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Pro Guide to Ductless Mini Split HVAC Systems

The ductless mini split system (DMSS) has been around for decades but, until recently, it was generally found only in Japan and Europe.

The system is now becoming popular in North America due to its versatility and efficient design.

How the Ductless Mini Split System Works

The ductless mini split system works much like a traditional refrigerant-based central AC system; with a condenser kept outdoors and the rest indoors, but the similarity ends there.

Instead of relying on your forced air furnace system to cool your home, a DMSS uses multiple air handlers throughout your home to cool individual spaces called zones.


The condenser sits on a concrete slab outside, just as your traditional split system AC unit. Refrigeration and communication lines lead from the unit and into your home to split off to up to eight separate air handlers.

These lines are snaked through your walls and attached to the air handlers and remain completely out of view.

Air Handlers

Air handlers draw outside air past coils which treat the air. The air is then moved through a nearly silent blower (no louder than leaves rustling in a gentle breeze), past a high grade air filter that can be washed, and then into your interior space.

If you opt for the heat pump style air handlers, the ductless mini split system can supply both your heating and your cooling needs.


Each air handler represents an HVAC zone. You may create up to eight zones fed by a single outdoor condenser. The number of zones is usually dictated by the shape of your home’s interior space.

Open space designs, such as homes with the living, dining and kitchen spaces all within one set of walls will need only one zone to cover all three rooms.

Enclosed spaces, such as bedrooms, would constitute one zone each and an open basement another single zone.You can also include your garage or workshop if you wish.

The Advantages of Going Ductless

The ductless mini split HVAC system has many advantages over traditional systems not least of which is being able to install in homes with no ductwork.

There are a lot of people spending the early spring and fall of each year wrestling heavy and unsightly window AC units into place or into storage. The DMSS is the answer to ending that twice yearly struggle, but there is so much more to these systems.

An Answer Where None Existed

Homes with baseboard heating, new additions, or without any ductwork used to be relegated to depending on those portable AC units for their cooling needs.

It was either that or face the massive expense and effort of installing ducting in a structure not suited to such efforts.

Once the ductless mini split HVAC system entered our market, it changed everything. Now the hopeless have hope and those portable units can be retired along with their huge energy bills.

Increased Efficiency

Multiple factors of the ductless mini split system increase the overall efficiency of the system. Each will be covered more thoroughly later but among these features are:

  • Ability to shut down zones
  • Direct air flow
  • Reduced condenser size

Fully Customizable

Due to their construction, the DMSS can be designed specifically to fit your home and budget. You can elect to use fewer zones, reducing the number of air handlers, or go full out and fill every space with it’s own air handler system.

You can also design your system for maximum aesthetic effect, hiding your air handlers in creative ways. LG even has one that is shaped (and used) like a piece of wall art.

Chances are, whatever you can envision for a ductless installation is already on the market.

Low Visual Impact

All air handlers are designed to have a low visual impact on your decor. Some are essentially invisible like the ceiling cassettes and LG’s Art Cool cassette. Others are quite visible but have a quiet look that invites theeye to slip on by instead of drawing focus.

Space Saving

Floor vents are a constant annoyance when trying to clean your floors or decide where to place furniture. With wall and ceiling mount air handlers, your ductless mini split system is out of the way and opens your entire floor space to your use.


The noise level of your air handlers is no more than a whisper. You won’t hear the fans at all, just the sound of the air moving into the space, and that only if you are near the unit.

Higher Indoor Air Quality

The EPA estimates that we spend up to 90% of our time indoors and that air pollution is two to five times higher indoors than outside.

Your ductless mini split system is the only HVAC system that is constantly drawing fresh air into your home while exhausting stale air back out.

The lack of ducting also prevents buildup of harmful pathogens, microorganisms and particulates. In forced air systems not only do these items collect in your ducting, but they are circulated through the air your family breathes as a matter of course.

Designing Your Ductless System

You will need to get measurements done, tests run, and calculations completed before you can start plotting your new ductless mini split system.

Once you know the capacities and ratings necessary for a balanced system you can get into the fun stuff but none of this will be quick. The end result, however, wil be worth the wait.

SEER Rating

The Seasonal Energy Efficiency Ratio (SEER) rating of a central air system is a measurement of cooling power vs required energy to achieve a set result. The higher the SEER rating the more efficient the unit.

