How to Install a Mr Cool Mini-Split AC
Mount the indoor handler, drill the wall penetration, position the condenser pad, connect pre-charged lines, and wire the electrical disconnect safely.
- Read the tools, materials, safety notes, and steps below for free.
- Tap Start Camera Coach when you want hands-free voice help.
- Allow camera and microphone. Point your phone at the work; the coach watches your progress and tells you the next step.
🧰 Required Tools & Equipment
- ✓ Cordless drill and driver
- ✓ 3.5-inch hole saw bit
- ✓ Torpedo level
- ✓ Two adjustable crescent wrenches
- ✓ Stud finder
- ✓ Wire strippers
- ✓ Hex key set
📦 Materials & Supplies
- ✓ Mr Cool DIY 18k BTU mini-split kit
- ✓ Composite equipment ground pad
- ✓ Exterior silicone sealant
- ✓ 60A non-fused outdoor electrical disconnect box
- ✓ 1/2-inch liquid-tight flexible conduit whip
- ✓ Decorative line set wall cover kit
⚠️ Safety Checkpoints & Warnings
- • Shut off the dedicated 240V breaker at the main electrical panel and verify zero voltage with a multimeter before touching wires.
- • Inspect the wall cavity with a stud finder and inspection scope to guarantee no electrical cables or plumbing pipes sit in the hole saw path.
- • Do not open sealed pre-charged line set caps until the exact moment of connection to prevent moisture and debris contamination.
📋 Step-by-Step Guide (6 Steps)
Mount the Indoor Unit Wall Bracket
Locate the wall studs using a stud finder and mark the center points on the wall. Hold the metal mounting plate against the wall at least 6 inches below the ceiling, align it with the studs, and set a torpedo level on the top lip. Drive structural screws through the bracket into the studs, adding heavy-duty drywall anchors into auxiliary holes for extra stability.
- • Metal bracket is screwed flush against drywall with no gaps.
- • Level bubble is centered across the top flange of the bracket.
- • Mounting only into drywall without catching at least one structural wall stud.
- • Placing the bracket tilted toward the refrigerant side instead of level or slightly tilted toward the drain side.
Bore the Wall Sleeve Penetration
Mark the 3.5-inch exit hole location using the bracket template knockout on the designated line-exit side. Chuck the hole saw bit into your drill and begin drilling through the interior drywall at a 5-degree downward angle toward the outside. Continue drilling through the exterior sheathing and siding, then push the plastic wall sleeve through from the interior and trim it flush outside.
- • A clean 3.5-inch round hole angling visibly downward through the exterior wall.
- • Plastic sleeve seated flush on the interior wall opening.
- • Drilling horizontally or upward, which causes condensate to drain backward into the interior wall cavity.
- • Blowing through exterior vinyl or fiber-cement siding without slowing drill speed, causing siding blowouts.
Hang the Indoor Air Handler
Straighten the copper piping, drain line, and communication cable straight out behind the indoor air handler chassis. Carefully feed the bundle through the wall sleeve while lifting the air handler up to the mounting plate. Hook the top clips of the unit onto the upper bracket ridge, then press firmly on the lower corners until the bottom clips snap locked.
- • Indoor unit sits perfectly flat against the wall with no gap at the top.
- • Pipes, drain hose, and wire bundle extend cleanly out of the exterior wall sleeve.
- • Kinking the copper stub pipes while bending them to pass through the wall hole.
- • Failing to snap the lower locking clips, leaving the bottom of the unit hanging off the wall.
Set the Condenser Pad and Position Outdoor Unit
Clear and level a 2x3 foot section of ground next to the exterior wall sleeve, keeping at least 12 inches of wall clearance for airflow. Place the composite equipment pad onto the leveled soil or gravel base and place rubber vibration isolation pads over the mounting slots. Lift the outdoor condenser onto the pad and secure the foot brackets into the pad slots.
- • Condenser sits level and steady on the composite pad with 12+ inches of rear clearance to the siding.
- • Rubber isolation pads are sandwiched under all four metal mounting feet.
- • Placing the pad on loose, un-compacted soil, causing the unit to tilt after the first rain.
- • Mounting the unit too close to the exterior wall, restricting air intake across the condenser coil.
Connect the Quick-Connect Pre-Charged Line Sets
Unroll the pre-charged line set along the exterior wall, routing it cleanly from the wall hole to the condenser service valves. Remove the protective dust caps and hand-thread the line set nuts onto the condenser valve male fittings until they bottom out. Place one adjustable wrench on the base valve body to hold it stationary, and use the second wrench to fully tighten the nut until thread resistance completely stops.
- • Hex nuts are bottomed out metal-to-metal with zero visible brass threads showing.
- • Line set curves gently along the wall without sharp 90-degree kinks.
- • Turning the nut without a backup wrench on the valve, which twists and ruptures internal factory copper joints.
- • Cross-threading the brass fittings by using a wrench before hand-tightening.
Wire the Electrical Whip and Communication Cable
Feed the indoor communication cable through the condenser wire conduit knockout and secure wires into terminals 1, 2, 3, and Ground matching the indoor color code. Run the 240V liquid-tight whip from the outdoor disconnect box into the condenser power block terminals L1, L2, and Ground. Replace all weather covers, apply silicone caulk around the wall penetration sleeve, insert the disconnect pullout handle, and energize the breaker.
- • Wire terminals clamped tightly over bare copper with no exposed stray wire strands.
- • Outdoor electrical access panel and disconnect handle securely closed and caulked around wall sleeve.
- • Mismatched communication wiring order between indoor and outdoor terminal blocks (e.g., swapping 1 and 2).
- • Forgetting to seal the exterior wall sleeve with silicone, allowing water and insect intrusion.
Credit: inspired by an original tutorial by Silver Cymbal — watch the original on YouTube.
Don’t have everything?
- No 3.5-inch hole saw bit? Keyhole saw or multi-tool after drilling a circle of closely spaced 1/4-inch pilot holes
- No Composite equipment ground pad? Four 16x16-inch solid concrete patio pavers leveled on crushed gravel