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EPA 608 Type III Practice Test
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Type III covers low-pressure appliances — chiefly the centrifugal chillers that cool large buildings, running refrigerants such as R-11, R-123, and R-1233zd whose saturation pressure sits below 45 psia at 104°F, which means these machines operate in a vacuum. These 25 questions drill the numbers that make Type III its own discipline: evacuation to 25 mm Hg absolute, the 10 psig maximum leak-test pressure for low-pressure centrifugal chillers, recovery and recharging techniques for machines under vacuum, and ASHRAE Standard 15 equipment-room requirements.
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Question 1 of 25.Under EPA regulations, an appliance is classified as low-pressure when it uses a refrigerant whose liquid-phase saturation pressure at 104°F is:
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Under EPA regulations, an appliance is classified as low-pressure when it uses a refrigerant whose liquid-phase saturation pressure at 104°F is:
- Below 45 psig
- Above 45 psia
- Below 45 psia (correct answer)
- Below 25 mm Hg
The regulatory definition is a liquid-phase saturation pressure below 45 psia (pounds per square inch absolute) at 104°F, which captures refrigerants such as R-11, R-113, R-123, and R-245fa. "Below 45 psig" is the tempting choice because the number matches, but the definition uses absolute pressure — 45 psig equals roughly 59.7 psia, a meaningfully higher threshold. The 25 mm Hg option mixes up units and context — the classification threshold is expressed in psia, not in millimeters of mercury.
Which pair of refrigerants would you expect to find in low-pressure centrifugal chillers?
- R-11 and R-123 (correct answer)
- R-22 and R-410A
- R-134a and R-404A
- R-502 and R-717
R-11 (a CFC) and R-123 (an HCFC) boil above normal room temperature, so chillers built around them operate in a vacuum and fall under Type III. R-134a is the tempting distractor because it is also used in centrifugal chillers, but it is a high-pressure refrigerant covered by Type II; R-22, R-410A, R-404A, R-502, and R-717 (ammonia) likewise serve high-pressure equipment.
While a low-pressure chiller is running, a small leak in the evaporator section will most likely result in:
- Rapid loss of the liquid refrigerant charge
- Air and moisture being drawn into the machine (correct answer)
- Oil being forced out of the compressor
- Evaporator pressure rising above atmospheric
The evaporator of an operating low-pressure chiller sits in a deep vacuum, so a leak pulls air and moisture inward rather than letting refrigerant escape; the purge unit must then work to remove the air. Rapid charge loss is the tempting answer because that is exactly what a leak does on high-pressure equipment, but it requires internal pressure above atmospheric — the opposite of a low-pressure machine's normal operating condition.
The purge unit on a low-pressure chiller normally takes its suction from the:
- Bottom of the evaporator
- Compressor oil sump
- Liquid line leaving the condenser
- Top of the condenser (correct answer)
Air and other non-condensables cannot liquefy at condenser conditions, so they collect above the refrigerant at the highest point of the condenser, which is where the purge unit draws them off for separation. The bottom of the evaporator is the tempting choice because it is a familiar service point on these machines, but it is the lowest spot in the system, where liquid refrigerant — not air — accumulates.
A low-pressure chiller's purge unit begins running far more often than it has historically. The most likely explanation is:
- Air is leaking into the system (correct answer)
- The machine is overcharged with refrigerant
- Condenser water flow is too high
- The rupture disc has burst
Because the machine operates in a vacuum, any leak admits air, and the purge unit cycles to remove it — steadily increasing purge run time is the classic sign that the system has a leak needing repair. A burst rupture disc is the tempting choice since it would also admit air, but a disc failure is a sudden, obvious event that opens the shell wide to the atmosphere, not a cause of gradually growing purge activity. Overcharge and condenser water flow do not introduce non-condensables.
Air that has accumulated in the condenser of a low-pressure chiller will cause:
- Lower than normal head pressure
- Frost on the evaporator shell
- Higher than normal head pressure (correct answer)
- A drop in the chilled-water temperature
Non-condensable air blankets the condenser tube surfaces and adds its own partial pressure to the refrigerant's, so head pressure climbs and efficiency drops until the purge unit removes the air. "Lower head pressure" is the tempting reversal — it feels intuitive that a machine running in a vacuum would lose pressure when compromised, but air entering the shell adds pressure; it never lowers it.
A technician using recovery equipment manufactured after November 15, 1993, is preparing to open a low-pressure appliance for a major repair such as compressor removal. EPA regulations require the appliance first to be evacuated to:
- 0 psig
- 25 mm Hg absolute (correct answer)
- 25 in. Hg gauge vacuum
- 50 mm Hg absolute
With recovery equipment manufactured or imported on or after November 15, 1993, the required evacuation level for low-pressure appliances is 25 mm Hg absolute — nearly a complete vacuum, equivalent to roughly 29 in. Hg on a gauge. "25 in. Hg vacuum" is the classic trap: it repeats the number 25 but describes a far shallower vacuum of about 125 mm Hg absolute; that level survives in the rule only as a grandfather provision for recovery equipment built before the November 1993 cutoff. Neither 0 psig nor 50 mm Hg reaches the depth of vacuum the rule demands for a major repair.
