Installer put a 24,000 BTU mini-split with a 115-foot lineset from the roof down to a first-floor head, ran the lines through a mess of elbows, didn't add any refrigerant beyond the factory charge, and set the outdoor unit on the ground under a deck with about 8 inches of clearance above the fan.

This install violates multiple fundamentals. Here's what was missed:

1. Refrigerant charge for extended lineset Factory charge covers ~15–25 ft. At 115 ft, you need ~1.5–2.5 lbs additional R-410A (check manufacturer’s spec — typically 0.16–0.32 oz/ft per line). Running on factory charge starves the compressor, causes high superheat, overheating, and poor capacity. Add charge by weight only — not by pressure.

2. Excessive equivalent length from elbows Every 90° elbow = 3–5 ft equivalent length. A "mess of elbows" likely pushes equivalent length past 150–180 ft. Most 24k units max out at 100–165 ft equivalent length. If exceeded:

• Pressure drop kills subcooling
• Oil return fails → compressor damage
• Capacity drops 15–30%

Fix: Re-route with minimal bends, use long-radius elbows, or upsize liquid line (if mfr allows).

3. Outdoor unit clearance violation 8" above fan discharge violates every manufacturer’s minimum (typically 24–60" vertical clearance). Recirculation of hot discharge air raises head pressure → overheating on hot days. Unit must be relocated — minimum 24" above fan, 12" sides/back, per install manual and NEC 110.26 / IMC 304.1.

4. Roof-to-first-floor vertical drop 115 ft vertical = ~50 psi static head. Requires:

• Proper oil traps every 15–20 ft vertical rise (per mfr)
• Correct pipe sizing for oil return at low load
• Check valve if specified

Bottom line: This needs a qualified HVAC tech with EPA 608 cert to recover, evacuate, recharge by weight, verify airflow, and relocate the condenser. Not a DIY fix.

The installer missed several critical installation requirements, leading to poor performance and overheating:

1. Excessive Lineset Length: A 115-foot lineset is far beyond the typical maximum for a 24,000 BTU mini-split (usually 50–100 ft, depending on manufacturer). Excessive length increases pressure drop, reduces refrigerant flow, and impairs heat transfer — especially problematic in cooling mode on hot days. → Check manufacturer’s specs (e.g., Mitsubishi, Daikin, Fujitsu): most limit lineset to 66–100 ft for this capacity.

1. No Additional Refrigerant Charge: Factory charge is only for a short lineset (usually 15–25 ft). For every foot beyond that, refrigerant must be added per manufacturer’s guidelines (often 0.2–0.6 oz/ft). → At 115 ft, likely missing 18–54 oz of refrigerant, causing low suction pressure, poor cooling, and compressor overheating.

1. Poor Lineset Routing: Excessive elbows increase equivalent length and pressure drop. Each 90° elbow adds ~5–10 ft of equivalent length. A “mess of elbows” likely made the effective length much worse.

1. Inadequate Outdoor Unit Clearance: Only 8 inches above the fan violates minimum clearance requirements (typically 12–24 inches above and on all sides for proper airflow). → Restricted airflow causes high head pressure, reduced condensing efficiency, and overheating — especially under a deck where hot air recirculates.

What to do:

• Recover refrigerant, evacuate system, and recharge to manufacturer’s spec (including lineset length adjustment).
• Shorten or re-route lineset to minimize elbows and stay within max length.
• Relocate outdoor unit to a shaded, open area with ≥12–24 inch clearance on all sides and above.
• Verify voltage and wiring (undersized wire can also cause issues).

This is not a DIY fix — refrigerant handling requires EPA 608 certification. Call a licensed HVAC tech to correct the charge, lineset, and placement. Operating as-is risks compressor failure.

(Ref: IMC 303.3, manufacturer installation manuals, AHRI standards)