A technician suspects that air worked its way into a cylinder of recovered refrigerant during a job. How can that suspicion be checked without opening the cylinder?
Correct Answer
D) Let the cylinder sit until it settles at a steady temperature, then compare its pressure to the saturation pressure for that refrigerant at that temperature
A cylinder holding only refrigerant with liquid and vapor together sits at the saturation pressure for its temperature. Non-condensable gas adds its own pressure on top of that, so the cylinder reads higher than the chart. The test is to let the cylinder rest in a stable place long enough for the liquid, the vapor and the steel to reach one temperature, measure that temperature, then compare the gauge reading to the saturation value. A reading meaningfully above the chart points to air in the cylinder.
Why This Is the Correct Answer
Saturation pressure is fixed by temperature for a given refrigerant, so it acts as a built-in reference. Any pressure above that reference has to come from a gas that will not condense. Letting the cylinder stabilize first is essential, because a cylinder that was just filled or just moved from a hot truck has no single temperature.
Why the Other Options Are Wrong
Option A: Weigh the cylinder and compare the result against the tare weight stamped on the collar, because trapped air adds weight the refrigerant would not account for
Weight tells you how much is in the cylinder, not what is in it. Air at these pressures weighs almost nothing, so a contaminated cylinder and a clean one read essentially the same against the stamped tare.
Option B: Shake the cylinder and listen for how much liquid moves inside, since trapped air leaves the liquid extra room to slosh around
Sloshing gives a rough sense of liquid level and nothing at all about the gas above it. Non-condensables sit in the vapor space, which is exactly the part a shake test cannot sense.
Option C: Compare the cylinder pressure against the pressure of a second cylinder of the same size and refrigerant standing next to it on the truck
A second cylinder is a reference only if you already know it is clean and at the same temperature, and neither is established here. The saturation chart is the reference that depends on no assumptions.
Memory Technique
Chart says one number, gauge says higher - that extra pressure is air riding along.
Reference Hint
Recovered refrigerant must meet the industry purity standard before reuse in another owner's equipment, 40 CFR 82.157. Non-condensables are one of the specified contaminants.
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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