As the recovery unit begins pulling the charge out of a chiller, what should the technician do with the machine's purge unit?
Correct Answer
D) Shut it off, so it does not discharge refrigerant vapor while the shell pressure is falling
Running the purge before recovery starts is good practice, because it takes non-condensable gas out while the machine is still at normal pressures and the purge can separate refrigerant properly. Once recovery begins the picture changes: the pressure in the condenser drops, the purge can no longer tell refrigerant from air, and everything it discharges goes outdoors. Shutting it off at the start of the recovery keeps that refrigerant in the machine where the recovery unit will capture it.
Why This Is the Correct Answer
A purge separates refrigerant from air by condensing the refrigerant, and that separation depends on the condenser being at its normal pressure. During recovery the pressure collapses, the separation fails and the purge simply pushes refrigerant vapor out of its exhaust. Turning it off at the start of the recovery is what keeps the charge in the machine and out of the atmosphere.
Why the Other Options Are Wrong
Option A: Set it to continuous, so the shell reaches the required level faster than recovery alone
A purge cannot pull a machine down. Setting it to run continuously only increases how much refrigerant leaves through its exhaust.
Option B: Leave it running, so it keeps stripping non-condensable gas out of the shell as it empties
The purge separates properly only at normal operating pressure. Once recovery starts, what it removes is refrigerant rather than air.
Option C: Switch its exhaust into the recovery hose, so whatever it removes goes into the cylinder
Purge exhaust piping is small and routed outdoors, and rerouting it into the recovery hose is neither practical nor a recognized procedure.
Memory Technique
Purge first, then pull. A purge running on a collapsing machine is just a chimney.
Reference Hint
The purge unit is run before recovery begins and shut off during recovery, because it cannot separate refrigerant from air at reduced pressure.
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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