A small leak is suspected somewhere inside an evaporator coil, in tubing buried among the fins and the rows of the bundle. What makes that kind of leak so hard to pin down?
Correct Answer
B) Airflow through the coil and the depth of the tube bundle scatter escaping vapor before a probe can pick it up
Two things work against the technician here. The blower moves a large volume of air across the coil and dilutes escaping vapor to nothing, and the leak may be several rows deep where no probe can reach. The practical approach is to shut the blower off and let the coil sit so vapor can collect, then probe the underside and downstream face slowly. If that fails, dye and a return visit or an isolated nitrogen pressure test on the coil alone will settle it. Corrosion pinholes in coil tubing are a common failure on older equipment.
Why This Is the Correct Answer
Detection depends on refrigerant vapor concentrating near the leak long enough to be sensed. Moving air destroys that concentration, and a leak buried in the middle of a tube bundle is physically inaccessible to a probe tip, so both the chemistry and the geometry work against a quick find.
Why the Other Options Are Wrong
Option A: Coil leaks only open up while the system is shut down, so no test run with the unit going will find them
A leak is a hole and it does not open and close with the unit's operating state. Pressure changes make one easier or harder to find, which is not the same as being undetectable.
Option C: The aluminum fins shield the tubing so an electronic detector cannot sense refrigerant anywhere inside the bundle
Fins do not block a detector chemically; they block the probe physically and the moving air dilutes the sample. Treating aluminum as a shield swaps an access problem for an instrument problem.
Option D: Evaporator coils always operate under a vacuum, so nothing ever escapes from them to be detected
An evaporator on a properly charged high-pressure system runs above atmospheric pressure. Only a badly undercharged low-temperature system pulls its low side down into a vacuum.
Memory Technique
Moving air hides leaks. Kill the fan and let the vapor puddle.
Reference Hint
Leaks must be located, repaired and verified under 40 CFR Part 82, Subpart F. Isolating a coil for a nitrogen test is standard practice.
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?
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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?
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