Core: Installation and Commissioning of Domestic Refrigeration and Air Conditioning Units
Scope
This is the highest-value core domain: site survey, mounting, piping, evacuation, charging and performance verification of split-type air conditioners and domestic refrigerators/chests.
Before installation
Estimate load from room volume, occupancy and glazing or use the manufacturer's sizing table; undersized and oversized units both fail. Check wall strength for the bracket (solid anchor into concrete, not hollow block), service clearances on the manual's diagram, a drain route falling about 1:100, and a dedicated circuit with breaker and grounding sized from the nameplate, not the wire.
Piping and evacuation
Keep ends capped. Purge with dry nitrogen at a slow flow while brazing, otherwise oxidation flakes travel to the capillary or expansion valve. Pressure-test with dry nitrogen at the manual's figure (around 350–400 psig for R-22 systems, 550 psig for R-410A), hold with temperature compensation, then triple-evacuate below 500 microns and perform a standing vacuum test with the pump isolated.
Charging and commissioning
Weigh in the nameplate charge when the line length is standard; if longer, add per metre from the manual. Otherwise charge by superheat (fixed orifice) or subcooling (TXV). Commission with readings: ambient, suction and liquid pressures, superheat, subcooling, air-on/air-off temperature difference, amp draw against nameplate, voltage, insulation resistance, drain test, and every remote-control function.
Worked example
Vacuum reaches 480 microns; isolated for 10 minutes it rises to 1,600 microns. The nitrogen pressure test held with no drop, so a leak is unlikely - the rise indicates moisture boiling off. Do not simply add refrigerant. Repeat the nitrogen sweep and triple evacuation, then re-test. If it still fails, isolate sections to find the leak.
Traps
Charging "by feel"; skipping the nitrogen purge and later blaming a blocked capillary; using the system's own refrigerant to pressure-test; ignoring maximum pipe length and elevation difference; failing to record commissioning readings.