A technician reaches the required level, closes the machine up, and finds refrigerant pressure building again hours later. What is the most likely reason?
Correct Answer
B) Refrigerant dissolved in the compressor oil is still boiling out of the oil
Refrigerant dissolves into the compressor oil and comes out of solution slowly, especially when the oil is cold and the machine is quiet. Long after the vessel reaches the required level, that dissolved refrigerant continues to migrate out of the oil and raise the pressure. Experienced technicians expect it, warm the oil and keep recovering, or come back and pull the machine down again before opening it. Mistaking it for a leak sends the diagnosis in the wrong direction.
Why This Is the Correct Answer
Oil holds a meaningful quantity of refrigerant in solution, and it releases that refrigerant only as fast as heat and time allow. Once the recovery machine stops, the dissolved refrigerant keeps boiling out and the pressure in the closed vessel climbs. Warming the oil sump and continuing recovery is what actually finishes the job.
Why the Other Options Are Wrong
Option A: The rupture disc is letting refrigerant back in from the relief piping
The rupture disc is a one time device that either holds or bursts. It does not feed refrigerant back into the machine from the relief line.
Option C: The purge unit is returning refrigerant it had stored earlier
The purge unit discharges non-condensables; it is not a storage vessel that returns a charge to the machine later. Whatever it separates goes back into the chiller during normal operation, not after a recovery.
Option D: Air entering the machine is carrying refrigerant back through the hoses
Air entering the machine raises pressure with air, not with refrigerant, and hoses do not carry refrigerant backward into a vessel under vacuum.
Memory Technique
Oil is a sponge full of refrigerant. Squeeze it with heat and time, or it drips into the room when you open up.
Reference Hint
Refrigerant dissolved in compressor oil continues to release after recovery, so the machine must be pulled down again before opening.
More epa-608-type-3 Questions
Some jobs on a chiller count as a major repair under the refrigerant rules, which changes what a technician is allowed to do with a badly leaking machine. Which job falls into that category?
An owner asks how many pounds of refrigerant the rules allow to be left inside a chiller once the recovery has been signed off. What is the correct answer to give him?
The motor of a hermetic centrifugal chiller sits inside the pressure boundary rather than outside it on a shaft. What follows from that construction?
An oxygen monitor is used to decide whether a chiller machine room is safe to enter after a refrigerant release. Below what oxygen reading is the atmosphere treated as oxygen deficient?
A low-pressure chiller's rupture disc has a discharge line running from it. Where does that line have to terminate?
A refrigerant vapor detector in a chiller machine room reaches its alarm level. Besides sounding, what is that alarm expected to do?
Which piece of equipment requires a technician to hold Type III certification before it may be serviced?
What property of the refrigerant is what actually places an appliance into the low-pressure category?
During normal operation, what condition exists inside the evaporator of a running low-pressure centrifugal chiller?
In what unit is the required final recovery vacuum for a low-pressure appliance normally expressed?
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