EPA Section 608 Universal Certification ExamType III (Low-Pressure Appliances)Medium
When charging a low-pressure chiller, why is it critical to introduce refrigerant into the system as a vapor until the system pressure rises above 0 psig?
- ATo ensure accurate measurement of the refrigerant charge.
- BTo prevent the liquid refrigerant from freezing the water in the chiller tubes.
- CTo avoid damaging the charging manifold and hoses.
- DTo prevent the liquid refrigerant from rapidly boiling and causing a pressure spike.
Show answer & explanationAnswer & explanation
Correct answer: B. To prevent the liquid refrigerant from freezing the water in the chiller tubes.
Introducing liquid refrigerant into a deep vacuum (below 0 psig) in a low-pressure chiller can cause it to flash freeze the water in the chiller tubes, potentially damaging them. Charging vapor first raises the pressure above freezing point.
Why the other options are wrong
- A. Accurate measurement is achieved by weighing the charge, regardless of initial vapor or liquid introduction.
- C. Charging manifold and hoses are designed to handle liquid refrigerant, so this is not the reason.
- D. Liquid refrigerant boiling in a vacuum causes a pressure drop, not a spike, as it draws heat from its surroundings (the water in the tubes).
Low-Pressure Chiller Charging Safety
When charging a low-pressure chiller, always introduce refrigerant as a vapor until system pressure is above 0 psig to prevent freezing and bursting of the chiller's water tubes.
- Charge vapor first.
- Until pressure is above 0 psig.
- Prevents freezing of water in tubes.
- Liquid refrigerant flashes to vapor in vacuum, drawing heat.
Memory trick: Vapor first, or the 'Water Works' will freeze and burst!