From what point on a low-pressure chiller does the purge unit normally take its suction?
Correct Answer
B) The top of the condenser, where non-condensable gases gather
Non-condensable gases do not condense with the refrigerant, so they accumulate in the coolest, highest part of the condenser and blanket the tubes there. That is where the purge unit takes its suction, drawing off the gas mixture, separating out what refrigerant it can, and discharging the rest. Taking suction anywhere else would either pull liquid refrigerant or miss the accumulation entirely, which is why the purge connection is always at the top of the condenser.
Why This Is the Correct Answer
Air and other non-condensables collect at the top of the condenser because they remain gaseous while the refrigerant around them condenses and drains away. Pulling from that point gives the purge unit the richest concentration of non-condensable gas and the least refrigerant, which is what makes the purge efficient.
Why the Other Options Are Wrong
Option A: The bottom of the evaporator, below the liquid refrigerant level
Below the liquid level the purge would draw liquid refrigerant, which is the opposite of what it is meant to remove.
Option C: The compressor discharge line, ahead of the condenser inlet
The discharge line carries the full flow of hot refrigerant vapor. Non-condensables have not separated out yet at that point.
Option D: The oil sump, where gases separate out of the lubricant
The oil sump collects lubricant and dissolved refrigerant. It is not where non-condensable gases accumulate in the refrigerant circuit. Drawing from the sump would pull oil and dissolved refrigerant rather than the air that needs removal.
Memory Technique
Gases that will not condense float to the top of the condenser. That is where the purge goes fishing.
Reference Hint
Purge units take suction at the top of the condenser, where non-condensable gases accumulate above the condensing refrigerant.
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?
People Also Study
Business & Financial Management
120 questions · 70% to pass
Contract Administration
60 questions · 70% to pass
Project Management
60 questions · 70% to pass
Related Study Resources
Previous Question
A purge unit on a chiller discharges to the outdoors several times an hour. How does that discharge stand against the prohibition on releasing refrigerant?
Next Question
A technician remembers that the evacuation table splits appliances at a two hundred pound charge. How does that split apply to a chiller holding one hundred and fifty pounds of R-123?