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EPA 608 Type III
Practice Test

Type III covers low-pressure appliances: centrifugal chillers whose evaporator runs below atmospheric pressure. That single fact drives the whole section. Because the machine is under vacuum in normal operation, leaks pull air and water *in* rather than pushing refrigerant out, so purge units, non-condensable removal, freeze protection during recovery, and the ten-psig ceiling on pressurizing the vessel are the topics that dominate. It is a niche certification and a well-paid one.

100
Questions
25
Per Attempt
70%
To Pass
Lifetime
Cert Validity
Practice
Take the Type III Practice Test
25 questions drawn at random from a bank of 100. Every answer comes with an explanation, and you can retake it as many times as you like.
Question 1 of 250 correct so far
Leak detection on a vacuum machine

A standing vacuum test on a low-pressure chiller is used to:

Scope
What EPA 608 Type III Covers
Low-pressure appliances — centrifugal chillers operating below atmospheric pressure.
Low-pressure appliance characteristics
18 practice questions in the bank below.
Purge units and non-condensables
13 practice questions in the bank below.
Pressure limits and rupture discs
13 practice questions in the bank below.
Recovery and freeze protection
16 practice questions in the bank below.
Required evacuation levels
9 practice questions in the bank below.
Leak detection on a vacuum machine
11 practice questions in the bank below.
Refrigerant charging
7 practice questions in the bank below.
Machine room safety and exposure limits
13 practice questions in the bank below.
Who needs this section
Technicians and building engineers who work on large centrifugal chillers using R-11, R-123, or R-514A.

Key Takeaways

The EPA 608 Type III exam is 25 multiple-choice questions and requires 70% to pass. It covers low-pressure appliances — centrifugal chillers operating below atmospheric pressure. Certification never expires, and the exam is open-book.

  • Free practice bank: 100 questions, every answer explained
  • 25 questions per attempt, randomized · unlimited retakes
  • Core must be passed alongside any Type section
  • Exam cost is typically $20–$40 at an EPA-approved testing organization
Answer Key
All 100 Type III Questions Explained
The full bank with correct answers and the reasoning behind each one. Use it to study before you test, or to review after an attempt.

1. A low-pressure appliance is one that uses a refrigerant with a boiling point at atmospheric pressure:

  1. Above 10°F, so the evaporator operates in a vacuum
  2. Between −50°F and 10°F
  3. Below −50°F
  4. Exactly 32°F
Answer: A — Above 10°F, so the evaporator operates in a vacuum
R-11 boils near 75°F and R-123 near 82°F at atmospheric pressure, so the evaporator of a running centrifugal chiller sits below atmospheric pressure. Everything distinctive about Type III follows from that single fact — leaks draw air and water in rather than pushing refrigerant out.

2. Because a low-pressure chiller operates under a vacuum, a leak in the evaporator will:

  1. Release refrigerant to the machine room
  2. Draw air and moisture into the machine
  3. Have no effect until the machine is shut down
  4. Cause immediate high head pressure
Answer: B — Draw air and moisture into the machine
Air and water vapor enter through a leak while the machine runs, which is why non-condensables accumulate in low-pressure machines and why they need purge units at all. Refrigerant does escape when the machine is off and warms above atmospheric pressure, so both directions matter across a full cycle.

3. The function of a purge unit on a low-pressure chiller is to:

  1. Circulate oil through the compressor
  2. Add refrigerant automatically when the charge is low
  3. Remove air and moisture that have leaked into the machine, with minimal refrigerant loss
  4. Regulate condenser water flow
Answer: C — Remove air and moisture that have leaked into the machine, with minimal refrigerant loss
Non-condensables raise condensing pressure and cut capacity, so the purge separates them from refrigerant vapor and discharges them. High-efficiency purges lose only a fraction of the refrigerant that older units did, which is why replacing an aging purge is often the single highest-return emissions fix on a chiller.

4. A purge unit that is running far more often than normal indicates:

  1. The chiller is operating efficiently
  2. The refrigerant charge is too high
  3. The condenser water is too cold
  4. The machine has a leak allowing air into the system
Answer: D — The machine has a leak allowing air into the system
Purge runtime is the best leak indicator a low-pressure machine gives you — more air coming in means more purging. Tracking purge hours over time is standard practice, and a sudden increase should trigger a leak search rather than a bigger purge.

5. When pressurizing a low-pressure chiller for leak testing, pressure must never exceed:

  1. 5 psig
  2. 10 psig
  3. 25 psig
  4. 50 psig
Answer: B — 10 psig
Ten psig is the ceiling, because the rupture disc on a low-pressure machine is typically set at 15 psig and blowing it releases the entire charge to atmosphere. This limit is the single most-tested fact in Type III.

6. The rupture disc on a low-pressure chiller is typically rated at:

  1. 10 psig
  2. 15 psig
  3. 30 psig
  4. 150 psig
Answer: B — 15 psig
Fifteen psig is the standard setting, which is why the leak-test ceiling is 10 psig — a deliberate margin. The disc protects a vessel that was never designed for meaningful positive pressure, so treating it as a safety limit rather than a target is the whole point.

7. Which gas may be used to raise the pressure in a low-pressure chiller for leak testing?

  1. Dry nitrogen, regulated and limited to 10 psig
  2. Compressed air from a shop compressor
  3. Oxygen
  4. Carbon dioxide
Answer: A — Dry nitrogen, regulated and limited to 10 psig
Dry nitrogen through a regulator is the only acceptable choice, and the 10 psig limit still applies. Oxygen is an explosion hazard with oil, and shop air carries moisture into a machine where water contamination is a serious and expensive problem.

8. The required evacuation level for a low-pressure appliance before opening it for service is:

  1. 10 inches of mercury
  2. 25 mm of mercury absolute
  3. 15 inches of mercury
  4. 500 microns
Answer: B — 25 mm of mercury absolute
Twenty-five millimeters of mercury absolute — about 25,000 microns — is the low-pressure requirement, and it applies to equipment on both sides of the November 1993 manufacture date under the current table. The inches-of-mercury figures belong to high-pressure appliances.

9. During refrigerant recovery from a low-pressure chiller, the greatest risk to the machine is:

  1. Overheating the compressor motor
  2. Contaminating the oil
  3. Freezing water in the evaporator or condenser tubes and rupturing them
  4. Overfilling the recovery cylinder with vapor
Answer: C — Freezing water in the evaporator or condenser tubes and rupturing them
Pulling the machine into a deep vacuum lowers the refrigerant's saturation temperature and can drive tube-side water below freezing, splitting tubes. Standard practice is to drain or circulate the water, and to monitor temperature so the vessel stays above 32°F throughout recovery.

