A technician must pull a 400 lb charge out of a supermarket rack before replacing the receiver, and the store has only a few hours of downtime. Where should the recovery machine inlet be connected to move the most refrigerant in the least time?
Correct Answer
C) The liquid line at the receiver, because pulling liquid moves far more refrigerant per minute than pulling vapor
Liquid refrigerant is hundreds of times denser than vapor, so every minute the machine runs it moves vastly more refrigerant when it is pulling liquid than when it is pulling vapor. On a large charge, technicians start on the liquid line or the receiver liquid valve, take out as much liquid as possible, and only then switch to the vapor side to clean up what is left. Pulling only vapor on a several hundred pound charge can stretch a job across an entire shift. Head pressure alone will not empty a system, and push-pull works by moving liquid, not vapor.
Why This Is the Correct Answer
Density is the whole story. A pound of liquid occupies a tiny fraction of the volume of a pound of vapor, so a recovery machine handling liquid clears the charge many times faster. Starting on the liquid line and finishing on the vapor side is the standard sequence on any large high-pressure system.
Why the Other Options Are Wrong
Option A: The suction service valve, because vapor passes through a recovery machine faster than liquid does out of a system
This has the physics backwards. Vapor is far less dense, so a machine pulling vapor moves only a small fraction of the mass per minute that it moves when it is pulling liquid.
Option B: The compressor discharge port, because standing head pressure pushes the charge out on its own at first
System pressure alone pushes out some refrigerant at the start but equalizes quickly and cannot bring the rack down to the required level. A self-contained machine has to finish the job.
Option D: The suction line in push-pull mode, because push-pull transfers only work off the vapor side of the rack
Push-pull is a liquid transfer method. The machine pulls vapor off the recovery cylinder and pushes it into the appliance so liquid flows out of the liquid line into the cylinder.
Memory Technique
A gallon of liquid beats a roomful of vapor: pull liquid first, mop up vapor last.
Reference Hint
Recovery practice under 40 CFR 82.156: remove liquid first on large charges, finish on vapor to reach the required level.
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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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?