temperature control in larger spaces.

Evaporator Coil

A vital term in air conditioning terminology is the evaporator coil, which is inside the air handler or attached to the furnace. Its job is to absorb heat from the indoor air as the refrigerant works through it. This cooled air is then circulated back through your ducts. Over time, mold on evaporator coil surfaces can develop if moisture isn't properly drained, so routine maintenance is important.

Furnace

The furnace is the primary component of your heating system. Using gas, electricity, or oil, the furnace heats air and pushes it through the HVAC duct system via a blower motor. Modern furnaces work with your central AC and thermostat, forming part of a complete HVAC solution. Knowing furnace terminology such as AFUE (Annual Fuel Utilization Efficiency) can help you compare efficiency ratings when replacing or upgrading your unit.

Heat Pump

A heat pump is a flexible HVAC system that heats and cools your home by moving heat rather than generating it. In summer, it removes heat from inside your house and releases it outdoors. In winter, it moves heat from the outdoor air—even in cold temperatures—and brings it inside. Heat pumps are common in milder climates where freezing temperatures are rare.

Split System

A split system includes both an indoor and outdoor unit. The outdoor unit holds the compressor and condenser coil, while the indoor unit includes the air handler and evaporator coil. Most residential HVAC systems in the U.S. are split systems, offering high energy efficiency and flexibility in installation.

Thermostat

A thermostat is the control device for your HVAC system. It lets you set the desired temperature and triggers the heating or cooling cycle accordingly. Today's smart thermostats offer features like remote control, learning algorithms, and integration with home automation systems. If you're upgrading your HVAC, a smart thermostat can significantly enhance comfort and efficiency.

IAQ (Indoor Air Quality)

Indoor air quality refers to the healthiness of the air inside your home. Factors that impact IAQ include ventilation, humidity, airborne pollutants, and filter efficiency. A well-designed HVAC system with HEPA filtration, UV lights, or air purifiers can significantly improve IAQ, reducing allergens, odors, and mold.

SEER and AFUE Ratings

SEER (Seasonal Energy Efficiency Ratio) measures cooling efficiency for air conditioners and heat pumps. The higher the SEER, the more efficient the system. AFUE (Annual Fuel Utilization Efficiency) measures the efficiency of furnaces. For example, an AFUE rating of 90 means 90% of the fuel becomes usable heat.

These key metrics in HVAC buying guides can influence long-term energy savings.

Return and Supply Vents

Supply vents blow conditioned air into a room, while return vents draw air back into the system to be reconditioned. Maintaining clean, unobstructed vents ensures proper circulation and system balance.

Condensate Drain

The condensate drain removes moisture collected from the evaporator coil during the cooling process. If the line becomes clogged, it can lead to leaks, mold, or water damage near the indoor unit.

Filter

Every HVAC system includes an air filter to trap dust, debris, and allergens before air is circulated. Regular replacement is crucial. A clogged filter can reduce efficiency, strain your system, and diminish air quality. Filters come in multiple types, such as fiberglass, pleated, electrostatic, and HEPA.

Making Sense of HVAC Terminology

Familiarizing yourself with HVAC terminology makes communicating with your service technician easier, understanding maintenance requirements, and making smart decisions when upgrading or replacing your system. Whether you're reading a quote, evaluating options, or discussing symptoms with a professional, having a working HVAC vocabulary can make a big difference.

Even basic knowledge of air conditioning and furnace terminology helps reduce confusion and speed up the repair or installation process. If you're new to homeownership, this introduction to HVAC terms serves as a great first step toward confidently managing your home's comfort.

Call CMB Air when you need help with your heating system. We offer a wide variety of heating services ranging from HVAC replacement, HVAC blower motor, heating installation and replacement, heating repair and maintenance, heat pump installation, heat pump repair, and heat pump replacement. Get in touch with our experts at (813) 447-1443.