Many large low-pressure chillers are built with an onboard device for moving the charge out of the machine. What is that device called?
Correct Answer
C) The pump-out unit
A pump-out unit is a small compressor and receiver package built onto or beside the chiller so the charge can be moved into storage without dragging a portable recovery machine into the room. It is not the purge unit, which does the opposite job of removing air from the machine during operation. Technicians frequently use the onboard pump-out unit for recovery, but it still has to bring the machine down to the required level and the refrigerant still has to be handled under the same rules.
Why This Is the Correct Answer
The pump-out unit is factory installed for exactly this purpose: transferring the refrigerant charge between the chiller and a storage vessel so the machine can be opened for service. Using it saves setup time, but the technician remains responsible for reaching the required recovery level before opening the machine.
Why the Other Options Are Wrong
Option A: The economizer
An economizer is a capacity and efficiency device in the refrigerant circuit. It plays no part in removing the charge from the machine.
Option B: The purge unit
The purge unit removes air and other non-condensable gases during normal operation. It is not built to move the refrigerant charge out.
Option D: The oil eductor
An oil eductor moves oil within the lubrication system. It has nothing to do with recovering the refrigerant charge. Confusing it with the pump-out unit usually comes from unfamiliarity with the machine's piping.
Memory Technique
Purge pulls air, pump-out pulls the charge. P for purge, air; P for pump-out, pounds.
Reference Hint
Low-pressure chillers often include a factory pump-out unit for transferring the charge; the purge unit is a separate device for non-condensables.
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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