Installation, Commissioning and Testing
Before the pipe is cut
Site survey decides everything: indoor unit clearances, outdoor airflow, wall strength, drain fall and the electrical point. Follow the manual for minimum and maximum pipe length, maximum elevation and additional charge per metre; typical domestic splits allow 3–15 m of run and 5–10 m of level difference. Fit an oil trap where the outdoor unit sits above the indoor coil.
The sequence that earns marks
- Mount brackets and hang units level.
- Flare and torque connections to the specified value - do not over-torque.
- Braze with dry nitrogen flowing through the pipe to prevent internal oxidation.
- Pressure test with dry nitrogen at the specified test pressure (often 1.5× working pressure) and hold it.
- Evacuate to 500 microns (about 66 Pa) and hold for at least 30 minutes; a rise means moisture or a leak.
- Release or charge refrigerant by weight, then record it.
- Check drain slope, insulation, earthing and insulation resistance.
Worked example
A free pipe limit of 5 m, but the site needs 12 m, and the manual says add 20 g/m beyond 5 m. Additional charge = (12 − 5) × 20 = 140 g, added as liquid, then verified by subcooling of 5–8 K at the condenser outlet.
Traps
Brazing without nitrogen, so scale ends up in the TXV; using the compressor as a vacuum pump; skipping the standing vacuum test; and commissioning without recording ambient temperature, pressures and superheat.