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EPA 608 Type 3 practice test

Printable version. Original practice questions written from EPA's published rules, not questions from the real exam. The answer key, with an explanation for every answer, is at the end.

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Questions

Leak detection

1. A technician needs to raise the pressure inside an idle R-123 chiller to leak test it. Which method should be tried first?

  1. A Hot water in the tubes or a built-in heater such as Prevac
  2. B Dry nitrogen fed straight into the shell from a regulated cylinder
  3. C A trace of R-22 pushed with nitrogen
  4. D Compressed air from the shop line

2. Why must an idle low-pressure chiller usually be brought above atmospheric pressure before it is leak tested?

  1. A Leak detectors only work above 15 psig
  2. B EPA requires every low-pressure leak test to be done at exactly 10 psig
  3. C R-123 cannot be detected while it is a liquid
  4. D Below atmosphere, leaks pull air in instead of pushing refrigerant out

3. Which sign most strongly suggests a leak in an operating R-11 centrifugal chiller?

  1. A High superheat with oil stains on a hermetic compressor
  2. B Frost forming on the liquid line
  3. C Chilled water leaving colder than its set point
  4. D The purge unit runs much more than usual

4. Why does a leak in a low-pressure chiller make the purge unit work harder?

  1. A Refrigerant escaping out through the leak forces the purge to make up the loss
  2. B The leak lowers the oil level, starving the purge pump
  3. C The leak raises evaporator pressure above atmospheric
  4. D Air drawn in through the leak collects as noncondensables to be purged

5. What is the highest pressure normally used when leak testing a low-pressure centrifugal chiller?

  1. A 0 psig
  2. B 15 psig
  3. C 10 psig
  4. D 30 psig

6. Why should a technician not go above 10 psig when leak testing an R-123 chiller?

  1. A To stay safely below the rupture disc setting
  2. B Nitrogen dissolves into R-123 above 10 psig
  3. C Table 1 caps test pressures at 10 psig
  4. D The purge unit shuts down above 10 psig

7. An 800-pound R-123 chiller cooling an office building has leaked above the 10% rate. Under 40 CFR 82.157(g), how often must leak inspections be done?

  1. A Once per calendar year, until it stays under the rate for one year
  2. B Once every three months, until four quarters in a row are under the rate
  3. C Once a month, until the chiller is retired
  4. D Only once, right after the repair

8. Who must perform the leak inspections required on a low-pressure chiller that has exceeded its leak rate?

  1. A Any building employee with a leak detector
  2. B An EPA inspector, on a set schedule
  3. C The chiller manufacturer, under warranty
  4. D A certified technician, using methods suited to that appliance

9. Which method, used by itself, does not meet EPA's definition of a leak inspection on an R-11 chiller?

  1. A An electronic leak detector
  2. B A standing vacuum decay test
  3. C A bubble test at the joints
  4. D An ultrasonic leak test

10. An R-11 chiller with 500 pounds of refrigerant is a "chronically leaking appliance" if it leaks what share of its full charge in one calendar year?

  1. A 100 percent or more
  2. B 50 percent or more
  3. C 125 percent or more
  4. D 30 percent or more

11. An R-123 chiller leaked 140 percent of its full charge during 2025. What must the owner do?

  1. A Report to EPA within 30 days of the chiller reaching 125 percent of its charge
  2. B Report to EPA by December 31, 2025, with a retirement date
  3. C Report to EPA by March 1, 2026, describing efforts to find and fix leaks
  4. D Keep records on site; no report is needed unless EPA asks

12. An owner monitors an R-11 chiller with an automatic leak detection system instead of doing the required leak inspections. How often must the system be audited or calibrated?

  1. A Once a year
  2. B Once a month
  3. C Every three years
  4. D Only when it is first installed

13. How does running warm water through the tubes raise the pressure inside an idle R-11 chiller?

  1. A Warming the refrigerant raises its saturation pressure
  2. B The water mixes with the refrigerant and adds volume
  3. C The warm water drives the compressor to build pressure
  4. D The heat condenses air out of the shell

14. Why is heating the refrigerant preferred over nitrogen for pressurizing an R-123 chiller for a leak test?

  1. A Nitrogen reacts with R-123 to form acids
  2. B Nitrogen must be purged out later, and refrigerant goes with it
  3. C Nitrogen cannot raise the pressure of a chiller above atmospheric
  4. D Hot water finds leaks by changing the water color

Leak repair requirements

15. An R-123 centrifugal chiller with 900 pounds of charge cools an office tower. Under 40 CFR Part 82, above what annual leak rate must it be repaired?

  1. A 20 percent
  2. B 30 percent
  3. C 35 percent
  4. D 10 percent

16. An owner runs a 400-pound R-123 system in a cold-storage warehouse for perishable food. Under 40 CFR Part 82, what is its leak rate?

  1. A 10 percent
  2. B 30 percent
  3. C 15 percent
  4. D 20 percent

17. A 700-pound R-11 chiller cools reactors at a pharmaceutical plant. Under 40 CFR Part 82, what is its leak rate?

  1. A 10 percent
  2. B 30 percent
  3. C 20 percent
  4. D 125 percent

18. A technician adds refrigerant to a 600-pound R-123 comfort cooling chiller and the calculation shows it is over its leak rate. No process shutdown is involved. How long does the owner have to repair the leaks?

  1. A 14 days
  2. B 30 days
  3. C 90 days
  4. D 120 days

19. Fixing the leaks on an R-11 process chiller will require shutting down the industrial process it serves. How long does the owner have to complete repairs?

  1. A 30 days
  2. B 60 days
  3. C 120 days
  4. D One year

20. After a successful initial verification test on a repaired R-123 chiller that was not evacuated, how soon must the follow-up verification test be done?

  1. A Within 30 days
  2. B Within 10 days
  3. C Within 24 hours
  4. D Within 12 months

21. A leak repair on an R-11 chiller required evacuating the machine. When must the initial verification test be performed?

  1. A After the full charge has been restored
  2. B Before any refrigerant is added back
  3. C Within one year of the repair
  4. D Only after the follow-up test passes

22. When must the owner of a 1,000-pound R-123 chiller calculate its leak rate?

  1. A Every time refrigerant is added, with a few exceptions
  2. B Once each calendar year
  3. C Only when the purge unit runs excessively
  4. D Only when the charge falls below half

23. The owner of a leaking R-11 chiller decides to retire it instead of repairing it. What are the deadlines for the retirement plan?

  1. A Write the plan within 60 days; finish the work within two years
  2. B Write the plan within 30 days; finish the work within six months
  3. C Write the plan within one year; finish the work within five years
  4. D Write the plan within 30 days; finish the work within one year

24. A 900-pound centrifugal chiller uses R-245fa, an HFC. Do the 40 CFR 82.157 leak repair rules apply to it?

  1. A Yes; every low-pressure chiller holding over 50 pounds is covered by section 82.157
  2. B Yes, but only if the chiller serves an industrial process
  3. C No; it covers only ozone-depleting refrigerants, and HFCs fall under Part 84
  4. D No; low-pressure chillers are exempt from all leak repair rules

25. When may refrigerant released by a chiller's purge unit be left out of the annual leak rate calculation?

  1. A When the purge unit is a high-efficiency model approved by the manufacturer
  2. B When less than 1 pound is purged each month
  3. C When it is destroyed at a verified efficiency of 98 percent or more
  4. D When the chiller holds less than 500 pounds

26. The owner of an R-123 chiller leaking above its rate has its refrigerant recovered and shuts the chiller down for the winter. What happens to the 30-day repair deadline?

  1. A It is automatically extended to 120 days
  2. B It is suspended until refrigerant is added back
  3. C It is cancelled and never resumes
  4. D It keeps running while the chiller is off

27. A technician adds 45 pounds of R-123 to a 700-pound chiller. What must the technician give the owner when the service is finished?

  1. A A copy of the technician's card, sent on to EPA
  2. B Nothing; the owner keeps all records alone
  3. C A record that includes the amount and type of refrigerant added
  4. D A reclamation certificate showing the added refrigerant meets AHRI 700

28. After leaks on an R-11 chiller are repaired, when are they presumed repaired under 40 CFR 82.157(d)?

  1. A As soon as the initial verification test passes
  2. B After 30 days of normal operation
  3. C If no more refrigerant is added for 12 months
  4. D When purge run time returns to normal

Recovery techniques

29. A technician is starting recovery on a 1,000-pound R-123 chiller. Which should be removed first?

  1. A The refrigerant vapor
  2. B The liquid refrigerant
  3. C The noncondensable gases
  4. D The compressor oil

30. After all the liquid has been removed from a large R-11 chiller, why must the technician still run vapor recovery?

  1. A A large amount of refrigerant remains as vapor in the shells
  2. B The vapor may be vented once the liquid is out
  3. C The vapor is mostly air and must be checked
  4. D Vapor recovery is only needed on R-123 chillers, not on R-11 chillers

31. To what temperature should the oil in a low-pressure chiller be heated before it is drained?

  1. A 85 °F
  2. B 130 °F
  3. C 50 °F
  4. D 180 °F

32. Why is the oil in an R-123 chiller heated before it is removed?

  1. A Warm oil releases dissolved refrigerant, so less escapes with it
  2. B Heating destroys acid so the oil can be reused
  3. C Heating raises the shell pressure to the 5 psig limit for oil changes
  4. D Heating boils water out of the oil for disposal

33. Why should water be kept circulating through the tubes of a chiller while its refrigerant is being evacuated?

  1. A To keep the purge unit running during recovery
  2. B To keep the water in the tubes from freezing
  3. C To cool the recovery unit's compressor
  4. D To stop the oil from foaming in the sump

34. At what pressure is the high-pressure cut-out typically set on a recovery device used with low-pressure appliances?

  1. A 10 psig
  2. B 5 psig
  3. C 15 psig
  4. D 35 psig

Recharging techniques

35. When charging refrigerant into an evacuated low-pressure centrifugal chiller, what should go in first?

  1. A Vapor
  2. B Liquid
  3. C Nitrogen
  4. D Oil

36. Why is vapor charged before liquid into an evacuated R-123 chiller?

  1. A Liquid would damage the compressor bearings
  2. B Vapor charging is required to meet the evacuation levels in Table 1
  3. C Liquid boils very cold in a deep vacuum and can freeze tube water
  4. D Vapor carries the oil back into the sump

37. Through which connection should refrigerant be charged into a low-pressure centrifugal chiller?

  1. A The purge unit connection
  2. B The evaporator charging valve
  3. C The compressor discharge line
  4. D The condenser relief connection

38. While charging R-123 into a chiller that was evacuated, what should be done with the water in the tubes?

  1. A Stop the pumps to lower the heat load
  2. B Close the valves to trap water in the tubes
  3. C Leave it alone; charging cannot cause freezing
  4. D Keep it circulating, or drain it

Recovery requirements

39. Under 40 CFR 82.152, what makes an appliance a "low-pressure appliance"?

  1. A Its refrigerant has a saturation pressure below 45 psig at 77 °F
  2. B Its refrigerant's saturation pressure is below 45 psia at 104 °F
  3. C Its refrigerant has a saturation pressure below 170 psia at 104 °F
  4. D Its evaporator runs below atmospheric pressure when operating

40. Which group lists only refrigerants that 40 CFR 82.152 names as examples for low-pressure appliances?

  1. A R-12, R-134a, R-500 and R-114
  2. B R-22, R-410A, R-407C and R-404A
  3. C R-11, R-123, R-113 and R-245fa
  4. D R-13, R-23, R-503 and R-508B

41. A technician using a recovery machine built in 2019 is about to open an R-123 centrifugal chiller to replace the compressor. To what level must the chiller be evacuated first?

  1. A 10 inches of Hg vacuum
  2. B 25 mm Hg absolute
  3. C 15 inches of Hg vacuum
  4. D 0 psig

42. A contractor still owns a recovery unit manufactured in 1991. What evacuation level must it reach on an R-11 chiller before the chiller is scrapped?

