Piping, Refrigerant Handling, and Brazing
Clean, dry, and leak-free
Refrigerant lines are sized from manufacturer tables using equivalent length, which includes fittings and vertical risers, so that pressure drop and oil return both stay acceptable. Use ACR copper, cut with a tubing cutter, deburr, and keep dry nitrogen flowing through the line while brazing. Without a purge, the inside of the tube oxidizes and those flakes travel to the drier and compressor.
Filler metal selection matters: copper to copper typically uses 5 to 15 percent silver phos-copper, which is self-fluxing; copper to brass or steel needs higher silver content plus flux. Heat the joint, not the filler, and protect valves, TXV bodies, and nearby surfaces with a heat sink or wet rag. On flares, use the specified torque, avoid overtightening, and lubricate per the manufacturer's instruction.
Refrigerant handling rules: never vent refrigerant to the atmosphere, recover into DOT-approved cylinders filled to 80 percent, label them, and follow EPA Section 608 requirements for certification, leak repair, and evacuation before opening a system.
Traps: brazing without a nitrogen purge; using the wrong silver content on a dissimilar joint; soft-soldering a high-side joint; undersized suction lines that cause high superheat and oil starvation; omitting an oil trap on a long vertical riser.
Worked example: a 2-ton split with a 25 ft line set commonly uses 3/4 in. suction and 3/8 in. liquid, but always confirm against the table for the specific model before ordering line sets.