An apprentice reads a required level of zero inches of mercury vacuum on the evacuation table and asks what the gauge should show when the job is done. What does that entry actually describe?
Correct Answer
D) The appliance has been brought down to atmospheric pressure
Inches of mercury vacuum is measured downward from atmospheric pressure, so zero inches of vacuum means no vacuum at all, which is atmospheric pressure. A compound gauge reading zero on its pressure scale is at the required level. The entry does not say the appliance is empty; vapor at atmospheric pressure is still refrigerant, and that is simply what the rule accepts for the appliance categories that carry this figure.
Why This Is the Correct Answer
Vacuum readings on a compound gauge count downward from atmospheric pressure, so a requirement of zero inches of vacuum is a requirement to reach atmospheric pressure and no further. The appliance is not empty at that point, but the pressure driving refrigerant out through an opened joint is gone, which is what the rule is aiming at for these categories.
Why the Other Options Are Wrong
Option A: The appliance has been left with a slight positive holding charge
Leaving positive pressure means the appliance has not reached the level. Refrigerant would push out of the joint as soon as it was opened.
Option B: The appliance has been emptied of every trace of refrigerant
No evacuation level anywhere in the table asks for a completely empty appliance, and no recovery machine could deliver one. Vapor always remains.
Option C: The appliance has been pulled to the deepest vacuum available
Pulling as deep as the equipment allows is good practice before recharging, but it is not what a zero inch entry requires before the appliance is opened.
Memory Technique
Count the inches downhill from atmosphere. Zero steps down means you are still standing at the top.
Reference Hint
Inches of mercury vacuum are measured down from atmospheric pressure, so zero inches equals atmospheric pressure.
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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