SEER ratings came about during the energy crisis of the 70’s, but regulation didn’t begin until the 90’s. In 2015 the latest, and much more stringent, regulations were set into law and the nation was split into three regions with individual SEER regulations.

These regions are based on Heating Degree Days (HDD) and this information was used to set the minimum SEER rating for each region based on expected annual use. You can view the regions in this document to see where your home falls and what the minimum SEER rating is for your region.

Choosing the SEER rating of your system is a matter of personal preference and how far into the future you wish to plan.

A raise in the SEER rating can potentially save you up to 10% on your energy costs, which can help offset the added expense of going for absolute efficiency.

SEER regulations require a SEER rating of 13 to 14 but you can purchase systems with SEER ratings running past 20.

Load Calculation

Load, in reference to HVAC systems, is how much air your house holds and can move in a given amount of time, measured in tons. This number is essential and must be accurate.

The best way to load test a home is to hire an HVAC contractor to test your home with their specialized equipment.

If you prefer to take another route, this calculator (scroll down to the second chart and click on “Extra Options”) will give a general range, or you can use this brochure from the department of energy.


You need to decide which areas of your home will constitute individual zones. Once you have decided on your zone selections, you will combine several other factors to arrive at the necessary BTU rating for each zone.

You can use the load calculator (remember to keep your answers specific to the zone in question) from earlier as a starting point, but you also need to consider the following:

  • Normal occupancy levels – add 600 BTU’s for each person above one
  • Kitchens – add 4000 BTU’s if the zone contains your kitchen
  • Your home’s age – for old or simply drafty homes add 30% to your BTU calculation

Once you have arrived at your BTU need for each zone, pick the appropriate sized air handler (at or a little above the zone requirement) to fulfill each zone’s needs.

It is possible each zone will have different requirements. This is no problem because you can mix and match air handler strengths and types in any configuration you wish.


One of the nifty things about the ductless mini split system is that you can use a smaller condenser to support a larger load. First, add the BTU ratings of each zone to arrive at your total BTU requirement for the system.

Your condenser BTU rating can be up to up to 30% lower than the combined rating of your air handlers. So, if you have 4 zones at 15K, 10K, 10K and 20K respectively, you can run the combined load of 55K BTU’s with a 40K condenser with no loss in function and no damage to the condenser.

Just make certain that the condenser you pick is rated for at least 70% of the combined load of all your zones. This quirk of the ductless mini split systems can be a real money saver.

Air Handler Types

There are four main types of air handlers, not counting LG’s proprietary Art Cool units, each with their advantages and disadvantages.

All four have the advantage of delivering direct, fresh and filtered air with a balanced moisture content into your space. The four air handling systems are as follows:

1. Wall Hung

Wall hung units are attached high up on exterior facing walls and look like simple rectangles. They are very obviously ‘there’ but can be staged for aesthetic effect.

Just be certain to adhere to manufacturer requirements for airflow. All power, refrigeration and drain lines are run behind the unit and into your wall and are not visible.

2. Floor Mounted

The floor units are arranged much like the old school radiators of times gone by (or in New York walk ups). All lines are also hidden behind the unit and run through your walls.

The units have a smaller footprint than radiators and have a smooth look. They also provide better heating as warm air tends to rise.

There exists on the internet page after page of ‘ideas’ for camouflaging your floor mounted air handler. We have yet to see one that doesn’t seriously impede their function.

Choosing a floor mounted unit is a choice based on practicality, not aesthetics. Please don’t select floor mounted units thinking you can hide them.

3. Ceiling Cassettes

Ceiling cassettes mount nearly flush with your ceiling but require 12” – 14” of free space above your ceiling to mount correctly. Their location in your ceiling makes them less noticeable and can simplify the process of running the lines to the unit.

They have two main advantages over the other types of units. First, they can be mounted central to the zone space, increasing their efficiency.

Second, decorative covers can be purchased to turn them into an interior feature or make them all but disappear.

Ceiling mount units are available for homes without free space above the ceilings. There is no way to make them aesthetically pleasing as they stick out several inches from your ceiling.

4. Ducted

Ducted air handlers exist to get around space restrictions or other practical concerns that none of the other units can accommodate. These units are mounted under the floor with short runs of ducting.