  1. A 25 inches of Hg vacuum, a looser level for older units
  2. B 4 inches of Hg vacuum, the usual pre-1993 level
  3. C 25 mm Hg absolute, the same as newer equipment
  4. D 0 psig, since older units cannot pull a vacuum

43. One R-123 chiller holds 150 pounds and another holds 1,200 pounds. Using recovery equipment made in 2020, what evacuation levels apply before each is opened for a major repair?

  1. A 10 inches of Hg vacuum for the smaller, 15 inches for the larger
  2. B 0 psig for the smaller, 25 mm Hg absolute for the larger
  3. C 15 inches of Hg vacuum for both chillers
  4. D 25 mm Hg absolute for both chillers

44. Roughly what reading on an inches-of-mercury vacuum gauge corresponds to 25 mm Hg absolute?

  1. A About 25 inches of Hg vacuum
  2. B About 15 inches of Hg vacuum
  3. C About 29 inches of Hg vacuum
  4. D About 10 inches of Hg vacuum

45. Which of these jobs on an R-11 chiller is a major repair under 40 CFR 82.152?

  1. A Tightening the bolts on a pump flange
  2. B Removing the evaporator for replacement
  3. C Replacing a sight glass with a 2-square-inch opening for 10 minutes
  4. D Changing a gauge on a quarter-inch access port

46. Apart from removing a major component, a repair is "major" if it uncovers an opening of more than how much flow area for more than how long?

  1. A More than 2 square inches for more than 30 minutes
  2. B More than 4 square inches for more than 60 minutes
  3. C More than 10 square inches for more than 15 minutes
  4. D More than 4 square inches for more than 15 minutes

47. A technician will replace a small valve on an R-11 chiller, uncovering about 1.5 square inches for 10 minutes. The chiller will not be evacuated to the atmosphere afterward. What does the rule require before the valve is opened?

  1. A Evacuate the chiller to 15 inches of Hg vacuum
  2. B Pressurize the chiller to 10 psig with nitrogen
  3. C Pressurize the chiller to no higher than 0 psig
  4. D Evacuate the chiller to 4 inches of Hg vacuum

48. Which method may a technician use to bring an R-123 chiller up to 0 psig before a non-major repair?

  1. A Controlled hot water or a built-in heating device such as Prevac
  2. B Dry nitrogen from a regulated cylinder, with the nitrogen purged afterward
  3. C Compressed shop air fed through the purge connection
  4. D Carbon dioxide from a cylinder, purged afterward

49. Why does 40 CFR 82.156(a)(1)(ii) let an R-113 machine finish pressurizing with nitrogen before a non-major repair, but bar nitrogen for the same job on R-11 and R-123 machines?

  1. A R-113 is not an ozone-depleting refrigerant
  2. B R-113 boils above 85 °F at atmospheric pressure; R-11 and R-123 do not
  3. C R-113 machines always hold less than 200 pounds, so less refrigerant is at risk
  4. D Nitrogen reacts chemically with R-11 and R-123

50. A leaking evaporator on an R-11 chiller cannot reach 25 mm Hg absolute without pulling in enough air to badly contaminate the refrigerant. What is the highest pressure the leaking component may be left at before it is opened?

  1. A 0 psig
  2. B 5 psig
  3. C 10 psig
  4. D 15 inches of Hg vacuum

51. On a leaking R-123 chiller, the condenser can be valved off from the leaking evaporator and does not leak itself. If the condenser is to be opened, to what level must it be evacuated?

  1. A 25 mm Hg absolute
  2. B 0 psig, the same as the leaking evaporator
  3. C 10 inches of Hg vacuum
  4. D No evacuation is needed once it is isolated

52. How does the required evacuation level for disposing of an R-123 chiller compare with the level for a major repair on the same chiller?

  1. A Disposal is stricter: 500 microns
  2. B Disposal is looser: 0 psig
  3. C They are the same: 25 mm Hg absolute
  4. D Disposal is looser: 10 inches of Hg vacuum

53. After pulling an R-11 chiller down to 25 mm Hg absolute, a technician valves off the recovery unit and waits. Within a few minutes the pressure in the chiller starts to rise. What does this most likely mean?

  1. A Liquid refrigerant is still boiling off in the chiller or its oil
  2. B The recovery unit has tripped its high-pressure cut-out
  3. C The purge unit is feeding air back into the shell through its vent line
  4. D The reading is normal and the chiller can be opened

54. Before servicing a low-pressure chiller, a technician wants to drain the oil only. If this is not a major repair, what is the highest pressure the chiller or isolated section may be at when it is opened for the oil change?

  1. A 0 psig
  2. B 10 psig
  3. C 5 psig
  4. D 15 psig

55. What must a technician do after recovering refrigerant from an R-123 chiller and before opening it for a major repair?

  1. A Get written permission from the building owner
  2. B Send a sample of the recovered refrigerant to a lab for analysis
  3. C Verify the required evacuation level has been reached
  4. D Notify EPA within 30 days of the repair

56. Instead of evacuating an entire R-11 chiller, may a technician evacuate only the section being serviced?

  1. A No, the whole chiller must always be evacuated before it is opened
  2. B Only if the chiller holds less than 200 pounds
  3. C Only if the recovery unit was made before 1993
  4. D Yes, if its refrigerant can be isolated in a system receiver

57. A shop buys a new recovery machine in 2025 to use on R-123 chillers. What must be true of the machine?

  1. A It is approved by the chiller manufacturer
  2. B It is certified by an EPA-approved equipment testing organization
  3. C It is registered with EPA by the technician
  4. D It is certified by the organization that tested and certified the technician

58. Which of these repairs on an R-123 chiller is not a major repair under 40 CFR 82.152?

  1. A Removing the compressor for a rebuild
  2. B Removing an auxiliary heat exchange coil
  3. C Uncovering a 6-square-inch opening for 30 minutes
  4. D Uncovering a 3-square-inch opening for 20 minutes

59. During a non-major repair on a low-pressure chiller pressurized to 0 psig, the section being worked on cannot be isolated from the rest of the machine. What does 40 CFR 82.156(a)(1)(ii) require?

  1. A Run the purge unit for the whole repair
  2. B Raise the pressure to 10 psig first
  3. C Shut off all water flow through the tubes
  4. D Cover the openings

60. Using recovery equipment made in 2021, what levels apply before major repairs on a 300-pound R-123 chiller and a 300-pound R-134a chiller?

  1. A 25 mm Hg absolute for the R-123; 15 inches of Hg vacuum for the R-134a
  2. B 25 mm Hg absolute for both chillers
  3. C 15 inches of Hg vacuum for both chillers
  4. D 10 inches of Hg vacuum for the R-123; 25 mm Hg absolute for the R-134a

61. The low-pressure evacuation level is given as 25 mm Hg absolute. What is "absolute" pressure measured from?

  1. A Local atmospheric pressure
  2. B The refrigerant's saturation pressure
  3. C A perfect vacuum
  4. D The chiller's normal operating pressure

Refrigeration

62. What is the main job of the purge unit on a low-pressure chiller?

  1. A Remove oil from the refrigerant
  2. B Add refrigerant when the charge is low
  3. C Pump down the evaporator for service
  4. D Remove air and other noncondensables

63. Why does air get into R-11 and R-123 chillers when it does not get into an R-410A system?

  1. A R-11 and R-123 absorb air from the oil and release it in the condenser
  2. B Low-pressure chillers have no sealed joints
  3. C Air is carried in with the chilled water
  4. D Parts of the low-pressure chiller run below atmospheric pressure

64. From which part of a low-pressure chiller does the purge unit normally draw its sample?

  1. A The top of the condenser
  2. B The bottom of the evaporator
  3. C The compressor oil sump
  4. D The chilled-water return line

65. What happens to an R-123 chiller when air builds up in it?

  1. A Condensing pressure falls and capacity rises
  2. B Condensing pressure rises and efficiency drops
  3. C Evaporator pressure rises above atmospheric
  4. D Nothing changes until the air reaches the compressor

66. At standard atmospheric pressure, R-123 boils at about what temperature?

  1. A -41 °F
  2. B 82 °F
  3. C -15 °F
  4. D 118 °F

67. An idle R-11 chiller sits in a 70 °F equipment room, with the refrigerant at room temperature. What pressure would the shell be at?

  1. A Slightly below atmospheric, a small vacuum
  2. B About 70 psig
  3. C Exactly 0 psig, as for any idle chiller
  4. D About 15 psig, the rupture disc setting

68. During normal operation, which part of an R-123 chiller is most likely to be above atmospheric pressure?

  1. A The evaporator
  2. B The compressor suction
  3. C The condenser
  4. D The cooler liquid line

69. Besides air itself, what harmful contaminant comes into a low-pressure chiller when room air leaks in through a joint on its vacuum side?

  1. A Moisture from the surrounding air
  2. B Compressor oil from other machines
  3. C Carbon dioxide that freezes in the tubes
  4. D Higher-pressure refrigerant such as R-22

Safety

70. According to EPA's test topics on ASHRAE Standard 15, what sensor is needed in a chiller equipment room whatever refrigerant is used?

  1. A A carbon monoxide detector
  2. B An oxygen-deprivation sensor
  3. C A smoke detector
  4. D A humidity sensor

71. Under ASHRAE Standard 15, what device must an equipment room with an R-123 chiller have?

  1. A A sprinkler head above the chiller
  2. B A floor drain beside the rupture disc
  3. C A carbon dioxide extinguisher
  4. D A refrigerant sensor that detects R-123

72. Why does an R-123 equipment room need a refrigerant sensor and not just an oxygen-deprivation sensor?

  1. A R-123 is flammable in normal room air
  2. B R-123 is lighter than air and rises out of reach of the oxygen sensor
  3. C Oxygen sensors do not work in chiller rooms
  4. D R-123 can harm people at levels far too low to cut oxygen

73. After a large R-11 leak in an equipment room, where is the refrigerant vapor most likely to collect?

  1. A Near the ceiling
  2. B Evenly through the room within seconds
  3. C Only inside the chiller cabinet
  4. D Near the floor and in pits or low spots

74. A technician will raise an R-113 machine's pressure with nitrogen for a leak test. What must be on the nitrogen cylinder?

  1. A A check valve and nothing else
  2. B A flow meter set to the chiller tonnage
  3. C A pressure regulator, with a relief valve downstream
  4. D No fittings; open the cylinder valve slowly

75. Why must the hot water used to pressurize an R-11 chiller for a leak test be controlled?

  1. A Too much heat could raise pressure past the rupture disc setting
  2. B Hot water can cause the R-11 to ignite
  3. C Hot water dissolves the tube coatings
  4. D Hot water turns R-11 into a toxic decomposition gas above about 100 °F

Answer key

Leak detection

1. A technician needs to raise the pressure inside an idle R-123 chiller to leak test it. Which method should be tried first?
  • Hot water in the tubes or a built-in heater such as PrevacCorrect answer
  • Dry nitrogen fed straight into the shell from a regulated cylinder
  • A trace of R-22 pushed with nitrogen
  • Compressed air from the shop line

Why “Hot water in the tubes or a built-in heater such as Prevac” is correct

EPA's test topics put heating first for low-pressure systems: run hot water through the tubes or use a built-in heating and pressurization device such as Prevac. Warming the refrigerant raises its own pressure, so nothing has to be purged out afterward. Nitrogen comes second.

Source: EPA: Test Topics

Why the other answers are wrong

  • Dry nitrogen fed straight into the shell from a regulated cylinder — Nitrogen is the second choice, used only when heating cannot raise the pressure enough.
  • A trace of R-22 pushed with nitrogen — Trace gas with nitrogen is a high-pressure leak test practice, not the first choice for a low-pressure chiller.
  • Compressed air from the shop line — Compressed air brings in moisture and noncondensables and is not a leak test gas for chillers.
2. Why must an idle low-pressure chiller usually be brought above atmospheric pressure before it is leak tested?
  • Leak detectors only work above 15 psig
  • EPA requires every low-pressure leak test to be done at exactly 10 psig
  • R-123 cannot be detected while it is a liquid
  • Below atmosphere, leaks pull air in instead of pushing refrigerant outCorrect answer

Why “Below atmosphere, leaks pull air in instead of pushing refrigerant out” is correct

At room temperature an R-11 or R-123 chiller sits near or below atmospheric pressure. Any leak then draws air inward, so there is no refrigerant escaping for a detector or bubble solution to find. Raising the internal pressure slightly above atmosphere makes the leaks push refrigerant out where they can be located.