10. The recommended sequence when recovering a full charge from a low-pressure chiller is to:

  1. Recover vapor first, then liquid
  2. Heat the charge to 125°F before recovery
  3. Recover only vapor and leave the liquid
  4. Recover liquid first, then finish with vapor
Answer: D — Recover liquid first, then finish with vapor
Liquid moves far more refrigerant per minute, so taking the liquid first gets the bulk out quickly and leaves only the vapor tail for the slow part of the job. Heating the charge to 125°F is a cylinder-storage limit, not a recovery technique, and would be dangerous here.

11. To leak-test a low-pressure chiller that is under a vacuum, a technician can:

  1. Raise the pressure with controlled heat or regulated nitrogen to no more than 10 psig, then test
  2. Apply soap bubbles to the exterior while the machine is in a vacuum
  3. Pressurize to 50 psig with nitrogen for a clearer signal
  4. Run the machine at full load and listen
Answer: A — Raise the pressure with controlled heat or regulated nitrogen to no more than 10 psig, then test
A leak under vacuum draws air in, so bubbles will not form and an electronic detector has nothing to sniff. Raising pressure — using controlled warm water through the tubes or regulated nitrogen — makes the leak detectable, always staying below the 10 psig ceiling.

12. ASHRAE Standard 15 requires a machine room containing a chiller to have:

  1. A fire sprinkler above the compressor only
  2. A refrigerant monitor and alarm with mechanical ventilation
  3. A dedicated water supply
  4. No special provisions if the chiller is under 100 tons
Answer: B — A refrigerant monitor and alarm with mechanical ventilation
A refrigerant vapor detector, an alarm, and mechanical ventilation are the core requirements, because refrigerant is heavier than air and a release in an enclosed room is an oxygen-displacement hazard. Self-contained breathing apparatus should be available outside the room, not inside it.

13. R-123 has a much lower allowable exposure limit than R-11, which means a technician should:

  1. Use R-123 only outdoors
  2. Ignore the difference, since both are non-toxic
  3. Treat R-123 exposure more seriously and rely on monitors and ventilation
  4. Wear a dust mask when working near R-123
Answer: C — Treat R-123 exposure more seriously and rely on monitors and ventilation
R-123 carries a substantially lower occupational exposure limit than R-11, so the same concentration that would be tolerable with R-11 is not with R-123. Monitors, ventilation, and — for entry into a high-concentration area — supplied-air respiratory protection are the answer. A dust mask does nothing against vapor.

14. Water in the tubes of a low-pressure chiller is most likely to enter the refrigerant circuit through:

  1. The purge unit discharge
  2. The rupture disc
  3. The oil sump vent
  4. A tube leak in the evaporator or condenser bundle, drawn in by the vacuum
Answer: D — A tube leak in the evaporator or condenser bundle, drawn in by the vacuum
The tube bundle carries water on one side and refrigerant under vacuum on the other, so a tube failure pulls water straight into the charge. Water contamination is expensive to correct — it requires recovery, drying, and often reclamation of the entire charge — which is why tube-side leak testing is a routine part of chiller service.

15. When recovering refrigerant from a low-pressure chiller, the recovery machine should be sized so that:

  1. It can complete recovery quickly enough that the vessel does not cool toward freezing
  2. It runs as slowly as possible
  3. It matches the chiller compressor horsepower exactly
  4. It can also serve as the purge unit
Answer: A — It can complete recovery quickly enough that the vessel does not cool toward freezing
A large charge and an undersized machine means hours of recovery during which the vessel steadily cools — the freeze risk again. Type III recovery machines are sized for the charge and often used with the chiller's own heat source or circulating water to keep temperature up.

16. When adding refrigerant to a low-pressure chiller that is in a deep vacuum, refrigerant should be introduced:

  1. As liquid into the evaporator immediately
  2. As vapor until the pressure and temperature rise above freezing, then as liquid
  3. As vapor only, for the entire charge
  4. Through the purge unit
Answer: B — As vapor until the pressure and temperature rise above freezing, then as liquid
Charging liquid into a machine under a deep vacuum causes it to flash violently and can freeze the tubes. Bringing the pressure up with vapor first raises the saturation temperature above freezing; once the machine is safely above 32°F, the remainder can go in as liquid.

17. Purge unit efficiency is usually expressed as:

  1. The pounds of air removed per hour
  2. The horsepower of the purge compressor
  3. The amount of refrigerant lost per pound of air purged
  4. The percentage of runtime
Answer: C — The amount of refrigerant lost per pound of air purged
A purge must discharge non-condensables, and the question is how much refrigerant goes out with them. Older units lost several pounds of refrigerant per pound of air; modern high-efficiency purges lose a small fraction of that, which is both an emissions and a cost argument for upgrading.

18. Which refrigerant is used in low-pressure centrifugal chillers?

  1. R-410A
  2. R-134a
  3. R-404A
  4. R-123
Answer: D — R-123
R-123 is the classic low-pressure chiller refrigerant, succeeding R-11, with R-514A appearing in newer machines. R-134a is used in medium-pressure centrifugals, which fall under Type II — a distinction worth knowing before you show up to a chiller job with the wrong certification.

19. Before entering a machine room where a large refrigerant release is suspected, a technician should:

  1. Ventilate the space and use self-contained breathing apparatus if the concentration is unknown
  2. Enter quickly and hold their breath
  3. Open a window and wait five minutes
  4. Enter with a colleague watching from the doorway
Answer: A — Ventilate the space and use self-contained breathing apparatus if the concentration is unknown
Refrigerant displaces oxygen and gives little warning before it impairs judgment. Ventilate first, monitor, and use supplied-air protection if the concentration is unknown — a filtering respirator will not help against oxygen deficiency, and holding your breath is how people are found unconscious at floor level.

20. A low-pressure chiller has been evacuated to the required level. Pressure then rises steadily with the recovery machine isolated. This indicates:

  1. The evacuation is complete and the machine is ready to open
  2. Refrigerant is still boiling out of the oil, or air is leaking in
  3. The rupture disc has failed
  4. The purge unit is operating correctly
Answer: B — Refrigerant is still boiling out of the oil, or air is leaking in
A rising vacuum means something is still adding to the pressure. Refrigerant coming out of solution in the oil is the benign explanation; an inward leak is the other, and both require action before the machine is opened. This is exactly why the rule expects the level to be reached and verified, not just briefly touched.

21. A ruptured disc on a low-pressure chiller should be:

  1. Patched and returned to service
  2. Replaced with a higher-rated disc to prevent recurrence
  3. Replaced with a disc of the correct rating, after determining why it ruptured
  4. Removed and the opening plugged
Answer: C — Replaced with a disc of the correct rating, after determining why it ruptured
A rupture disc is a one-time safety device and must be replaced with the correct rating — installing a higher-rated disc defeats the protection the vessel was designed around. Finding the cause matters just as much, since a disc rarely blows without a reason such as over-pressurization during service.

