Field Purge Procedure — Tech Practice (Shortcut vs Vacuum Standard)

Purge vs Vacuum — when to use which

Check: **Purge definition**: forcing refrigerant into the system to push out about 70% of the air — a fixed shortcut to vacuum work. About 30% of air remains in the system, slightly lowering efficiency vs. precise vacuum. **Vacuum required** (techs must use): new install / compressor replacement / coil replacement / post-leak repair full system / system idle >1 year. **Purge acceptable** (field practice): gas top-up only (small add) / service-port hose change / brief partial service. Manual = always specifies vacuum. Field = use purge due to time/cost pressure. **A2L refrigerants (R-32, R-454B) = NEVER purge** (air mixing causes flammability risk).

What to do: **Field purge procedure** (R-22/R-410A systems only): 1) Connect cylinder to manifold low side. 2) Crack open manifold low-side valve slightly → gas flows from cylinder into system (1–2 sec). 3) Briefly loosen the hose end at manifold high side (open hex slightly) → air+gas mixture vents (3–5 sec). 4) Re-tighten hose end. 5) Proceed with charging. **Drawbacks**: not precise, doesn't remove moisture. **Recommendation**: only when time-pressed; vacuum is always the correct answer when possible.