Source: EPA: Test Topics

Why the other answers are wrong

  • Leak detectors only work above 15 psig — Detectors do not need 15 psig, and that pressure would be unsafe on a low-pressure chiller.
  • EPA requires every low-pressure leak test to be done at exactly 10 psig — No rule sets a leak test pressure; 10 psig is a maximum, not a required value.
  • R-123 cannot be detected while it is a liquid — The issue is the direction of flow through the leak, not the state of the refrigerant.
3. Which sign most strongly suggests a leak in an operating R-11 centrifugal chiller?
  • High superheat with oil stains on a hermetic compressor
  • Frost forming on the liquid line
  • Chilled water leaving colder than its set point
  • The purge unit runs much more than usualCorrect answer

Why “The purge unit runs much more than usual” is correct

Most of a low-pressure chiller runs below atmospheric pressure, so leaks let air in rather than letting refrigerant out. The purge unit has to run to remove that air, so excessive purging is the main warning sign of a leak.

Source: EPA: Test Topics

Why the other answers are wrong

  • High superheat with oil stains on a hermetic compressor — Those are typical leak signs on high-pressure systems, not the classic low-pressure sign.
  • Frost forming on the liquid line — Frost on a liquid line points to a restriction, not to air leaking into a low-pressure chiller.
  • Chilled water leaving colder than its set point — Overcooling is a control issue and does not indicate a refrigerant leak.
4. Why does a leak in a low-pressure chiller make the purge unit work harder?
  • Refrigerant escaping out through the leak forces the purge to make up the loss
  • The leak lowers the oil level, starving the purge pump
  • The leak raises evaporator pressure above atmospheric
  • Air drawn in through the leak collects as noncondensables to be purgedCorrect answer

Why “Air drawn in through the leak collects as noncondensables to be purged” is correct

Air and moisture enter wherever the machine is below atmospheric pressure. The air does not condense, so it gathers in the condenser and the purge unit must remove it. The more air that leaks in, the more often the purge runs.

Source: EPA: Test Topics

Why the other answers are wrong

  • Refrigerant escaping out through the leak forces the purge to make up the loss — The purge handles noncondensables entering the machine, not refrigerant escaping it.
  • The leak lowers the oil level, starving the purge pump — The purge unit does not depend on the chiller oil level.
  • The leak raises evaporator pressure above atmospheric — A leak into a vacuum side does not raise the evaporator above atmosphere.
5. What is the highest pressure normally used when leak testing a low-pressure centrifugal chiller?
  • 0 psig
  • 15 psig
  • 10 psigCorrect answer
  • 30 psig

Why “10 psig” is correct

EPA's test topics ask for the maximum leak test pressure without giving a number, and trade training teaches 10 psig. Low-pressure chiller shells are protected by a rupture disc, which on Trane CenTraVac chillers breaks at 15 psig, so staying at or under 10 psig keeps a margin below it. Some manufacturers set a lower limit (Trane specifies 8 psig of dry nitrogen), and the unit's own manual governs.

Source: EPA: Test Topics; Trane CVHE-SVX005E-EN, CenTraVac IOM (15 psig rupture disk); Trane CTV-SVX05H-EN, R-123 handling guide (8 psig leak test)

Why the other answers are wrong

  • 0 psig — 0 psig is atmospheric pressure, which is not enough to push refrigerant out through a leak.
  • 15 psig — 15 psig is a common rupture disc setting, so testing there risks bursting the disc.
  • 30 psig — 30 psig is well beyond what a low-pressure chiller shell is protected for.
6. Why should a technician not go above 10 psig when leak testing an R-123 chiller?
  • To stay safely below the rupture disc settingCorrect answer
  • Nitrogen dissolves into R-123 above 10 psig
  • Table 1 caps test pressures at 10 psig
  • The purge unit shuts down above 10 psig

Why “To stay safely below the rupture disc setting” is correct

Low-pressure chiller shells are built for low pressures and protected by a rupture disc, which on Trane CenTraVac chillers breaks at 15 psig. Pushing a test past 10 psig risks blowing the disc and releasing the whole charge, so 10 psig is the commonly taught ceiling. A manufacturer may set a lower one, such as Trane's 8 psig.

Source: EPA: Test Topics; Trane CVHE-SVX005E-EN, CenTraVac IOM (15 psig rupture disk); Trane CTV-SVX05H-EN, R-123 handling guide (8 psig leak test)

Why the other answers are wrong

  • Nitrogen dissolves into R-123 above 10 psig — Dissolving nitrogen is not why the limit exists.
  • Table 1 caps test pressures at 10 psig — Table 1 sets evacuation levels, not leak test pressures.
  • The purge unit shuts down above 10 psig — The purge unit is not the reason for the test pressure limit.
7. An 800-pound R-123 chiller cooling an office building has leaked above the 10% rate. Under 40 CFR 82.157(g), how often must leak inspections be done?
  • Once per calendar year, until it stays under the rate for one yearCorrect answer
  • Once every three months, until four quarters in a row are under the rate
  • Once a month, until the chiller is retired
  • Only once, right after the repair

Why “Once per calendar year, until it stays under the rate for one year” is correct

For comfort cooling and other appliances, 40 CFR 82.157(g)(1)(iii) calls for a leak inspection once per calendar year after the appliance exceeds its leak rate. The inspections continue until leak rate calculations show it has not exceeded the rate for one year.

Source: 40 CFR 82.157(g)

Why the other answers are wrong

  • Once every three months, until four quarters in a row are under the rate — Quarterly inspections apply to commercial and industrial process refrigeration of 500 pounds or more, not comfort cooling.
  • Once a month, until the chiller is retired — No monthly schedule appears in the rule.
  • Only once, right after the repair — The rule requires inspections to continue until the appliance has stayed under its leak rate for a year.
8. Who must perform the leak inspections required on a low-pressure chiller that has exceeded its leak rate?
  • Any building employee with a leak detector
  • An EPA inspector, on a set schedule
  • The chiller manufacturer, under warranty
  • A certified technician, using methods suited to that applianceCorrect answer

Why “A certified technician, using methods suited to that appliance” is correct

40 CFR 82.157(g)(2) says leak inspections must be done by a certified technician using methods the technician judges appropriate for that appliance. The technician then gives the owner documentation of the results.

Source: 40 CFR 82.157(g)

Why the other answers are wrong

  • Any building employee with a leak detector — The rule calls for a certified technician, not just anyone with a detector.
  • An EPA inspector, on a set schedule — EPA does not perform the owner's required leak inspections.
  • The chiller manufacturer, under warranty — The rule does not require the manufacturer to do the inspection.
9. Which method, used by itself, does not meet EPA's definition of a leak inspection on an R-11 chiller?
  • An electronic leak detector
  • A standing vacuum decay testCorrect answer
  • A bubble test at the joints
  • An ultrasonic leak test

Why “A standing vacuum decay test” is correct

A leak inspection must find where the leaks are. Methods that only show that the appliance is leaking, such as standing pressure or vacuum decay tests, must be paired with a method that locates the leak, like an electronic detector, bubble test or ultrasonic test.

Source: 40 CFR 82.152

Why the other answers are wrong

  • An electronic leak detector — A properly maintained detector can locate leaks, so it qualifies.
  • A bubble test at the joints — Bubble tests locate leaks and are listed as a potential method.
  • An ultrasonic leak test — Ultrasonic testing is named in the definition as a method that can locate leaks.
10. An R-11 chiller with 500 pounds of refrigerant is a "chronically leaking appliance" if it leaks what share of its full charge in one calendar year?
  • 100 percent or more
  • 50 percent or more
  • 125 percent or moreCorrect answer
  • 30 percent or more

Why “125 percent or more” is correct

Under 40 CFR 82.157(j), owners of appliances with 50 pounds or more of refrigerant that leak 125 percent or more of the full charge in a calendar year must report to EPA. For this chiller that means losing 625 pounds or more in a year.

Source: 40 CFR 82.157(j)

Why the other answers are wrong

  • 100 percent or more — Losing the whole charge once is serious, but the reporting trigger is 125 percent.
  • 50 percent or more — 50 percent is far below the chronic leaker threshold.
  • 30 percent or more — 30 percent is the industrial process refrigeration leak rate, not the chronic leaker trigger.
11. An R-123 chiller leaked 140 percent of its full charge during 2025. What must the owner do?
  • Report to EPA within 30 days of the chiller reaching 125 percent of its charge
  • Report to EPA by December 31, 2025, with a retirement date
  • Report to EPA by March 1, 2026, describing efforts to find and fix leaksCorrect answer
  • Keep records on site; no report is needed unless EPA asks

Why “Report to EPA by March 1, 2026, describing efforts to find and fix leaks” is correct

Chronically leaking appliances, those losing 125 percent or more of full charge in a calendar year, trigger a report to EPA. 40 CFR 82.157(j) requires it by March 1 of the following year, describing the efforts made to identify leaks and repair the appliance.

Source: 40 CFR 82.157(j); 40 CFR 82.157(m)

Why the other answers are wrong

  • Report to EPA within 30 days of the chiller reaching 125 percent of its charge — The report is annual, due by March 1 of the following year.
  • Report to EPA by December 31, 2025, with a retirement date — The deadline is March 1 of the next year, and the report describes leak repair efforts.
  • Keep records on site; no report is needed unless EPA asks — Chronic leakers must submit a report; on-site records alone are not enough.
12. An owner monitors an R-11 chiller with an automatic leak detection system instead of doing the required leak inspections. How often must the system be audited or calibrated?
  • Once a yearCorrect answer
  • Once a month
  • Every three years
  • Only when it is first installed

Why “Once a year” is correct

40 CFR 82.157(g)(4) waives the quarterly or annual leak inspections on parts of an appliance that are continuously monitored by an automatic leak detection system. That system must be audited or calibrated annually, and the owner keeps records of it.

Source: 40 CFR 82.157(g)

Why the other answers are wrong

  • Once a month — The rule requires an annual audit or calibration, not monthly.
  • Every three years — Three years is too long; the rule says annually.
  • Only when it is first installed — A one-time setup is not enough; the system must be audited or calibrated every year.
13. How does running warm water through the tubes raise the pressure inside an idle R-11 chiller?
  • Warming the refrigerant raises its saturation pressureCorrect answer
  • The water mixes with the refrigerant and adds volume
  • The warm water drives the compressor to build pressure
  • The heat condenses air out of the shell

Why “Warming the refrigerant raises its saturation pressure” is correct

A refrigerant's pressure follows its temperature. Warming the R-11 in the shell boils more of it into vapor and lifts the pressure above atmospheric, so leaks push refrigerant outward. This is why controlled hot water is the preferred way to pressurize a low-pressure chiller.

Source: EPA: Test Topics

Why the other answers are wrong

  • The water mixes with the refrigerant and adds volume — The water stays inside the tubes and never mixes with the refrigerant.
  • The warm water drives the compressor to build pressure — The compressor is off; the pressure comes from the refrigerant itself.
  • The heat condenses air out of the shell — Heat does not condense air; it boils more refrigerant into vapor.
14. Why is heating the refrigerant preferred over nitrogen for pressurizing an R-123 chiller for a leak test?
  • Nitrogen reacts with R-123 to form acids
  • Nitrogen must be purged out later, and refrigerant goes with itCorrect answer
  • Nitrogen cannot raise the pressure of a chiller above atmospheric
  • Hot water finds leaks by changing the water color

Why “Nitrogen must be purged out later, and refrigerant goes with it” is correct

Any nitrogen added to a low-pressure chiller stays as a noncondensable gas and has to be purged out afterward, and some refrigerant goes with it. Heating the refrigerant raises pressure without adding anything that must be removed, which is why EPA ranks hot water and devices like Prevac ahead of nitrogen.

