EstatePass

Recovery & Evacuation — EPA 608 Practice Questions

49 questions · 33% of the Type II — High Pressure exam

Worked questions

1. 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?

  • AThe 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.

  • BThe 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.

  • The liquid line at the receiver, because pulling liquid moves far more refrigerant per minute than pulling vapor
  • DThe 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.

Why C is correct

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.

What this question is testing

This item tests practical recovery technique on large high-pressure systems and whether you understand why liquid recovery dominates the time budget on a big charge. It also checks that you can recognize push-pull as a liquid transfer method rather than a vapor method, and that system pressure alone cannot finish a recovery.

On the job

On big rack and chiller work, recovery time is the job. Techs plan the hookup before touching a valve: liquid first from the receiver king valve, a large-diameter hose to cut restriction, a scale under the cylinder, and a second cylinder staged and ready. Undersized hoses and vapor-only hookups are the two most common reasons a night shutdown runs into morning. Watching the sight glass and the cylinder weight tells you when the liquid is gone and it is time to switch over and finish on vapor.

Memory technique

A gallon of liquid beats a roomful of vapor: pull liquid first, mop up vapor last.

Exam tip

Any question asking how to recover a large charge quickly is pointing at liquid recovery or push-pull. Vapor recovery is the finishing step, never the fast one.

Where to look it up

Recovery practice under 40 CFR 82.156: remove liquid first on large charges, finish on vapor to reach the required level.

2. In push-pull recovery the machine draws vapor off the recovery cylinder and pushes it into the appliance while liquid flows out of the appliance's liquid line into that cylinder. What condition has to be met before this setup will actually transfer refrigerant?

  • AThe recovery cylinder must be warmed above the appliance's saturation temperature so the higher cylinder pressure drives the liquid through the transfer hose

    Push-pull works by lowering cylinder pressure, not by raising it. Heating a cylinder to build pressure reverses the direction of the transfer and is a serious overpressure hazard on its own.

  • BThe appliance's own compressor must run for the whole transfer, since it is what keeps the liquid column moving to the cylinder

    The recovery machine supplies the entire pressure difference. The appliance is normally off and locked out during a push-pull transfer, and a dead compressor does not stop the method from working.

  • CThe hookup must be made through the suction service valve, since liquid will not flow out through a liquid line service port

    Liquid has to leave through a liquid line or receiver port, which is the whole point of the hookup. Pulling from the suction valve gives vapor, and there is no liquid column left to push.

  • The appliance must hold enough liquid refrigerant for the machine to build and hold a pressure difference between the appliance and the cylinder

Why D is correct

The method works only while a pressure difference exists across a continuous column of liquid. A large liquid charge lets the machine establish and hold that difference long enough to move most of the refrigerant quickly, which is precisely why push-pull is a large-system technique.

What this question is testing

This tests understanding of the physical mechanism behind push-pull rather than a memorized hookup diagram, plus the judgment to know when the method is worth setting up. It also probes whether you can recognize dangerous or backwards descriptions of the technique.

On the job

Push-pull earns its keep on chillers and supermarket racks where hundreds of pounds sit in a receiver. Techs watch the sight glass in the transfer hose and the scale under the cylinder: bubbles in the glass and a stalled scale mean the liquid is gone. At that point you break down the push-pull hookup, go to standard vapor recovery, and finish. Overfilling is the real danger here, since liquid moves fast and the cylinder can pass the safe fill level in minutes if nobody is watching the scale.

Memory technique

Push vapor in, pull liquid out, and only bother when there is a lake of liquid to move.

Exam tip

Push-pull questions hinge on two things: it moves liquid, and it needs a large charge. Never heat a recovery cylinder to speed anything up.

Where to look it up

Push-pull is a liquid recovery technique for large charges; finish with vapor recovery and keep the cylinder within its safe fill level.

3. The evacuation table splits several of its rows into a column for equipment built before November 15, 1993 and a column for equipment built on or after that date. Which piece of equipment's build date decides which column a technician reads?

  • AThe date the appliance being serviced was manufactured

    This reverses the rule. The appliance's own age has no bearing on the required level; only its refrigerant and its normal charge place it on a row.

