To install a split AC system, mount the indoor unit, set the outdoor unit, run lines, evacuate to 500 microns, and commission safely.
Installing a split system calls for careful layout, clean workmanship, and a clear sequence. If you’re learning how to install a split ac system, start with planning. This guide shows the full process from site check to first cool air, including planning notes, mounting details, line routing, evacuation, wiring, and start-up checks.
Quick Planning Checklist
Before the first screw goes in, confirm the room load, line-set path, wall type, electrical path, and drainage route. Pick spots that allow clear airflow indoors and easy service outdoors. Keep the line length and lift within the model limits, and look at noise and snow risk outside.
| Item | Why You Need It | Notes |
|---|---|---|
| Stud finder & level | Hit framing and keep the back plate true | Mark centerline and anchor points |
| Hammer drill & hole saw (65–80mm) | Make the wall sleeve opening | Angle slightly down toward outside |
| Flaring tool & torque wrench | Make precise flares and tighten to spec | Use a flare gauge; follow torque chart |
| Brazing kit or flare nuts | Connect copper lines per model | Most ductless units use flares |
| Nitrogen with regulator | Pressure test and purge during brazing | Target 200–300 psi test range |
| Vacuum pump & micron gauge | Dehydrate and verify deep vacuum | Pull to 500 microns and hold |
| Manifold set & hoses | Connect to service ports | Keep hoses short and clean |
| 12/2 or 14/2 cable, outdoor disconnect | Provide power and shutoff near the unit | Follow breaker and wire size on nameplate |
| Condensate tubing & pump (if needed) | Carry drain water outside or to a safe point | Maintain slope; trap per manual |
| Line-set insulation & UV wrap | Prevent heat gain and sun damage | Seal seams and edges well |
How To Install A Split AC System: Full Workflow
1) Site Survey And Layout
Pick an indoor wall that is straight, free of plumbing, and away from heat sources. Leave service space to swing the front panel and remove filters. Typical clearances: 6–12 inches above the top, 2–4 inches on sides, and clear air path across the room. Outdoors, use a pad or wall brackets on solid masonry or framing. Keep clearance behind and above the condenser per the model sheet, avoid roof drip lines, and leave room for coil cleaning.
2) Mount The Indoor Back Plate
Hold the template or metal plate level on the wall, mark holes, and anchor into studs or rated anchors. Drill the sleeve hole with a slight outward pitch. Insert the sleeve; seal around the sleeve to block insects and water.
3) Hang The Indoor Unit And Prep Lines
Form gentle bends in the copper tubes with a spring bender. Keep radius smooth to avoid kinks. Slide the unit onto the plate. Route the drain hose on the low side with continuous slope. Wrap tubes, drain, and control cable as one bundle for a clean pass through the hole.
4) Set The Outdoor Unit
Place the condenser on a level pad or brackets. Shim if needed to shed rainwater away from feet. Bolt down to reduce vibration. Plan the service loop and protection from pets, lawn tools, and snow. Many models allow line runs up to about 50 feet and long lifts; check the data sheet for your exact limits.
5) Run The Line Set
Keep copper clean and capped until flare time. If the run is exposed, add line-hide channels. Avoid oil traps unless the manual shows one. Keep total length within spec; longer runs may need added charge per ounce-per-foot rules in the manual.
6) Make Flares And Tighten To Spec
Cut square, ream carefully, and make a smooth flare. A drop of POE oil on the flare face can help finish. Align by hand, start threads by hand, then pull with a torque wrench to the chart value. This step stops leaks more than any sealant ever could.
7) Pressure Test With Nitrogen
Attach the manifold, bring pressure up slowly, and stop in the 200–300 psi range unless your manual lists a different value. Soap test each joint and watch the gauges. Hold for the time your brand recommends; a stable needle confirms tight work.
8) Evacuate To A Deep Vacuum
Hook the pump with short hoses and a core-removal tool. Pull down to 500 microns on the gauge. Close valves and observe the rise. A slow rise that stays low shows a dry, tight system. If it climbs fast, hunt for leaks and try again.