Source: EPA: Test Topics; 40 CFR 82.156(a)(1)(ii)

Why the other answers are wrong

  • Nitrogen reacts with R-123 to form acids — Nitrogen is inert and does not react with R-123.
  • Nitrogen cannot raise the pressure of a chiller above atmospheric — Nitrogen can easily raise pressure; the problem is getting it back out.
  • Hot water finds leaks by changing the water color — Hot water only raises pressure; it does not mark leaks.

Leak repair requirements

15. An R-123 centrifugal chiller with 900 pounds of charge cools an office tower. Under 40 CFR Part 82, above what annual leak rate must it be repaired?
  • 20 percent
  • 30 percent
  • 35 percent
  • 10 percentCorrect answer

Why “10 percent” is correct

Comfort cooling appliances, and other appliances with 50 pounds or more of an ozone-depleting refrigerant not otherwise covered, have a 10 percent leak rate under 40 CFR 82.157(c)(2)(iii). Chillers serving offices are comfort cooling.

Source: 40 CFR 82.157(c); EPA: Leak Repair Requirements

Why the other answers are wrong

  • 20 percent — 20 percent applies to commercial refrigeration, not comfort cooling.
  • 30 percent — 30 percent applies to industrial process refrigeration.
  • 35 percent — 35 percent is not a leak rate in the current rule.
16. An owner runs a 400-pound R-123 system in a cold-storage warehouse for perishable food. Under 40 CFR Part 82, what is its leak rate?
  • 10 percent
  • 30 percent
  • 15 percent
  • 20 percentCorrect answer

Why “20 percent” is correct

EPA classes cold-storage warehouse equipment as commercial refrigeration. Commercial refrigeration appliances with 50 pounds or more of an ozone-depleting refrigerant have a 20 percent leak rate.

Source: 40 CFR 82.157(c); EPA: Leak Repair Requirements

Why the other answers are wrong

  • 10 percent — 10 percent applies to comfort cooling and other appliances.
  • 30 percent — 30 percent is for industrial process refrigeration.
  • 15 percent — 15 percent is not a leak rate in Part 82.
17. A 700-pound R-11 chiller cools reactors at a pharmaceutical plant. Under 40 CFR Part 82, what is its leak rate?
  • 10 percent
  • 30 percentCorrect answer
  • 20 percent
  • 125 percent

Why “30 percent” is correct

Equipment directly linked to industrial processes, such as chemical and pharmaceutical manufacturing, is industrial process refrigeration. Its leak rate under 40 CFR 82.157(c)(2)(ii) is 30 percent.

Source: 40 CFR 82.157(c); EPA: Leak Repair Requirements

Why the other answers are wrong

  • 10 percent — 10 percent is the comfort cooling rate.
  • 20 percent — 20 percent is the commercial refrigeration rate.
  • 125 percent — 125 percent is the chronic leaker reporting threshold, not a repair trigger.
18. A technician adds refrigerant to a 600-pound R-123 comfort cooling chiller and the calculation shows it is over its leak rate. No process shutdown is involved. How long does the owner have to repair the leaks?
  • 14 days
  • 30 daysCorrect answer
  • 90 days
  • 120 days

Why “30 days” is correct

40 CFR 82.157(d) gives owners 30 days from when refrigerant is added to an appliance exceeding its leak rate to identify and repair the leaks. The longer 120-day period applies only when an industrial process shutdown is required.

Source: 40 CFR 82.157(d); EPA: Leak Repair Requirements

Why the other answers are wrong

  • 14 days — 14 days is shorter than the rule requires.
  • 90 days — 90 days is not the repair deadline in the rule.
  • 120 days — 120 days applies only when an industrial process shutdown is needed.
19. Fixing the leaks on an R-11 process chiller will require shutting down the industrial process it serves. How long does the owner have to complete repairs?
  • 30 days
  • 60 days
  • 120 daysCorrect answer
  • One year

Why “120 days” is correct

When an industrial process shutdown is needed to make the repair, 40 CFR 82.157(d) substitutes 120 days for the usual 30-day repair period. The same 120-day window applies to the initial verification test.

Source: 40 CFR 82.157(d); EPA: Leak Repair Requirements

Why the other answers are wrong

  • 30 days — 30 days is the normal deadline when no process shutdown is needed.
  • 60 days — 60 days is not a repair period in the rule.
  • One year — One year is the time to carry out a retrofit or retirement plan, not to repair leaks.
20. After a successful initial verification test on a repaired R-123 chiller that was not evacuated, how soon must the follow-up verification test be done?
  • Within 30 days
  • Within 10 daysCorrect answer
  • Within 24 hours
  • Within 12 months

Why “Within 10 days” is correct

40 CFR 82.157(e)(2) requires a follow-up verification test within 10 days of the successful initial test. If the appliance was evacuated for the repair, the 10 days run from when it reaches normal operating conditions.

Source: 40 CFR 82.157(e)

Why the other answers are wrong

  • Within 30 days — 30 days is the repair deadline, not the follow-up test window.
  • Within 24 hours — The rule allows 10 days, not one day.
  • Within 12 months — 12 months relates to presuming leaks repaired, not to follow-up testing.
21. A leak repair on an R-11 chiller required evacuating the machine. When must the initial verification test be performed?
  • After the full charge has been restored
  • Before any refrigerant is added backCorrect answer
  • Within one year of the repair
  • Only after the follow-up test passes

Why “Before any refrigerant is added back” is correct

When a repair requires evacuating the appliance or part of it, 40 CFR 82.157(e)(1)(ii) says the initial verification test must be done before adding any refrigerant. That proves the repaired leaks hold before charge goes back in.

Source: 40 CFR 82.157(e)

Why the other answers are wrong

  • After the full charge has been restored — For evacuated repairs the test comes before charging, not after.
  • Within one year of the repair — The initial test is due within the 30-day (or 120-day) repair window.
  • Only after the follow-up test passes — The initial test comes first; the follow-up test comes after it.
22. When must the owner of a 1,000-pound R-123 chiller calculate its leak rate?
  • Every time refrigerant is added, with a few exceptionsCorrect answer
  • Once each calendar year
  • Only when the purge unit runs excessively
  • Only when the charge falls below half

Why “Every time refrigerant is added, with a few exceptions” is correct

Under 40 CFR 82.157(b), the owner must calculate the leak rate every time refrigerant is added, unless the addition follows a retrofit, a new installation, or qualifies as a seasonal variance. The technician who adds refrigerant supplies the records needed for that calculation.

Source: 40 CFR 82.157(b)

Why the other answers are wrong

  • Once each calendar year — The calculation is tied to each refrigerant addition, not to the calendar.
  • Only when the purge unit runs excessively — Excessive purging is a warning sign, but it is not what triggers the calculation.
  • Only when the charge falls below half — The rule does not wait for the charge to drop by half.
23. The owner of a leaking R-11 chiller decides to retire it instead of repairing it. What are the deadlines for the retirement plan?
  • Write the plan within 60 days; finish the work within two years
  • Write the plan within 30 days; finish the work within six months
  • Write the plan within one year; finish the work within five years
  • Write the plan within 30 days; finish the work within one yearCorrect answer

Why “Write the plan within 30 days; finish the work within one year” is correct

40 CFR 82.157(h) requires a retrofit or retirement plan within 30 days of the appliance exceeding its leak rate when the owner chooses not to repair. The work must be finished within one year of the plan's date unless EPA grants more time.

Source: 40 CFR 82.157(h); EPA: Leak Repair Requirements

Why the other answers are wrong

  • Write the plan within 60 days; finish the work within two years — Both periods are too long; the rule allows 30 days and one year.
  • Write the plan within 30 days; finish the work within six months — The work may take up to one year from the plan date, not six months.
  • Write the plan within one year; finish the work within five years — These periods are far longer than the rule allows.
24. A 900-pound centrifugal chiller uses R-245fa, an HFC. Do the 40 CFR 82.157 leak repair rules apply to it?
  • Yes; every low-pressure chiller holding over 50 pounds is covered by section 82.157
  • Yes, but only if the chiller serves an industrial process
  • No; it covers only ozone-depleting refrigerants, and HFCs fall under Part 84Correct answer
  • No; low-pressure chillers are exempt from all leak repair rules

Why “No; it covers only ozone-depleting refrigerants, and HFCs fall under Part 84” is correct

Since 2020, 40 CFR 82.157 applies only to appliances with 50 pounds or more of an ozone-depleting (class I or II) refrigerant, such as R-11 or R-123. A chiller like this, with 15 pounds or more of an HFC like R-245fa, is covered instead by the separate leak repair rule in 40 CFR 84.106.

Source: 40 CFR 82.157(a); 40 CFR 84.106

Why the other answers are wrong

  • Yes; every low-pressure chiller holding over 50 pounds is covered by section 82.157 — 82.157 applies only to appliances with 50 pounds or more of a class I or class II refrigerant.
  • Yes, but only if the chiller serves an industrial process — The use of the chiller does not bring an HFC appliance under 82.157.
  • No; low-pressure chillers are exempt from all leak repair rules — HFC appliances of 15 pounds or more, other than residential and light commercial air conditioning, have their own leak repair rules under 40 CFR Part 84.
25. When may refrigerant released by a chiller's purge unit be left out of the annual leak rate calculation?
  • When the purge unit is a high-efficiency model approved by the manufacturer
  • When less than 1 pound is purged each month
  • When it is destroyed at a verified efficiency of 98 percent or moreCorrect answer
  • When the chiller holds less than 500 pounds

Why “When it is destroyed at a verified efficiency of 98 percent or more” is correct

40 CFR 82.157(k) lets owners exclude purged refrigerant from the leak rate only when it is destroyed at a verifiable destruction efficiency of 98 percent or greater. The owner must keep monitoring records and notify EPA the first time the exclusion is used.

Source: 40 CFR 82.157(k); 40 CFR 82.157(l)

Why the other answers are wrong

  • When the purge unit is a high-efficiency model approved by the manufacturer — A high-efficiency purge reduces losses, but only destroyed refrigerant can be excluded.
  • When less than 1 pound is purged each month — There is no small-quantity exclusion for purged refrigerant.
  • When the chiller holds less than 500 pounds — Charge size does not decide whether purged refrigerant counts.
26. The owner of an R-123 chiller leaking above its rate has its refrigerant recovered and shuts the chiller down for the winter. What happens to the 30-day repair deadline?
  • It is automatically extended to 120 days
  • It is suspended until refrigerant is added backCorrect answer
  • It is cancelled and never resumes
  • It keeps running while the chiller is off

Why “It is suspended until refrigerant is added back” is correct

Evacuating an appliance to at least atmospheric pressure and temporarily shutting it down is "mothballing." Under 40 CFR 82.157(d)(3), the repair time frames are suspended while mothballed and resume on the day refrigerant is added again.

Source: 40 CFR 82.157(d); 40 CFR 82.152; EPA: Leak Repair Requirements

Why the other answers are wrong

  • It is automatically extended to 120 days — The 120-day period is for industrial process shutdowns, not mothballing.
  • It is cancelled and never resumes — The clock picks up again when the appliance gets refrigerant back.
  • It keeps running while the chiller is off — Mothballing suspends the time frames.
27. A technician adds 45 pounds of R-123 to a 700-pound chiller. What must the technician give the owner when the service is finished?
  • A copy of the technician's card, sent on to EPA
  • Nothing; the owner keeps all records alone
  • A record that includes the amount and type of refrigerant addedCorrect answer
  • A reclamation certificate showing the added refrigerant meets AHRI 700

Why “A record that includes the amount and type of refrigerant added” is correct

40 CFR 82.157(b) and (l)(2) require anyone adding or removing refrigerant on an appliance of 50 pounds or more to give the owner a record of the service. It includes the appliance, date, work done, the technician's name, and the amount and type of refrigerant added.

