What must a technician do with the charging hoses before opening them to a machine that is holding a deep vacuum?
Correct Answer
D) Purge them with refrigerant vapor so no trapped air is carried into the machine
A hose full of room air holds air and moisture, and a machine in a deep vacuum will pull all of it inside the instant the valve opens. Purging the hoses with refrigerant vapor sweeps the air out first so only refrigerant enters. On a low-pressure machine that matters more than on most equipment, because the air becomes a non-condensable load the purge unit has to work off, and the moisture becomes acid in the oil. It costs a few seconds and saves hours.
Why This Is the Correct Answer
Purging the hose with refrigerant displaces the air and water vapor sitting in it, so nothing but refrigerant crosses into the machine. Since the machine is in a deep vacuum, whatever is in that hose goes in fast and completely, which makes the purge step worth doing every time.
Why the Other Options Are Wrong
Option A: Leave the ends open to the room so the pressures can equalize first to the machine
Opening the hose to the room fills it with air and moisture, which the deep vacuum then pulls straight into the machine. Equalizing that way defeats the purpose of holding the vacuum.
Option B: Fill them with dry nitrogen and cap the ends until they are needed
Nitrogen left in the hose is still a non-condensable gas being pushed into the machine, and the purge unit then has to work it back out. Capping the ends does not change what is inside.
Option C: Chill them in an ice bath so any moisture condenses out of the hose
Chilling a hose does not clear the air inside it, and a cold hose gathers condensation on the outside rather than drying the inside. The trapped air still goes into the machine.
Memory Technique
A hose full of air is a hose full of trouble on a vacuum machine. Sweep it first.
Reference Hint
Purge charging hoses with refrigerant before opening them to a machine under vacuum, so air and moisture are not drawn in.
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
A building owner is relocating a working R-123 chiller to another property that the same owner controls. What has to happen to the charge before the machine is disconnected?
Next Question
A chiller charged with R-123 has been shut down long enough to warm to a room temperature of about seventy degrees F. What does a gauge on the machine show?