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Ductless Mini-Split

Ductless Mini-Split systems come in a variety of styles and applications. Let’s review what equipment components are available The Ductless Mini-Split delivers heating and cooling without using duct. Some of the variations are,

  1. Single Zone
  2. Multiple Zones
  3. Air Conditioning Only
  4. Air Conditioning and Heating
  5. High Wall Units
  6. Cassettes
  7. Floor Console Units
  8. Ducted Units
  9. Remote Wireless Controllers
  10. Wired Controllers

Ductless Mini-Split Single Zone

A Single Zone has one out door unit and one indoor unit. Many in our industry also refer to this as a 1:1 system. Single Zone systems are usually more energy efficient than a multiple zone system. Perfect for a room addition to heat and cool, or for a garage or seldom used space. Pictured is a Carrier single zone outdoor heat pump, which has a rated cooling and heating capacity of 9,000 Btu/h. With a cooling efficiency rating of 30.5 SEER and a heating efficiency rating of 10.5 HSPF. The inverter compressor technology for this ductless mini-split heat pump produces a variable cooling range between 1,535 to 12,966 Btu/h and a heating range between 2,388 to 13,648 Btu/h. These ranges are common to all ductless mini-splits. The diversity of range is one of the advantages of these systems over most conventional systems.

Ductless Mini-Split Single Zone Heat Pump

Ductless Mini-Split Single Zone Heat Pump

Ductless Mini-Split Multiple Zones

Ductless Mini-Splits with multiple zones have one outdoor unit and two or more indoor units. A feature of multiple zone mini-splits that the consumer must understand is how the zones
operate when heating and cooling. For the residential application, all zones of one outdoor unit can operate in the cooling or off mode, and in the heating or off mode. However, one zone cannot be heating and another zone cooling.

Manufacturers offer a variety of efficiencies for multiple zone outdoor heat pumps, and the number of indoor units that connect to the outdoor unit will vary by manufacturer and their respective models. Flex Zone made by Fujitsu will serve 2 to 8 zones, and Daikin ductless mini-splits have that same range. This is a picture of a Carrier multiple zone heat pump that can serve from 2 to 9 indoor units. In multiple zone heat pumps the efficiency will decrease as the number of zones increases. Each of the zones is controlled individually, and as noted above one zone cannot be cooling while others are heating, and visa versa. With Multiple Zones equipment, the indoor units operate independent of each. Conventional equipment can also have zones that run independently, but there are issues the minimum CFM’s and increased static pressure when only a few of several zones are operating at the same time. Most conventional centralized equipment produces a certain amount of CFM’s at different fan speeds, with a specific range of static pressure. When all zones are open and running, there can still be problems with the bypass air. Bypass air is used to dump excess air into the return air duct which creates another set of problems. Multiple Zones equipment is a good solution when individual control is needed in different spaces. Ductless Mini-Splits offer an alternative solution.

Ductless Mini-Split Multiple Zone Heat Pump

Air Conditioning Only

Depending on where you live or what type of heating system you have, the ductless mini-split that is dedicated to air conditioning is a selection to be considered. A house with hot water radiant or baseboard heating and no air conditioning will find a good fit with this air conditioning only mini-split. They are less expensive that a heat pump that heats and cools. Many businesses use the air conditioning mini-split to cool server rooms.

Air Conditioning and Heating

Just like a conventional split system heat pump, these ductless mini-splits provide cooling and heating. The same outdoor unit provides cooling when it is hot outside, and heating when it is cool to cold outside. The heat pump mode is referred to as air conditioning in reverse. The refrigerant used is R410a and boils at -61*F. For more information on heat pumps, read our article What is an Air Source Heat Pump and how does it Work?

High Wall Units

The high wall unit is very popular, easy to install, and the most efficient indoor unit. The high wall is usually installed on an outside wall near with the outdoor unit. The outside wall installation has a mounting bracket that is secured to the wall, and a hole is drilled through the wall. Piping and electrical are run through the hole and connected to the outdoor unit. The indoor unit connects to same piping and electrical, and the mounts on the bracket. High wall units are also installed on interior walls. The unit pictured above is 9,000 Btu/h that can throw air almost 30’ across the room. The CFM will vary from 206 to 412 depending on the fan speed.