Source: 40 CFR 82.157(b); 40 CFR 82.157(l)

Why the other answers are wrong

  • A copy of the technician's card, sent on to EPA — Certification cards are not sent to EPA after service.
  • Nothing; the owner keeps all records alone — The technician must provide the service record to the owner.
  • A reclamation certificate showing the added refrigerant meets AHRI 700 — Reclamation certificates are not part of the service record the rule requires.
28. After leaks on an R-11 chiller are repaired, when are they presumed repaired under 40 CFR 82.157(d)?
  • As soon as the initial verification test passes
  • After 30 days of normal operation
  • If no more refrigerant is added for 12 monthsCorrect answer
  • When purge run time returns to normal

Why “If no more refrigerant is added for 12 months” is correct

The rule says leaks will be presumed repaired if there is no further refrigerant addition for 12 months after the repair, or if the required leak inspections find no leaks. Otherwise the next leak rate calculation must confirm the rate is below the trigger.

Source: 40 CFR 82.157(d)

Why the other answers are wrong

  • As soon as the initial verification test passes — Passing the initial test is required, but it is not the presumption in the rule.
  • After 30 days of normal operation — 30 days is the repair deadline, not the presumption period.
  • When purge run time returns to normal — Purge run time is a useful sign but is not the legal test.

Recovery techniques

29. A technician is starting recovery on a 1,000-pound R-123 chiller. Which should be removed first?
  • The refrigerant vapor
  • The liquid refrigerantCorrect answer
  • The noncondensable gases
  • The compressor oil

Why “The liquid refrigerant” is correct

Most of a chiller's charge sits in the shell as liquid. Moving that liquid out first removes the bulk of the refrigerant quickly; the remaining vapor is recovered afterward.

Source: EPA: Test Topics

Why the other answers are wrong

  • The refrigerant vapor — Vapor recovery comes after the liquid has been removed.
  • The noncondensable gases — Noncondensables are handled by the purge, not removed first during recovery.
  • The compressor oil — Oil removal is a separate step and is not how recovery begins.
30. After all the liquid has been removed from a large R-11 chiller, why must the technician still run vapor recovery?
  • A large amount of refrigerant remains as vapor in the shellsCorrect answer
  • The vapor may be vented once the liquid is out
  • The vapor is mostly air and must be checked
  • Vapor recovery is only needed on R-123 chillers, not on R-11 chillers

Why “A large amount of refrigerant remains as vapor in the shells” is correct

A big chiller has a lot of internal volume, so many pounds of refrigerant are still present as vapor after the liquid is gone. Vapor recovery must continue until the appliance reaches 25 mm Hg absolute.

Source: EPA: Test Topics; 40 CFR 82.156(a), Table 1

Why the other answers are wrong

  • The vapor may be vented once the liquid is out — Venting refrigerant vapor is prohibited.
  • The vapor is mostly air and must be checked — The vapor is refrigerant, not mostly air.
  • Vapor recovery is only needed on R-123 chillers, not on R-11 chillers — Both refrigerants need vapor recovery to reach 25 mm Hg absolute.
31. To what temperature should the oil in a low-pressure chiller be heated before it is drained?
  • 85 °F
  • 130 °FCorrect answer
  • 50 °F
  • 180 °F

Why “130 °F” is correct

EPA's test topics call for heating the oil to 130 °F before removing it. Warm oil holds less dissolved refrigerant, so less refrigerant leaves with the oil.

Source: EPA: Test Topics

Why the other answers are wrong

  • 85 °F — 85 °F is the boiling-point line used in the pressurization rule, not the oil temperature.
  • 50 °F — 50 °F is too cool; the oil would still hold a lot of refrigerant.
  • 180 °F — 180 °F is hotter than the accepted practice.
32. Why is the oil in an R-123 chiller heated before it is removed?
  • Warm oil releases dissolved refrigerant, so less escapes with itCorrect answer
  • Heating destroys acid so the oil can be reused
  • Heating raises the shell pressure to the 5 psig limit for oil changes
  • Heating boils water out of the oil for disposal

Why “Warm oil releases dissolved refrigerant, so less escapes with it” is correct

Refrigerant dissolves in chiller oil, and cold oil holds more of it. Heating the oil to about 130 °F drives the refrigerant out so it can be recovered rather than released when the oil is drained.

Source: EPA: Test Topics; EPA: Service Practice Requirements

Why the other answers are wrong

  • Heating destroys acid so the oil can be reused — Heating oil does not neutralize acid.
  • Heating raises the shell pressure to the 5 psig limit for oil changes — The 5 psig limit is a maximum, not a target the oil must reach.
  • Heating boils water out of the oil for disposal — The purpose is to drive refrigerant out of the oil, not water.
33. Why should water be kept circulating through the tubes of a chiller while its refrigerant is being evacuated?
  • To keep the purge unit running during recovery
  • To keep the water in the tubes from freezingCorrect answer
  • To cool the recovery unit's compressor
  • To stop the oil from foaming in the sump

Why “To keep the water in the tubes from freezing” is correct

As pressure drops during evacuation, the remaining refrigerant boils at lower and lower temperatures and can chill the tubes below 32 °F. Circulating the water, or draining it, prevents the water from freezing and cracking the tubes.

Source: EPA: Test Topics

Why the other answers are wrong

  • To keep the purge unit running during recovery — The purge unit does not depend on water flow in the tubes.
  • To cool the recovery unit's compressor — The chiller tube water does not cool the recovery machine.
  • To stop the oil from foaming in the sump — Oil foaming is not the reason for circulating water.
34. At what pressure is the high-pressure cut-out typically set on a recovery device used with low-pressure appliances?
  • 10 psigCorrect answer
  • 5 psig
  • 15 psig
  • 35 psig

Why “10 psig” is correct

EPA's test topics ask for this cut-out level, and trade training gives it as 10 psig. The low setting keeps the recovery unit from pushing a chiller or low-pressure recovery vessel toward its rupture disc, which is commonly set at 15 psig. Recovery units built for higher-pressure refrigerants cut out at hundreds of psig.

Source: EPA: Test Topics; Trane CVHE-SVX005E-EN, CenTraVac IOM (15 psig rupture disk)

Why the other answers are wrong

  • 5 psig — 5 psig is the oil-change limit in the regulation, not the cut-out setting.
  • 15 psig — 15 psig is the typical rupture disc setting that the cut-out is meant to stay below, not the cut-out itself.
  • 35 psig — 35 psig is far above the setting used for low-pressure recovery.

Recharging techniques

35. When charging refrigerant into an evacuated low-pressure centrifugal chiller, what should go in first?
  • VaporCorrect answer
  • Liquid
  • Nitrogen
  • Oil

Why “Vapor” is correct

An evacuated chiller is in a deep vacuum. Charging vapor first raises the pressure safely before liquid is introduced, which protects the tubes from freezing.

Source: EPA: Test Topics

Why the other answers are wrong

  • Liquid — Liquid charged into a deep vacuum can flash and freeze the water in the tubes.
  • Nitrogen — Nitrogen is not part of charging and would have to be purged.
  • Oil — Oil is not charged ahead of refrigerant to protect the tubes.
36. Why is vapor charged before liquid into an evacuated R-123 chiller?
  • Liquid would damage the compressor bearings
  • Vapor charging is required to meet the evacuation levels in Table 1
  • Liquid boils very cold in a deep vacuum and can freeze tube waterCorrect answer
  • Vapor carries the oil back into the sump

Why “Liquid boils very cold in a deep vacuum and can freeze tube water” is correct

At a deep vacuum, refrigerant boils at temperatures far below 32 °F. Liquid charged at that point flashes and chills the tubes enough to freeze the water and crack them. Vapor raises the pressure first so the liquid will not boil that cold.

Source: EPA: Test Topics

Why the other answers are wrong

  • Liquid would damage the compressor bearings — The concern is freezing water in the tubes, not compressor bearings.
  • Vapor charging is required to meet the evacuation levels in Table 1 — Table 1 sets evacuation levels, not charging methods.
  • Vapor carries the oil back into the sump — Charging vapor first has nothing to do with oil return.
37. Through which connection should refrigerant be charged into a low-pressure centrifugal chiller?
  • The purge unit connection
  • The evaporator charging valveCorrect answer
  • The compressor discharge line
  • The condenser relief connection

Why “The evaporator charging valve” is correct

EPA's test topics state that centrifugal chillers should be charged through the evaporator charging valve. Charging vapor first and then liquid through that valve is the standard procedure for these machines.

Source: EPA: Test Topics

Why the other answers are wrong

  • The purge unit connection — The purge connection removes noncondensables; it is not for charging.
  • The compressor discharge line — Centrifugals are not charged through the compressor discharge.
  • The condenser relief connection — Relief connections are for pressure protection, not charging.
38. While charging R-123 into a chiller that was evacuated, what should be done with the water in the tubes?
  • Stop the pumps to lower the heat load
  • Close the valves to trap water in the tubes
  • Leave it alone; charging cannot cause freezing
  • Keep it circulating, or drain itCorrect answer

Why “Keep it circulating, or drain it” is correct

The same freezing risk that exists during evacuation exists during charging, until the pressure is above the 32 °F saturation point. Keeping water moving through the tubes, or draining them, protects the tubes.

Source: EPA: Test Topics

Why the other answers are wrong

  • Stop the pumps to lower the heat load — Still water in the tubes is what is at risk of freezing.
  • Close the valves to trap water in the tubes — Trapped, still water can freeze and burst the tubes.
  • Leave it alone; charging cannot cause freezing — Charging into a vacuum can freeze the tubes, which is why vapor goes first.

Recovery requirements

39. Under 40 CFR 82.152, what makes an appliance a "low-pressure appliance"?
  • Its refrigerant has a saturation pressure below 45 psig at 77 °F
  • Its refrigerant's saturation pressure is below 45 psia at 104 °FCorrect answer
  • Its refrigerant has a saturation pressure below 170 psia at 104 °F
  • Its evaporator runs below atmospheric pressure when operating

Why “Its refrigerant's saturation pressure is below 45 psia at 104 °F” is correct

EPA sorts appliances by the saturation pressure of their refrigerant at 104 °F. A refrigerant whose liquid-phase saturation pressure is below 45 psia at that temperature makes the appliance low-pressure, which is why R-11 and R-123 centrifugal chillers fall in this class and follow the 25 mm Hg absolute evacuation level.

Source: 40 CFR 82.152

Why the other answers are wrong

  • Its refrigerant has a saturation pressure below 45 psig at 77 °F — The definition uses psia, not psig, and is set at 104 °F, not room temperature.
  • Its refrigerant has a saturation pressure below 170 psia at 104 °F — 170 psia at 104 °F is the top of the medium-pressure range, not the low-pressure limit.
  • Its evaporator runs below atmospheric pressure when operating — Many low-pressure chillers do run in a vacuum, but the legal definition is based on saturation pressure at 104 °F.
40. Which group lists only refrigerants that 40 CFR 82.152 names as examples for low-pressure appliances?
  • R-12, R-134a, R-500 and R-114
  • R-22, R-410A, R-407C and R-404A
  • R-11, R-123, R-113 and R-245faCorrect answer
  • R-13, R-23, R-503 and R-508B

Why “R-11, R-123, R-113 and R-245fa” is correct

The definition of a low-pressure appliance lists R-11, R-123, R-113 and R-245fa as examples. All four have saturation pressures below 45 psia at 104 °F, which is why they are found in centrifugal chillers that operate near or below atmospheric pressure.

Source: 40 CFR 82.152

Why the other answers are wrong

  • R-12, R-134a, R-500 and R-114 — These are higher-pressure refrigerants; none of them is a low-pressure example in the definition.
  • R-22, R-410A, R-407C and R-404A — These run at much higher pressures and are typical of Type II equipment.
  • R-13, R-23, R-503 and R-508B — These are the examples EPA gives for very high-pressure appliances.
41. A technician using a recovery machine built in 2019 is about to open an R-123 centrifugal chiller to replace the compressor. To what level must the chiller be evacuated first?
  • 10 inches of Hg vacuum
  • 25 mm Hg absoluteCorrect answer
  • 15 inches of Hg vacuum
  • 0 psig

Why “25 mm Hg absolute” is correct

Table 1 in 40 CFR 82.156(a) sets one level for every low-pressure appliance: 25 mm Hg absolute. Replacing the compressor is a major repair, so the full Table 1 level applies before the chiller is opened.

