A technician wants to remove the Schrader cores from a rooftop unit's service ports so that evacuation will go faster. What has to be true, or what tool is needed, before a core is unscrewed?
Correct Answer
D) The port must hold no pressure, or a core removal tool must isolate it
A valve core sits directly against system pressure, and the last thread is all that holds it. Backing it out of a pressurized port launches the core and releases whatever the system holds. Either the section has already been brought to its required level so no pressure remains, or a core removal tool is fitted, which threads onto the port and carries its own valve so the core can be withdrawn into a sealed body and the port closed behind it.
Why This Is the Correct Answer
The core is held only by its threads against full system pressure, so unscrewing it from a pressurized port fires the core out and releases refrigerant. Cores are pulled either after the section has reached its required evacuation level, or with a core removal tool that seals over the port and lets the core be withdrawn behind its own valve without any release.
Why the Other Options Are Wrong
Option A: The port must be at ambient temperature so the core threads release cleanly
Temperature has nothing to do with it. A port at any temperature will discharge its contents the moment the core clears its last thread.
Option B: The system must be running so the port sits on the low side of the circuit
Running the system does not empty the port. The low side still holds pressure, and on many systems it holds a great deal of it.
Option C: The core must be loosened slowly so pressure bleeds off around the threads
Loosening slowly does not bleed pressure safely past the threads. The core reaches a point where the remaining threads let go all at once.
Memory Technique
A core under pressure is a small brass bullet in a threaded barrel. Do not unscrew the barrel.
Reference Hint
Valve cores are removed only from a depressurized port or through a core removal tool that isolates the port.
More epa-608-type-2 Questions
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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?
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