The correct sequence for recovering the charge from a low-pressure chiller is:
- Vapor removal only, since liquid cannot exist in a vacuum
- Oil removal first, then liquid, then vapor
- Push the charge out with dry nitrogen, then evacuate
- Liquid removal first, followed by recovery of the remaining vapor (correct answer)
The bulk of the charge is removed quickly as liquid, and the recovery machine's compressor then pulls the remaining vapor down to 25 mm Hg absolute. "Vapor only" is tempting because the machine operates in a vacuum, but at those saturation conditions plenty of liquid refrigerant sits in the evaporator, and moving the whole charge as vapor would take an enormous amount of time given vapor's huge specific volume at low pressure. Nitrogen would mix with and contaminate the refrigerant.
Why must water be kept circulating through a low-pressure chiller's evaporator and condenser tubes while the refrigerant charge is being removed?
- To keep tube water from freezing and rupturing the tubes (correct answer)
- To keep the recovered refrigerant warm enough to condense
- To flush mineral deposits out of the tube bundle
- To keep air from entering the waterside of the machine
As refrigerant boils off during recovery it absorbs heat from the tube bundles; if the water in the tubes is left standing, it can freeze, and the expanding ice can rupture tubes — a very expensive failure. Flowing water continually brings in heat and stays above freezing. The condensing answer is the tempting one because it also involves heat transfer, but condensing the recovered refrigerant is the job of the recovery unit's own condenser, not the chiller's water circuits.
During recovery, the last of the refrigerant vapor can be removed from a low-pressure chiller more quickly by:
- Packing the evaporator shell in ice
- Adding nitrogen to raise the shell pressure
- Circulating warm water through the chiller's tubes (correct answer)
- Throttling the recovery unit's suction valve
Warming the vessel raises the refrigerant's vapor pressure and boils refrigerant out of the oil and off cold internal surfaces, letting the recovery machine capture vapor that would otherwise linger for hours. Nitrogen is the tempting choice because it also raises shell pressure, but it mixes with the refrigerant, contaminating the recovered charge and requiring a purge that would vent refrigerant. Chilling the shell or throttling the suction would both slow recovery down.
Before oil is drained from a low-pressure machine, the oil should first be heated to approximately:
- 100°F
- 130°F (correct answer)
- 175°F
- 212°F
Low-pressure refrigerants are highly soluble in cool oil, so a surprising amount of refrigerant rides out with an unheated oil drain. Warming the oil to about 130°F drives the dissolved refrigerant out so it can be recovered rather than released. 100°F is the tempting near-miss — it is warm but not hot enough to liberate the refrigerant effectively — while temperatures approaching 212°F are unnecessary and risk degrading the oil.
The rupture disc fitted to a low-pressure chiller is designed to relieve at:
- 5 psig
- 10 psig
- 15 psig (correct answer)
- 25 psig
Low-pressure chillers are protected by a rupture disc that bursts at 15 psig, venting the shell before over-pressure can damage the vessel. The lower figures are tempting because a machine that spends its life in a vacuum seems as though it would need only minimal protection, but 15 psig is the standard relief rating for the disc on a low-pressure chiller.
When pressurizing a low-pressure chiller to locate leaks, the pressure must never exceed:
- 10 psig (correct answer)
- 15 psig
- 25 psig
- 30 psig
Leak testing on a low-pressure machine is limited to a maximum of 10 psig. The tempting answer is 15 psig because it is the other pressure number associated with Type III equipment, but 15 psig is the relief setting of the rupture disc — pressurizing to that level would burst the disc and release the refrigerant, which is exactly why the test limit sits a safe margin below it.
Which is the recommended way to build pressure in a low-pressure chiller for leak testing?
- Pressurize with dry nitrogen to 30 psig
- Warm the machine with electric heating blankets on the shell (correct answer)
- Run the chiller's compressor with condenser water shut off
- Add compressed shop air until the gauge reads positive
Controlled heat — electric heating blankets on the shell or warm water in the tube bundles — raises the refrigerant's saturation pressure gradually, and the technician stops before the 10 psig limit. Nitrogen at 30 psig is the tempting distractor because nitrogen is standard for high-pressure systems, but 30 psig is triple the allowed test pressure and double the rupture disc rating. Shop air adds moisture and non-condensables, and deadheading the compressor risks damaging the machine.