Source: 40 CFR 82.156(a), Table 1

Why the other answers are wrong

  • 10 inches of Hg vacuum — 10 inches of Hg vacuum is a Table 1 level for some medium- and high-pressure appliances, not low-pressure ones.
  • 15 inches of Hg vacuum — 15 inches of Hg vacuum applies to medium-pressure appliances with 200 pounds or more; a low-pressure chiller must go much deeper.
  • 0 psig — 0 psig is far too shallow for a major repair on a low-pressure appliance.
42. A contractor still owns a recovery unit manufactured in 1991. What evacuation level must it reach on an R-11 chiller before the chiller is scrapped?
  • 25 inches of Hg vacuum, a looser level for older units
  • 4 inches of Hg vacuum, the usual pre-1993 level
  • 25 mm Hg absolute, the same as newer equipmentCorrect answer
  • 0 psig, since older units cannot pull a vacuum

Why “25 mm Hg absolute, the same as newer equipment” is correct

For most appliance types Table 1 gives a looser level for recovery equipment made before November 15, 1993. The low-pressure row is the exception: both columns read 25 mm Hg absolute, so the age of the recovery unit does not change the target.

Source: 40 CFR 82.156(a), Table 1

Why the other answers are wrong

  • 25 inches of Hg vacuum, a looser level for older units — The current Table 1 lists 25 mm Hg absolute in both the pre- and post-November 15, 1993 columns for low-pressure appliances.
  • 4 inches of Hg vacuum, the usual pre-1993 level — 4 inches of Hg vacuum is a pre-1993 level for some higher-pressure appliances, not for low-pressure ones.
  • 0 psig, since older units cannot pull a vacuum — Table 1 does not relax the low-pressure level for older recovery equipment.
43. One R-123 chiller holds 150 pounds and another holds 1,200 pounds. Using recovery equipment made in 2020, what evacuation levels apply before each is opened for a major repair?
  • 10 inches of Hg vacuum for the smaller, 15 inches for the larger
  • 0 psig for the smaller, 25 mm Hg absolute for the larger
  • 15 inches of Hg vacuum for both chillers
  • 25 mm Hg absolute for both chillersCorrect answer

Why “25 mm Hg absolute for both chillers” is correct

Table 1 splits medium- and high-pressure appliances at 200 pounds of charge, but the low-pressure row has no size split. Any low-pressure appliance, whatever its charge, must be evacuated to 25 mm Hg absolute before a major repair or disposal.

Source: 40 CFR 82.156(a), Table 1

Why the other answers are wrong

  • 10 inches of Hg vacuum for the smaller, 15 inches for the larger — That 200-pound split is how Table 1 treats medium-pressure appliances, not low-pressure ones.
  • 0 psig for the smaller, 25 mm Hg absolute for the larger — There is no 0 psig option for a major repair on a low-pressure appliance of any size.
  • 15 inches of Hg vacuum for both chillers — 15 inches of Hg vacuum is a medium-pressure level; low-pressure appliances go to 25 mm Hg absolute.
44. Roughly what reading on an inches-of-mercury vacuum gauge corresponds to 25 mm Hg absolute?
  • About 25 inches of Hg vacuum
  • About 15 inches of Hg vacuum
  • About 29 inches of Hg vacuumCorrect answer
  • About 10 inches of Hg vacuum

Why “About 29 inches of Hg vacuum” is correct

25 mm Hg is just under 1 inch of mercury measured from a perfect vacuum. Standard atmosphere is 29.9 inches of mercury, so a gauge that reads vacuum below atmosphere would show roughly 29 inches of Hg vacuum at 25 mm Hg absolute.

Source: 40 CFR 82.156(a), Table 1; EPA: Test Topics

Why the other answers are wrong

  • About 25 inches of Hg vacuum — This mixes up millimetres with inches; 25 mm Hg is only about 1 inch of mercury absolute.
  • About 15 inches of Hg vacuum — 15 inches of Hg vacuum leaves about 15 inches of mercury absolute, far above 25 mm Hg.
  • About 10 inches of Hg vacuum — 10 inches of Hg vacuum is a shallow vacuum used for some higher-pressure appliances.
45. Which of these jobs on an R-11 chiller is a major repair under 40 CFR 82.152?
  • Tightening the bolts on a pump flange
  • Removing the evaporator for replacementCorrect answer
  • Replacing a sight glass with a 2-square-inch opening for 10 minutes
  • Changing a gauge on a quarter-inch access port

Why “Removing the evaporator for replacement” is correct

A major repair is one that removes the compressor, condenser, evaporator or an auxiliary heat exchange coil, or that uncovers more than 4 square inches of flow area for more than 15 minutes. Removing the evaporator meets the first test outright.

Source: 40 CFR 82.152

Why the other answers are wrong

  • Tightening the bolts on a pump flange — Tightening bolts does not open the refrigerant circuit, so it is not a repair under the evacuation rules at all.
  • Replacing a sight glass with a 2-square-inch opening for 10 minutes — This opening is under 4 square inches and under 15 minutes, so the repair is not major.
  • Changing a gauge on a quarter-inch access port — A small, brief opening like this does not meet either test for a major repair.
46. Apart from removing a major component, a repair is "major" if it uncovers an opening of more than how much flow area for more than how long?
  • More than 2 square inches for more than 30 minutes
  • More than 4 square inches for more than 60 minutes
  • More than 10 square inches for more than 15 minutes
  • More than 4 square inches for more than 15 minutesCorrect answer

Why “More than 4 square inches for more than 15 minutes” is correct

The definition in 40 CFR 82.152 treats any repair that uncovers more than 4 square inches of flow area for more than 15 minutes as major, even if no major component is removed. Both conditions must be met for the opening alone to make the repair major.

Source: 40 CFR 82.152

Why the other answers are wrong

  • More than 2 square inches for more than 30 minutes — Both numbers are wrong; the regulation uses 4 square inches and 15 minutes.
  • More than 4 square inches for more than 60 minutes — The time limit is 15 minutes, not an hour.
  • More than 10 square inches for more than 15 minutes — The area threshold is 4 square inches, not 10.
47. A technician will replace a small valve on an R-11 chiller, uncovering about 1.5 square inches for 10 minutes. The chiller will not be evacuated to the atmosphere afterward. What does the rule require before the valve is opened?
  • Evacuate the chiller to 15 inches of Hg vacuum
  • Pressurize the chiller to 10 psig with nitrogen
  • Pressurize the chiller to no higher than 0 psigCorrect answer
  • Evacuate the chiller to 4 inches of Hg vacuum

Why “Pressurize the chiller to no higher than 0 psig” is correct

For a non-major repair that is not followed by evacuation to the atmosphere, 40 CFR 82.156(a)(1)(ii) lets a low-pressure appliance be opened once it is pressurized to no higher than 0 psig. Bringing the pressure up to atmosphere keeps air and moisture from rushing in and refrigerant from rushing out when the valve is opened.

Source: 40 CFR 82.156(a)(1)(ii); 40 CFR 82.152

Why the other answers are wrong

  • Evacuate the chiller to 15 inches of Hg vacuum — 15 inches of Hg vacuum is a medium-pressure level and is not the non-major repair rule for low-pressure appliances.
  • Pressurize the chiller to 10 psig with nitrogen — The goal is 0 psig, and R-11 chillers may not use nitrogen or other methods that require later purging.
  • Evacuate the chiller to 4 inches of Hg vacuum — 4 inches of Hg vacuum is a pre-1993 level for higher-pressure appliances, not the low-pressure non-major rule.
48. Which method may a technician use to bring an R-123 chiller up to 0 psig before a non-major repair?
  • Controlled hot water or a built-in heating device such as PrevacCorrect answer
  • Dry nitrogen from a regulated cylinder, with the nitrogen purged afterward
  • Compressed shop air fed through the purge connection
  • Carbon dioxide from a cylinder, purged afterward

Why “Controlled hot water or a built-in heating device such as Prevac” is correct

Low-pressure appliances whose refrigerant boils at or below 85 °F at standard atmospheric pressure, such as R-11 and R-123, must not be pressurized with methods that require later purging. Warming the refrigerant with controlled hot water or a built-in heating and pressurization device raises its own vapor pressure instead.

Source: 40 CFR 82.156(a)(1)(ii); EPA: Test Topics

Why the other answers are wrong

  • Dry nitrogen from a regulated cylinder, with the nitrogen purged afterward — R-123 boils below 85 °F at atmospheric pressure, so methods such as nitrogen that need later purging are not allowed.
  • Compressed shop air fed through the purge connection — Air is a noncondensable that would have to be purged out and would contaminate the refrigerant.
  • Carbon dioxide from a cylinder, purged afterward — CO2 would also need to be purged out later, which the rule forbids for R-123.
49. Why does 40 CFR 82.156(a)(1)(ii) let an R-113 machine finish pressurizing with nitrogen before a non-major repair, but bar nitrogen for the same job on R-11 and R-123 machines?
  • R-113 is not an ozone-depleting refrigerant
  • R-113 boils above 85 °F at atmospheric pressure; R-11 and R-123 do notCorrect answer
  • R-113 machines always hold less than 200 pounds, so less refrigerant is at risk
  • Nitrogen reacts chemically with R-11 and R-123

Why “R-113 boils above 85 °F at atmospheric pressure; R-11 and R-123 do not” is correct

The rule draws its line at a boiling point of 85 °F at 29.9 inches of mercury. Refrigerants that boil at or below that temperature, like R-11 and R-123, can be warmed to atmospheric pressure fairly easily, so no purging method is allowed. R-113 boils well above 85 °F, so heat is used as far as it will go and nitrogen may make up the rest to atmospheric pressure.

Source: 40 CFR 82.156(a)(1)(ii)

Why the other answers are wrong

  • R-113 is not an ozone-depleting refrigerant — R-113 is a CFC and is ozone-depleting; the distinction is its boiling point.
  • R-113 machines always hold less than 200 pounds, so less refrigerant is at risk — Charge size plays no part in this rule.
  • Nitrogen reacts chemically with R-11 and R-123 — Nitrogen is inert; the rule is about the purging that nitrogen would require afterward.
50. A leaking evaporator on an R-11 chiller cannot reach 25 mm Hg absolute without pulling in enough air to badly contaminate the refrigerant. What is the highest pressure the leaking component may be left at before it is opened?
  • 0 psigCorrect answer
  • 5 psig
  • 10 psig
  • 15 inches of Hg vacuum

Why “0 psig” is correct

When leaks make the Table 1 level unattainable, 40 CFR 82.156(a)(2) requires evacuating the leaking component to the lowest level that can be reached without substantially contaminating the refrigerant. That level may not be higher than 0 psig.

Source: 40 CFR 82.156(a)(2); EPA: Service Practice Requirements

Why the other answers are wrong

  • 5 psig — 5 psig is the limit for oil changes, not for leaking components.
  • 10 psig — 10 psig is a leak-test limit for low-pressure chillers, not an evacuation level.
  • 15 inches of Hg vacuum — The rule does not set a fixed vacuum here; it requires the lowest level reachable without substantial contamination, never above 0 psig.
51. On a leaking R-123 chiller, the condenser can be valved off from the leaking evaporator and does not leak itself. If the condenser is to be opened, to what level must it be evacuated?
  • 25 mm Hg absoluteCorrect answer
  • 0 psig, the same as the leaking evaporator
  • 10 inches of Hg vacuum
  • No evacuation is needed once it is isolated

Why “25 mm Hg absolute” is correct

The leaky-appliance provision says to isolate leaking from non-leaking components wherever possible, then evacuate the non-leaking ones to the levels in Table 1. For a low-pressure appliance that is 25 mm Hg absolute; only the leaking parts get the lowest-attainable, no-higher-than-0-psig treatment.