  • BThe date the appliance was last charged with refrigerant

    When an appliance was last charged says nothing about which standard applies. No line of the evacuation table turns on service history.

  • The date the recovery or recycling equipment was manufactured
  • DThe date the technician's certification was originally issued

    Certification date affects nothing about evacuation levels. A technician certified last month and one certified in 1994 read the same table the same way.

Why C is correct

The two columns exist because equipment standards changed. Recovery and recycling equipment manufactured on or after November 15, 1993 had to be certified against a tougher standard, and the evacuation table asks those machines to reach deeper levels. The technician therefore looks at the date plate on the recovery machine to choose the column, and at the appliance only to choose the row.

What this question is testing

This tests a conceptual point that governs every numeric question on the table. A candidate who can recall all six figures but attaches the date split to the wrong piece of equipment will answer half the large-appliance questions incorrectly.

On the job

Shops commonly own machines of several vintages, and the one that goes on the truck is often whichever is charged and free. Before the hoses go on, the technician should read the date plate on the machine and then decide the target, because the same chiller can legally be left at four inches with one machine and must go to ten with another. Rental machines make this worse, since the technician has no history with the unit and has to look.

Memory technique

The machine picks the column, the appliance picks the row. Two plates, two jobs.

Exam tip

Rows come from the appliance, columns come from the machine. Say it that way and the table stops being confusing.

Where to look it up

The November 15, 1993 split in the evacuation table refers to the build date of the recovery or recycling equipment.

4. An apprentice reads a required level of zero inches of mercury vacuum on the evacuation table and asks what the gauge should show when the job is done. What does that entry actually describe?

  • AThe appliance has been left with a slight positive holding charge

    Leaving positive pressure means the appliance has not reached the level. Refrigerant would push out of the joint as soon as it was opened.

  • BThe appliance has been emptied of every trace of refrigerant

    No evacuation level anywhere in the table asks for a completely empty appliance, and no recovery machine could deliver one. Vapor always remains.

  • CThe appliance has been pulled to the deepest vacuum available

    Pulling as deep as the equipment allows is good practice before recharging, but it is not what a zero inch entry requires before the appliance is opened.

  • The appliance has been brought down to atmospheric pressure

Why D is correct

Vacuum readings on a compound gauge count downward from atmospheric pressure, so a requirement of zero inches of vacuum is a requirement to reach atmospheric pressure and no further. The appliance is not empty at that point, but the pressure driving refrigerant out through an opened joint is gone, which is what the rule is aiming at for these categories.

What this question is testing

This tests whether the candidate understands the unit the table is written in, rather than just memorizing the numbers. Confusion between vacuum measured downward from atmospheric and absolute pressure measured upward from a perfect vacuum is a recurring source of errors across sections.

On the job

Apprentices consistently misread this entry in one of two directions, either treating it as trivial and cutting into a system that still shows pressure, or treating it as a deep vacuum and running the machine for an hour on a residential split. The practical test is the compound gauge sitting on zero and staying there after the machine is valved off, since a reading that climbs back up shows refrigerant still boiling out of the oil.

Memory technique

Count the inches downhill from atmosphere. Zero steps down means you are still standing at the top.

Exam tip

Bigger inches of vacuum means deeper. Zero inches of vacuum is the shallowest entry in the table, not the deepest.

Where to look it up

Inches of mercury vacuum are measured down from atmospheric pressure, so zero inches equals atmospheric pressure.

5. A system charged with a zeotropic blend has lost most of its charge through a large leak, and the leak has now been repaired. What should be done with the small amount of refrigerant still in the system?

  • ALeave it in place and add fresh blend until the nameplate weight is reached

    Topping off works with a single-component refrigerant. On a blend that has lost most of its charge as vapor, it produces a mixture that matches no published data.

  • Recover it, then evacuate and weigh in a full charge of fresh blend
  • CLeave it in place and add only the heavier component of the blend

    Blend components are not sold separately and no technician may compound one in the field. Trying to correct composition by addition is not a service practice.

  • DRecover it and return it to this same system once the repair is verified

    Returning the remainder to the same appliance is permitted in general, but this particular remainder is no longer the labelled product, so it would carry the problem back in.