22. A standing vacuum test on a low-pressure chiller is used to:

  1. Measure the refrigerant charge
  2. Check condenser water flow
  3. Verify purge unit efficiency
  4. Determine whether the machine holds a vacuum, indicating it is leak-free and dry
Answer: D — Determine whether the machine holds a vacuum, indicating it is leak-free and dry
After evacuation, isolating the pump and watching the level over time distinguishes a tight, dry machine from one that leaks or still contains moisture. It is the same principle as the standing vacuum test on any system — it just matters more here, because a low-pressure machine spends its working life under vacuum.

23. Refrigerant recovered from a low-pressure chiller must be:

  1. Recovered into an approved container suitable for low-pressure refrigerant, never vented
  2. Recovered into a standard high-pressure DOT cylinder rated for R-410A
  3. Left in the machine and sealed
  4. Discharged into the machine room ventilation system
Answer: A — Recovered into an approved container suitable for low-pressure refrigerant, never vented
Low-pressure refrigerants are usually recovered into drums or tanks intended for them, since they sit below atmospheric pressure at room temperature. Whatever the container, the venting prohibition applies to R-123 and R-11 exactly as it does to any other refrigerant.

24. Compared with a high-pressure system of equal capacity, a low-pressure chiller typically:

  1. Holds a much smaller refrigerant charge
  2. Holds a much larger refrigerant charge, so a release is proportionally more significant
  3. Requires no leak monitoring
  4. Operates entirely above atmospheric pressure
Answer: B — Holds a much larger refrigerant charge, so a release is proportionally more significant
Large centrifugal machines hold hundreds or thousands of pounds, which is why they sit well above the 50-pound threshold for leak repair requirements and why a single incident matters. It is also why purge efficiency, tube integrity, and careful recovery practice carry real financial weight on this equipment.

25. Non-condensables accumulating in a low-pressure chiller will:

  1. Lower condensing pressure and improve efficiency
  2. Have no effect until the charge is low
  3. Raise condensing pressure, reduce capacity, and increase energy use
  4. Cause the evaporator to flood
Answer: C — Raise condensing pressure, reduce capacity, and increase energy use
Air occupies condenser volume and adds its own partial pressure, so the compressor works against a higher head for the same cooling. On a large centrifugal that shows up directly on the electric bill, which is why purge runtime is tracked as an operating metric and not just a maintenance detail.

26. Self-contained breathing apparatus for a chiller machine room should be stored:

  1. Inside the machine room next to the chiller
  2. In the service technician’s vehicle only
  3. In the building lobby
  4. Outside the machine room, where it can be reached without entering a contaminated space
Answer: D — Outside the machine room, where it can be reached without entering a contaminated space
Equipment you have to enter the hazard to retrieve is not protection. Storing it immediately outside the room means a technician can gear up before entry, which is the entire scenario the requirement exists for.

27. Before recovering the charge from a low-pressure chiller, condenser and chilled-water circuits should be:

  1. Drained, or kept circulating warm water, to prevent tubes from freezing as the vessel cools
  2. Left full and static
  3. Pressurized to 50 psig
  4. Isolated and vented to atmosphere
Answer: A — Drained, or kept circulating warm water, to prevent tubes from freezing as the vessel cools
Static water in the tubes is exactly what freezes when the refrigerant side is pulled into a deep vacuum. Draining removes the risk; circulating water keeps the bundle above freezing while recovery proceeds. Either is acceptable, doing neither is how tube bundles split.

28. Oil in a low-pressure chiller is typically:

  1. Circulated with the refrigerant throughout the system
  2. Contained in a separate sump serving the compressor bearings and gears, largely isolated from the refrigerant circuit
  3. Not used at all
  4. Injected into the evaporator to improve heat transfer
Answer: B — Contained in a separate sump serving the compressor bearings and gears, largely isolated from the refrigerant circuit
Centrifugal machines lubricate bearings and the gear train from a dedicated sump rather than relying on oil circulating with the refrigerant, as a reciprocating system does. Oil analysis on that sump is a standard predictive-maintenance tool and often the earliest warning of moisture or acid in the machine.

29. A low-pressure chiller loses vacuum overnight after evacuation. The technician should first:

  1. Charge refrigerant and return the machine to service
  2. Replace the rupture disc
  3. Determine whether the rise is from a leak or from moisture still boiling, then locate and repair any leak
  4. Raise the pressure to 25 psig and listen
Answer: C — Determine whether the rise is from a leak or from moisture still boiling, then locate and repair any leak
A vacuum that rises and then stabilizes near a value consistent with water vapor points to remaining moisture; one that keeps climbing toward atmospheric points to a leak. Charging over either problem guarantees a repeat failure, and 25 psig would exceed the 10 psig ceiling and risk the rupture disc.

30. Refrigerant added to a low-pressure chiller should be:

  1. Any refrigerant of similar boiling point that is available
  2. Added only while the machine is running at full load
  3. Mixed with nitrogen to raise pressure
  4. The refrigerant specified by the manufacturer, since substituting changes capacity, materials compatibility, and safety classification
Answer: D — The refrigerant specified by the manufacturer, since substituting changes capacity, materials compatibility, and safety classification
Low-pressure machines are engineered around a specific refrigerant — impeller design, materials, seals, and the safety classification of the machine room all follow from it. Substituting is not a field decision, and mixing refrigerants makes the entire large charge unreclaimable.

31. A low-pressure refrigerant is defined as one boiling at what temperature at atmospheric pressure?

  1. Below -50°C
  2. Between -50°C and 10°C
  3. Above 10°C
  4. Above 100°C
Answer: C — Above 10°C
Low-pressure refrigerants boil above 10°C at atmospheric pressure — R-11, R-113, and R-123 are the classic examples. That high boiling point is why their evaporators sit in a vacuum during normal operation, which drives nearly every distinctive Type III procedure.

32. Which refrigerants are found in low-pressure centrifugal chillers?

  1. R-410A and R-32
  2. R-11, R-113, and R-123
  3. R-404A and R-507
  4. R-717 and R-744
Answer: B — R-11, R-113, and R-123
R-11 and R-113 are the legacy CFC low-pressure refrigerants and R-123 is the HCFC that replaced R-11 in centrifugal chillers. The high-pressure refrigerants listed are Type II equipment, and ammonia and CO2 are industrial refrigerants outside this category.

33. Why does a low-pressure chiller operate with its evaporator below atmospheric pressure?

  1. To save energy
  2. Because the refrigerant\u2019s saturation pressure at typical chilled-water temperatures is below atmospheric
  3. To prevent leaks
  4. To reduce noise
Answer: B — Because the refrigerant\u2019s saturation pressure at typical chilled-water temperatures is below atmospheric
At the 35 to 40°F evaporator temperature a chiller works at, a low-pressure refrigerant\u2019s saturation pressure is below one atmosphere. The machine therefore runs in a vacuum on the low side, which means leaks draw air and moisture in rather than pushing refrigerant out.

