Besides a leak in the shell, what commonly loads a low-pressure machine with non-condensable gas?
Correct Answer
A) Careless service work that leaves the machine standing open to the room
Every hour a machine stands open, or every hose connected without purging the air out of it, adds non-condensable gas that the purge unit will have to remove afterward. On a machine that will be pulled into a deep vacuum this is manageable, but only if the technician evacuates properly before charging. Skipping that step hands the purge unit a load it was never sized for, and the plant sees the result as elevated purge run time and refrigerant loss for months.
Why This Is the Correct Answer
Service work is a major source of air in these machines: open manways, unpurged hoses, gauge lines and repeated connections all admit room air. Proper evacuation after the work and disciplined hose purging during charging are what keep that air from becoming the purge unit's permanent burden.
Why the Other Options Are Wrong
Option B: Operating the chiller at part load for extended periods each year
Part load operation affects efficiency and surge behavior but introduces no non-condensable gas. A machine can run lightly loaded for years with a purge unit that barely cycles.
Option C: Charging the machine slightly above its nameplate refrigerant weight on the plate
A slight overcharge changes liquid levels and head pressure but adds refrigerant, not air. The purge unit has nothing extra to remove, since refrigerant condenses normally in the condenser.
Option D: Using a heavier grade of oil than the manufacturer specified on refill
The wrong oil grade causes lubrication and oil return problems rather than air in the condenser. Oil trouble shows up as bearing temperature and oil return symptoms, not as rising purge run time.
Memory Technique
The biggest hole in the machine is the one you opened. Close it, evacuate it, then charge it.
Reference Hint
Air enters low-pressure machines through service work as well as leaks, which is why full evacuation is required before recharging.
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?
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During normal operation, what condition exists inside the evaporator of a running low-pressure centrifugal chiller?
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What property of the refrigerant is what actually places an appliance into the low-pressure category?
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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?