Why B is correct

A large vapor leak fractionates a zeotropic blend, so the refrigerant left in the system is enriched in the heavier components. Adding fresh blend on top of it produces a mixture of unknown composition with the wrong pressure and temperature behavior. Recovering the remainder and weighing in a complete fresh charge is the only way to get the system back to a known refrigerant at a known weight.

What this question is testing

This tests the practical consequence of blend behavior, which the exam builds several questions around. The candidate has to connect what happens physically during a vapor leak with what the charge on the ticket has to be at the end of the job.

On the job

This is a daily decision in commercial refrigeration now that blends have replaced most single-component refrigerants. The tell is the size of the loss: a system that is a couple of pounds low can be topped up, while one that emptied itself through a split tube has almost certainly fractionated. The recovered remainder is not waste either. It goes to a reclaimer, who sorts and reprocesses it to specification.

Memory technique

A blend that has bled off is a recipe with ingredients missing. You cannot fix a recipe by pouring in more of the finished dish.

Exam tip

Small loss, top it up. Big loss on a blend, take it all out and start clean.

Where to look it up

Zeotropic blends fractionate during a vapor leak, so a large loss calls for full recovery and a fresh weighed charge.

44 more in the bank

Answers and explanations for these are in the app.

  • A technician pumps an R-410A charge out of a rooftop unit into a DOT cylinder using a machine that has no cleaning circuit, replaces the condenser coil, then puts the same refrigerant back in. What has the technician done to that refrigerant?
  • System-dependent recovery equipment relies on the appliance's own compressor and internal pressure to move refrigerant into a bag or cylinder. Why is that method the wrong choice for a 7.5-ton commercial split system?
  • On a compressor changeout the technician first pulls the charge into a cylinder, and later, after the new compressor is brazed in, pulls the system down with a vacuum pump. What separates those two operations?
  • A technician is pulling the remaining vapor charge out of a high-pressure system with a recovery machine and wants the job to move as fast as it safely can. Where should the recovery hoses be connected?
  • Before recovering refrigerant into a recovery cylinder that has never been used, a technician evacuates the cylinder with a vacuum pump. Why does that step matter?
  • A technician keeps the recovery cylinder on a scale throughout a recovery job instead of judging the fill level by lifting the cylinder. What is that scale there to prevent?
  • Recovery on a rooftop unit is crawling along on a very cold day, with the appliance and its remaining charge sitting at outdoor temperature. How does the cold slow the job down?
  • Recovery has stalled because pressure in the recovery cylinder has climbed until the machine can no longer push refrigerant into it. What is the correct way to get the transfer moving again?
  • 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?
  • A technician has finished pulling the liquid charge out of a large system, and the sight glass in the recovery hose has gone clear. What still has to be done before the system may be opened?
  • A technician is running a push-pull recovery and is watching the sight glass in the liquid hose feeding the recovery cylinder. What does it mean when that sight glass clears and stays clear?
  • A contractor is buying a recovery machine that will be used on high-pressure commercial equipment. What does the rule require of that machine?
  • A technician has a vacuum pump on a system that took on moisture, and the reading falls quickly at first and then stalls at a level well above the target. Why does the last of the water take so long to come out?
  • Rather than one very long single pull, a technician evacuates a contaminated system three times and breaks the vacuum with dry nitrogen between the pulls. Why does that approach clean the system more thoroughly?
  • A technician relies on an electronic micron gauge rather than the manifold's compound gauge to decide when evacuation is complete. Why is the compound gauge not good enough for that decision?
  • After isolating the vacuum pump, a technician watches the micron reading climb steadily and keep climbing without ever leveling off. What does that behavior point to?
  • A helper suggests running the appliance's own compressor to assist the vacuum pump in pulling the system down after a repair. Why is that the wrong move?
  • After evacuating a system that was full of moisture, a technician changes the oil in the vacuum pump before starting the next job. What does moisture-contaminated pump oil do?
  • To speed up evacuation on a large system, a technician removes the schrader valve cores and connects large diameter hoses directly to the service ports. Why does that make such a difference?
