A system is charged with a zeotropic blend whose components boil at different temperatures. Why is refrigerant taken out of the liquid line rather than drawn off as vapor whenever the job allows it?
Correct Answer
D) Vapor leaving the system carries the lighter components first
A zeotropic blend does not boil at a single temperature. The more volatile components leave the liquid first, so vapor drawn off the top of a charge is richer in those components and what stays behind is richer in the heavier ones. Pulling liquid takes the blend out at its intended proportions. It is also much faster, which is why liquid recovery is the default on any system with enough charge to justify it.
Why This Is the Correct Answer
The components of a zeotropic blend have different boiling points, so vapor coming off a charge is not the same mixture as the liquid it came from. Drawing vapor separates the blend, leaving a charge in the system and a cylinder of refrigerant that no longer match the original composition. Taking liquid out of the liquid line keeps the proportions intact and moves far more refrigerant per minute.
Why the Other Options Are Wrong
Option A: Liquid moves through the machine at a lower discharge pressure
Discharge pressure at the machine is set by the cylinder and by ambient conditions, not by whether the refrigerant enters as liquid or vapor.
Option B: Liquid recovery avoids the need to weigh what comes out of the system
Everything that comes out is weighed either way. The cylinder stays on a scale throughout recovery regardless of the method used.
Option C: Vapor cannot be condensed by a recovery machine into a cylinder
Recovery machines condense vapor as their normal mode of operation. Vapor recovery is slow, but it works and it finishes every job.
Memory Technique
The light ones leave first, like the fastest people out a door. Take the whole crowd at once by taking liquid.
Reference Hint
Zeotropic blends fractionate: vapor drawn off a charge is richer in the lighter, more volatile components.
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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