A low-pressure chiller has taken on several gallons of water from a burst tube, and that water is standing in the bottom of the evaporator shell. What has to happen before a vacuum pump goes on the machine?
Correct Answer
C) The standing water has to be drained out physically, because a pump cannot boil off that much
A vacuum pump removes water as vapor, and boiling off gallons of liquid water that way would take days and would freeze what remains as the evaporation cools it. The free water comes out through the shell's low point drain first. Only after the liquid is gone does the pump have a job it can finish, pulling the last of the moisture out of the oil film, the insulation and the metal surfaces, ideally with warm water circulating through the tubes.
Why This Is the Correct Answer
Evacuation removes moisture only as vapor, and the heat needed to boil liquid water comes out of the shell itself, so the remaining water chills toward freezing and the process stalls. Draining the free water through the low point first removes most of the moisture in minutes, leaving the pump with the film and the absorbed moisture it can actually handle.
Why the Other Options Are Wrong
Option A: The standing water has to be tested for acid first, because that reading sets the pump down time
An acid test on the water tells you about the damage already done, but it does nothing about the gallons of liquid sitting in the shell.
Option B: The standing water can be left alone, because a deep vacuum freezes it into a harmless plug
Ice in the bottom of a chiller is not harmless. It holds moisture in the machine, it sublimes slowly under vacuum, and it keeps the evacuation from ever finishing.
Option D: The standing water has to be warmed by the condenser pumps, because heat lets the pump remove it
Warm water through the tubes is the right technique once the liquid is out, but it will not make a vacuum pump swallow several gallons of standing water.
Memory Technique
Bucket first, pump second. Nobody boils a puddle with a vacuum pump.
Reference Hint
Free water is drained from the shell's low point before evacuation; a vacuum pump can only remove moisture as vapor.
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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