Install a Ductless Mini-Split

Before you start

•Head and condenser locations chosen: head with clear throw and condensate drainage, condenser with airflow clearance and a path for the line set.
•Line-set length measured and compared to the maker's PRECHARGE limit (most units precharge for ~25 ft / 7.5 m); know the per-foot add and the precharge cap.
•Correct breaker, disconnect, and 14/4 (or sized) connecting cable on hand; flare line set sized to the unit's ports (commonly 1/4 in liquid / 3/8 in or 1/2 in suction).

Tools & materials

Level + tape + stud finder · Core drill (2.5–3.5 in bit) + wall sleeve and sealant · Flaring tool (with ridgid/clutch-type yoke), tube cutter, deburr/reamer tool · Calibrated torque wrench(es) for flare nuts · Nitrogen + regulator, micron gauge, 2-stage vacuum pump, charging scale

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Mount the indoor head

Fasten and level the wall bracket
Anchor the mounting plate to studs or with proper drywall/masonry anchors. Set it dead level — a head tilted the wrong way will overflow the condensate pan instead of draining to the drain side.
Tools: 4-ft level
Target: Bracket level within ~1/8 in across its width; slight pitch toward the drain side is acceptable
Core-drill the wall penetration
Bore the through-wall hole on the drain/line-set side, sloped slightly DOWNWARD to the outside so condensate and water can never run back inside. Insert a wall sleeve and seal the annulus with the supplied putty/sealant after the lines are run.
Target: Hole pitched ~5–10° down to the exterior; sleeve + sealant to keep pests/water out
⚠ Scan for wiring and plumbing before drilling. A core bit through a hidden circuit or pipe is a serious hazard.

Set the outdoor unit

Set the condenser on pads/brackets with clearances
Set the outdoor unit on a composite pad, stand, or wall brackets, level so the base drains and oil returns. Honor the maker's clearances around the coil and discharge so it can breathe.
Target: Level within ~1/4 in; typically ≥ 12 in coil-side, ≥ 24 in service-side, no recirculation of discharge air (verify nameplate)

Make the flare connections

Cut, deburr/ream, and form clean flares
Square-cut the soft copper, deburr/ream so chips don't enter the system, slip the flare nut on FIRST, then form a smooth, even 45° flare with a clutch-type flaring tool. A cracked or off-center flare will leak. A drop of refrigerant oil on the flare face helps it seat.
Target: Flare face smooth, concentric, no cracks/burrs; flare nut on the tube before flaring
Torque the flare nuts to spec
Hand-start the nuts square (no cross-threading), then torque with a calibrated wrench — back the body with a second wrench. Under-torque leaks; over-torque splits the flare. Use the line-size ranges as a guide and confirm against the maker's table.
Tools: Torque wrench, Backing wrench
Target: 1/4 in ~10–13 ft·lb, 3/8 in ~24–30 ft·lb, 1/2 in ~36–43 ft·lb, 5/8 in ~45–55 ft·lb (verify per maker)
⚠ Never use the flare nut to 'snug up' a poorly formed flare — re-flare it.

Pressure-test & evacuate

Pressure-test with dry nitrogen
Pressurize the line set + indoor coil with dry nitrogen and leak-check every flare with bubbles or an electronic detector. Find leaks now — never use the vacuum to hunt leaks.
Tools: Nitrogen + regulator
Target: Hold maker's test pressure (commonly ~150–550 psig for the line set) and confirm no decay over the hold period
⚠ Use a regulator and never exceed the low-side test rating. Do not pressure-test with oxygen or acetylene — explosion hazard.
Pull a deep vacuum
Connect large-bore hoses, run the 2-stage pump down, then valve off and run a decay test. Moisture left in a mini-split's tiny passages and the compressor oil will cause acid and capillary/EEV trouble.
Tools: Micron gauge, 2-stage vacuum pump
Target: Pull ≤ 500 microns and hold with minimal rise on the decay test
⚠ Never start the compressor under vacuum — it can arc the windings.

Release charge & finish

Release the factory charge (and add only if needed)
With a good vacuum, back out the service-port stems to release the precharged refrigerant into the system. Only WEIGH IN additional refrigerant if the line set exceeds the precharge limit — add the maker's per-foot amount for the overage, not a guess.
Tools: Allen/hex keys, Charging scale
Target: Add charge only for line length over the precharge limit, at the maker's grams/ft (or oz/ft); fully back-seat both service valves
⚠ Open the valves fully and cap the service ports — a partially open stem starves the system and ices the coil.
Insulate the line set and route condensate
Insulate BOTH lines (or at minimum the suction line per spec) continuously, including at the flares, to stop sweating and capacity loss. Run the condensate drain with continuous downhill slope to a legal termination — no traps or low spots that airlock.
Target: Continuous closed-cell insulation, no gaps; condensate sloped ≥ 1/8 in per ft with no rises
Energize and commission
Land the connecting cable per the wiring diagram, energize, run in cooling and heating, and confirm the head ramps, the condenser fan/compressor run quietly, and the delta-T and amps are sane.
Tools: Clamp meter
Target: Compressor amps ≤ nameplate; reasonable supply/return ΔT; no error codes on the head