Because DIY systems are rarely available in brick-and-mortar stores, online shopping may be your only option. Fortunately, there are numerous online vendors. The system’s size is specified in BTUs. The greater the number, the greater the capacity for cooling. Calculate the heat loss of the room before selecting the appropriate size mini-split. Several websites make these calculations easier to understand.
Don’t wing it; an undersized system won’t keep up, and an oversized system will cycle on and off too frequently, reducing the service life of the condenser. We installed a $1,100, 12,000-BTU heating and cooling system. The other materials required came to about $275.
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The installation is mostly basic DIY stuff, as you’ll see in the steps below: measuring, drilling holes, driving screws… Typically, the most difficult challenge is supplying power to the system. You may be able to draw power from a nearby underloaded 20-amp circuit with a small system. More than likely, you’ll want to dedicate a new circuit to the mini-split. Depending on how easy it is to run a cable from the main panel to the unit, this could be a minor or major project.
We were able to run a cable from the basement up through the garage wall, through the attic, down and out the exterior wall, and into a disconnect box by cutting, and later patching, three small holes in the drywall. The power is then transferred from the disconnect to the condenser. The evaporator is powered by a cable that runs alongside the line set. Our electrical supply bill came to around $160. A local electrician estimated the cost of the work to be around $500. If you have some electrical knowledge but need some extra help, don’t forget to contact your local electrical inspector. It is not an inspector’s responsibility to act as a consultant, but most will offer advice and outline code requirements. Expert assistance and assurance that the job is done correctly-not bad for the price of an electrical permit.
The condenser requires a flat surface to rest on. A concrete pad could be poured, but a plastic condenser pad is quick and easy. We used condenser wall brackets to mount ours. The fabric sleeve that covers the line set is neither attractive nor easy to clean. A plastic line set cover kit is the solution. The temperature in the room is controlled by a handheld controller. Wi-Fi and Bluetooth control are available on some mini-splits.
The Typical Process
Place the Mounting Bracket in place. Install the evaporator on an exterior wall inside the room, away from direct sunlight, doorways, and dust sources.
Make sure there are no wires, pipes, or ducts in this area of the wall that would interfere with making a hole for the line set. Mark the stud locations and screw the bracket to them.
Make a Pilot Hole
To allow condensate from the evaporator to drain outside, the line set hole must slope slightly downward to the outside. Begin by drilling a pilot hole from the inside out. Then, go outside and double-check that there are no trim or other obstructions that will make drilling the full-size hole difficult.
Complete the Full-Size Hole
Remove any insulation and inspect the wall cavity for obstructions before cutting with a hole saw from the inside. Drill from the outside to complete the hole.
The Line Set
Carefully uncoil the line set from the evaporator’s back. Feed the line set through the hole with the help of an assistant outside. The assistant should gently bend the line set downward and to the side as it emerges to reach the condenser. Maintain the rigid plastic collar that surrounds the line set at the end that connects to the condenser. The drain line is the shortest and comes in last, below the other lines. Add the drain extension and secure the joint with electrical tape.
Wrap the foam sleeve around the section of line that was set within the hole and replace any insulation that was disturbed in the wall cavity. Then, using the mounting bracket, hang the evaporator. While you’re doing this, your assistant may need to feed a few more inches of the line you’ve set up outside. Insert the two-piece plastic trim into the hole on the outside to protect the line set from any sharp edges.
Place the condenser on a pad on the ground or on a wall bracket so that the refrigerant lines can easily reach it. Route the line set so that it stays close to the building’s exterior and does not jump over any obstacles. This makes installing a cover easier. Check that the condenser is at least 3 feet away from any walls or bushes. Avoid placing it in areas where ice or packed snow may fall on it, or where other appliances may vent. A location on the structure’s east or north side maximizes cooling efficiency.
This step varies depending on the manufacturer. A locking lever presses the line connections together in this system. Before turning on the compressor, check the refrigerant lines for kinks and double-check the electrical connections. Then go inside and adjust the thermostat with the handheld controller.
Cover the Line
Insulate and seal the hole in the outside wall, then cover the line set with cut-to-length sections of plastic or metal channel. Place the back half of the channel behind the line set, plumb it, and screw it to the wall. Because our line set travels horizontally to the compressor, we drilled a hole in the channel corner to allow the drain line to exit straight down.
Does It Work?
A mini-split system is made up of two main parts: an indoor evaporator that cools the air and an outdoor condenser that dissipates heat. They’re linked by a line set, which is a piece of tubing that runs through a baseball-sized hole in the wall, carrying hot refrigerant outside and cold refrigerant inside.