Beyond logging purge run time, what routine laboratory check tells a chiller owner that air and moisture have been getting into the machine?
- AA hardness test of the condenser water, showing how much scale is forming inside the tubes
Water side hardness tells you about scale and water treatment. It says nothing about what has entered the refrigerant side.
- A sample of the refrigerant and oil analyzed for moisture content and acid formation
- CA vibration survey of the compressor, showing whether the bearings have begun to wear
Vibration analysis catches mechanical wear, some of which is caused by acid attack, but it reports the consequence rather than the moisture that produced it.
- DA power reading at the starter, showing how far the machine has drifted from its design draw
Power draw rises with non-condensable gas as well as with fouling and load, so it cannot distinguish air ingress from several other causes.
Why B is correct
Laboratory analysis of the refrigerant and the oil measures the two things air ingress actually leaves behind: moisture and acid. Because the results are numbers rather than impressions, they can be trended across years, which turns a vague concern about a leaking machine into evidence an owner can act on and budget for.
What this question is testing
This tests knowledge of the evidence trail around a leaking low-pressure machine. The exam is checking that the candidate connects air ingress to moisture and acid rather than treating a leak only as a loss of refrigerant.
On the job
Large plants put chiller oil and refrigerant analysis into the annual maintenance contract, and the report is one page of numbers with a trend line. It is the single most useful document for arguing that a leak has to be fixed now rather than next year, because the owner can see acid climbing. After a repair and an oil change, the following year's sample is what proves the machine is clean again.
Memory technique
The oil remembers every gallon of air the machine ever drank. Send it to the lab and ask.
Exam tip
Air in means water in, and water in means acid. Anything that measures moisture and acid is measuring the leak.
Where to look it up
Annual refrigerant and oil analysis for moisture and acid documents air ingress into a low-pressure machine.