34. What is the practical consequence of a low-side vacuum for leak behaviour?

  1. Refrigerant escapes faster
  2. Air, moisture, and non-condensables are drawn into the machine instead of refrigerant leaking out
  3. Leaks seal themselves
  4. No consequence
Answer: B — Air, moisture, and non-condensables are drawn into the machine instead of refrigerant leaking out
A leak below atmospheric pressure runs inward. That is why purge-unit run time is the primary leak indicator on a low-pressure chiller — you do not see refrigerant loss at the leak, you see air accumulating inside the machine.

35. Low-pressure chillers most commonly use which compressor type?

  1. Reciprocating
  2. Centrifugal
  3. Scroll
  4. Rotary vane
Answer: B — Centrifugal
Centrifugal compressors move the very large volumetric flows that low-pressure refrigerants require at modest pressure ratios. Scroll and reciprocating compressors are positive-displacement machines better suited to the smaller volumes and higher pressures of Type II equipment.

36. Compared with a high-pressure system, a low-pressure chiller of the same capacity holds:

  1. Much less refrigerant
  2. A much larger refrigerant charge, often hundreds or thousands of pounds
  3. The same charge
  4. No refrigerant
Answer: B — A much larger refrigerant charge, often hundreds or thousands of pounds
Low-pressure refrigerant vapour is far less dense, so a given cooling capacity needs a much larger mass of refrigerant and physically enormous vessels. Charges in the hundreds or thousands of pounds are routine, which is why recovery on these machines is a long operation.

37. R-123 belongs to which chemical family?

  1. CFC
  2. HCFC
  3. HFC
  4. HFO
Answer: B — HCFC
R-123 is a hydrochlorofluorocarbon. It carries a much lower ODP than the R-11 it replaced because the hydrogen lets it break down in the troposphere, but it is not zero, which is why R-123 has itself been subject to phaseout on the HCFC schedule.

38. What happens to a low-pressure chiller\u2019s internal pressure when it is shut down and warms to room temperature?

  1. It stays in a vacuum
  2. It rises toward or above atmospheric as the refrigerant warms
  3. It drops further
  4. It becomes zero absolute
Answer: B — It rises toward or above atmospheric as the refrigerant warms
Saturation pressure follows temperature, so a machine left off and allowed to warm can rise to or above atmospheric. That matters for both leak behaviour and the rupture disc, and it is why a shut-down chiller is not automatically a chiller in a vacuum.

39. What is the primary function of a purge unit on a low-pressure chiller?

  1. To add refrigerant
  2. To remove air and other non-condensables that leak into the machine, while returning refrigerant to it
  3. To circulate oil
  4. To cool the motor
Answer: B — To remove air and other non-condensables that leak into the machine, while returning refrigerant to it
Because the low side runs in a vacuum, air steadily works its way in. The purge unit collects non-condensables at the top of the condenser, separates out the refrigerant, returns it to the machine, and expels the air.

40. Excessive purge unit run time indicates:

  1. Normal operation
  2. An air leak into the machine
  3. Too much refrigerant
  4. A dirty condenser only
Answer: B — An air leak into the machine
Purge run time is the standard leak indicator on low-pressure equipment. A machine that purges far more than its baseline is drawing air in somewhere, and the run-time log is what turns that into a trend you can act on.

41. How do non-condensables affect a low-pressure chiller\u2019s performance?

  1. They improve heat transfer
  2. They raise condensing pressure and reduce efficiency and capacity
  3. They lower head pressure
  4. They have no effect
Answer: B — They raise condensing pressure and reduce efficiency and capacity
Air collects in the condenser, occupies surface that should be condensing refrigerant, and adds its own partial pressure. Head pressure rises, the compressor works harder for less cooling, and on a centrifugal machine it can push the compressor toward surge.

42. A high-efficiency purge unit is valued because it:

  1. Purges faster
  2. Discharges very little refrigerant along with the air it removes
  3. Uses no power
  4. Needs no maintenance
Answer: B — Discharges very little refrigerant along with the air it removes
Older purge designs vented a meaningful quantity of refrigerant with every purge cycle. High-efficiency units recover nearly all of it before expelling the air, which cuts both emissions and refrigerant cost — and the rule limits how much purge units may release.

43. Refrigerant discharged by a purge unit is:

  1. Exempt from all rules
  2. Still a regulated release, which is why purge efficiency is limited by rule
  3. Always harmless
  4. Reclaimed automatically
Answer: B — Still a regulated release, which is why purge efficiency is limited by rule
A purge discharge is a refrigerant release like any other, and the rule places limits on purge unit emissions. That is the regulatory reason to keep purge units maintained and to replace inefficient legacy units.

44. Tracking purge unit run time over weeks is useful because:

  1. It predicts weather
  2. A rising trend identifies a developing air leak before it damages performance
  3. It measures oil level
  4. It is required daily
Answer: B — A rising trend identifies a developing air leak before it damages performance
A single reading means little; the trend is the diagnostic. A steadily climbing purge time says the machine is drawing more air than it used to, which points to a leak worth finding while it is still small.

45. What is the purpose of the rupture disc on a low-pressure chiller?

  1. To measure pressure
  2. To relieve pressure to prevent vessel failure if internal pressure rises dangerously
  3. To purge air
  4. To drain oil
Answer: B — To relieve pressure to prevent vessel failure if internal pressure rises dangerously
The rupture disc is a one-time pressure relief that bursts before the vessel does. It is a safety device, never a service port, and a ruptured disc means the whole charge has been lost and the cause must be found before the machine is recharged.

46. A low-pressure chiller\u2019s rupture disc is typically rated at what pressure?

  1. Around 15 psig
  2. Around 150 psig
  3. Around 400 psig
  4. Around 1,000 psig
Answer: A — Around 15 psig
Low-pressure vessels are thin-walled because they never see high pressure in service, so the relief device is set low — around 15 psig is typical. That low rating is exactly why pressurising one of these machines for a leak test is so dangerous.

47. Why must a low-pressure chiller never be pressurised with nitrogen above the rupture disc rating?

  1. Nitrogen is expensive
  2. The disc will burst and the vessel itself can be damaged at pressures a high-pressure system tolerates easily
  3. It contaminates the oil
  4. It is permitted
Answer: B — The disc will burst and the vessel itself can be damaged at pressures a high-pressure system tolerates easily
These vessels are designed for a vacuum and a few psig, not for a standard pressure test. Applying the pressures normal on Type II equipment will blow the disc and can deform or rupture the shell — this is the single most dangerous mistake on Type III equipment.

48. What should be done if a rupture disc has burst?

  1. Replace it and recharge immediately
  2. Determine why pressure rose, repair the cause, replace the disc, and evacuate before recharging
  3. Tape it over
  4. Ignore it if the machine runs
Answer: B — Determine why pressure rose, repair the cause, replace the disc, and evacuate before recharging
A burst disc is a symptom. Something raised the pressure — often loss of condenser water with the machine running, or a fire. Replacing the disc without finding the cause leaves the machine to do it again, and the vessel must be evacuated of air and moisture before it is recharged.

