A plant operator suggests leaving the chiller's purge unit running overnight to empty the machine so the crew can open it in the morning. Why will that plan not work?
Correct Answer
A) The purge unit removes only non-condensable gas, so the charge still has to be pulled with recovery equipment
A purge unit exists to take air and other non-condensable gases off the top of the condenser and put them outside. It is built to reject a few ounces of gas at a time and it separates refrigerant back out rather than sending it away. Nothing about it removes the refrigerant charge, and using it as a recovery device would be a deliberate release. The charge comes out with certified recovery equipment, and the machine then has to reach the required level before anyone opens it.
Why This Is the Correct Answer
The purge unit and the recovery unit do opposite jobs. The purge separates non-condensable gas from refrigerant and keeps the refrigerant in the machine, while recovery equipment removes the refrigerant itself and puts it into a cylinder. Leaving the purge running would remove almost no charge, and any refrigerant it did send out would be an illegal release rather than recovery.
Why the Other Options Are Wrong
Option B: The purge unit removes only liquid refrigerant, so the vapor still has to be pulled with recovery equipment
This has the purge unit backward. It takes its suction from the vapor space at the top of the condenser and never handles the liquid charge at all.
Option C: The purge unit runs too slowly overnight, so the charge has to be pulled with recovery equipment by morning
Speed is not the issue. Even given a week the purge unit would not empty the machine, because removing the charge is not what it is designed or permitted to do.
Option D: The purge unit discharges into the machine room, so the charge has to be pulled with recovery equipment instead
Purge discharge is piped outdoors, and that routing is correct rather than a defect. The reason the plan fails is what the purge removes, not where it sends it.
Memory Technique
Purge takes out what does not belong. Recovery takes out what does.
Reference Hint
Only certified recovery equipment may remove the refrigerant charge; a purge unit removes non-condensable gas.
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?
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