A leaking joint on a commercial system has been brazed and the technician now has nitrogen, a vacuum pump and the refrigerant charge available. In what order should those three steps be carried out?
Correct Answer
A) Pressure test with nitrogen, then evacuate, then weigh in the charge
The pressure test comes first because a failed joint should be found while the system is still open and empty, when correcting it costs nothing but time. Evacuation follows, to pull out the nitrogen along with the air and moisture that came in during the repair. The charge goes in last. Any other order either puts refrigerant into a system that has not been proven tight or breaks a vacuum that was just achieved.
Why This Is the Correct Answer
Testing with nitrogen before evacuating means a bad joint is discovered while the system holds nothing of value and can be reopened at once. Evacuation then removes the nitrogen, the air and the moisture together and leaves the system dry. Charging last means refrigerant only ever enters a system that has already been proven tight and dry.
Why the Other Options Are Wrong
Option B: Evacuate first, then weigh in the charge, then pressure test with nitrogen
Charging before any pressure test puts refrigerant into a system that may still be leaking, and a failed joint then has to be recovered all over again.
Option C: Weigh in the charge, then pressure test with nitrogen, then evacuate
Charging first and testing afterward means the nitrogen would be added on top of a refrigerant charge, producing a mixture that has to be recovered rather than released.
Option D: Evacuate first, then pressure test with nitrogen, then weigh in the charge
Evacuating and then pressurizing with nitrogen throws away the vacuum, forcing a second evacuation before the system can be charged.
Memory Technique
Test, dry, fill. Three words in the only order that does not make you do it twice.
Reference Hint
After a repair: nitrogen pressure test, then evacuation, then weigh in the charge.
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?
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