A technician has just taken a water-contaminated charge out of a chiller with a split tube, and the next job that day is a clean machine across town. What has to be done to the recovery unit first?
- AIts high pressure switch has to be reset so that the next machine can be pulled down deeper
Resetting a pressure switch has nothing to do with contamination, and a recovery unit's protective switches are not what limits how deep it can pull.
- Its filters and its oil have to be changed so that the next machine is not contaminated
- CIts nameplate has to be relabeled so that the next machine's paperwork shows the refrigerant
The nameplate identifies the equipment, not its last load. Paperwork does nothing about the moisture and acid actually sitting inside the machine.
- DIts cylinder fittings have to be swapped so that the next machine gets a clean hose set
New hoses are worth having, but the contamination that matters is inside the recovery unit's own filter, lines and oil, and swapping fittings does not touch it.
Why B is correct
Recovery equipment carries whatever it has just pumped. Moisture and acid soak into the compressor oil and load the filter, and both will be pushed into the next appliance the unit is connected to. Changing the oil and filter and evacuating the machine between jobs is the standard practice that keeps contamination from moving between customers.
What this question is testing
This tests cross-contamination awareness, which sits between the regulations and good practice. The exam looks for candidates who think about what the equipment carries between jobs rather than treating the recovery unit as a neutral pump.
On the job
Shops that do chiller work keep a spare filter core and a quart of oil on the truck for exactly this. The technician who skips it on a Friday afternoon can put a compressor burnout's worth of acid into a machine that was healthy that morning, and the failure will not show up until the following season. Some contractors keep a separate recovery unit tagged for contaminated work so the question never comes up.
Memory technique
The recovery machine remembers its last job. Change its oil and filter before it tells the next customer about it.
Exam tip
Whatever came out of the last machine is still in the recovery unit until you change the filter and the oil.
Where to look it up
Recovery equipment must be maintained so it does not carry contamination from one appliance into the next.