A technician is sweeping an electronic leak detector along the brazed joints of an R-134a rack looking for a small leak. How should the probe be handled to give the best chance of finding it?
Correct Answer
C) Moved slowly along the underside of each joint about an inch away, since these refrigerant vapors are heavier than air and settle downward
Common refrigerant vapors are heavier than air, so what escapes from a joint drifts down rather than up. The probe belongs below the joint, close to it, and moving slowly enough for the sensor to respond, roughly an inch or two per second. Sweeping fast or holding the probe a foot away lets the tech walk right past a small leak. Standing in one place samples the room instead of the joint and tells you nothing about which fitting is bad. Cutting fans and drafts before the sweep also matters, since moving air disperses the vapor before the sensor sees it.
Why This Is the Correct Answer
Refrigerant vapor is denser than air and falls away from the leak, so the sensor has the best chance of picking it up just below and very close to the joint. Slow movement gives the detector time to respond, which is what catches small leaks.
Why the Other Options Are Wrong
Option A: Held about a foot back from the joints and swept quickly along the line, so the sensor does not saturate on background vapor and false-trigger
Distance and speed both work against the sweep. A foot of separation lets the plume disperse below what the sensor can detect, and a fast pass gives it no time to respond, so a small leak is walked right past.
Option B: Passed a few inches above each joint and moved slowly, since refrigerant vapor is lighter than air and drifts upward
This treats refrigerant as a light gas. Common refrigerant vapors are heavier than air and sink away from the joint, so a probe held above it samples clean air while the leak is escaping downward.
Option D: Parked in one spot in the machine room for several minutes to sample the whole space, then moved to the far wall
A stationary probe reads general room background instead of a specific fitting. It may confirm that refrigerant is escaping somewhere in the room, but it will never say which joint needs the repair.
Memory Technique
Refrigerant falls, so hunt low and go slow.
Reference Hint
Electronic detector practice: probe below the joint, roughly one inch away, moving about one to two inches per second.
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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