While they remove the advantage of completely open floor space with their vent covers, they will allow the use of a mini split system where no other air handler will work.

Another version of these units mounts within existing spaces where your floor vent existed. They are only visible as a standard floor vent as with a traditional ducted system.

Costs of Moving to a Ductless System

For homeowners who thought they had no options, the ductless system is a prayer answered and for those who are looking for increased comfort, space and efficiency they are the perfect answer.

Ductless mini split HVAC systems are not inexpensive systems. They are, in every sense of the term, an investment.

Purchasing the System*

Purchase prices for a ductless mini split HVAC system varies widely due to the many available configurations.

The low end is $1300 for a single zone system with the high running over $12,000 for maximum zone coverage.

Individual components, recommended when picking out a large or complicated system, fall in the following price ranges:

  • Condenser Unit                                  $600 to $5,300
  • Wall Mount Air Handlers                   $600 to $5,000
  • Floor Mount Air Handlers                  $600 to $4,000
  • Ceiling Cassette Air Handlers           $500 to $3,200
  • Ceiling Mount Air Handlers               $1,100 to $7,300
  • Ducted Air Handlers                          $540 to $5,000
  • LG Art Cool Air Handler                    $600 to $700
  • Installation Kit                                    $300 to $500
  • Refrigerant Lines                                $5 per foot

*prices based on heat pump systems – pure AC prices are up to 60% higher


Manufacturer warranties only cover defective parts and manufacturing errors and never cover labor. We don’t recommend purchasing extensions as these problems generally show up in the first 90 days.

Some big box stores offer decent protection plans but be sure they cover labor and parts. We’ve found that with large systems like this your best option is a home systems protection plan.

Tax Rebates and Incentives

Local, state and federal government programs incentivize the installation of energy efficient systems in our homes. Visit the EnergyStar site to see what you need to do to qualify for a federal tax rebate.

You can also use this site to look up other programs that are available to help you with the costs of going green, though be warned many of the listed programs are no longer in effect. There are many options to explore such as:

  • Federal loans, grants and tax credits
  • State and local incentive programs
  • Manufacturer incentive rebates
  • “Green” loans from traditional lenders

Energy Use

Running a ductless mini split system will save you money, regardless of region or local electricity costs. They are just that efficient, with factors extending beyond the SEER rating.

You can use this simple calculator to estimate your energy costs.


The simple answer is don’t. First of all, it is illegal from local to federal laws, to buy, sell or possess refrigerants by anyone without an up to date license.

It is also much more difficult to install AC than you think, and ductless systems are complicated systems. You should also consider the following:

  • Release of refrigerants, accidental or otherwise, is a $10,000 fine per day per item (consider the cost of an unnoticed slow leak dating back to your installation)
  • It is illegal to buy, sell or possess refrigerants without a proper license
  • The reward for turning in someone who buys, sells, or possesses refrigerants without a license or who releases refrigerant is $10,000
  • Improper installation of certain systems can damage your home’s structural integrity
  • All warranties are null and void – including most home warranties
  • Home insurance won’t cover damages from a self installed system

Please do not install your own AC system unless you are a licensed HVAC technician. It is an all around bad idea.


Installation of a ductless mini split system will take more time than installing a traditional system but the costs are otherwise similar. On average, installation will run between $3,000 and $8,000. This calculator will help you develop your installation budget though it only considers one and two zone systems.

Additional Costs

Certain factors will add to your installation cost such as:

  • Number of zones
  • Exterior wall material – wooden vs brick or stone
  • Accessibility issues
  • Ease of snaking lines through your walls
  • Electrical infrastructure – if new boxes are necessary
  • Air handler types – some are easier to install than others


Certain aspects of installing a ductless mini split system can be exacting and you should check to ensure they were done properly. Watch that your installer does the following:

  • Places a rubber mat between your condenser and its concrete slab
  • Uses the correct gauge for communication wires
  • Uses grommets and insulation for all exterior pass-throughs
  • Angles drain lines properly – could cause structural failures in your walls if angled poorly
  • Doesn’t allow crimping of any lines
  • Doesn’t allow stress on communication lines
  • Makes sure air handlers are installed securely

Once your custom system is in place and running, you and your family will enjoy a comfortable indoor climate, cleaner indoor air and lower energy bills for decades to come. Good luck!

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