How to Install a Ductless Air Conditioner

Adding an A/C system sounds 
 like a job for pros only. And 
 usually it is. But two non-pros installed this ductless “mini-split” system in a garage in one day.

The installation was fast and easy because of the special line set. It comes prefilled, or 
“precharged,” with refrigerant and includes connectors that don’t require special skills or tools. Just mount the two main units and connect the line set to the condenser. Some mini-splits include an easy-install line set, but most don’t.

A mini-split system can be installed in a home, a garage, a cabin or a shed. Some offer heating as well as cooling, and some include multiple evaporators to serve multiple rooms. Depending on features and size, most DIY mini-splits cost from $700 to $2,000.

Choosing the System

Very few brick-and-mortar stores carry DIY systems, so online shopping may be your only option. Luckily there are many online suppliers. The size of the system is listed in BTUs (British thermal units). The higher the number, the greater the cooling capacity. To select the right size mini-split, calculate the heat loss of the room. Several websites simplify these calculations.

Don’t just guess; an undersized system won’t keep up, and an oversized system will cycle on and off too frequently, shortening the condenser’s service life. We installed a ClimateRight 12,000-BTU heating and cooling system that costs about $1,100. The other necessary materials totaled about $275.

Providing Power

In the steps below, you’ll see that installation is mostly basic DIY stuff: measuring, drilling holes, driving screws … Usually the biggest challenge is running power to the system. With a small system, you may be able to draw power from a nearby underloaded 20-amp circuit. More likely, you’ll want to install a new circuit dedicated to the mini-split. That can be a small job or a major project depending on how easy it is to run cable from the main panel to the unit.

By cutting—and later patching—three small holes in drywall, we were able to run cable from the basement up through the garage wall, through the attic, then down and out the exterior wall and into a disconnect box. (The disconnect provides an easy, certain way to turn off power when servicing the unit.) Power then runs from the disconnect to the condenser. Cable running alongside the line set powers the evaporator. Our bill for electrical supplies was about $160. A local electrician estimated that work at about $500.

If you have some electrical know-how but need extra guidance, don’t forget your local electrical inspector. It’s not an inspector’s job to act as a consultant, but most will give you some advice and outline code requirements. Expert help and certainty that the job is done right—not bad for the cost of an electrical permit.

Other Materials

The condenser needs a level surface 
to rest on. You could pour a concrete pad, but a plastic condenser pad 
($50 and up online) is instant and easy. We mounted ours on condenser wall brackets ($45 online).

The fabric sleeve covering the line set isn’t attractive or easy to keep clean. The solution is a plastic line set cover kit, which costs about $55 online.

Remote Control

A handheld controller is used to adjust the room temperature. Some mini-splits offer Wi-Fi and Bluetooth control.

Install the Mounting Bracket

• Mount the evaporator inside the room on an exterior wall away from direct sunlight, doorways and sources of dust.
• Make sure this area of the wall is free of wires, pipes and ducts that would interfere with making a hole for the line set.
• Mark the stud locations and fasten the bracket to them with screws.

Next, read: 21 air conditioner maintenance and home cooling tips.

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