Evacuation is often called “vacuum” or “pulling a vacuu […]
Evacuation is often called “vacuum” or “pulling a vacuum,” and it’s one of the most important parts of the HVACR installation and repair process where the refrigerant circuit is involved.
Our goal should be to keep the closed refrigeration circuit clean, dry, and tight — just like I was taught since the very first week of HVAC school.
The only things we want inside the system are the proper refrigerant and the correct oil in the factory-designated quantities. Things like air, moisture, dirt, copper shavings, oxides, or anything else that isn’t refrigerant or oil should be kept out.
This means we use good practices while assembling the field connections and doing repairs by following these important steps.
Keep tubing sealed with original plugs/caps, or tape if needed, prior to assembly.
Confirm fittings and refrigerant circuit components are clean and free of debris.
Eliminate contaminants from the tubing by cleaning before cutting.
Ream in such a way that shavings won’t fall into the lines.
Protect open pipework so that no rainwater or condensation can enter the lines.
Install and/or replace filter/driers as appropriate.
Purge with nitrogen before and after fitting and brazing the tubing.
Flow nitrogen while brazing to prevent a buildup of cupric oxide (nasty black flakes) inside the copper tubing.
Inspect joints all the way around with a mirror.
Perform a standing pressure test with high-pressure nitrogen, according to manufacturer recommendations.