49. Water-side pressure in the condenser tubes exceeding refrigerant-side pressure means:

  1. Nothing important
  2. The chiller runs better
  3. Refrigerant leaks into the water
  4. A tube leak will admit water into the refrigerant, contaminating the charge
Answer: D — A tube leak will admit water into the refrigerant, contaminating the charge
On a low-pressure machine the refrigerant side is usually the lower pressure, so a tube failure sends water inward. Water in the refrigerant and oil forms acids quickly, which is why a suspected tube leak is investigated urgently.

50. How is a suspected condenser tube leak usually confirmed?

  1. By purge run time alone
  2. It cannot be confirmed
  3. By listening
  4. By pressure-testing the water side or performing a leak test on the tube bundle, and by testing the oil and refrigerant for water
Answer: D — By pressure-testing the water side or performing a leak test on the tube bundle, and by testing the oil and refrigerant for water
Isolating and testing the water side, combined with checking the oil and refrigerant for moisture, localises the failure. Purge run time signals air ingress generally but does not distinguish a tube leak from a gasket or seal leak.

51. What is the freeze hazard during recovery from a low-pressure chiller?

  1. The refrigerant freezes
  2. The purge unit freezes
  3. The oil freezes
  4. Pulling too deep a vacuum too quickly can freeze water in the tubes and rupture them
Answer: D — Pulling too deep a vacuum too quickly can freeze water in the tubes and rupture them
As pressure drops, the remaining refrigerant boils and absorbs heat from the water still in the tubes. Water can reach freezing point and burst the tube bundle — a repair far more expensive than the recovery. Circulating water or draining it, and pulling down gradually, prevents it.

52. How is the freeze hazard managed during low-pressure recovery?

  1. By keeping condenser and chilled water circulating, or draining the tubes, and monitoring temperature while pulling down gradually
  2. By recovering as fast as possible
  3. By adding antifreeze to the refrigerant
  4. It cannot be managed
Answer: A — By keeping condenser and chilled water circulating, or draining the tubes, and monitoring temperature while pulling down gradually
Moving water carries heat to the tubes and keeps them above freezing, and draining removes the hazard entirely. Watching refrigerant temperature as the vacuum deepens is the feedback that tells you whether to slow down.

53. Why does recovery from a low-pressure chiller take so long?

  1. The refrigerant is thick
  2. The machine is cold
  3. The charge is very large and the low saturation pressure gives little differential to drive recovery
  4. Regulations require slow recovery
Answer: C — The charge is very large and the low saturation pressure gives little differential to drive recovery
Two factors compound: charges run to hundreds or thousands of pounds, and a low-pressure refrigerant sits near or below atmospheric, so there is almost no pressure pushing it toward the recovery machine. Recovering liquid first is what makes the job practical.

54. Recovering liquid refrigerant first from a low-pressure chiller is preferred because:

  1. It is required
  2. It cleans the oil
  3. It prevents freezing
  4. Liquid moves far more mass per minute than the low-density vapour
Answer: D — Liquid moves far more mass per minute than the low-density vapour
Low-pressure refrigerant vapour is extremely low in density, so vapour recovery on a thousand-pound charge is impractically slow. Transferring liquid moves the bulk quickly and leaves only the vapour tail for the recovery machine.

55. A recovery machine used on low-pressure equipment must be capable of:

  1. Pulling the required vacuum on a system that starts near or below atmospheric pressure
  2. Operating at 500 psig only
  3. Purging air
  4. Charging oil
Answer: A — Pulling the required vacuum on a system that starts near or below atmospheric pressure
A machine designed for high-pressure work expects a positive inlet pressure to feed it. Low-pressure recovery starts near atmospheric and must continue down into a vacuum, which needs equipment specified for that duty.

56. What should be done with water in the chiller tubes before a long shutdown following recovery?

  1. Leave it
  2. Add refrigerant to it
  3. Drain or otherwise protect the tubes against freezing
  4. Pressurise it
Answer: C — Drain or otherwise protect the tubes against freezing
With the refrigerant gone there is no process load, but ambient conditions can still freeze standing water and split the tubes. Draining, or ensuring freeze protection, is standard practice before a machine is left down.

57. A low-pressure appliance being opened for major service must be evacuated to what level using equipment manufactured on or after November 15, 1993?

  1. 4 inches Hg vacuum
  2. 10 inches Hg vacuum
  3. 25 mm Hg absolute
  4. 29 inches Hg vacuum
Answer: C — 25 mm Hg absolute
Low-pressure appliances are specified in absolute terms: 25 mm of mercury absolute. The inches-of-mercury-vacuum figures belong to high-pressure appliances, and mixing up the two scales is the classic Type III error.

58. Using recovery equipment manufactured before November 15, 1993 on a low-pressure appliance, the required evacuation level is:

  1. 25 mm Hg absolute
  2. 25 inches Hg vacuum
  3. 10 inches Hg vacuum
  4. No requirement
Answer: A — 25 mm Hg absolute
The 25 mm of mercury absolute requirement applies to low-pressure appliances regardless of whether the recovery equipment predates November 15, 1993. Unlike the high-pressure tiers, this figure does not change with equipment age.

59. Why is the low-pressure evacuation requirement expressed in mm Hg absolute rather than inches Hg vacuum?

  1. Tradition
  2. They mean the same number
  3. It is a translation error
  4. Because the target is a deep vacuum best expressed as an absolute pressure, not as a depth below atmospheric
Answer: D — Because the target is a deep vacuum best expressed as an absolute pressure, not as a depth below atmospheric
Inches of mercury vacuum measures how far below atmospheric you are, and it loses resolution exactly where low-pressure work happens. An absolute scale states the remaining pressure directly, which is the meaningful quantity when the machine normally runs in a vacuum anyway.

60. 25 mm Hg absolute is approximately what in microns?

  1. 250 microns
  2. 2,500 microns
  3. 25,000 microns
  4. 25 microns
Answer: C — 25,000 microns
One millimetre of mercury is 1,000 microns, so 25 mm Hg absolute is 25,000 microns. That is a moderate vacuum — far shallower than the 500-micron target used for dehydration, because the purpose here is refrigerant removal rather than boiling off water.

61. After reaching the required evacuation level on a low-pressure machine, the technician should:

  1. Isolate and confirm the vacuum holds, since a rising pressure indicates remaining refrigerant or an air leak
  2. Open it immediately
  3. Add nitrogen
  4. Start the purge unit
Answer: A — Isolate and confirm the vacuum holds, since a rising pressure indicates remaining refrigerant or an air leak
Valving off and watching the gauge distinguishes a real endpoint from a momentary reading. A rise that levels off means refrigerant is still boiling out; one that keeps climbing means air is being drawn in through a leak.

