How to Install a Split AC
Mount and connect a split-system air conditioner, including indoor backplate leveling, wall penetration drilling, line flare coupling, vacuuming, and wiring.
- Read the tools, materials, safety notes, and steps below for free.
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🧰 Required Tools & Equipment
- ✓ Hammer drill with 65mm core bit
- ✓ Torpedo level
- ✓ Adjustable open-end wrenches (pair)
- ✓ HVAC manifold gauge set
- ✓ Rotary vane vacuum pump
- ✓ Hex/Allen key set
- ✓ Wire strippers and screwdrivers
- ✓ Torque wrench with flare adapters
📦 Materials & Supplies
- ✓ Indoor mounting backplate and anchors
- ✓ Insulated copper suction and liquid lines
- ✓ Condensate drain hose
- ✓ 4-core electrical interconnect cable
- ✓ PVC pipe wrap tape
- ✓ Wall penetration sleeve and sealing putty
⚠️ Safety Checkpoints & Warnings
- • Turn off the dedicated AC circuit breaker at the main distribution board before touching any wiring.
- • Wear eye protection and a dust mask when operating the core drill through masonry.
- • Ensure the outdoor bracket is anchored into solid structural masonry, not superficial plaster or cladding.
📋 Step-by-Step Guide (7 Steps)
Mount the Indoor Backplate
Hold the metal mounting plate against the interior wall at least 15 cm below the ceiling. Use a torpedo level across the top edge to ensure horizontal alignment, mark anchor holes, drill into masonry, insert wall plugs, and drive screws firmly.
- • Backplate sits dead flat against the wall with no wobble when pulled.
- • Torpedo level bubble is centered between guidelines atop the plate.
- • Mounting the plate tilted, causing condensate overflow inside the room.
- • Failing to leave sufficient clearance from the ceiling for return airflow.
Drill the Wall Penetration Hole
Mark a 65mm to 75mm hole location positioned slightly lower than the indoor unit's pipe knockout. Drill through the wall angling the core bit downwards toward the exterior at roughly a 5-degree slope. Insert a protective PVC wall sleeve into the finished hole.
- • Clean circular opening with a visible downward exterior slope.
- • Plastic wall sleeve fully lines the penetration.
- • Drilling straight or angling upwards, preventing gravity water drainage and causing leaks.
- • Drilling directly into structural rebar or electrical conduit.
Bundle and Route Indoor Unit Lines
Straighten the copper tail pipes on the indoor unit carefully without kinking. Align the copper lines, drain hose (placed at the very bottom), and 4-core electrical cable together. Wrap tightly with PVC finishing tape starting from the unit body outward.
- • Neat, cylindrical wrapped bundle with the drain hose resting at the lowest point.
- • Refrigerant line ends remain tightly capped with plastic plugs.
- • Placing the drain hose on top of copper pipes inside the bundle, causing trapped airlocks.
- • Bending copper lines too sharply by hand, crushing the inner diameter.
Mount the Indoor Unit and Hang Outdoor Condenser
Feed the bundled lines through the wall sleeve while lifting the indoor unit onto the top hooks of the backplate, then press firmly until the bottom clips snap shut. Fasten the outdoor L-brackets onto the exterior wall using heavy-duty expansion bolts and set the condenser unit onto rubber anti-vibration pads.
- • Indoor unit is locked flush to the wall with zero gap at bottom latches.
- • Outdoor unit sits level on vibration isolation dampers with all four foot-bolts tight.
- • Failing to engage the bottom retention clips of the indoor unit.
- • Omitting rubber vibration pads under outdoor unit feet, causing loud wall resonance.
Connect Flare Fittings at Both Units
Align the flared copper pipe ends squarely with the male threaded brass fittings on both units. Thread flare nuts on by hand for at least 3-4 full turns to prevent cross-threading, then tighten using two wrenches—one holding the base fitting and one driving the flare nut to specified torque.
- • Flare nuts seated completely against fitting shoulders without exposed threads.
- • Opposing wrench marks visible where counter-torque was applied to protect internal valves.
- • Using a single wrench without backing up the service valve, twisting and snapping the pipe.
- • Overtightening flare nuts, cracking the copper flare lip.
Evacuate the System with Vacuum Pump
Connect the blue low-pressure gauge hose to the outdoor unit service port and the yellow center hose to the vacuum pump. Turn on the vacuum pump, open the manifold valve, and pull the system down below 500 microns (or maximum pump vacuum, at least -30 inHg) for 20 minutes. Close the manifold valve and monitor for 10 minutes to verify the needle holds steady.
- • Low-pressure gauge needle pinned firmly below zero into deep vacuum (-30 inHg / <500 microns).
- • Manifold valve closed with pump off, and needle does not drift upward toward zero over 10 minutes.
- • Opening service valves before pulling a full vacuum, trapping air and moisture in the compressor.
- • Stopping the vacuum process after only 2 minutes without a decay test.
Release Refrigerant and Wire Terminals
Remove valve stem caps on the outdoor unit. Use an Allen key to open the liquid (narrow) valve 90 degrees for 5 seconds to pressurize, close it, check joints with soapy water, then fully back-seat both liquid and suction valves. Wire the 4-core cable to matching numbered terminals (1, 2, 3, Earth) on both units and replace all service covers.
- • Both Allen valve stems wound fully counter-clockwise against their stops with brass caps tightened.
- • Terminal wiring color sequences match identically between indoor and outdoor terminal blocks (e.g., 1=Brown, 2=Blue, 3=Black, Earth=Yellow/Green).
- • Mismatched terminal wiring numbers between indoor and outdoor boards, frying the inverter PCB.
- • Leaving the Allen service valves half-opened, causing severe refrigerant throttling.
Credit: inspired by an original tutorial by Lucky Ac Technician — watch the original on YouTube.
Don’t have everything?
- No Core drill bit? Standard masonry drill bit to drill a perimeter of small holes, then knock out the center with a cold chisel
- No Torque wrench with flare adapters? Two standard open-end wrenches, tightening hand-tight plus an exact 1/4 to 1/2 turn