Upgrading your heating and cooling system can involve a lot of home renovations, but it doesn’t have to. A whole-house ductless system offers an efficient solution without the need for extensive ductwork. In the video above, This Old House plumbing and heating expert Richard Trethewey provides an in-depth look at whole-house ductless systems. We also explain how to install a whole-house ductless system below.
How Ductless Systems Work
Ductless heat pumps transfer heat from one area to another. When you set them to cooling mode, they remove heat from inside your home and push it outside. You can reverse the process by switching to heating mode so that the same system extracts heat from the outdoor air and brings it inside. This heat transfer works because refrigerant circulates between the indoor and outdoor units.
Benefits of Whole-House Ductless Systems
Many homeowners are opting for whole-house ductless systems, also known as mini-split systems, because of their energy savings and flexibility. Here are some of their advantages:
- Easy installation: Since the unit doesn’t have ductwork, installation is less invasive.
- Energy efficiency: Ductless systems can be more efficient than traditional HVAC systems, so a homeowner may have lower energy bills.
- Improved air quality: The system has built-in air filtration, which removes dust, allergens, and other particles from the air.
- Quiet operation: Indoor units don’t make a lot of noise.
- Zoned comfort: You can control each indoor unit separately, so you can customize the temperature in different rooms.
Planning Your Whole-House Ductless Installation
There are a few steps you can take to prepare for the installation process.
Assessing Your Home’s Needs
The first step in planning your ductless system installation is to assess your home’s heating and cooling needs. This depends on the layout and size of your home, the number of rooms or zones you want to condition, and your local climate.
A professional HVAC technician can perform a heat load calculation to figure out your system’s correct sizing. This calculation accounts for several factors, including your home’s square footage, insulation levels, and window placement.
Choosing the Right System Components
After your home assessment, you’ll have to choose the components for the ductless system, which includes the following:
- A branch box to distribute refrigerant to multiple indoor units
- An outdoor condensing unit
- Multiple indoor air handlers, such as wall-mounted, ceiling-mounted, or ducted
- Programmable thermostats for each zone
- Refrigerant lines to connect the indoor and outdoor units
Your home’s layout and individual preferences will help you decide the number and type of indoor units you’ll need. Trethewey explains that you can connect a single outdoor unit to multiple indoor air handlers, which provides zoned comfort throughout the home.
Installation Process for a Ductless System
Installing a whole-house ductless system is a complex task, so unless you’re an avid DIYer with significant plumbing and electrical experience, we recommend you hire an HVAC technician to complete the project.
Whether you’re a homeowner with the right skill set or you plan on hiring a professional, understanding the process can help you make informed decisions and have a successful installation. Here’s how to install your whole-house ductless system.
Outdoor Unit Installation
Place the outdoor condensing unit on a stable, level surface, which can be a concrete pad or mounted on brackets attached to the exterior wall. For the system to work properly in colder climates, you have to mount the unit above the snow line. Your contractor will factor in the following:
- Adequate airflow around the unit
- Aesthetic considerations and impact on your home’s exterior appearance
- Local building codes and zoning regulations
- Proximity to the indoor units
Indoor Unit Installation
You can install indoor air handlers in various configurations according to your home’s layout and your preferences. Options include the following:
- Ceiling-mounted units: These work in rooms with limited wall space.
- Ducted units: You can hide ducted units in attics or crawl spaces to provide conditioned air through short duct runs.
- Wall-mounted units: Homeowners choose these for open areas and individual rooms.
Each indoor unit requires a connection to the outdoor unit via refrigerant lines, a condensate drain line, and electrical wiring. Here’s how the HVAC technician will install your unit:
- Choose the appropriate locations for each indoor unit.
- Create small openings in walls or ceilings for refrigerant lines and wiring.
- Mount the indoor units securely.
- Connect refrigerant lines, drain lines, and electrical connections.
- Insulate and seal all penetrations to maintain energy efficiency.
Refrigerant Line and Branch Box Installation
The refrigerant lines connect the outdoor unit to the indoor units. This is how the system transfers heat. For multi-zone systems, your contractor will use a branch box to distribute refrigerant to multiple indoor units. Here’s what’s involved in this step:
- Charging the system with the correct amount of refrigerant
- Connecting smaller refrigerant lines from the branch box to each indoor unit
- Ensuring all the refrigerant lines are properly insulated
- Evacuating the lines to remove air and moisture
- Running refrigerant lines from the outdoor unit to the branch box
- Pressure testing the system to check for leaks
Electrical Connections and Thermostat Installation
Each indoor unit needs electrical connections and a thermostat for individual zone control. The installation process includes the following steps:
- Connect power and control wiring between the outdoor and indoor units.
- Configure the system for optimal performance and energy efficiency.
- Install programmable thermostats for each zone.
- Run electrical wiring from the main electrical panel to the outdoor unit.
System Testing and Commissioning for a Whole-House Ductless Unit
After an HVAC contractor installs the system, an evaluation of the system will confirm whether it works properly. They’ll perform a series of tests to ensure the system is functioning correctly and efficiently.
Performance Verification
The contractor will run the system through various modes to verify proper operation:
- Checking heating and cooling performance in each zone
- Making sure the air flows correctly from each indoor unit
- Testing the thermostat and programming
- Verifying proper refrigerant charge and system pressures
Energy Efficiency Optimization
There are a few things you can do to maximize the energy efficiency of your new ductless system:
- Adjust the fan speeds and refrigerant flow rates.
- Care for the system through proper use and maintenance.
- Optimize thermostat settings for each zone.
Maintenance and Care for Ductless Systems
Your whole-house ductless system requires regular maintenance to continue to run smoothly. Taking the steps listed below will also extend its lifespan.
Regular Maintenance Tasks
To keep your system in top condition, perform these tasks regularly:
- Inspect indoor and outdoor units for signs of damage or wear.
- Keep outdoor units clear of debris and vegetation.
- Clean or replace air filters in indoor units monthly.
- Schedule professional maintenance at least once a year.
- Clean indoor unit coils and fans annually.
Professional Service
When you schedule your annual appointment with an HVAC technician, they’ll service your system by performing complex tasks. A qualified HVAC technician can check refrigerant levels and system pressures, clean and inspect all components, and identify and address potential issues before they become major problems. We recommend finding an HVAC technician who has experience handling whole-house ductless systems.
Resources
Mitsubishi Electric Cooling & Heat manufactured all the heating and cooling equipment, including the outdoor condenser, indoor wall-mounted unit, and indoor air handlers. Expert advice with this installation was provided by N.E.T.R. Inc.