Common A/C Terms Every Homeowner Should Know

Technician instructing homeowner on themostat use - Thomas & Galbraith Heating, Cooling, & Plumbing

Do common air conditioning terms create confusion when you shop for a new air conditioner, or chat with a technician about repair and maintenance needs for your current cooling system? Many industries have their own terminology, and HVAC is no different – but if you aren’t familiar, it may seem difficult to decode.

A better understanding of common air conditioning terms helps you better understand equipment specifics when you evaluate new cooling systems for your Indianapolis home. If your current cooling system breaks down this summer, air conditioning terms regarding components and other system aspects are going to come up in conversation with your technician. Knowing these basic air conditioning terms helps you better understand the issues your system faces and what repairs are needed.

Our goal is to make the world of air conditioning terms less confusing! We always want you to feel comfortable with the services and equipment you purchase, so we’ve laid out some easy to understand definitions for common air conditioning terms you encounter when shopping for a new cooling system or working with a technician.

When it’s time to replace your air conditioner or if your current system needs repair, Thomas & Galbraith is available to assist you. Our team takes the time to answer your questions and make sure you understand the air conditioning terms that tell you all about your unit. Take a look at the air conditioning terms defined below to best prepare yourself for your appointment!

Air Conditioning Terms about System Types

  • Air conditioner: Air conditioner is often used as a broad term describing cooling equipment, but in fact there are many types of cooling equipment. An air conditioner is what most people call the condensing unit of a split system central air conditioner. This is the unit that sits outside your home and is connected to the indoor unit through the line set. Air conditioners cool your home through the transfer of heat from inside to the outdoors.
  • Ductless mini split: A ductless mini split doesn’t use ducts for air delivery. Instead, it uses air handling units installed directly into a space, which are connected to the outdoor heat pump or air conditioner. One outdoor unit can support multiple air handlers, allowing for zoned cooling in the home.
  • Heat pump: A heat pump is a type of HVAC system that cools a home in the same manner an air conditioner does, through the transfer of heat where heat is moved to the outdoor air or a ground or water source, if it’s a geothermal heat pump. Unlike air conditioners however, a heat pump is also capable of providing heat for a home.
  • Packaged air conditioners: In a packaged air conditioner, a single cabinet holds all cooling system components – it is not a split system. They are available for installation in homes but are commonly found in commercial buildings. Packaged units can be installed near the building’s exterior on the ground, or on the roof, which is common for commercial buildings with flat roofs.
  • Split system: Split system cooling is common in Cincinnati homes. These systems have an indoor air handler or furnace, and an outdoor air conditioner or heat pump. Inside are the evaporator coil and air movement components, and the system’s compressor and condenser are in the outdoor unit. In this central air conditioning system, air is circulated to living areas through a duct system.

Air Conditioning Terms about Cooling System Components

  • Air handler: The air handler is located inside a home and circulates air cooled by the air conditioner or heat pump. Some air handlers may also have auxiliary heat as well as filtration.
  • Evaporator coil: This is an inside component which handles the first step of cooling. As warm air passes over the evaporator coil, it extracts the excess heat via the refrigerant that circulates within the coil.
  • Condenser coil: This coil is located in the outdoor unit and is the last stage of the cooling process. The condenser coil allows heat to be released from the refrigerant into the outside air.
  • Compressor: The compressor is type of pump which is located in the outdoor unit. It pressurizes and raises the temperature of refrigerant before it passes through to the condenser coil.
  • Condensate drip pan and drain: The drip pan is located below the evaporator coil and collects moisture that is a byproduct of the cooling process. Water flows through the drip pan to the attached condensate drain line, and out of the home.
  • Ducts: In a central cooling system, ducts are used to direct conditioned air from the cooling system into living areas. Ducts are made from sheet metal or sometimes flex tube, and are typically ran through attics, basements, crawl spaces, and walls. The supply ducts carry cooled air to living areas, and returned from the living areas to the cooling system through return ducts.
  • Expansion valve: This cooling system component reduces the pressure and temperature of refrigerant before it enters the evaporator coil, which also converts it from liquid to gas form. Refrigerant and voltage flow are also controlled by the expansion valve.
  • Filter: Filters protect air conditioning system components by removing contaminants from the air that circulates through the system. As a bonus, this contaminant removal also produces better indoor air quality.
  • Line set: The line set is the two refrigerant lines that run between the indoor and outdoor cooling components. The liquid line is a smaller, uninsulated copper pipe and the suction line is larger and insulated.
  • Plenum: The plenum is the section that connects the indoor unit to the return ductwork.
  • Refrigerant: Cooling systems use refrigerant to absorb and transfer heat throughout the cooling process. If you have an older cooling system, it may use R-22, or Freon refrigerant. Freon is currently undergoing a phase-out in favor of environmentally friendly alternatives, such as R-410a, also called Puron.
  • Reversing valve: In a heat pump cooling system, the reversing valve is responsible for switching between heating and cooling. An air conditioner does not have a reversing valve because it is unable to be used for heating.

