What is a mini split?
Mini Split air conditioners bridge the gap between window air conditioners and central systems in terms of cost, energy efficiency,
installation difficulty, and power.
Mini Split air conditioners have a split design, like central A/C; they separate the "hot" and cold" parts of the air conditioner. Unlike
central A/C, mini splits don't use ductwork; the two sides of the air conditioner are connected by coolant lines, a condensate line,
and electrical lines. This is why they are sometimes referred to as ductless air conditioners. Mini splits are wall-mounted on the
inside and outside of a wall. Most mini split air conditioners have one outdoor unit, but some have as many as four air handlers
that all connect to one outdoor unit.
Though the specifications of each individual mini split air conditioner may vary, the two parts can generally be separated by
distances of up to 40 feet (of coolant, drain, and electrical connections). They can commonly differ in their altitude by about 15 feet
at a maximum. The drain, coolant, and electrical lines are usually bundled together in 3" conduit.
Another benefit to mini split air conditioners is that many units also function as heat pumps, so they can cool in the summer and
heat in the winter for year-round comfort.
Choosing a mini split air conditioner
BTU requirements
This is probably the first and most important consideration. You want to get a unit with a capacity as closely matched to your
needs as possible. A unit that is not powerful enough will run constantly and will never properly cool the room. A unit that is too
powerful will "short cycle"; it will cycle on and off over and over again, only remaining on for short periods of time. Short cycling is
bad for the compressor. It could substantially shorten the life of the air conditioner, and it will not dehumidify appropriately; so
while the air in your room might be a comfortable temperature, there could be an uncomfortable level of humidity. The ideally
sized unit will run at its maximum capacity on the few hottest days of the year and run somewhat under capacity at other times.
0-300 sq ft=9,000 BTU
300-415 sq ft=12,000 BTU
415-615 sq ft=18,000 BTU
615-800 sq ft=24,000 BTU
Energy efficiency
You should be mindful of the SEER of the air conditioner that you choose. A higher SEER is better, and a higher SEER air
conditioner often costs less in the long run than a less efficient unit. Additionally, many local utility companies offer discounts on
high SEER air conditioners.
Consultation with the installing HVAC professional
Before purchasing a mini split, you should consult with the HVAC professional who will be installing it. They will help you with the
above-listed considerations.
Installation
Mini split air conditioners should be installed by certified HVAC professionals. To find an installer in your area, check the yellow
pages for HVAC, heating, or air conditioning.
Installation questions
Why does an HVAC professional need to install a mini-split?
Mini split air conditioners require some complex installation, including cutting holes in your walls to run the conduit for the
coolant, electrical, and drainage lines. Also mini splits are not usually sold charged with refrigerant, and you need a certified
HVAC professional to charge them with the proper amount of the proper refrigerant. The HVAC contractor will also need to
provide the copper tubing for the lines.
Why aren't mini splits sold charged with refrigerant?
Due to the installation process, refrigerant must be added to the mini split air conditioner after installation.
How large of a hole will be cut in my wall for the conduit?
Generally, the conduit requires a hole of about 3" diameter.