62. Why can a low-pressure machine not simply be leak-tested at normal operating pressure?

  1. It has no leaks
  2. Detectors do not work on R-123
  3. Its low side runs in a vacuum, so leaks draw air inward rather than pushing refrigerant out where a detector could sense it
  4. It is illegal
Answer: C — Its low side runs in a vacuum, so leaks draw air inward rather than pushing refrigerant out where a detector could sense it
An electronic detector needs refrigerant escaping past the leak to sense. With the low side under vacuum there is nothing coming out, so conventional sniffing finds nothing even on a machine that is clearly admitting air.

63. What is a common way to raise a low-pressure chiller to atmospheric pressure for leak testing?

  1. Add nitrogen to 100 psig
  2. Add air
  3. Run the compressor
  4. Warm the refrigerant with the water circuit or a controlled heat source so its saturation pressure rises to slightly above atmospheric
Answer: D — Warm the refrigerant with the water circuit or a controlled heat source so its saturation pressure rises to slightly above atmospheric
Gently warming the refrigerant raises its saturation pressure past atmospheric so leaks push outward and a detector can find them. The heat source is controlled and the pressure watched, because the rupture disc sits only around 15 psig.

64. What is the maximum pressure a low-pressure chiller should be raised to for leak testing?

  1. Well below the rupture disc rating, typically only a few psig above atmospheric
  2. 150 psig
  3. 100 psig
  4. There is no limit
Answer: A — Well below the rupture disc rating, typically only a few psig above atmospheric
With a disc rated near 15 psig, a test pressure of a few psig above atmospheric is the working ceiling, and manufacturer guidance governs. Applying Type II test pressures to a low-pressure vessel will blow the disc and can damage the shell.

65. A pressure test on a low-pressure machine is monitored with:

  1. A high-pressure manifold gauge
  2. A clamp meter
  3. An instrument with adequate resolution near atmospheric pressure, such as an electronic or mercury-column gauge
  4. A thermometer only
Answer: C — An instrument with adequate resolution near atmospheric pressure, such as an electronic or mercury-column gauge
A 0 to 500 psig manifold gauge cannot resolve the few psi that matter here — the entire test range sits inside the needle width. An instrument scaled to the region around atmospheric pressure is required to see anything meaningful.

66. If a leak is suspected but the machine is in a vacuum, what indirect evidence is available?

  1. Oil colour only
  2. Water temperature
  3. Compressor amps only
  4. Purge unit run time and non-condensable accumulation
Answer: D — Purge unit run time and non-condensable accumulation
A machine drawing air in reveals itself through the purge unit working harder and through non-condensables building in the condenser. Those indicators point to a leak; raising the machine above atmospheric is what lets you locate it.

67. Why must air drawn into a low-pressure chiller be treated as a serious problem?

  1. It carries moisture, which with refrigerant and oil forms acids, and it degrades capacity and efficiency
  2. It is harmless
  3. It only affects noise
  4. It improves cooling
Answer: A — It carries moisture, which with refrigerant and oil forms acids, and it degrades capacity and efficiency
Air brings water vapour with it. Moisture plus refrigerant plus heat produces acids that attack the machine internally, while the non-condensables themselves raise head pressure and cut capacity. Both reasons make a chronic air leak worth chasing.

68. What is the recommended exposure limit concept that governs machine room refrigerant monitoring?

  1. The flash point
  2. The boiling point
  3. An allowable exposure limit such as the refrigerant\u2019s AEL or TLV, below which routine exposure is considered acceptable
  4. The ODP
Answer: C — An allowable exposure limit such as the refrigerant\u2019s AEL or TLV, below which routine exposure is considered acceptable
Refrigerants carry published allowable exposure limits — R-123\u2019s is notably low compared with many refrigerants. Machine room monitors are set against those limits, and R-123\u2019s stringency is a large part of why plant rooms holding it are so carefully monitored.

69. Machine rooms containing low-pressure chillers require:

  1. No special provisions
  2. Carpeted floors
  3. Only a fire extinguisher
  4. Refrigerant vapour monitoring and mechanical ventilation that activates on detection
Answer: D — Refrigerant vapour monitoring and mechanical ventilation that activates on detection
A large release in an enclosed plant room can displace oxygen and expose workers above the allowable limit. Continuous monitoring tied to alarms and mechanical ventilation is the standard requirement, with ASHRAE 15 as the reference.

70. Self-contained breathing apparatus is required in a machine room when:

  1. Entering an area where refrigerant concentration may exceed safe limits, such as after a large release
  2. Never
  3. Doing routine gauge readings
  4. Changing oil
Answer: A — Entering an area where refrigerant concentration may exceed safe limits, such as after a large release
Once concentration may exceed the exposure limit or oxygen may be displaced, a dust mask or half-face respirator is useless — neither supplies oxygen. SCBA is the required protection for entry after a significant release.

71. Why is a standard dust mask inadequate protection against refrigerant vapour?

  1. It is too tight
  2. It is too expensive
  3. It filters particulates and supplies no oxygen, so it offers no protection against vapour or oxygen displacement
  4. It works fine
Answer: C — It filters particulates and supplies no oxygen, so it offers no protection against vapour or oxygen displacement
A particulate mask does nothing about a gas, and nothing at all about an atmosphere short of oxygen. The hazard in a refrigerant release is displacement, and only supplied-air equipment addresses it.

72. What should a technician do first upon finding a machine room refrigerant alarm active?

  1. Enter and investigate
  2. Open the chiller
  3. Silence the alarm
  4. Do not enter — evacuate the area, ensure ventilation is running, and enter only with appropriate protection
Answer: D — Do not enter — evacuate the area, ensure ventilation is running, and enter only with appropriate protection
Walking into an alarming plant room is how technicians are killed. The sequence is keep out, ventilate, account for people, and enter only with SCBA once the atmosphere is known — the alarm exists precisely to stop the instinctive entry.

73. R-123 requires particular care because:

  1. It has a comparatively low allowable exposure limit
  2. It is flammable
  3. It has a high ODP
  4. It is a CFC
Answer: A — It has a comparatively low allowable exposure limit
R-123\u2019s allowable exposure limit is low relative to many other refrigerants, so a concentration that would be unremarkable with another refrigerant can matter here. That is the reason for tight monitoring in R-123 plant rooms.

74. How is a low-pressure chiller typically charged?

  1. As vapour through the suction line
  2. With nitrogen first
  3. As liquid into the evaporator or condenser, often drawn in by the machine\u2019s own vacuum
  4. Through the purge unit
Answer: C — As liquid into the evaporator or condenser, often drawn in by the machine\u2019s own vacuum
Because the machine sits in a vacuum, it will draw liquid refrigerant in on its own once the charging line is opened. Liquid charging also avoids the very slow transfer that low-density vapour would give.

75. Before charging a low-pressure chiller after service, the machine must be:

  1. Pressurised with air
  2. Run for an hour
  3. Filled with water
  4. Evacuated to remove air and moisture
Answer: D — Evacuated to remove air and moisture
Charging into a machine full of air traps non-condensables and moisture in the charge from the start, giving high head pressure and acid formation. Evacuation to the required level comes first, every time.

