Installation and Commissioning
Core concepts
Candidates must know proper installation practices: equipment placement, clearances, line sets, brazing with nitrogen purge, evacuation, leak testing, and charging. Understand evacuation to 500 microns, holding a vacuum, and triple evacuation. Know charging methods-weigh-in, superheat, and subcooling-and when each applies. Familiarize yourself with electrical connections, disconnect sizing, condensate drainage, and thermostat wiring. Commissioning includes verifying airflow, refrigerant charge, and temperature split.
Traps in questions
A common trap is charging by pressure alone without considering ambient and indoor conditions. Another is skipping nitrogen purge during brazing, which creates oxidation inside lines. Questions may confuse evacuation levels-500 microns is a target, not a guarantee; a rising vacuum indicates moisture or leaks. Do not assume factory charge is correct for long line sets. Ensure condensate traps and secondary drain pans are installed.
Worked example
After evacuation to 500 microns and a 10-minute hold with no rise above 1,000 microns, proceed to charge. For a TXV system, set subcooling per manufacturer (often 10–12°F). Rule of thumb: always verify airflow before adjusting charge, since low airflow skews readings.
Study tip
Create a commissioning checklist covering vacuum, charge, airflow, and electrical verification.