I've got a condenser that has to sit 110 feet of line from the air handler, with the air handler 30 feet above the condenser.

Key considerations for your 110 ft, 30 ft lift installation:

Refrigerant Velocity & Oil Return

• At 30 ft lift, ensure adequate refrigerant velocity to carry oil back to the compressor. Larger lines reduce velocity—balance with manufacturer's recommended velocities (typically 1,000-2,000 fpm for suction line).
• Install oil traps at the evaporator and intermediate points if using a tandem compressor setup.

Pressure Drop & Efficiency

• 110 ft of line creates significant pressure drop. Oversize liquid line to minimize this (typically 3/8" to 1/2" depending on tonnage).
• Insulate all lines, especially the suction line, to prevent heat gain and maintain efficiency.

Code & Safety

• Electrical: Per NEC Article 440, ensure proper wire sizing for voltage drop over 110 ft. Use larger gauge wire if needed.
• Support: Secure copper every 4-6 ft per IPC and manufacturer specs. Use proper hangers to handle thermal expansion.
• Vibration: Install vibration isolators at both ends to prevent noise transmission.

Manufacturer Requirements

• Check installation manual for maximum line length and height restrictions—some units have limits.
• Verify refrigerant charge calculation includes the extended line set.

Professional Note: This installation requires EPA certification for refrigerant handling and should be performed by a licensed HVAC technician. Improper charging or line sizing can cause compressor failure.

Critical factors beyond line sizing:

1. Oil Return & Velocity (Most Critical)

• Suction line sizing: Must maintain 1,500–2,500 fpm velocity for oil return at minimum load. Oversizing kills velocity → compressor failure. Use manufacturer's long-line tables, not generic charts.
• Double suction risers required on 30-ft vertical rise (per most OEMs >25 ft). Size lower riser for minimum capacity, upper for maximum. Install trap at bottom of each riser.

2. Refrigerant Charge & Subcooling

• Liquid line: 110 ft × 0.5 oz/ft (3/8") = ~55 oz extra charge. Verify subcooling at both units.
• Liquid line solenoid valve (LLSV) at condenser + pump-down cycle prevents migration during off-cycle. Required by most OEMs >50 ft.

3. Pressure Drop & Capacity Loss

• Suction drop: Target <2°F saturation loss (≈3-5 psi R-410A). Each 1 psi ≈ 0.5°F capacity loss.
• Liquid drop: Must maintain ≥5°F subcooling at AHU TXV inlet after 30-ft lift (≈13 psi static head) + friction loss.

4. Compressor Protection

• Crankcase heater mandatory (migration risk).
• Hard start kit if single-phase (long-line start torque).
• Low-pressure switch set for long-line pressure drop.

5. Piping Details

• Invert traps at condenser suction outlet (prevents oil logging).
• Support every 4 ft (suction) / 6 ft (liquid) — vibration kills joints.
• Nitrogen purge while brazing — 110 ft = massive oxidation risk.

Code/Std: IMC 1107.2 (piping support), manufacturer's long-line guidelines (Carrier 32-8000, Lennox LLSG, etc.), ASHRAE 15.9 (refrigerant charge limits).

Verify: Actual OEM long-line guide for your model. Generic rules fail at 110 ft/30 ft lift.