Safety, Tools, and Shop Practices
This domain tests the physical work habits the exam expects on every job: personal protection, energy control, refrigerant and torch handling, recovery, evacuation, and correct use of instruments.
Energy and personal protection
- Safety glasses with side shields, cut-resistant gloves, and arc-rated clothing when working in energized panels (NFPA 70E).
- Lockout/tagout per OSHA 1910.147: open the disconnect, lock it, tag it, then verify dead with a meter before touching conductors.
- Never pressurize piping with oxygen. Use dry nitrogen through a regulator.
Cylinders and refrigerant
- Recovery cylinders are DOT-rated, filled to no more than 80 percent of water capacity, and used only for the refrigerant printed on the label.
- Store upright and capped, out of direct sun, secured in the truck.
- EPA Section 608 prohibits venting. Recover before opening any circuit, and keep a recovery machine and scale on the truck.
Torch, vacuum, and instruments
- Acetylene regulator setting is capped at 15 psig; flashback arrestors go on both hoses; maintain a fire watch after brazing near combustibles.
- Flow nitrogen at roughly 1 to 2 SCFH while brazing to prevent internal oxidation.
- Evacuate to 500 microns and pass a decay test. A manifold gauge cannot prove a vacuum.
Worked example
A recovery cylinder stamped 47.6 lb water capacity has a tare of 24 lb and a filling density of 0.79 for R-410A. Maximum gross weight is 47.6 x 0.79 = 37.6 lb, so the net charge allowed is 37.6 - 24 = 13.6 lb. Stop filling there, not when the cylinder feels heavy.
Traps that cost marks
- Using R-22 gauge sets on R-410A, whose pressures run roughly 60 percent higher.
- Brazing without a nitrogen purge, leaving scale that plugs driers and TXV screens.
- Judging evacuation by gauge needles instead of a micron gauge.
- Treating a full recovery cylinder as safe because it is still below ambient temperature.