What steps should you take to verify system cleanliness after brazing or major repairs?

• A. Purge with dry nitrogen, evacuate with a deep vacuum (micron-level), perform a leak check, confirm dryness with a micron gauge, and ensure no moisture or particulates remain.
• B. Leave system open to atmosphere to vent moisture.
• C. Attempt to evacuate only to 100 microns and call it done.
• D. Run system for 10 minutes and assume clean.

Answer: (C)

Removing air and moisture and confirming a clean, airtight state before charging is essential after brazing or major repairs. Purging with dry nitrogen pushes out ambient air and any moisture that may have been introduced, reducing the chance of moisture entering the system during subsequent steps. Then evacuating to a deep vacuum using a micron-level gauge pulls out remaining air and outgasses moisture, giving you a truly dry system. Verifying dryness with the micron gauge ensures the system has reached the point where residual moisture won’t cause corrosion, acid formation, or refrigerant degradation. A leak check is crucial to ensure there are no leaks that could reintroduce air or moisture later. Only after these checks should you proceed with charging.

Leaving the system open to atmosphere invites moisture and contaminants back in. Evacuating to a single, modest level such as 100 microns without verifying dryness and leaks isn’t reliable. Simply running the system for a short time doesn’t remove moisture or confirm cleanliness.