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Ductless Mini Split Buyers Guide

How do I choose a ductless split air conditioner? : The most important factors when choosing a ductless split air conditioner are BTUs, number of zones, installation type and Inverter options.
A single zone ductless split system will have a single evaporator, or air handler (indoor unit), and a single condenser (outdoor unit). Single zone systems account for most of the ductless systems available. If you want to cool more than one area with a single system, a multiple zone split applies two, three, or four (depending on the model) indoor units to one condenser. Normally its one unit per room – just make sure there is enough BTUs to cover the square footage in each room.
Single Zone
> Shop All Single Zone Ductless Systems
Single Zone
> Shop All Multi-Zone Ductless Systems

BTUs (British Thermal Units):
BTUs are units of power – the larger the area you need to cool or heat, the more BTUs you will need. This is very straight forward for a single zone split system. For multiple zone systems, both the outdoor units and the indoor units will have a set number of BTUs. One of the benefits of a ductless split system is that each indoor unit runs independently. Therefore, the total number of BTUs for the indoor units can exceed the outdoor unit’s BTU by up to 30%, but if all the indoor units are operating (on maximum) at once, the total BTU output will only meet the BTU capacity of the condenser. When cooling rooms with poor insulation, areas with high heat load (kitchens - server rooms), or southern or western sun exposures, stepping up to the next BTU size is recommended. See below chart for general sizing.
Maximum Room Size (sq. ft.) BTU's
425 9,000
600 12,000
800 15,000
980 18,000
1,250 21,000
1,440 24,000
1,600 27,000
1,800 30,000
2,000 32,000
2,245 36,000

Installation Type:
There are 4 different options of indoor units.  The most common and cost effective type is mounted on the wall.  Another type goes on the ceiling. Ceiling units can be suspended, recessed or concealed inside the ceiling.  Ceiling recessed offers the aesthetic appeal of central units where only the grille is visible with the convenience of ductless setup - but these types are more expensive than wall mounted. Ceiling Suspended are most expensive still but offer the option of being placed standing upright on the floor or suspended off a ceiling. Concealed Duct types usually only consist of central air conditioners.
wall-mounted wall-mounted wall-mounted wall-mounted

Inverter Type

There are 2 primary benefits for considering an Inverter type system over the baseline 13 SEER.  First, Inverter DC systems are much more energy efficient - with SEER ratings of 16 to above 22!  This means lower electric bills and more eco-friendly cooling / heating.  The 2'nd benefit applies to heating functions.  While the heat pump on a standard 13 SEER unit will begin to lose effectiveness once outdoor temperatures drop below 24 degrees F, an inverter system is capable of delivering it's full rated heating capacity at ambient temperatures down to 3 degrees F.  (check the ambient operational temperature specification for each system).  Inverter units are often 30-40% more expensive than there 13 SEER counterparts in the same class so whether or not to upgrade to an Inverter type is an important choice.  Often the additional investment cost of an Inverter system will pay itself off with lower electric bills in the matter of a few years.   These units are often Energy Star approved as well which means more possible savings in terms of state, local and / or federal tax rebates.  See below for more info on how Inverter DC systems work.



DC Inverter Air Conditioners are the ultimate cooling and heating technology of the HVAC field.  They are called "DC inverter" because the alternative current (AC) is converted to Direct Current (DC) then, direct current inverted back to Alternative current with desired frequency. The current supplied through the wall outlet has fixed frequency which is 60 Hertz. Different frequencies supplied to the compressor will result in different running speeds of the compressor. Inverter control systems use Pulse Amplitude Modulation (PAM) that is the most advanced and energy efficient method of inverting the current.  DC Inverter AC's bear special compressors that their speed could be changed by increasing or decreasing the frequency of the supplied power.  Therefore, unlike conventional split Air Conditioners/Heat Pumps which cycle between on and off repeatedly, the DC Inverter control system will monitor the room temperature and adjust the compressor speed automatically.

Conventional compressors turn on and off to maintain the room temperature at desired level.  This will result compressor to draw tremendous energy each time it starts up. This will also reduce the life-span of the compressor and other components that are turning on and off.  Once a conventional system is running, it runs at its maximum speed, consuming the maximum amount of energy in order to produce the maximum of cooling or heating to maintain the desired temperature.  The system will then cycle between on and off in an effort to maintain this temperature. When a DC Inverter compressor initially starts up, it runs with a higher speed to bring the room temperature to desired level rapidly, Once the set temperature is reached, it slows down and adjust its capacity just to counter the heat loss or heat gain of the building. Constant temperature is maintained.

Why buy an Inverter System
Why buy an Inverter System