Air Conditioning Terms about Cooling System Efficiency

  • BTU: British thermal unit (BTU) is the heat equivalent measure used to show the amount of energy needed to increase the temperature of a pound of water one degree Fahrenheit. It shows a cooling system’s heat removing capabilities.
  • BTU/H: British thermal units per hour tells how many BTUs of heat an air conditioner is capable of removing from a home in an hour.
  • Capacity: An air conditioner’s capacity is its ability to remove heat from a home. Capacity is measured in tons.
  • Energy Efficiency Ratio (EER): This efficiency measure is used for window units and heat pump cooling. The EER is the Btu/h divided by energy input into the system in watts. This is a consistent efficiency measure rather than a seasonal measure.
  • Minimum Efficiency Reporting Value (MERV): MERV is the measure of a filter’s efficacy, regarding the particle size and efficiency of removing airborne contaminants. MERV measures 1 at its lowest and up to 16 for the highest residential filters.
  • Seasonal Energy Efficiency Ratio (SEER): This is the measure of a heat pump or air conditioner’s energy efficiency. It shows the efficiency over a typical cooling season, measuring cooling output divided by total energy input over that time. The minimum SEER for new air conditioners in Ohio is 13; 14 for Kentucky. Higher SEER indicates higher energy efficiency.
  • Tons of cooling: The capacity of an air conditioner is measured in tons, and one ton equals 12,000 Btu/h.

Other Air Conditioning Terms You May Hear

  • Air balance: All HVAC system components need proper air flow to operate efficiently. A balanced system sends enough air to meet each component’s requirements at any time.
  • Air changes per hour: This is the number of times your home’s total indoor air volume is replaced with conditioned air or natural ventilation in one hour’s time. 
  • Air infiltration: Air infiltrates your home or cooling system through leaks and other issues, which increases cooling load and causes discomfort.
  • Charge the system: This term refers to charging your cooling system’s refrigerant. A technician uses gauges to measure the refrigerant’s pressure and determine if it is too low. Refrigerant is added to the system to bring it up to proper levels, which may be necessary after repairing a refrigerant leak. 
  • Cooling load: To size a new air conditioner, a technician performs a Manual J calculation, which determines a home’s cooling load, the rate heat must be removed from a home to keep it at the desired temperatures.
  • Static pressure: Static pressure is pressure within your home’s ducts, which interferes with air movement through the HVAC system when pressure levels are too high.

Call Thomas & Galbraith for Air Conditioning Help!

Have questions about the air conditioning terms discussed above? Talk to Thomas & Galbraith! Our NATE-certified cooling specialists help you better understand common air conditioning terms and get to know your cooling system! We are always happy to decode common air conditioning terms to help you know exactly what you get when you buy new air conditioning equipment or need a repair.

For air conditioning installation, repair, or maintenance in Cincinnati and the surrounding areas, contact Thomas & Galbraith today!

Subscribe for Savings and Tips in Your Email!