9) Open Valves And Commission
Crack the liquid valve first, then the gas valve. Power up, set cooling, and let the unit run. Check airflow, condensate, line frost, and amp draw. Walk through the wireless or wired controller setup and record model, serial, and readings for your records.
Installing A Split AC System Step By Step: Room-Ready Plan
Clearances, Holes, And Line Limits
Most installs pass a 2.5–3.5 inch hole for the bundle. Many brands list outdoor siting rules like minimum back and side clearance and a max line length near 50 feet. These points matter for airflow and service access.
Drainage That Never Backs Up
Run the drain with pitch and no sags. Keep the outlet clear of soil and leaves. In long runs or up-hill paths, a mini pump solves the lift. Add a clean trap only if the manual shows it. Test with a pitcher of water before you close the line-hide.
Electrical: Breaker, Cable, And Disconnect
Follow the nameplate for breaker size and wire gauge. Use the outdoor disconnect within sight of the condenser and keep clear working space. Tighten lugs to their torque spec, route cables cleanly, and strain-relieve at knockouts. Bond grounds at both ends.
Refrigerant Rules You Must Follow
Any task that opens the sealed circuit calls for a certified tech. Venting refrigerant is illegal. A licensed pro can recover, weigh, and recharge per the label. If your model uses pre-charged lines, follow the maker’s method to avoid releasing gas.
Pro Tips That Prevent Callbacks
Measure Twice, Drill Once
Locate studs and pipes, mark centerlines, and dry-fit the cover kit. A small layout check saves patching later.
Handle Copper With Care
Do not crush the tube oval when bending. Keep the flare face spotless. Cap every end between steps.
Shield The Bundle
UV wrap over insulation, seal every termination, and use drip loops on cables. A tidy run lasts longer and looks better.
Verify With Instruments
Micron gauge, clamp meter, and thermometer give a real picture. Trust the numbers during vacuum and start-up.
Links To Authoritative Guidance
To check legal and technical points while you work, read the Section 608 certification overview and the Energy Saver minisplit guide. These pages explain who can open a sealed circuit, typical wall-penetration sizes, and common run lengths.
Quality Control Checklist Before First Run
- Back plate level, anchors tight, and sleeve pitched outward
- Drain pitched, no kinks, outlet clear
- Line set insulated end-to-end, UV wrap intact
- Flares torqued to chart, no oil weeping
- Nitrogen test passed and held steady
- Vacuum reached 500 microns and held on rise test
- Disconnect within sight, lugs tight, breaker sized per label
- Controller paired, modes checked, and room reaches setpoint
Common Mistakes And Fast Fixes
| Symptom | Likely Cause | Fix |
|---|---|---|
| Water drip indoors | Drain pitched up or clogged | Clear line, add slope or pump |
| Poor cooling | Blocked airflow or low fan speed | Open vents, set fan higher, clean filters |
| Short cycling | Oversized unit or sensor placement | Relocate sensor, adjust settings, right-size next time |
| Hiss at flare joint | Under-torque or damaged flare | Remake flare and torque to spec |
| Frost on liquid line | Low charge or severe airflow loss | Clean coil, check charge by a licensed tech |
| Breaker trips | Incorrect wire size or loose lug | Correct gauge, re-land and torque |
| Buzzing condenser | Loose feet or line-set contact | Shim feet, add isolators, space the lines |
When To Call A Licensed Pro
Bring in a pro when you need refrigerant recovery or charging, when a leak shows up after a test, when wiring requires a new circuit, or when the outdoor siting needs cranes or roof work. A pro can weigh in added refrigerant for long runs, set dip switches for line length or low-ambient kits, and verify superheat or subcool targets where the manual calls for them.
Care And Maintenance After Install
Keep filters clean each month in peak season. Wash the outdoor coil with low-pressure water at the start of summer. Inspect insulation and UV wrap each spring. Check the slab or brackets after storms and tighten hardware if the base shifts. Run a heating and a cooling cycle in shoulder seasons to keep the system limber.
FAQ-Free Final Notes
You saw the end-to-end path for how to install a split ac system, from layout to start-up. Use the workflow above as your field card, and lean on brand manuals for exact torque, clearances, and charge rules. With steady pace and clean habits, the room cools on the first try.