During the final pull down on a low-pressure chiller the technician's absolute pressure gauge is holding steady at forty millimeters of mercury. What does that reading mean for the job?
Correct Answer
C) The machine is not there yet, and recovery has to continue until the reading falls further
Absolute pressure is measured up from a perfect vacuum, so a smaller number means a deeper vacuum. The requirement is twenty-five millimeters of mercury absolute, and forty is above it. The machine still holds more refrigerant than the rule allows and the recovery has to keep going. A reading that stalls at forty usually means air is being drawn in through a fitting, or that refrigerant is still boiling out of the oil charge.
Why This Is the Correct Answer
With absolute units the scale runs downward toward a perfect vacuum, so the requirement is a ceiling rather than a floor. Forty millimeters of mercury is higher than twenty-five, so the appliance has not reached the level and may not be opened. The technician keeps pulling and starts looking for what is holding the pressure up.
Why the Other Options Are Wrong
Option A: The machine has gone too deep, and the vacuum has to be broken back before opening
There is no such thing as too deep for the purposes of the rule. Going below the required figure is allowed and is often necessary before the machine will hold.
Option B: The machine is at the requirement, because forty millimeters is the figure for a chiller
Twenty-five millimeters is the chiller figure. Forty is a number a stalled recovery lands on, not a level anyone is permitted to stop at.
Option D: The machine is past the requirement, since forty is a larger number than the figure required
This reads the scale backward. In absolute units a larger number is a shallower vacuum, so forty millimeters is further from the target than twenty-five, not past it.
Memory Technique
Absolute pressure is a countdown, not a count-up. Zero would be a perfect vacuum.
Reference Hint
Absolute pressure counts up from a perfect vacuum, so the low-pressure requirement of twenty-five millimeters is reached by driving the reading down.
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
Liquid refrigerant has to move from the condenser back to the evaporator inside a low-pressure centrifugal chiller. Which device controls that flow?
Next Question
An owner objects to the rental line for a certified recovery unit, arguing that his refrigerant is being put right back where it came from. What does the rule require for taking it out?