  • A technician connects the vacuum pump to both the high side and the low side of a system rather than to a single service port. Why is that the better setup?
  • A technician recovers the charge from a system whose compressor suffered a motor burnout. What should happen to that recovered refrigerant?
  • A technician reaches the target vacuum, isolates the pump, and confirms that the reading holds steady for several minutes. What is the correct next step?
  • A residential split system holding eight pounds of R-22 must be opened to change the compressor, and the recovery machine on the truck carries a 2015 build date. What vacuum level does the appliance have to reach before the lines are cut?
  • A parallel rack normally holds three hundred fifty pounds of R-22, and the recovery machine being used on it was manufactured in 2005. How deep must the rack be pulled before the receiver is unbolted?
  • An air-cooled chiller normally holds two hundred sixty pounds of R-22, and the only recovery machine available carries a manufacturer's date plate reading 1990. What level must the chiller be brought to before it is opened?
  • A legacy low-temperature rack still charged with R-502 normally holds four hundred pounds, and the recovery machine in use was built in 2008. Which evacuation level applies before the suction header is cut open?
  • A legacy freezer system charged with R-12 normally holds ninety pounds, and the technician is using a recovery machine built in 2000. A helper says ninety pounds is well under two hundred, so the system only needs to come to atmospheric pressure. What level actually applies?
  • A rack whose nameplate lists a full charge of two hundred forty pounds has leaked down and now holds only about one hundred thirty pounds. Which figure decides whether the two hundred pound line of the evacuation table applies?
  • A process cooling system charged with R-22 lists a normal charge of exactly two hundred pounds, and the recovery machine is a current model. Which row of the evacuation table covers an appliance sitting precisely on the boundary?
  • The low stage of a cascade system is charged with R-13, a very high-pressure refrigerant, and the charge is under fifty pounds. What evacuation level does the table set for a very high-pressure appliance?
  • A rooftop unit has two completely separate refrigerant circuits, each holding one hundred twenty pounds of R-22, and only one circuit has to be opened. How is the evacuation requirement determined for the circuit being serviced?
  • After the required evacuation level has been reached and the repair is finished, many technicians keep pulling the system down to a few hundred microns before charging. What is the standing of that deeper vacuum?
  • Before recovering, a technician front seats the receiver outlet valve and runs the system until the low side pressure falls, storing most of the charge in the receiver. What has that accomplished for the recovery that follows?
  • A shop owns a single stage vacuum pump and a two stage vacuum pump of the same displacement. What does the second stage of the two stage pump give the technician?
  • 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?
  • A technician is sent to recover the charge from a twenty ton rooftop unit and the only machine available is one certified for use with small appliances. What does the equipment rule require here?
  • A packaged unit has been repaired and evacuated, and its nameplate lists a factory charge by weight. On a mild day with almost no load on the building, what is the most reliable way to put the charge back in?
  • A system has been open to the atmosphere for two days before its repair was completed. Beyond slowing the equipment down, what does moisture left in a running refrigeration system cause?
  • A technician arrives at a system that still holds part of its refrigerant charge and finds that nitrogen was added on top of it during an earlier visit. What is the concern about connecting the recovery machine and starting?
  • A liquid line sight glass on a recharged system includes a colored moisture indicating element. What does that element tell the technician about the system?
  • A vacuum pump has a gas ballast valve on its housing, and a technician opens it during the early part of a long evacuation on a wet system. What does opening that valve do?
  • The evacuation requirements for high-pressure appliances are stated in inches of mercury vacuum, while the low-pressure requirement is stated as an absolute pressure. What does that difference mean for the instrument a technician needs?
  • A technician front seats the suction and discharge service valves on a semi-hermetic compressor, isolating it from the rest of the system. What has to happen before the compressor is unbolted and lifted out?
  • A large appliance has been recovered down to fifteen inches of mercury vacuum and a brazed joint now has to be heated and taken apart. Why do technicians raise the system back to atmospheric pressure with dry nitrogen first?

Practice all 49 Recovery & Evacuation questions

Plus timed mock exams and a wrong book that follows you between the web and the app.

Start studying free

Other EPA 608 content areas