Type II — High-Pressure第 160 / 240 题
After evacuating a Type II R-410A system to a deep vacuum, a technician is ready to charge. Which practice supports an accurate final charge?
a.Weigh in the manufacturer's specified charge, then fine-tune using subcooling (TXV) or superheat (fixed orifice)
b.Charge until the low-side gauge reads any positive pressure
c.Add refrigerant until frost appears on the compressor
d.Charge vapor into the liquid line while off
解析
The most accurate approach is to weigh in the manufacturer's specified charge, then verify and fine-tune using subcooling on a TXV system or superheat on a fixed-orifice system. Judging by gauge pressure alone or by frost is unreliable and can lead to over- or undercharging. Blends like R-410A are charged as liquid, metered to protect the compressor.
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