I'm pulling the compressor on a 4-ton R-410A split.

Federal EPA Section 609 & 608 Requirements:

For a 4-ton R-410A system, you must recover refrigerant to at least 90% of the nameplate charge before opening the system. However, the EPA 608 Standard (40 CFR Part 82, Subpart F) requires recovery to no more than 0% of the system charge if the compressor is being replaced — meaning complete recovery is required.

Practical Steps:

1. Check the nameplate for total refrigerant charge (typically 4–6 lbs for a 4-ton system).
2. Use a recovery machine rated for R-410A (must handle high pressures).
3. Recover until the system reaches 0 psig (or as close as possible).
4. Verify with a scale — recovered refrigerant should match or exceed the nameplate value.

Legal Note: Under 40 CFR 82.117, it is illegal to vent R-410A to the atmosphere. You must recover all refrigerant before opening the system.

Safety: R-410A operates at much higher pressures than R-22. Use proper PPE and equipment rated for 410A.

Bottom Line: Recover 100% of the refrigerant before opening the system. This is both legally required and best practice.

Legally: 0 psig (atmospheric pressure).

Under EPA Section 608 (40 CFR §82.156), you must evacuate the appliance to atmospheric pressure (0 psig) before opening it for major repairs (like compressor replacement) if you are not recovering the refrigerant into a certified recovery machine.

However, the practical/legal standard is recovery, not venting.

1. You must recover the charge into a certified recovery cylinder using certified equipment (§82.156(b)).
2. Required vacuum levels for recovery equipment (manufactured after Nov 15, 1993): High-pressure appliances (R-410A): 0 psig (if recovery machine recovers < 200 lbs/min) or -10.2 psig (25" Hg vac) (if ≥ 200 lbs/min). Most field techs use machines requiring 0 psig.
3. After recovery, you may open the system.

Do not vent. Venting R-410A is a federal violation (Clean Air Act). Fines up to $44,539/day (2024 adjustment).

Best Practice: Pull a deep vacuum (≤ 500 microns / 29.9" Hg) after the repair and before recharging to ensure non-condensables/moisture are removed. Use a micron gauge, not manifold gauges.

Citation: 40 CFR §82.156(b)(1), (b)(2), (i).