A refrigerant cylinder is connected to the high side of a system for liquid charging and the compressor is then started with the cylinder valve still open. What is the danger in that arrangement?
Correct Answer
C) Discharge pressure can push back into the cylinder and overfill it
Once the compressor runs, the high side climbs above the pressure in the cylinder, and the cylinder becomes the low point in that path. Refrigerant then flows the wrong way, back into a container that already holds a charge, and a cylinder pushed past its fill limit and warmed by discharge gas is a rupture risk. Liquid charging into the high side is done with the compressor off, and the cylinder is closed and disconnected before it is started.
Why This Is the Correct Answer
With the compressor running, discharge pressure exceeds cylinder pressure, so the flow reverses and refrigerant is pushed back into the cylinder. A cylinder taking a return flow can pass its fill limit without the technician noticing, and it is being warmed at the same time. Liquid charging on the high side is therefore done with the system off, and the cylinder valve is closed before startup.
Why the Other Options Are Wrong
Option A: The cylinder will empty into the system faster than the metering device allows
Charging faster than a metering device would pass is exactly why high side liquid charging is done with the compressor off. The reverse flow is the hazard once it runs.
Option B: The refrigerant will fractionate as it passes backward through the hose
Fractionation happens when vapor is drawn off a blend. Liquid moving through a hose in either direction does not separate the components.
Option D: The liquid line will collapse under the vacuum the compressor creates
Refrigerant tubing does not collapse under any pressure a compressor develops. The pressure difference here drives flow, it does not crush the line.
Memory Technique
Start the compressor and the high side becomes uphill. Your cylinder is now at the bottom of the hill.
Reference Hint
Charge liquid into the high side only with the compressor off, and close the cylinder valve before startup.
More epa-608-type-2 Questions
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