Installation and Commissioning
Core concepts
Installation quality determines lifetime performance. Know pipe sizing and velocity limits, correct line sizing for suction and liquid, oil return and traps, pipe support spacing, isolation and vibration control, and brazing with nitrogen purge to prevent internal oxidation. Understand evacuation and dehydration: triple evacuation or deep vacuum with micron gauge, standing vacuum test, and why a vacuum gauge beats manifold gauges. Know charging methods by weight, by subcooling or superheat, and how to verify against design conditions. Commissioning includes electrical checks, rotation direction, control settings, safety proving, airflow balancing, and recording design versus actual values. Traps include accepting a pressure test as proof of dehydration, using the system compressor to evacuate, ignoring nitrogen purge, and commissioning without stable load conditions.
Traps
Questions often contrast pressure testing with leak testing and evacuation. Nitrogen is for pressure testing and purging, never oxygen. Record everything: a commissioning sheet is evidence.
Worked example
After brazing, pressure test with dry nitrogen to the specified test pressure, hold and check, then evacuate to below 500 microns and isolate the pump. If the micron reading rises and stabilises at a low value, moisture is likely; if it rises continuously, suspect a leak. Re-evacuate with a nitrogen sweep before charging by weight.
Rule of thumb
If it is not measured and written down, it is not commissioned.