If you’ve been looking for an alternative to fuel-burning furnaces, heat pumps and other standard home comfort equipment, you’ve probably heard something about ductless heating and cooling. Also called ductless mini-split heat pumps, these systems were developed in Japan in the 1970’s. Since then, they’ve become popular throughout Southeast Asia and Europe for their convenience and efficiency.
These same advantages are helping them gain popularity in North America, too. Because they’re not yet common here, though, it can be hard to get a clear picture of how these systems work, what situations they’re best suited for, and how they can benefit you.
If you’re considering installing a mini-split heat pump in your home, taking a little time to understand these systems can help you decide whether or not one is right for you.
What’s involved in a ductless system
A ductless system is a heat pump system designed for heating and cooling individual zones or rooms in a home. Unlike standard ducted heat pumps, furnaces and air conditioners, a ductless system doesn’t require ducts to provide air to your rooms. Instead, conditioned air is delivered directly from the indoor air handler. These systems consist of three main parts:
Outdoor unit – This relatively small unit contains a fan, refrigerant coil, compressor and expansion valve.
One or more indoor air-handling units – These units contain a coil and a fan to deliver conditioned air to the room. They’re usually mounted high on a wall or on the ceiling. Floor-standing units are another option. Each unit heats and cools one zone.
Conduit line – This line contains the refrigerant line, condensate drain and power cable. It runs through a 3-inch hole in the wall to connect the outdoor and indoor units.
How Ductless Systems Work
Mini-split heat pumps work very similarly to ducted heat pumps. Instead of generating heat using electricity or by burning fuel, they move heat already in the air. In heating mode, they draw heat from the outdoor air and transfer or "pump" it into your home.
In the outdoor unit, liquid refrigerant is pumped through the coil. The fan blows outdoor air over the coil, allowing the refrigerant to absorb heat from the air and expanding into a vapor as it does so. The vapor moves through the compressor where it increases in temperature and pressure.
From there, it flows to the indoor air handler. There it gives off heat, which the indoor fan blows into your room. As the refrigerant cools, it turns back into a liquid and flows back to the outdoor unit to start the cycle all over.
Like traditional air-source heat pumps, a ductless model contains a reversing valve that changes the direction of the refrigerant flow. This lets you switch between heating mode and cooling mode. In cooling mode, a ductless heat pump works in reverse, drawing heat out of your home and releasing it outdoors just as an air conditioner does.
Because the air handler is typically located in an inconspicuous spot, such as high up on the wall, you’ll have a remote control to operate the unit. The control lets you turn the unit on and off, change the temperature, and change operational modes.
Where Ductless Systems Are Most Useful
While mini-split systems can work well in nearly any home, there are a few situations for which they’re ideally suited.
Homes without ducts – Adding new ducts to an existing building is a messy and expensive job, often resulting in a ductwork design that’s far from optimal for energy efficiency. Installing a ductless system will save you from expensive construction work and ensure you get a highly energy-efficient system.
Finished attics and basements – If your current system has enough capacity, you may be able to extend your existing ductwork to heat or cool a newly renovated area. Even if you can, though, construction expenses are still involved. You may find installing a ductless unit is a faster, easier and less expensive alternative.
Additions – As with finished attics and basements, extending ductwork into a room addition isn’t always an option. A mini-split system may be the more cost-effective solution.
Mini-Splits Offer Superior Energy Efficiency
Because they use electricity to move heat rather than generate heat, heat pumps are more efficient than other electrical forms of heating or forced-air systems such as gas and oil furnaces. In fact, mini-split systems use around 25 to 50 percent less energy than traditional systems.
Today’s ductless systems achieve some of the highest efficiency ratings around. They come with Seasonal Energy Efficiency Ratios (SEER) as high as 22 and Heating Seasonal Performance Factors (HSPF) of up to 11.
These systems also have an efficiency advantage over traditional heat pumps for three reasons.
- No ducts – Ductwork can reduce a heating and cooling system’s efficiency by up to 30 percent through air leaks and heat transfer. While good ductwork design, insulation and air sealing reduce this loss, no duct system is 100 percent efficient. Mini-split systems have no ducts to reduce their efficiency.
- Energy-saving technology – Traditional heat pumps can run at only one speed regardless of the amount of heating or cooling you need. As a result, they tend to cycle on and off frequently in attempt to achieve your selected room temperature. This reduces the system’s efficiency and causes uncomfortable temperature swings. Ductless systems contain components, such as variable speed compressors, that let them run at more than one speed to save energy and provide more consistent temperatures.
- Better temperature control – Traditional ducted systems have a supply air register in every room. Closing these registers interferes with airflow through your system, so you end up wasting energy heating and cooling unused parts of your home. With a mini-split system, you’ll have an individually controlled air handler in each zone of your home, so you’ll save energy by heating and cooling only where you need to.
Maintaining Your System
With regular maintenance, a ductless system can work efficiently for 20 years or more. Keeping these systems in shape is fairly simple. You’ll need to replace or clean the filters every one to three months and brush any debris off the indoor coil once a year. To keep the outdoor unit free of leaves and other debris, spray it down with a gentle stream of water every few months.
Once a year, call in a technician to have the system professionally inspected. A technician can resolve issues that impair efficiency or cause excess wear on the system. This includes lubricating the motor, balancing the fan wheel, and testing the electrical connections.
Incentives for going ductless
Lower energy bills aren’t the only way ductless systems can save you money. With the financial incentives available, you may find one of these systems is a more cost-effective investment than a traditional heat pump or fuel-burning furnace. For example, many power companies offer rebates for buying a mini-split system to replace an electric resistance heating system. These rebates can total as much as a third of the purchase cost. Some companies also offer interest-free loans to those wanting to upgrade. Offers vary, though, so contact your power company to find out what’s available.
Determining your system size
The capacity of an indoor unit is measured in Btu. A 9,000 Btu unit can heat or cool a space of around 450 square feet. Units are commonly found in capacities of 9,000, 12,000, 18,000 and 24,000 Btu. Keep in mind that an indoor unit can only condition a space that isn’t divided by closed doors. If you have several separate rooms to condition, you may need more than one indoor unit.
The outdoor unit is sized to meet the demand of all the indoor units combined. A home with several zones may require more than one outdoor unit.
Local climate, the energy efficiency of your home, ceiling height and number of people in your home also affect the size of system you’ll need. A heating and cooling contractor experienced with these systems can help you get the most effective and energy-efficient size for your home.
Choosing an installer
Because ductless systems aren’t yet common in the U.S., not every heating and cooling professional knows how to design and install them. As with any other system, correct sizing and installation are critical for efficient operation.
When selecting a contractor for ductless installation, ask about training and experience. Whether you’re still debating whether a ductless system is right for your home or you’re ready to start installing a new system today, our find-a-contractor service at Comfort24-7.com can help you get in touch with an experienced, local contractor to help you in your Chicagoland home.