A chiller cannot be taken out of service yet, and the technician wants to narrow down where air is being drawn in while the machine keeps running. Which instrument can do that?
Correct Answer
A) An ultrasonic detector, which picks up the high frequency sound of air rushing through the opening
Air forced through a small opening by a pressure difference makes noise well above the range of human hearing, and an ultrasonic detector converts that to something an operator can hear in headphones. It works in exactly the situation where every refrigerant-sensing instrument fails, because on the vacuum side nothing is coming out to sense. It narrows the search to a flange or a seal so the crew knows where to concentrate when the machine finally comes down.
Why This Is the Correct Answer
Ultrasonic detection listens for turbulence rather than sniffing for refrigerant, so the direction of flow does not matter. On a running low-pressure machine the leak is drawing air in, which produces the same high frequency signature as gas escaping. It is the one detection method that works before the charge has been recovered and the shell pressurized.
Why the Other Options Are Wrong
Option B: A halide torch, which changes flame color when refrigerant vapor is drawn across the reaction plate
A halide torch responds to refrigerant reaching the flame, and on the vacuum side no refrigerant is coming out. An open flame near a chiller also risks producing toxic decomposition products.
Option C: An electronic halogen detector, which alarms when refrigerant is drawn past its sensing element
An electronic halogen detector needs refrigerant to escape past its tip. On a section under vacuum there is nothing for it to draw in.
Option D: An infrared refrigerant analyzer, which reads the refrigerant content of the air near the opening
An infrared analyzer is still a refrigerant sensor. It measures what is in the air around the machine, and a vacuum leak puts nothing there.
Memory Technique
Under vacuum you cannot smell the leak, but you can hear it.
Reference Hint
A leak drawing air into a machine under vacuum can be located by ultrasonic detection, because refrigerant sensing instruments need refrigerant to escape.
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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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?