Indoor/Outdoor System

By Anne Fonda

An indoor/outdoor system is an HVAC split system where one component is inside your home and one component is outside. It’s the most common type of residential HVAC system in the U.S.  Indoor and outdoor units need to be paired as a matched system to achieve optimal performance and energy efficiency. Mismatched components can fail early.

Types of these HVAC systems include:

The outdoor unit is either an air conditioner or a heat pump. The outdoor unit is also sometimes called the condenser unit. It contains the compressor, condenser coils, and a fan. The condenser coils condense the refrigerant and release heat into the outside air.

The air conditioner and heat pump both cool your home in the summer. The heat pump can also heat your home in the winter. A heat pump system can be ducted or ductless, and the heat pumps for a ducted system are built differently than the mini-split heat pumps that are part of a ductless system.

Learn more about how heat pumps work.

In a traditional ducted system, the indoor unit is either a furnace or an air handler. The indoor unit contains evaporator coils, a blower, and an air filter. The blower circulates air through the home both in winter and in summer. 

In the cooling cycle, the evaporator coils absorb heat from the indoor air and transfer it to the refrigerant, which then moves to the outside unit. In the heating cycle, the heat pump reverses the cycle, and the evaporator coils become hot coils instead of cold coils. As air crosses the coils, it heats up and is then circulated through your home.

A furnace burns gas or oil to produce heat, which is then distributed through the ductwork in a forced air system. Learn more about how a central heating and air system works. 

Ductless HVAC systems are still indoor/outdoor split systems, but since they’re a little different from the traditional ducted system, let’s briefly discuss them separately. In a nutshell, ductless systems are heating and cooling systems that work without the ductwork that a traditional central heating and air system has.

Instead, the outdoor heat pump connects to one or more indoor units via refrigerant lines. A ductless mini-split system (one indoor unit) or ductless multi-split system (up to 8 indoor units) can be a great heating and cooling solution for a room or home without existing ductwork. They can also be used to increase the comfort level in areas of a home with a central heating and air system.

Learn more about how ductless systems work.

Have more questions? Need help selecting a new HVAC system? Contact your local American Standard dealer for expert advice and product recommendations. 

A Content Writer with Trane Technologies, Anne Fonda researches topics and writes for Trane® and associated residential HVAC brands. She works in collaboration with Trane Technologies subject matter experts, offering easy-to-understand, informative content on complex topics. Her goal is to help consumers make informed decisions on the products and services they need. 

She has written for HVAC and other service provider websites for over 16 years. Before transitioning to web content writing, Anne had a 14-year stint as an award-winning journalist. She graduated cum laude from the University of Missouri-Columbia School of Journalism. When she’s not working, Anne enjoys playing word games, reading, gardening, spending time with family, and visiting gardens and museums.

Expert review by Mark Woodruff, Senior Product Manager, Ducted Outdoor