76. Overcharging a low-pressure chiller can cause:

  1. Liquid carryover to the compressor and elevated pressures
  2. Better efficiency
  3. Lower head pressure
  4. No effect
Answer: A — Liquid carryover to the compressor and elevated pressures
Too much charge floods the evaporator and raises the risk of liquid reaching the centrifugal compressor, along with higher operating pressures on a vessel with limited margin. Charging to the manufacturer\u2019s level and confirming operating conditions is the control.

77. Refrigerant added to a low-pressure machine should be:

  1. Any available refrigerant
  2. A blend
  3. The refrigerant the machine is designed for, virgin or reclaimed to AHRI 700
  4. Mixed with oil
Answer: C — The refrigerant the machine is designed for, virgin or reclaimed to AHRI 700
These machines are engineered around a specific refrigerant\u2019s pressure-temperature behaviour, and a centrifugal impeller is matched to it. Substituting another refrigerant changes capacity and can push the compressor into surge; the refrigerant must also meet AHRI 700 if it is not virgin.

78. Where should recovered low-pressure refrigerant be stored?

  1. In an open drum
  2. In a plastic tank
  3. In the chiller
  4. In DOT-approved containers rated for the refrigerant and filled to no more than 80% by weight
Answer: D — In DOT-approved containers rated for the refrigerant and filled to no more than 80% by weight
Low-pressure refrigerant is still stored in DOT-approved, in-date containers under the 80% fill limit. The low operating pressure of the machine does not change the storage rules — and a warmed container of any refrigerant will build pressure.

79. What is the typical low-side operating pressure of an R-123 chiller at design conditions?

  1. A vacuum, below atmospheric pressure
  2. Around 100 psig
  3. Around 50 psig
  4. Around 250 psig
Answer: A — A vacuum, below atmospheric pressure
At chilled-water temperatures R-123\u2019s saturation pressure is below one atmosphere, so the evaporator runs in a vacuum. Everything distinctive about Type III — inward leaks, purge units, the leak-test warming procedure — follows from that single fact.

80. The purge unit returns which substance to the chiller?

  1. Air
  2. Water
  3. Refrigerant separated from the non-condensables
  4. Oil only
Answer: C — Refrigerant separated from the non-condensables
A purge unit condenses and returns the refrigerant it captures along with the air, expelling only the non-condensables. How completely it does that separation is what distinguishes a high-efficiency purge from a legacy unit that vents refrigerant with every cycle.

81. A low-pressure chiller left with condenser water off while running risks:

  1. Nothing
  2. Better efficiency
  3. Lower head pressure
  4. Rising pressure and a possible rupture disc failure
Answer: D — Rising pressure and a possible rupture disc failure
With no water carrying heat away, the condenser cannot reject the compressor\u2019s work and pressure climbs toward the disc rating. Loss of condenser water with the machine running is one of the more common causes of a burst disc.

82. Soap bubble testing on a low-pressure machine works only when:

  1. The area under test is above atmospheric pressure so gas pushes outward
  2. The machine is in a vacuum
  3. The machine is cold
  4. Never
Answer: A — The area under test is above atmospheric pressure so gas pushes outward
Bubbles form because escaping gas pushes through the solution. Under vacuum nothing comes out, so the machine must first be raised slightly above atmospheric — carefully, given the low rupture disc rating — before bubbles mean anything.

83. Oxygen deprivation monitors in a machine room are used because:

  1. Refrigerant is toxic in small doses
  2. They detect fire
  3. Refrigerant vapour displaces air and can create an oxygen-deficient atmosphere without warning
  4. They measure humidity
Answer: C — Refrigerant vapour displaces air and can create an oxygen-deficient atmosphere without warning
Most refrigerants are heavier than air and give no reliable warning as they push oxygen out of a low-lying enclosed space. An oxygen monitor detects the condition that actually kills people, which a refrigerant-specific sensor alone may not.

84. During recovery, chilled water should ideally be:

  1. Drained immediately
  2. Replaced with refrigerant
  3. Heated to boiling
  4. Circulating, to carry heat to the tubes and prevent freezing
Answer: D — Circulating, to carry heat to the tubes and prevent freezing
Circulating water keeps supplying heat to the tube walls as the boiling refrigerant tries to take it away, holding them above freezing. Draining the tubes is the alternative, and either is better than leaving still water in place during a deep pull-down.

85. The evacuation requirement for low-pressure appliances applies when:

  1. The appliance is opened for major maintenance, service, or repair
  2. Only at disposal
  3. Only annually
  4. Never
Answer: A — The appliance is opened for major maintenance, service, or repair
The requirement attaches to opening the appliance for major service, the same trigger as on high-pressure equipment — removal of a major component. The level differs (25 mm Hg absolute), but the trigger is the same concept.

86. Compared with high-pressure equipment, low-pressure chillers are usually found in:

  1. Large commercial and institutional buildings
  2. Residential homes
  3. Vehicles
  4. Household refrigerators
Answer: A — Large commercial and institutional buildings
Centrifugal low-pressure chillers serve hospitals, universities, and large office buildings where cooling loads run to hundreds or thousands of tons. Their size and the plant room infrastructure they need put them out of reach of smaller applications.

87. A purge unit that runs continuously most likely indicates:

  1. Normal operation
  2. Too much refrigerant
  3. A significant air leak that needs to be found and repaired
  4. A failed chilled water pump
Answer: C — A significant air leak that needs to be found and repaired
Continuous purging means air is entering as fast as the unit can remove it. Beyond the efficiency penalty, the incoming moisture is forming acids, so this is treated as an urgent fault rather than a nuisance.

88. Rupture discs on low-pressure chillers should be:

  1. Replaced annually regardless
  2. Removed
  3. Painted over
  4. Inspected per manufacturer guidance and replaced after any rupture or sign of corrosion or fatigue
Answer: D — Inspected per manufacturer guidance and replaced after any rupture or sign of corrosion or fatigue
A disc is a single-use device that also degrades with corrosion and pressure cycling. Manufacturer guidance governs inspection, and any rupture or visible deterioration means replacement — along with finding out what caused it.

89. What instrument confirms the required 25 mm Hg absolute evacuation level?

  1. An absolute pressure instrument such as an electronic vacuum (micron) gauge
  2. A compound manifold gauge
  3. A clamp meter
  4. A thermometer
Answer: A — An absolute pressure instrument such as an electronic vacuum (micron) gauge
A compound gauge reads inches of mercury vacuum and has no useful resolution at this level. A micron gauge reads absolute pressure directly, and 25 mm Hg absolute is 25,000 microns on its scale.

90. After charging, non-condensables in a low-pressure chiller are removed by:

  1. Venting the condenser to atmosphere
  2. Adding more refrigerant
  3. The purge unit during operation
  4. Draining the oil
Answer: C — The purge unit during operation
The purge unit exists for exactly this, collecting non-condensables at the condenser and expelling them while keeping the refrigerant. Venting the condenser directly would release refrigerant along with the air, which is a violation.

