Steps to Install a Ductless Mini Split

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Steps to Install a Ductless Mini Split

These 9 steps help ensure a better ductless mini split installation

Most homeowners turn to a professional to install a ductless mini-split HVAC system. But mini splits are much easier to install than traditional systems, and if you have experience with plumbing and minor electrical work – and you enjoy working around your home – it’s possible to tackle the majority of this project yourself. That said, we always recommend going with a professional installation, both to guarantee it’s done properly and because of the self-installs void the manufacturer warranty.

Let’s repeat that, as it’s important: Failure to use a licensed HVAC technician to do the install will VOID THE WARRANTY — and manufacturer tech support will likely not even talk to you to troubleshoot or provide other support.

Plus, due to safety concerns and laws about the handling of refrigerant – and special tools needed – the completion of the project is also specifically best handled by an HVAC professional.

Be sure to read your mini split’s manual – each system has characteristics unique to its manufacturer. But here are 9 steps to help you install your ductless mini split and take control of your home’s climate:

Make sure you have the proper tools

Besides the mini-split system, you generally will need:

  • A level
  • A driver/drill
  • A 1 ½-inch hole saw
  • A jigsaw
  • Pliers
  • Wire strippers
  • A rotary hammer
  • A flaring tool
  • Masonry screws
  • Copper tubing
  • Two adjustable wrenches
  • Pipe insulation
  • A ground pad
  • PVC primer and cement
  • PVC pipe with a 1-inch diameter
  • Duct tape
  • C-clamps
  • Electrical cable

Let’s get started

  1. Step 1: Choose the best location for your indoor unit. Indoor units should be carefully placed in an unobstructed spot on an interior wall to ensure that it cools the entire room properly. Avoid direct sunlight and heat sources, and you generally need to leave at least six inches of open space around the top and sides. Keep the unit at least 3.3 feet from antenna, power, or connecting lines used for household staples like TVs, radios, telephones, or home security systems – the electrical “noise” from these sources could cause operational issues in your mini split. And while the units are whisper quiet, locating them too close to where you will be the most often can result in annoying background noise. You also want to make sure you don’t install the unit so it blows air directly on people in the room. For these reasons, wall units should be located at least eight feet from the floor, as well as to ensure that cold air isn’t blown toward the ceiling. Finally, make sure the wall is strong enough to hold your unit’s weight. You may need to construct a wood or metal frame for extra support.
  2. Step 2: Choose the best location for your outdoor unit. The outdoor unit should be situated away from hot, heavily-trafficked, or dusty areas. It generally needs 12 inches around its perimeter to ensure proper functioning. Read this carefully: the stated clearances to the front, sides, and rear cannot be compromised. They must be strictly followed to provide adequate airflow through your outdoor unit. A poorly located outdoor unit can reduce system capacity, cause your system to shut down, and even lead to premature equipment failure. Concealing the outdoor unit behind shrubs, an equipment screen, or anything else is fine – but the minimum clearances must be met.
  3. Step 3: Drill a hole for your lines. Turn off the electricity to the circuit before you start your project. Hold the mini split’s mounting bracket against the wall and – using your level to make sure it’s straight – mark the locations for the screw holes. Determine and mark the best place to drill a hole for the electrical, refrigeration, and condensate discharge lines based on the bracket’s openings. Be sure to consider the length of the lines and the distance they need to travel to reach the outside unit. Use your rotary hammer tool and a 3-inch diameter masonry coring bit to drill a 3-inch hole in your wall. Don’t drill all the way through the wall from the inside – once the bit’s pilot penetrates the wall, finish the hole from the outside. For proper drainage, make sure the hole slopes downward toward the exterior of your house.
  4. Step 4: Mount your mini split. Use the masonry screws to fasten the mounting bracket onto the wall and make sure it’s level. Install the indoor unit on the bracket, and run the utility lines through the hole you drilled to the outside. Attach a vertical chase directly below the hole on the exterior wall to house the refrigeration lines, condensate line, and electrical cable.
  5. Step 5: Extend the discharge line. Use PVC pipe to lengthen the mini split’s discharge line down so it stops a few inches above the ground. Press fit the PVC pipe into the line and use a piece of duct tape to secure the connection. Fasten the extended line to the chase with a metal C-clamp to keep it from moving. A word to the wise: Many of the problems reported in mini-splits involve the condensate line. Since the temperature of the condensation is often at or below the dew point temperature of the air, these lines should be insulated to prevent “sweating” during the cooling season. Heat tape should also be considered in the winter to prevent freezing. These types of problems are one of the reasons to use a professional licensed HVAC technician for an installation; both to replace parts and get technical support from the manufacturer if you run into an issue.
  6. Step 6: Extend the refrigeration lines. Carefully bend the copper refrigeration lines and fit them into the chase. Use two adjustable wrenches to remove the compression fittings from the ends of the copper lines. These lines will also need to be extended with extra copper tubing to reach the outside unit. Slide the brass nut from one of the copper refrigerant lines extending from your indoor unit onto the new length of copper tubing that you plan on connecting. Then use your flaring tool to flare the end of the new tubing and widen its diameter. Once that’s done, slide the copper refrigerant line from the mini-split into the tubing. Bring up the nut and hand-tighten to hold the copper tubing and refrigerant line together. Repeat to attach the remaining refrigerant line.
  7. Step 7: Set up the outdoor unit. Set the outdoor condensing unit onto a level pad adjacent to the chase. Use the adjustable wrenches to tighten the compression fittings on the refrigerant lines, and then wrap pipe insulation around each line.
  8. Step 8: Add electric power. Run a weather-tight conduit from an outdoor electrical box to the outdoor unit. Feed electrical wires through the conduit. Run a length of nonmetallic electrical cable from the outdoor unit through the hole in the wall to the indoor air handler. Finally, snap the cover onto the chase to hide and protect the lines and cable.
  9. Step 9: Wrap it up. Make all electrical connections at the indoor and outdoor units – checking the unit’s diagram to ensure everything is connected properly. It’s critical to follow the manufacturer’s instructions for wiring. Pressure test the system for leaks. This is done by attaching a nitrogen tank to the outdoor condenser’s service ports and testing with 100 to 200 psi. Spray a soap solution onto the connections to see if any bubbles appear. If they do, it indicates a leak. Use a vacuum pump to suck out all the nitrogen and moisture from the copper wire fittings, and then open the valves to release the refrigerant into the lines. Seal up the hole in the wall using expanding polyurethane foam. Turn on the electricity and test the air conditioner. Because these final steps involve several materials with safety concerns, you should hire a contractor to complete your mini split’s installation.

There are advantages to installing your mini split on your own, including significant cost savings, the personal satisfaction of completing your own project, and a known quality of workmanship. But it’s nevertheless recommended that you hire a contractor, which should ensure a professional installation.

And it bears repeating: Failure to use a licensed HVAC technician to do the install will VOID THE WARRANTY — and manufacturer tech support will likely not even talk to you to troubleshoot or provide other support.

ComfortUp is a provider of high-quality indoor and outdoor products and services that enable our customers to enjoy a more comfortable and energy-efficient lifestyle. Contact us to learn more about ductless mini split HVAC systems, and how we can help you gain control over your comfort.