Source: 40 CFR 82.156(a)(2); 40 CFR 82.156(a), Table 1

Why the other answers are wrong

  • 0 psig, the same as the leaking evaporator — The 0 psig ceiling is only for leaking components; non-leaking ones go to the Table 1 level.
  • 10 inches of Hg vacuum — 10 inches of Hg vacuum is not a low-pressure level in Table 1.
  • No evacuation is needed once it is isolated — Isolating the condenser does not excuse it from evacuation before it is opened.
52. How does the required evacuation level for disposing of an R-123 chiller compare with the level for a major repair on the same chiller?
  • Disposal is stricter: 500 microns
  • Disposal is looser: 0 psig
  • They are the same: 25 mm Hg absoluteCorrect answer
  • Disposal is looser: 10 inches of Hg vacuum

Why “They are the same: 25 mm Hg absolute” is correct

40 CFR 82.156(a) applies Table 1 both before opening an appliance and before disposing of it. Table 1 gives low-pressure appliances a single level, 25 mm Hg absolute, so disposal and a major repair share the same target unless leaks make it unattainable.

Source: 40 CFR 82.156(a); 40 CFR 82.156(a), Table 1

Why the other answers are wrong

  • Disposal is stricter: 500 microns — 500 microns is a common dehydration target, not the Table 1 disposal level.
  • Disposal is looser: 0 psig — Disposal is not relaxed to 0 psig for a non-leaking low-pressure appliance.
  • Disposal is looser: 10 inches of Hg vacuum — 10 inches of Hg vacuum is not the low-pressure level for any situation in Table 1.
53. After pulling an R-11 chiller down to 25 mm Hg absolute, a technician valves off the recovery unit and waits. Within a few minutes the pressure in the chiller starts to rise. What does this most likely mean?
  • Liquid refrigerant is still boiling off in the chiller or its oilCorrect answer
  • The recovery unit has tripped its high-pressure cut-out
  • The purge unit is feeding air back into the shell through its vent line
  • The reading is normal and the chiller can be opened

Why “Liquid refrigerant is still boiling off in the chiller or its oil” is correct

EPA's test topics stress waiting a few minutes after reaching the required vacuum. If the pressure climbs, liquid refrigerant is still in the system or dissolved in the oil and is flashing to vapor. Recovery must continue until the level holds.

Source: EPA: Test Topics; 40 CFR 82.156(a)

Why the other answers are wrong

  • The recovery unit has tripped its high-pressure cut-out — The recovery unit is valved off, so its cut-out would not change the chiller pressure.
  • The purge unit is feeding air back into the shell through its vent line — The purge removes noncondensables; it does not add air to the shell.
  • The reading is normal and the chiller can be opened — A rising pressure shows the evacuation is not finished and the chiller is not ready to open.
54. Before servicing a low-pressure chiller, a technician wants to drain the oil only. If this is not a major repair, what is the highest pressure the chiller or isolated section may be at when it is opened for the oil change?
  • 0 psig
  • 10 psig
  • 5 psigCorrect answer
  • 15 psig

Why “5 psig” is correct

For oil changes, 40 CFR 82.156(a)(1)(iii) allows the appliance to be evacuated or pressurized to no higher than 5 psig before opening, or the oil can be drained into a receiver that is brought to 5 psig or less. EPA notes that changing oil above 5 psig is a violation because oil holds a lot of dissolved refrigerant.

Source: 40 CFR 82.156(a)(1)(iii); EPA: Service Practice Requirements

Why the other answers are wrong

  • 0 psig — 0 psig is the general non-major limit; oil changes have their own, slightly higher 5 psig limit.
  • 10 psig — 10 psig is above the oil-change limit.
  • 15 psig — 15 psig is well above the limit and close to a typical rupture disc setting.
55. What must a technician do after recovering refrigerant from an R-123 chiller and before opening it for a major repair?
  • Get written permission from the building owner
  • Send a sample of the recovered refrigerant to a lab for analysis
  • Verify the required evacuation level has been reachedCorrect answer
  • Notify EPA within 30 days of the repair

Why “Verify the required evacuation level has been reached” is correct

40 CFR 82.156(a) says a technician must verify that the applicable level of evacuation has been reached in the appliance, or in the part being serviced, before it is opened. Recovering to a reading once is not enough if the pressure has not been confirmed.

Source: 40 CFR 82.156(a)

Why the other answers are wrong

  • Get written permission from the building owner — Owner permission is not what 40 CFR 82.156(a) requires before opening.
  • Send a sample of the recovered refrigerant to a lab for analysis — Lab analysis is part of reclamation, not a step before opening the appliance.
  • Notify EPA within 30 days of the repair — There is no EPA notice required before opening an appliance for repair.
56. Instead of evacuating an entire R-11 chiller, may a technician evacuate only the section being serviced?
  • No, the whole chiller must always be evacuated before it is opened
  • Only if the chiller holds less than 200 pounds
  • Only if the recovery unit was made before 1993
  • Yes, if its refrigerant can be isolated in a system receiverCorrect answer

Why “Yes, if its refrigerant can be isolated in a system receiver” is correct

40 CFR 82.156(a) lets technicians evacuate either the whole appliance or only the part to be serviced, provided the refrigerant in that part can be isolated to a system receiver. The isolated part must still reach the required evacuation level before it is opened.

Source: 40 CFR 82.156(a)

Why the other answers are wrong

  • No, the whole chiller must always be evacuated before it is opened — The rule expressly allows evacuating just the part being serviced when it can be isolated.
  • Only if the chiller holds less than 200 pounds — The isolation option does not depend on charge size.
  • Only if the recovery unit was made before 1993 — The age of the recovery equipment has nothing to do with the isolation option.
57. A shop buys a new recovery machine in 2025 to use on R-123 chillers. What must be true of the machine?
  • It is approved by the chiller manufacturer
  • It is certified by an EPA-approved equipment testing organizationCorrect answer
  • It is registered with EPA by the technician
  • It is certified by the organization that tested and certified the technician

Why “It is certified by an EPA-approved equipment testing organization” is correct

Recovery and recycling equipment made on or after November 15, 1993 must be certified by an EPA-approved equipment testing organization for the type of appliance it is meant for. A machine labeled for low-pressure appliances has been shown to reach the 25 mm Hg absolute level.

Source: 40 CFR 82.158; 40 CFR 82.156(a); EPA: Service Practice Requirements

Why the other answers are wrong

  • It is approved by the chiller manufacturer — Chiller manufacturer approval does not meet the federal certification requirement.
  • It is registered with EPA by the technician — Technicians do not register recovery machines with EPA.
  • It is certified by the organization that tested and certified the technician — Technician certifying organizations do not certify recovery equipment.
58. Which of these repairs on an R-123 chiller is not a major repair under 40 CFR 82.152?
  • Removing the compressor for a rebuild
  • Removing an auxiliary heat exchange coil
  • Uncovering a 6-square-inch opening for 30 minutes
  • Uncovering a 3-square-inch opening for 20 minutesCorrect answer

Why “Uncovering a 3-square-inch opening for 20 minutes” is correct

An opening makes a repair major only when it is more than 4 square inches of flow area and lasts more than 15 minutes. A 3-square-inch opening fails the area test even though it lasts 20 minutes, so that repair is not major.

Source: 40 CFR 82.152

Why the other answers are wrong

  • Removing the compressor for a rebuild — Removing the compressor is a major repair by definition.
  • Removing an auxiliary heat exchange coil — Removing an auxiliary heat exchange coil is listed as a major repair.
  • Uncovering a 6-square-inch opening for 30 minutes — This exceeds both 4 square inches and 15 minutes, so it is major.
59. During a non-major repair on a low-pressure chiller pressurized to 0 psig, the section being worked on cannot be isolated from the rest of the machine. What does 40 CFR 82.156(a)(1)(ii) require?
  • Run the purge unit for the whole repair
  • Raise the pressure to 10 psig first
  • Shut off all water flow through the tubes
  • Cover the openingsCorrect answer

Why “Cover the openings” is correct

When a low-pressure appliance is brought to 0 psig for a non-major repair, the rule adds that persons must cover openings when isolation is not possible. This limits air and moisture getting into the rest of the machine and refrigerant getting out.

Source: 40 CFR 82.156(a)(1)(ii)

Why the other answers are wrong

  • Run the purge unit for the whole repair — The rule asks for covered openings, not continuous purging.
  • Raise the pressure to 10 psig first — The rule sets a ceiling of 0 psig, not a target of 10 psig.
  • Shut off all water flow through the tubes — Stopping water flow is not part of this rule and risks other problems.
60. Using recovery equipment made in 2021, what levels apply before major repairs on a 300-pound R-123 chiller and a 300-pound R-134a chiller?
  • 25 mm Hg absolute for the R-123; 15 inches of Hg vacuum for the R-134aCorrect answer
  • 25 mm Hg absolute for both chillers
  • 15 inches of Hg vacuum for both chillers
  • 10 inches of Hg vacuum for the R-123; 25 mm Hg absolute for the R-134a

Why “25 mm Hg absolute for the R-123; 15 inches of Hg vacuum for the R-134a” is correct

R-123 is a low-pressure refrigerant, so its chiller must reach 25 mm Hg absolute. R-134a has a saturation pressure between 45 and 170 psia at 104 °F, making it medium-pressure; with 200 pounds or more and post-1993 equipment, Table 1 calls for 15 inches of Hg vacuum.

Source: 40 CFR 82.156(a), Table 1; 40 CFR 82.152

Why the other answers are wrong

  • 25 mm Hg absolute for both chillers — R-134a is a medium-pressure refrigerant, so its chiller follows the medium-pressure row, not the low-pressure one.
  • 15 inches of Hg vacuum for both chillers — R-123 is low-pressure and must go to 25 mm Hg absolute.
  • 10 inches of Hg vacuum for the R-123; 25 mm Hg absolute for the R-134a — This reverses the classes; the deep 25 mm Hg level belongs to the low-pressure R-123 chiller.
61. The low-pressure evacuation level is given as 25 mm Hg absolute. What is "absolute" pressure measured from?
  • Local atmospheric pressure
  • The refrigerant's saturation pressure
  • A perfect vacuumCorrect answer
  • The chiller's normal operating pressure

Why “A perfect vacuum” is correct

Absolute pressure counts up from zero, a perfect vacuum, while gauge pressure counts from atmosphere. 25 mm Hg absolute means only 25 millimetres of mercury of pressure remain in the appliance, which is a deep vacuum.

Source: 40 CFR 82.156(a), Table 1; EPA: Test Topics

Why the other answers are wrong

  • Local atmospheric pressure — Gauge readings are measured from atmosphere; absolute readings start at a perfect vacuum.
  • The refrigerant's saturation pressure — Saturation pressure is a property of the refrigerant, not a zero point for measurement.
  • The chiller's normal operating pressure — Operating pressure varies and is not a reference point for absolute measurement.

Refrigeration

62. What is the main job of the purge unit on a low-pressure chiller?
  • Remove oil from the refrigerant
  • Add refrigerant when the charge is low
  • Pump down the evaporator for service
  • Remove air and other noncondensablesCorrect answer

Why “Remove air and other noncondensables” is correct

Low-pressure chillers run partly below atmospheric pressure, so air and moisture can leak in. The purge unit removes these noncondensables and returns the refrigerant it separates from them to the chiller.

Source: EPA: Test Topics

Why the other answers are wrong

  • Remove oil from the refrigerant — Oil separation is not the purge unit's job.
  • Add refrigerant when the charge is low — The purge unit does not charge refrigerant.
  • Pump down the evaporator for service — Pump-down is done with recovery equipment or a pump-out unit, not the purge.
63. Why does air get into R-11 and R-123 chillers when it does not get into an R-410A system?
  • R-11 and R-123 absorb air from the oil and release it in the condenser
  • Low-pressure chillers have no sealed joints
  • Air is carried in with the chilled water
  • Parts of the low-pressure chiller run below atmospheric pressureCorrect answer

Why “Parts of the low-pressure chiller run below atmospheric pressure” is correct

An R-410A system stays above atmospheric pressure everywhere, so leaks push refrigerant out. In a low-pressure chiller the evaporator and other parts run in a vacuum, so leaks pull outside air and moisture in.

