Responded to emergency no-cooling call for elderly resident. Upon arrival, indoor temperature was 88°F. Diagnosed failed compressor in 10-year-old 2.5-ton split system. Compressor windings showed open circuit on ohmmeter test. Discussed replacement options with family member. Installed temporary 1.5-ton portable AC unit to provide immediate relief. Returned next day with new 3-ton 16 SEER system. Replaced both indoor and outdoor units. Upgraded from R-22 to R-410A refrigerant. Installed new line set to prevent contamination. Recharged system to 7.5 lbs per manufacturer specs. Verified proper operation: superheat 12°F, subcooling 11°F. Supply air temperature 53°F with 20°F delta T. Adjusted airflow to 400 CFM per ton. Programmed new Wi-Fi thermostat for optimal comfort and efficiency.