Oil is found under the brass cap of a service valve stem on a rooftop unit that loses a small amount of charge each season. What is leaking there?
Correct Answer
B) The packing around the valve stem, which seals against the stem shaft
A service valve stem passes through the valve body so it can be turned, and it is sealed by packing around the shaft. Every time the stem is turned that packing is disturbed, and on a valve that has been operated many times it starts to weep. The cap is there to catch it, which is why oil collects under the cap and why the cap is a required part rather than a dust cover. Tightening the packing nut or replacing the packing stops it.
Why This Is the Correct Answer
The stem is a rotating shaft passing through the pressure boundary, sealed by packing that wears and loosens with every use. Oil appearing under the cap is refrigerant and oil working past that packing. The valve cap is the secondary seal that catches it, which is why the cap must be refitted and tightened after every service call.
Why the Other Options Are Wrong
Option A: The brazed joint where the valve body meets the liquid line
A brazed joint at the valve body would show oil at the joint itself, on the outside of the valve, rather than collecting inside the stem cap.
Option C: The Schrader core in the gauge port on the side of the valve body
A leaking gauge port core shows oil at the port, under the separate port cap. That is a different cap on a different part of the valve.
Option D: The threads of the cap itself, which are not a sealing surface
Cap threads are not a pressure joint on their own, but the cap with its gasket is the secondary seal, which is why oil is found trapped beneath it.
Memory Technique
The cap is not a hat, it is a second door. Oil behind it means the first door leaks.
Reference Hint
Service valve stem packing seals a rotating shaft and weeps with wear; the cap is the secondary seal.
More epa-608-type-2 Questions
A walk-in cooler condensing unit holds a full charge of twenty-five pounds of R-404A, which is below the fifty pound threshold that brings an appliance under the leak repair provisions. What still applies to this unit?
An office building has thirty water source heat pumps on a common water loop, and each one left the factory assembled, hermetically sealed and charged with four pounds of R-410A. How is one of those units classified?
A data sheet for an unfamiliar refrigerant lists a boiling point of about fifty-five degrees Fahrenheit at atmospheric pressure. What does that tell a technician holding Core and Type II certification?
A technician holds Core, Type I and Type III certification and is sent to recover the charge from a twenty ton rooftop unit charged with R-410A. What does that combination of sections allow on this job?
A fleet garage technician holds only the vehicle air conditioning certification issued under Section 609 and is asked to recover the charge from the shop's own rooftop air conditioner. What does that credential allow?
A split system's outdoor unit, indoor coil and the line set the installer ran and brazed between them are being considered. For the purposes of the refrigerant rules, what makes up the appliance here?
On a new installation the line set is brazed to a factory charged outdoor unit and an indoor coil shipped under a nitrogen holding charge, with the outdoor unit's service valves still closed. What does the recovery requirement call for before that brazing?
A rooftop unit's data plate has weathered until the charge figure cannot be read, and the technician needs the full charge to place the appliance under the evacuation and leak provisions. Where should that figure come from?
A computer room air conditioning unit holds forty pounds of R-407C and connects to a remote air cooled condenser through refrigerant piping run and brazed by the installer. How is that unit classified?
A shop's office manager, who holds no technician certification, is sent to a supply house to pick up a new recovery machine for the commercial crew. What does the sales restriction require at that counter?
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 technician pumps an R-410A charge out of a rooftop unit into a DOT cylinder using a machine that has no cleaning circuit, replaces the condenser coil, then puts the same refrigerant back in. What has the technician done to that refrigerant?
Next Question
A rooftop unit has two completely separate refrigerant circuits, each holding one hundred twenty pounds of R-22, and only one circuit has to be opened. How is the evacuation requirement determined for the circuit being serviced?