Ductless Mini-Split High Wall Unit


The Cassette is less visible than the High Wall. The louvered panel mounts flush to the ceiling, with the rest of the cassette hidden in the ceiling space. We are accustomed to seeing ceiling grilles and vents in homes, schools and businesses, making the cassette grille less objectional to some consumers. When centered in the ceiling of a room, the cassette may provide more even temperatures in some applications. The supply air into the room comes through the four outer louvers that are on the four sides of the large return air grille in the center of the cassette. The cassette is not as energy efficient as the high wall unit. With several fan speeds a 12,000 Btu/h cassette can throw air up to 23’ with a CFM range between 265 and 353. For removing condensate created during the cooling cycle, a built-in condensate pump with a liquid safety switch is included. The pump allows condensate to be pumped up to 24” above the cassette into a graded pipe that removes the condensate from the building.

Ductless Mini-Split Cassette

Floor Console Units

You guessed correct, the Floor Console is installed just above the floor. High Wall units blow air out and horizontal, Cassettes blow the air downward, and Console Units blow the air upward. The direction of air throw is somewhat relative since the units have supply air louvers that move during fan operation. Console Units are ideal for areas where ceiling and wall restrictions do not allow High Wall and Cassette units to be installed per manufacturer instructions. Console installation on outside walls are easy compared to Cassette or Ducted. Inside wall installation of High Wall units can be a challenge, making the Console a good fit if they are done above a crawl space. Installation under a window sill is common. A wall recess 9” deep with a concave top is an acceptable method for certain manufacturers, as well as a half-concealed console.

Ductless Mini-Split Floor Console Unit

Ducted Units

Ironically the Ductless Mini-Split systems include the Ducted Unit. Like the previous three indoor units, the Ducted Unit heats and cools with refrigerant that flows to and from the outdoor unit. The Ducted Unit is not the same as a conventional heating and cooling system because it is not part of a central system. One Ducted Unit can be used for two or three rooms. Several Ducted Units may be used in a larger room, and each unit has separate temperature controls, providing zoned areas in one room. Ducted unit can be installed in and attic, above a suspended ceiling, or in a framed soffit type area if unit access is available. Ducted Units are not as energy efficient as High Wall Units, but they are more versatile in certain applications. High Wall, Cassette, and Console units generally serve one area. A Ducted Unit can provide tempered air to two or more rooms that are separated by walls and doors. The supply air diffusers and return air grilles used for this system are identical to those used with conventional equipment and duct.

Ductless Mini-Split Ducted Unit

Remote Wireless Controllers

Remote Wireless Controllers look like your television remote controller. There several unique features that differ from the traditional wall thermostat. A wall bracket can be installed to hold the Remote Wireless Controller. Assume you want to take a nap on the couch, or watch television in the recliner, take the controller with you. When the controller is where you are, adjustments can be made in temperature, fan speeds, and so forth with leaving your position. The indoor temperature can be sensed at the indoor unit by using the I Feel function. All four of the indoor units have an internal temperature sensor. The high wall and console units are in the space being heated or cooled, and those sensors will more accurately sensor the space temperature. The duct and cassette units are not generally in the space because these units are in a ceiling or attic space and have their sensor in the return air, and that temperature may be 10*F higher than the room(s) they heat or cool. To have comfort where you are in the space the Follow Me function will make the controller the temperature sensor. In addition to fan speed, temperature selection, and sensor location, the controller has other features. Child lock, Clock, Timer, Turbo, X-Fan, Quiet, Sleep, and other functions. When we install multiple indoor units that use the remote wireless controller, we use small colored dots and install one on the equipment and one on the controller.

Wired Controllers

Just like the thermostat in a conventional heating and cooling system, the Wired Controller for a Ductless Mini-Split is attached to the wall and has a dedicated wire bundle that attaches to the indoor unit and the Wired Controller. The Wired Controller has most of the functions found in the Remote Wireless Controller, even the Follow Me function that senses the temperature at the controller. Some believe the Wired Controller has several benefits over the Remote Wireless Control. The Wire Control cannot be lost, and it cannot be mixed up with other Wired Controllers which can happen with the Remote Wireless. When coming into the space you will not have to search for the controller. Checking the controller in the middle of the night is simple because you know where it is, and the backlight is convenient. Depending on the manufacturer and model, some indoor units, usually Ducted Units, can only be controlled with the Wired Controller. Why? The Wireless Remote Controllers use infrared technology to communicate with the indoor unit infrared sensor. If the indoor unit is in the attic or above a ceiling the infrared communication will not happen.

Wired Remote Controller

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