Type II — High-PressureCâu 155 / 240
A technician is selecting a vacuum pump to properly dehydrate a Type II R-410A system. Why is a dedicated vacuum pump used instead of the recovery machine to pull the final vacuum?
a.Vacuum pumps are only for low-pressure chillers
b.Recovery machines pull a deeper vacuum than any vacuum pump
c.Only a vacuum pump reaches deep micron levels
d.Using a vacuum pump lets the technician vent refrigerant safely
Giải thích
A vacuum pump is designed to reach the deep vacuum, often several hundred microns, required to boil moisture out of the system, while a recovery machine is built to move refrigerant, not to achieve that deep dehydration vacuum. Reaching a low, stable micron level ensures moisture and noncondensables are removed. A vacuum pump is never used to vent refrigerant.
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Câu hỏi liên quan cùng chủ đề
- A technician measures subcooling of 3°F on a TXV-equipped R-410A system when the manufacturer specifies 10°F of subcooling. What does the low subcooling most likely indicate?
- Before opening a Type II system for a compressor change, a technician recovers the refrigerant. Which sequence best protects both the technician and the environment?
- A technician performs a standing pressure (leak) test on a repaired Type II system using dry nitrogen. Over several hours the pressure holds steady with no drop. What does this indicate?
- A technician retrofitting an R-22 system to an HFC replacement changes the oil and refrigerant. Which additional component is most commonly replaced during the retrofit?
- A technician is unsure which required vacuum applies to a high-pressure appliance during recovery. Which two factors determine the required evacuation level?
- A technician recovers refrigerant from a heat pump in heating mode and is unsure which service port to use. On a heat pump, why must the technician understand the reversing valve position when recovering or charging?
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