HVAC Basics: Ductless Heating and Cooling Systems

By Anne Fonda

Ductless HVAC systems, also known as ductless mini-split systems, connect an outdoor condensing unit with one or more indoor units to heat and cool (or just cool) specific zones of your home without the use of ductwork. They use the same heat transfer technology as a split system heat pump.

They’re an all-electric, energy-efficient heating and air conditioning solution. Work with your local Trane dealer for proper sizing, system design, and mini-split installation.

Explore the components of a ductless system

Ductless systems are easy to install, plus they’re extremely energy efficient and customizable to your home. An outdoor, inverter-driven ductless heat pump unit is placed outside your house on an HVAC pad or elevated stand.

That outdoor unit is connected to one or more indoor mini-split units by communication wires, cables, and refrigerant lines. You can control the systems with a wall controller, a remote control, or a smartphone app.

Trane recommends Mitsubishi mini-splits. Mitsubishi Electric pioneered ductless systems in Asia in the late 1950s. We have partnered with Mitsubishi to bring this technology to the residential mainstream in the United States

Where are ductless systems best suited?

Ductless systems, or mini-splits, are a great option for homeowners who need to heat and/or cool a space without ductwork. This can be a single space, like a garage, sunroom, or home office. Some people like to add a ductless mini-split AC system to a garage or room over the garage that doesn’t get enough cool air in the summer.

But ductless systems can also be a good heating and cooling solution for an entire home. For example, a lake or mountain cabin built without ductwork could use an upgrade to a more efficient heating and cooling system. Or a historic older home where putting in ductwork would destroy the nature of the home could benefit from a ductless mini-split system.

Single-zone mini-split vs. multi-zone mini-split systems

Ductless systems can be single-zone or multi-zone systems, depending on the outdoor heat pump and the number of indoor mini-split units. Single-zone systems have only one port on the outdoor unit and one corresponding indoor unit. Therefore, it can control the temperature in just one room or area in your home.

Multi-zone ductless systems have multiple ports on the outdoor unit, so there can be multiple corresponding indoor units. That means, multi-zone ductless systems can heat and cool multiple rooms or areas throughout the home, with the temperature in each room being controlled independently. It’s important to know that all units will either heat or cool. For example, you can’t have one unit cool while the others are heating.

Professional mini-split installation: What to expect

After working with your Trane dealer to determine if a single-zone or multi-zone system will work best for you, they will design the system to meet your heating and cooling needs. This will include choosing the optimal locations for the indoor units and the outdoor unit.

Once you approve, they will order the components and schedule an installation day. Here’s what you can expect from the mini-split installation process:

1. Install the indoor unit(s).

Once you have identified the location(s), the HVAC technician will install the indoor unit(s). Wall-mounted head units are most common in residential applications and attach to a mounting bracket. The technician will drill 3” holes in the wall to accommodate the refrigerant lines, electrical wiring, and drainage lines. All of those lines will connect to the outdoor heat pump.

2. Lay an outdoor pad or install a platform and install the outdoor unit.

The outdoor mini-split heat pump should not be directly on the ground; it will need to sit on top of a pad, so it does not shift around on dirt or rocks. Your HVAC technician will position the pad on leveled ground, high enough to allow water to drain away from the unit during the defrost cycle.

Another option for the outdoor unit is to place it on a platform with wall brackets attached to the side of your home. This can protect it from snow drifts or high water.

3. Connect refrigerant lines and cables to the outdoor unit.

Next, your technician will connect the refrigerant line set and electrical lines from the indoor unit to the appropriate outdoor connections. This can be more complicated with multi-zone systems because there is more than one indoor unit.

4. Complete the job.

From there, your ductless expert will complete any remaining tasks necessary both in and outside your home and test the system so you can enjoy your home in comfort

Anne Fonda, Content Writer

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 Ryan Goodwin, Senior Product Manager, Ductless and Side Discharge Products

Ductless Systems FAQs

Do you need a professional to install a mini-split system?

Absolutely. Because ductless mini-split installation requires extensive knowledge of HVAC, electrical, and plumbing work, you must have an experienced professional install these systems. A Mitsubishi mini-split system must be installed by a licensed HVAC professional for the warranty to be valid. Any repairs must be performed by an HVAC professional as well.

How much does it cost to install a mini-split?

Mini-split installation costs vary depending on the size of the home and whether a single-zone or multi-zone ductless system is being installed. Mitsubishi Electric systems are top of the line and will cost more than less advanced and less reliable systems. For accurate pricing, reach out to your local Trane dealer.

How can I find who does mini-split installation near me?

Many local Trane dealers install Mitsubishi mini-split systems. Mitsubishi Diamond Contractors have received training on system design and installation. Contact your local Trane dealer today to get an estimate.