When charging refrigerant into an evacuated low-pressure centrifugal chiller, what should go in first?
Recharging techniques · EPA 608 Type III. The correct answer, and the reasoning behind it.
Charging vapor before liquid, and charging centrifugals through the evaporator valve.
The question
When charging refrigerant into an evacuated low-pressure centrifugal chiller, what should go in first?
- VaporCorrect answer
- Liquid
- Nitrogen
- Oil
Why “Vapor” is correct
An evacuated chiller is in a deep vacuum. Charging vapor first raises the pressure safely before liquid is introduced, which protects the tubes from freezing.
Source: EPA: Test Topics
Why the other answers are wrong
- Liquid — Liquid charged into a deep vacuum can flash and freeze the water in the tubes.
- Nitrogen — Nitrogen is not part of charging and would have to be purged.
- Oil — Oil is not charged ahead of refrigerant to protect the tubes.
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Unofficial, not affiliated with the EPA or any EPA-approved certifying organization. Questions are original practice written from public EPA material, not real exam questions.