Source: EPA: Test Topics

Why the other answers are wrong

  • R-11 and R-123 absorb air from the oil and release it in the condenser — The refrigerant does not draw air out of the oil.
  • Low-pressure chillers have no sealed joints — Chillers are sealed; air enters through leaks because of the pressure difference.
  • Air is carried in with the chilled water — The water and refrigerant are separated by tube walls.
64. From which part of a low-pressure chiller does the purge unit normally draw its sample?
  • The top of the condenserCorrect answer
  • The bottom of the evaporator
  • The compressor oil sump
  • The chilled-water return line

Why “The top of the condenser” is correct

Noncondensables travel with the refrigerant vapor to the condenser, where the refrigerant condenses and the air does not. The air gathers at the top of the condenser, so that is where the purge draws from.

Source: EPA: Test Topics

Why the other answers are wrong

  • The bottom of the evaporator — Noncondensables do not collect at the bottom of the evaporator.
  • The compressor oil sump — The oil sump is not where noncondensables gather.
  • The chilled-water return line — The water circuit is separate from the refrigerant circuit.
65. What happens to an R-123 chiller when air builds up in it?
  • Condensing pressure falls and capacity rises
  • Condensing pressure rises and efficiency dropsCorrect answer
  • Evaporator pressure rises above atmospheric
  • Nothing changes until the air reaches the compressor

Why “Condensing pressure rises and efficiency drops” is correct

Air in the condenser adds its own pressure to the refrigerant's and takes up surface that should be condensing refrigerant. Head pressure rises, the compressor works harder, and efficiency falls.

Source: EPA: Test Topics

Why the other answers are wrong

  • Condensing pressure falls and capacity rises — Air raises condensing pressure, it does not lower it.
  • Evaporator pressure rises above atmospheric — Air collects in the condenser and does not lift the evaporator above atmosphere.
  • Nothing changes until the air reaches the compressor — Noncondensables hurt performance as soon as they collect in the condenser.
66. At standard atmospheric pressure, R-123 boils at about what temperature?
  • -41 °F
  • 82 °FCorrect answer
  • -15 °F
  • 118 °F

Why “82 °F” is correct

R-123 boils near 82 °F (27.8 °C) at 29.9 inches of mercury, and R-11 near 75 °F (23.8 °C). Because those boiling points sit close to room temperature, R-123 and R-11 chillers sit near atmospheric pressure when idle and run in a vacuum in the evaporator.

Source: EPA: Test Topics; Hudson Technologies R-123 and R-11 P-T charts

Why the other answers are wrong

  • -41 °F — -41 °F is the boiling point of R-22, a much higher-pressure refrigerant.
  • -15 °F — -15 °F is close to the boiling point of R-134a.
  • 118 °F — 118 °F is close to the boiling point of R-113.
67. An idle R-11 chiller sits in a 70 °F equipment room, with the refrigerant at room temperature. What pressure would the shell be at?
  • Slightly below atmospheric, a small vacuumCorrect answer
  • About 70 psig
  • Exactly 0 psig, as for any idle chiller
  • About 15 psig, the rupture disc setting

Why “Slightly below atmospheric, a small vacuum” is correct

R-11 boils at about 75 °F at atmospheric pressure. At 70 °F its saturation pressure is a little below atmospheric, so the idle chiller holds a slight vacuum, which is why leaks draw air in even when it is off.

Source: EPA: Test Topics; Hudson Technologies R-123 and R-11 P-T charts

Why the other answers are wrong

  • About 70 psig — 70 psig is typical of a medium- or high-pressure refrigerant, not R-11.
  • Exactly 0 psig, as for any idle chiller — Pressure depends on the refrigerant's temperature; it is not always 0 psig.
  • About 15 psig, the rupture disc setting — An idle R-11 chiller at 70 °F is nowhere near 15 psig.
68. During normal operation, which part of an R-123 chiller is most likely to be above atmospheric pressure?
  • The evaporator
  • The compressor suction
  • The condenserCorrect answer
  • The cooler liquid line

Why “The condenser” is correct

R-123 condenses at temperatures above its 82 °F boiling point, so the condenser can sit slightly above atmospheric pressure. The evaporator, working at chilled-water temperatures, stays in a vacuum.

Source: EPA: Test Topics; Hudson Technologies R-123 and R-11 P-T charts

Why the other answers are wrong

  • The evaporator — The evaporator of a low-pressure chiller runs in a vacuum.
  • The compressor suction — The suction side is at evaporator pressure, below atmosphere.
  • The cooler liquid line — Liquid feeding the evaporator is near evaporator pressure, not condenser pressure.
69. Besides air itself, what harmful contaminant comes into a low-pressure chiller when room air leaks in through a joint on its vacuum side?
  • Moisture from the surrounding airCorrect answer
  • Compressor oil from other machines
  • Carbon dioxide that freezes in the tubes
  • Higher-pressure refrigerant such as R-22

Why “Moisture from the surrounding air” is correct

Outside air carries water vapor. When a vacuum-side leak draws air in, moisture comes too, and moisture in a chiller can form acids and damage the machine. The purge unit helps remove it.

Source: EPA: Test Topics

Why the other answers are wrong

  • Compressor oil from other machines — Oil does not come in from outside through a leak.
  • Carbon dioxide that freezes in the tubes — Air holds only a trace of carbon dioxide, and it does not freeze at chiller temperatures.
  • Higher-pressure refrigerant such as R-22 — Other refrigerants are not drawn in from room air in any meaningful amount.

Safety

70. According to EPA's test topics on ASHRAE Standard 15, what sensor is needed in a chiller equipment room whatever refrigerant is used?
  • A carbon monoxide detector
  • An oxygen-deprivation sensorCorrect answer
  • A smoke detector
  • A humidity sensor

Why “An oxygen-deprivation sensor” is correct

EPA's topic list states that ASHRAE Standard 15 equipment rooms need an oxygen-deprivation sensor with all refrigerants, so that is the answer on the 608 test. The wording comes from the 1992 edition of the standard. Since 1994, Standard 15 has instead required a refrigerant detector in every machinery room that sounds an alarm and starts ventilation at or below the refrigerant's exposure limit (now the Standard 34 OEL), which an oxygen sensor alone cannot do.

Source: EPA: Test Topics; ASHRAE Interpretation IC 15-1992-11 (oxygen sensor wording, 1994); ASHRAE 15-2016 Addendum c (detector set point at OEL)

Why the other answers are wrong

  • A carbon monoxide detector — Carbon monoxide comes from combustion, not refrigerant leaks.
  • A smoke detector — Smoke detectors do not warn of refrigerant displacing oxygen.
  • A humidity sensor — Humidity sensors do not protect workers from refrigerant leaks.
71. Under ASHRAE Standard 15, what device must an equipment room with an R-123 chiller have?
  • A sprinkler head above the chiller
  • A floor drain beside the rupture disc
  • A carbon dioxide extinguisher
  • A refrigerant sensor that detects R-123Correct answer

Why “A refrigerant sensor that detects R-123” is correct

EPA's test topics list a refrigerant sensor as an ASHRAE Standard 15 equipment-room requirement for R-123. The sensor warns people of a leak before they are exposed to harmful levels; R-123's exposure limit is 50 ppm. Current editions of Standard 15 require such a detector, set at or below the refrigerant's OEL, for every refrigerant.

Source: EPA: Test Topics; ASHRAE 15-2016 Addendum c (detector set point at OEL); Trane CTV-SVX05H-EN, R-123 handling guide

Why the other answers are wrong

  • A sprinkler head above the chiller — Sprinklers are fire protection, not refrigerant monitoring.
  • A floor drain beside the rupture disc — A drain does not detect refrigerant.
  • A carbon dioxide extinguisher — An extinguisher does not detect refrigerant.
72. Why does an R-123 equipment room need a refrigerant sensor and not just an oxygen-deprivation sensor?
  • R-123 is flammable in normal room air
  • R-123 is lighter than air and rises out of reach of the oxygen sensor
  • Oxygen sensors do not work in chiller rooms
  • R-123 can harm people at levels far too low to cut oxygenCorrect answer

Why “R-123 can harm people at levels far too low to cut oxygen” is correct

An oxygen sensor alarms only after leaked refrigerant has pushed oxygen down to about 19.5 percent, which takes several percent refrigerant in the air. R-123 is in the higher-toxicity group under ASHRAE Standard 34, with an exposure limit of 50 ppm, so a refrigerant detector is needed to warn far earlier. Current Standard 15 requires that kind of detector for every refrigerant.

Source: EPA: Test Topics; ASHRAE 15-2016 Addendum c (detector set point at OEL); ASHRAE Standard 34

Why the other answers are wrong

  • R-123 is flammable in normal room air — R-123 is classed as non-flammable; the concern is toxicity.
  • R-123 is lighter than air and rises out of reach of the oxygen sensor — R-123 vapor is heavier than air and collects in low places.
  • Oxygen sensors do not work in chiller rooms — Oxygen sensors work; they just respond too late for a toxic refrigerant.
73. After a large R-11 leak in an equipment room, where is the refrigerant vapor most likely to collect?
  • Near the ceiling
  • Evenly through the room within seconds
  • Only inside the chiller cabinet
  • Near the floor and in pits or low spotsCorrect answer

Why “Near the floor and in pits or low spots” is correct

Fluorocarbon refrigerant vapors are heavier than air, so they settle to the floor and fill pits, trenches and basements. That is where oxygen can be pushed out first and where the danger to workers is greatest.

Source: EPA: Test Topics; ASHRAE Standard 15

Why the other answers are wrong

  • Near the ceiling — R-11 vapor is heavier than air and sinks rather than rises.
  • Evenly through the room within seconds — Heavy vapor does not mix evenly; it settles.
  • Only inside the chiller cabinet — Leaked vapor spreads into the room and settles low.
74. A technician will raise an R-113 machine's pressure with nitrogen for a leak test. What must be on the nitrogen cylinder?
  • A check valve and nothing else
  • A flow meter set to the chiller tonnage
  • A pressure regulator, with a relief valve downstreamCorrect answer
  • No fittings; open the cylinder valve slowly

Why “A pressure regulator, with a relief valve downstream” is correct

A full nitrogen cylinder holds far more pressure than a low-pressure chiller shell can take. A regulator and relief valve keep the test pressure under control and at or below the 10 psig ceiling, or the manufacturer's lower limit if it gives one.

Source: EPA: Test Topics; Trane CTV-SVX05H-EN, R-123 handling guide (8 psig leak test)

Why the other answers are wrong

  • A check valve and nothing else — A check valve does not limit the pressure delivered to the machine.
  • A flow meter set to the chiller tonnage — Flow meters do not protect the shell from overpressure.
  • No fittings; open the cylinder valve slowly — A nitrogen cylinder holds very high pressure and must never feed a chiller without a regulator.
75. Why must the hot water used to pressurize an R-11 chiller for a leak test be controlled?
  • Too much heat could raise pressure past the rupture disc settingCorrect answer
  • Hot water can cause the R-11 to ignite
  • Hot water dissolves the tube coatings
  • Hot water turns R-11 into a toxic decomposition gas above about 100 °F

Why “Too much heat could raise pressure past the rupture disc setting” is correct

Warming the refrigerant raises its pressure, and overheating it can raise the pressure past the rupture disc and release the charge. That is why EPA's topics speak of controlled hot water and why the test pressure is held at or under 10 psig.

Source: EPA: Test Topics; Trane CVHE-SVX005E-EN, CenTraVac IOM (15 psig rupture disk)

Why the other answers are wrong

  • Hot water can cause the R-11 to ignite — R-11 is not flammable.
  • Hot water dissolves the tube coatings — The concern is refrigerant pressure, not tube coatings.
  • Hot water turns R-11 into a toxic decomposition gas above about 100 °F — R-11 does not decompose at hot-water temperatures.

Unofficial, not affiliated with the EPA or any EPA-approved certifying organization. Questions are original practice written from public EPA material, not real exam questions.