91. Before entering a machine room after a suspected large release, a technician should:

  1. Enter quickly to assess
  2. Open the chiller first
  3. Hold their breath
  4. Ventilate, verify the atmosphere with monitors, and use SCBA if concentrations or oxygen levels are unsafe
Answer: D — Ventilate, verify the atmosphere with monitors, and use SCBA if concentrations or oxygen levels are unsafe
Ventilation and instrument verification come before entry, and SCBA covers the case where the atmosphere is not yet safe. Holding your breath is not a control — oxygen-deficient atmospheres incapacitate faster than most people expect.

92. Why are low-pressure chiller vessels physically large?

  1. Low-pressure refrigerant vapour has very low density, so large volumes must be moved and condensed
  2. For easier service
  3. To hold water
  4. For appearance
Answer: A — Low-pressure refrigerant vapour has very low density, so large volumes must be moved and condensed
Low vapour density means a large volumetric flow for a given cooling capacity, and the heat exchangers must be sized to match. The thin-walled construction that goes with low design pressure is also why these vessels tolerate so little test pressure.

93. An electronic leak detector is used on a low-pressure machine:

  1. While it is in a vacuum
  2. Only on the water side
  3. After the machine has been brought slightly above atmospheric pressure
  4. Never
Answer: C — After the machine has been brought slightly above atmospheric pressure
The detector needs refrigerant escaping to sense it, and that only happens once the interior is above atmospheric. The warming is done carefully and the pressure watched, because the rupture disc leaves very little headroom.

94. Transferring liquid refrigerant from a chiller to a storage vessel is often done by:

  1. Gravity alone
  2. Heating the storage vessel
  3. Compressed air
  4. Using a pump or a pressure differential created by the recovery machine
Answer: D — Using a pump or a pressure differential created by the recovery machine
A transfer pump or a machine-generated pressure difference moves liquid far faster than gravity or vapour recovery could. Warming the storage vessel would work against you by raising the pressure you are pushing into.

95. Purge unit maintenance is important because:

  1. A poorly maintained unit vents more refrigerant and removes non-condensables less effectively
  2. It is decorative
  3. It affects water flow
  4. It is not important
Answer: A — A poorly maintained unit vents more refrigerant and removes non-condensables less effectively
A neglected purge unit fails on both counts: it lets refrigerant go out with the air, which is a regulated release, and it leaves non-condensables behind, which costs capacity. Maintenance protects both compliance and efficiency.

96. The relatively low design pressure of low-pressure vessels means:

  1. They are unsafe
  2. They cannot hold refrigerant
  3. Service procedures must respect much lower pressure limits than high-pressure equipment
  4. They need no relief device
Answer: C — Service procedures must respect much lower pressure limits than high-pressure equipment
These vessels are perfectly safe within their design envelope — the hazard comes from applying high-pressure habits to them. Test pressures, nitrogen use, and relief settings all scale down, and the rupture disc is the last line of defence.

97. Mixing up "25 mm Hg absolute" with "25 inches Hg vacuum" would result in:

  1. The same outcome
  2. A DOT violation
  3. A deeper vacuum than needed
  4. Evacuating to a far shallower level than required, leaving refrigerant behind
Answer: D — Evacuating to a far shallower level than required, leaving refrigerant behind
Twenty-five inches of mercury vacuum is only about 127 mm Hg absolute — roughly five times the remaining pressure the rule allows. Stopping there leaves a substantial quantity of refrigerant in the machine to escape when it is opened.

98. Ventilation in a machine room should:

  1. Exhaust to the outside, drawing from low in the room where heavy refrigerant vapour collects
  2. Recirculate air
  3. Be turned off during service
  4. Only run in summer
Answer: A — Exhaust to the outside, drawing from low in the room where heavy refrigerant vapour collects
Refrigerant vapour is heavier than air and pools at floor level, so a low intake exhausting outdoors is what actually clears it. Recirculating simply redistributes the hazard, and shutting ventilation off during service removes protection exactly when it is needed.

99. The main reason Type III is a separate certification is that:

  1. Low-pressure machines are rare
  2. They use different oil
  3. Their vacuum operation, large charges, thin-walled vessels, and purge systems demand procedures that differ fundamentally from high-pressure work
  4. They are newer
Answer: C — Their vacuum operation, large charges, thin-walled vessels, and purge systems demand procedures that differ fundamentally from high-pressure work
Every distinctive Type III procedure — inward leaks, warming for leak tests, purge units, freeze protection, an absolute-pressure evacuation target, a 15 psig rupture disc — follows from the refrigerant boiling above 10°C. Applying Type II habits to these machines damages them.

100. A technician recovering from a large chiller should monitor water temperature because:

  1. It affects the refrigerant colour
  2. It indicates the charge level
  3. It is required hourly
  4. Falling water temperature warns that tubes are approaching freezing as the refrigerant boils off
Answer: D — Falling water temperature warns that tubes are approaching freezing as the refrigerant boils off
The water temperature is the early warning for the freeze hazard. Watching it as the vacuum deepens tells you when to slow the pull-down or increase water flow, before ice forms and splits the tube bundle.
Other Sections
Keep Practicing
Practice Test

EPA 608 Core

Refrigerant fundamentals, regulations, safety, and recovery practice.

100 questions
Practice Test

EPA 608 Type I

Small appliances — factory-sealed systems holding 5 pounds of refrigerant or less.

100 questions
Practice Test

EPA 608 Type II

High-pressure and very high-pressure appliances — residential and commercial AC, heat pumps, and refrigeration.

100 questions
Full Exam

EPA 608 Universal

All four sections in one 100-question attempt, scored section by section.

100 questions

Read the full EPA 608 certification guide for exam costs, testing organizations, and how to choose between Type I, II, III, and Universal.

FAQ
EPA 608 Type III Questions
How many questions are on the EPA 608 Type III exam?
The Type III section is 25 multiple-choice questions. 25 multiple-choice questions taken with Core, proctored and open-book, 70% to pass. Fewer technicians hold Type III than any other, which is exactly why chiller work pays.
What score do I need to pass EPA 608 Type III?
You need 70% — 18 of 25 questions — to pass. Each section is scored independently, so passing Core does not offset a failing Type III score, and you must pass both to be certified for type iii work.
Who needs EPA 608 Type III certification?
Technicians and building engineers who work on large centrifugal chillers using R-11, R-123, or R-514A. Low-pressure appliances — centrifugal chillers operating below atmospheric pressure.
Is this practice test the real EPA 608 exam?
No. This is free study material written from the published rule in 40 CFR Part 82, Subpart F — it does not reproduce exam content. The real exam is proctored and administered by an EPA-approved certifying organization, and it is open-book, so bring your study guide.
Does EPA 608 Type III certification expire?
No. Section 608 certification is issued for life under the current rule. There is no renewal requirement and no continuing education, though you must keep proof of certification at your place of business.
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