How to Install an Inverter Split AC
Learn how to mount the indoor and outdoor units, core-drill wall passages, connect insulated copper piping, pull a deep vacuum, and commission an inverter split AC.
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🧰 Required Tools & Equipment
- ✓ Rotary hammer drill with 2.5-3 inch core bit
- ✓ Torpedo level
- ✓ Flaring tool and tube cutter set
- ✓ Open-ended torque wrenches
- ✓ HVAC vacuum pump and manifold gauge set
- ✓ Hex key set (Allen wrenches)
- ✓ Wire strippers and screwdrivers
📦 Materials & Supplies
- ✓ Indoor and outdoor AC units with mounting plate
- ✓ Insulated copper line set (liquid and suction lines)
- ✓ PVC condensate drain hose
- ✓ Outdoor wall bracket or rubber anti-vibration pads
- ✓ 4-core electrical interconnect cable
- ✓ Wall anchor bolts and vinyl wrapping tape
⚠️ Safety Checkpoints & Warnings
- • Switch off the main electrical breaker supplying the AC circuit before handling wiring.
- • Wear safety goggles, ear protection, and a dust mask when drilling the through-wall core hole.
- • Do not open refrigerant service valves until the line set is completely evacuated below 500 microns.
📋 Step-by-Step Guide (7 Steps)
Mount the Indoor Unit Backplate
Position the metal mounting plate against the interior wall, leaving at least 15 cm of clearance from the ceiling. Use a torpedo level to ensure the plate is perfectly horizontal, then mark and drill anchor points into the wall studs or masonry. Secure the plate firmly using the provided screws and heavy-duty wall plugs.
- • Metal bracket firmly affixed flush against the wall
- • Bubble resting dead-center in the torpedo level placed along the bracket's top edge
- • Mounting the bracket tilted away from the drain side, causing water to pool inside the unit
- • Using weak drywall anchors that pull out under the unit's weight
Drill the Piping Hole Through the Wall
Mark the exit hole location on the wall relative to the indoor bracket knockout plate. Drill a 2.5 to 3-inch hole with a rotary core bit, angling the drill downward toward the exterior at roughly a 5-degree slope. Insert a protective PVC wall sleeve into the finished opening to protect the lines.
- • Clean, circular opening passing completely through the exterior wall
- • Downward slope visible from the indoor entry point to the outdoor exit point
- • Drilling horizontally or upward, which causes condensate water to back up and overflow inside the room
- • Shattering exterior brick or stucco by forcing the hammer drill too aggressively at breakthrough
Route and Prepare Indoor Lines
Carefully uncoil and bend the indoor copper tail pipes toward the wall hole without kinking the soft copper. Feed the 4-core communication cable into the indoor terminal block, matching terminals 1, 2, 3, and Ground. Bundle the insulated copper pipes, drain hose, and electrical cable tightly together using non-adhesive vinyl tape, keeping the drain hose at the very bottom of the bundle.
- • Wiring firmly seated in terminal block with labeled colors matched to numbers
- • Tightly wrapped single bundle with the ribbed drain hose positioned strictly underneath the copper lines
- • Placing the drain hose above the copper lines in the bundle, leading to condensation flow restriction
- • Kinking the copper tubes while bending by hand without a pipe bender
Hang Indoor Unit and Mount Outdoor Condenser
Feed the bundled lines through the sleeved wall hole and hook the top of the indoor unit onto the mounting plate, snapping the lower clips into place. Mount the outdoor condenser on heavy-duty wall brackets or a ground pad with vibration-isolating rubber feet. Verify the outdoor unit sits level and maintains at least 30 cm of rear airflow clearance.
- • Indoor unit latched flush against the wall with no gap along the top or bottom seam
- • Outdoor unit resting level on rubber isolator feet with visible clearance from the exterior wall
- • Failing to snap the bottom latching tabs of the indoor unit into the wall plate
- • Placing the outdoor condenser too close to a wall, choking air intake
Connect Flare Fittings and Outdoor Wiring
Cut the copper lines to length at the outdoor unit, deburr the inner edges, and slide the flare nuts on before making clean 45-degree flares. Align the flare cones to the outdoor service valves and tighten the nuts using two wrenches—a backing wrench on the valve body and a torque wrench on the nut. Connect the interconnecting wires to the outdoor terminal block, matching the exact color-to-number mapping used indoors.
- • Smooth, crack-free copper flare seated squarely against the brass valve port
- • Torque wrench clicked at manufacturer specification with a backup wrench holding the valve body steady
- • Terminal block wiring sequence perfectly mirroring the indoor unit (1 to 1, 2 to 2, 3 to 3, G to G)
- • Forgetting to slide the flare nut onto the copper tube before flaring the end
- • Tightening the flare nut with a single wrench, twisting and damaging the thin brass valve body
Evacuate the System with a Vacuum Pump
Attach the manifold blue low-side hose to the outdoor unit service port and the middle yellow hose to the vacuum pump. Turn on the vacuum pump, open the manifold valve, and run the evacuation until the gauge pulls below 500 microns (or deep vacuum on analog dials). Close the manifold valve, turn off the pump, and let the system sit for 15 minutes to verify the gauge needle does not rise.
- • Manifold gauge needle settled at -30 inHg (-1 bar) or digital micron gauge reading below 500 microns
- • Gauge needle remains rock-steady for 15 minutes after shutting the pump off
- • Skipping the vacuum process and simply purging refrigerant through the lines, which introduces moisture and voids warranty
- • Turning off the vacuum pump before closing the manifold valve, pulling pump oil into the AC lines
Release Refrigerant and Commission the Unit
Disconnect the charging hose from the service port. Use an Allen wrench to fully open the high-pressure liquid valve counterclockwise, then open the low-pressure suction valve until both back-seat gently. Replace and hand-tighten all brass service caps securely, restore main power, and run the AC in cooling mode at minimum temperature to confirm cold air output.
- • Hex valve stems fully unscrewed counterclockwise until lightly seated against their stops
- • All brass caps replaced and wrench-snugged
- • Indoor display lit and blower discharging steady cold air
- • Leaving the service valves half-opened, restricting refrigerant flow to the compressor
- • Forgetting to replace the valve brass dust caps, leading to slow micro-leaks through the stem O-rings over time
Credit: inspired by an original tutorial by Bablu — watch the original on YouTube.
Don’t have everything?
- No Torque wrench set? Dual adjustable open-end wrenches (requires careful manual tightening to avoid over-torque)
- No Core drill bit? Standard masonry drill bit with multiple perimeter holes stitched together, then chiseled out