Low-pressure appliances — centrifugal chillers running refrigerants like R-123: 25 mm Hg absolute, when you pressurize instead of evacuate, the 0-psig and 5-psig opening rules, and why heat comes before nitrogen. Every answer shows the rule and its citation.
Rules current as of October 21, 2026.
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Studying for the real exam, or a certified tech checking the new rules? Either way, if an old study guide disagrees with an answer here, the citation under the answer is the one to trust.
