A chiller's purge unit that once ran a few minutes each hour is now running nearly continuously. What does that tell the technician?
Correct Answer
A) Air is leaking into the machine and the leak needs to be found and repaired
Purge run time is the most useful leak indicator on a low-pressure machine, because a vacuum side leak sends nothing out for a detector to find. The purge only runs when there is non-condensable gas to remove, so a large increase in run time means a large increase in air entering the machine. The correct response is to log the trend, find the leak and repair it, not to accept the higher run time as the machine's new normal.
Why This Is the Correct Answer
The purge unit only works when non-condensables are present, so its run time is a direct measure of how much air is entering the machine. A jump from minutes per hour to nearly continuous operation means a leak has opened up somewhere on the vacuum side and needs to be located and repaired.
Why the Other Options Are Wrong
Option B: The purge unit needs a larger refrigerant charge of its own to keep up with the load
Some purge designs carry a small refrigerant charge, but a shortage would weaken the purge unit rather than make it run constantly. Continuous running means there is real gas to remove.
Option C: The chilled water flow through the evaporator has dropped off on that circuit
Reduced chilled water flow shows up as poor capacity and temperature complaints. It does not create non-condensable gas in the condenser for the purge unit to pull out.
Option D: The machine has been overcharged with refrigerant during the last service
Overcharging affects refrigerant levels and head pressure, but it adds refrigerant rather than air. The purge unit has nothing extra to remove, because refrigerant condenses normally in the condenser.
Memory Technique
The purge is a stethoscope. When it starts working overtime, the machine is bleeding air somewhere.
Reference Hint
Increasing purge unit run time indicates air is entering a low-pressure appliance and a leak must be located and repaired.
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
An operator asks how the required low-pressure recovery level compares with the vacuum scale printed on an ordinary compound gauge. Roughly how far below atmospheric pressure does that level sit at sea level?
Next Question
A chiller holds a standing vacuum test overnight without losing anything, yet its purge runs constantly once the machine is back in operation. Where should the technician look?