How to Install a Ductless Mini-Split: An 8-Step Guide – Della

Installing your own Della ductless mini-split is a rewarding project that gives you complete control over your home's comfort. This guide provides the 8 essential steps for a safe and successful installation.

Safety First: A Crucial Warning This installation involves lifting heavy equipment and making electrical connections. We strongly recommend having a helper. If you are not completely comfortable and knowledgeable about handling your home's electrical wiring, please hire a licensed electrician for that portion of the job. Read this entire guide before you begin.

Before You Start: Tools & Materials Checklist

To ensure a smooth process, gather these items first:

Drill with masonry & standard bits
3-inch hole saw
Adjustable wrench set & Torque wrench
Pipe bending tool
Pipe flaring tool (if cutting lines)
Vacuum pump with pressure gauge
Bubble level (or a smartphone level app)
Measuring tape & pencil
Screwdriver set
Pliable sealing putty & exterior-grade silicone caulk

Step 1: Choose the Optimal Location

Proper placement is critical for efficiency and comfort.

For the Indoor Unit:
- Mount it 7 to 8 feet high on a strong, load-bearing wall.
- Ensure at least 6 inches of clearance from the ceiling and 3 feet of open space in front for clear airflow.
- Avoid locations with direct sunlight, moisture (like above a sink), or within 10 ft of TVs or radios to prevent interference.
For the Outdoor Unit:
- Place it on a flat, stable surface (like a concrete pad or wall bracket) in a shaded, well-ventilated area.
- Maintain at least 12 inches of clearance on all sides.
- Elevate it 4-6 inches off the ground to prevent water and debris buildup.
- Keep it at least 3 feet away from any heat sources, like a dryer vent.

Step 2: Install the Mounting Brackets

A perfectly level installation is non-negotiable to prevent future problems.

Indoor Bracket: Use a bubble level to ensure the mounting plate is perfectly horizontal. Even a slight tilt—about the thickness of a coin—can cause the unit to drain improperly and leak water. Use toggle bolts for drywall and appropriate anchors for concrete or brick.
Outdoor Bracket/Pad: If using wall brackets, ensure they include rubber anti-vibration pads to reduce operational noise. After installation, gently shake the brackets; they should be completely solid.

Step 3: Drill the Hole for the Line Set

This hole connects the indoor and outdoor units.

Drill a 3-inch diameter hole from the inside to the outside, angling it slightly downward. This slope ensures rainwater cannot flow back into your home.
Pro-Tip: To avoid drilling too deep, wrap a piece of masking tape around your drill bit at the desired depth (e.g., 8 inches) as a visual stop guide.
Insert the included wall sleeve or grommet to protect the lineset from abrasion.

Step 4: Connect the Electrical and Line Sets

Carefully thread the copper pipes, drainage hose, and electrical cables through the wall hole.

Refrigerant Lines: When tightening the flare nuts with a torque wrench, listen for two distinct “clicks”—this is an auditory confirmation of a proper, leak-proof seal.
Electrical Wires: Match the wire colors precisely. Wrap each connection thoroughly with electrical tape. For maximum safety, plug the unit into a dedicated outlet and avoid sharing the circuit with other high-power appliances.

Step 5: Install the Drainage Hose

Proper drainage is crucial to prevent water damage.

Attach the hose firmly to the indoor unit’s drain port.
Route the hose on a continuous downward slope (about 1 inch of slope for every 3 feet of length) to an appropriate drainage location outside. Use a level to verify the angle.
Cold Climate Tip: In regions with freezing winters, wrap the exterior portion of the hose with pipe insulation or install a specialized anti-freeze heating cable to prevent ice blockages.

Step 6: Vacuum the Refrigerant Lines

This critical step, often skipped by amateurs, removes air and moisture that can destroy your system's efficiency and lifespan.

Connect a vacuum pump to the service port on the outdoor unit.
Run the pump until the pressure gauge reads below 500 microns. Close the valve and turn off the pump.
The vacuum should hold steady for at least 15 minutes. If it doesn't, you have a leak.
DIY Leak Test: Apply soapy water to the flare nut connections. If bubbles form, you've found the leak. Retighten the connection and repeat the vacuum test.

Step 7: Test the Unit

Power on the system and allow 15 minutes for it to reach full operation.

Check Performance: Use a thermometer to measure the air coming out of the indoor vent. It should be at least 15°F (8°C) cooler than the room's ambient temperature.
Listen: The noise level should be comparable to a quiet conversation.
Test Functions: Use the remote to test all modes, especially "Dry" and "Turbo," and ensure the louvers are swinging correctly.

Step 8: Seal the Wall Hole

The final step is to create a weatherproof, pest-proof seal.

Pest Prevention: First, stuff stainless steel wool into the gaps around the line set. Rodents and insects hate chewing through it.
Seal Inside: Use pliable sealing putty to fill the interior gap. It’s better than spray foam as it remains flexible and is easier to remove for future maintenance.
Seal Outside: Apply an exterior-grade silicone caulk around the line set on the outside wall. Smooth the bead with a wet finger for a perfect, weatherproof seal.