A low-pressure chiller is evacuated to 1 mm Hg for a standing vacuum test. Under ASHRAE Guideline 3, the machine should be further leak-checked if its pressure rises above:
- 1.5 mm Hg
- 2 mm Hg
- 2.25 mm Hg
- 2.5 mm Hg (correct answer)
ASHRAE Guideline 3 treats a rise from 1 mm Hg to a level above 2.5 mm Hg during the standing vacuum test as evidence that the machine leaks and needs further checking. The 2 mm Hg option is tempting because a doubling of pressure sounds alarming, but a modest rise that stays at or below 2.5 mm Hg can be caused merely by residual moisture or refrigerant off-gassing from the oil and does not by itself condemn the machine.
Before opening a low-pressure appliance for a repair that is NOT major and will not be followed by evacuation to the environment, EPA regulations require the machine's pressure to be:
- Reduced to 25 mm Hg absolute
- Reduced to 10 in. Hg vacuum
- Left at its normal operating vacuum
- Raised to 0 psig (correct answer)
Because the machine normally sits in a vacuum, opening it as-is would draw air and moisture inside; the rule therefore requires pressurizing a low-pressure appliance up to 0 psig (atmospheric) before it is opened for non-major work. Evacuating to 25 mm Hg absolute is the tempting answer because it is the famous Type III number, but that deep evacuation is what the rule reserves for major repairs, not for the non-major work described here.
Which method may NOT be used to bring an R-123 chiller up to atmospheric pressure before a non-major repair?
- Circulating warm water through the tube bundles
- Adding nitrogen to the shell (correct answer)
- Wrapping the shell with electric heating blankets
- Letting the machine warm to equipment-room temperature
EPA prohibits any pressure-raising method that would require subsequent purging, because purging the added gas would vent refrigerant with it — so nitrogen cannot be used, and controlled heat (warm water, heating blankets, or simply letting the machine warm up) is used instead. Nitrogen is the tempting answer precisely because it is the normal way to break a vacuum on high-pressure equipment; the only regulatory exception to the purging ban is for machines using R-113.
Which of the following jobs on a low-pressure chiller is classified as a MAJOR repair under EPA regulations?
- Replacing the condenser (correct answer)
- Replacing a purge-unit solenoid valve
- Changing a chilled-water temperature sensor
- Repacking a refrigerant-side service valve
EPA defines major maintenance, service, or repair as work involving removal of the compressor, condenser, evaporator, or auxiliary heat exchanger — and it triggers the requirement to evacuate the machine to 25 mm Hg absolute first. Repacking a refrigerant-side valve is the tempting distractor because it does open the refrigerant circuit, but it is non-major work, for which the machine is instead brought up to 0 psig before opening.
When charging an evacuated low-pressure chiller, liquid refrigerant should not be introduced until the system pressure corresponds to a saturation temperature of at least:
- 30°F
- 32°F
- 36°F (correct answer)
- 43°F
Charging begins with vapor because liquid released into a deep vacuum flashes violently, chilling the machine enough to freeze water in the tubes. Vapor is added until the pressure corresponds to a saturation temperature above 36°F, and only then is liquid charged. The tempting answer is 32°F since that is water's freezing point, but charging at exactly 32°F leaves no safety margin — the 36°F threshold keeps tube surfaces safely above freezing.
After vapor charging has raised the pressure to a safe level, liquid refrigerant is charged into a low-pressure machine through the:
- Purge unit connection on the condenser
- Compressor discharge service port
- Rupture disc flange
- Evaporator charging valve (correct answer)
Liquid is charged through the charging valve on the evaporator, the lowest access point on the machine, which delivers the liquid directly to where it belongs. The purge connection is the tempting choice because it is another familiar refrigerant-side port, but it sits at the top of the condenser and exists to remove air and non-condensables — charging liquid there would flood the purge system rather than fill the evaporator.
A comfort-cooling chiller holding 600 lbs of R-123 must have its leaks repaired when the annualized leak rate exceeds:
- 5%
- 10% (correct answer)
- 20%
- 30%
For appliances with a full charge of 50 lbs or more of an ozone-depleting refrigerant, the leak-repair trigger rates are 10% for comfort cooling, 20% for commercial refrigeration, and 30% for industrial process refrigeration. The 20% and 30% figures are tempting because they come from the same regulatory table, but they apply to the other appliance categories — a building air-conditioning chiller is comfort cooling and carries the strictest 10% trigger.
Once a comfort-cooling chiller with more than 50 lbs of refrigerant is found leaking above its trigger rate, the owner generally must repair the leaks within:
- 7 days
- 14 days
- 30 days (correct answer)
- 120 days
Leaks must be repaired within 30 days of discovering that the trigger rate has been exceeded, unless the owner instead develops a plan within that time to retrofit or retire the appliance. The 120-day figure is the tempting distractor because it does appear in the rule, but it is an extension available only to industrial process refrigeration when repairs require shutting down the process — it does not apply to comfort-cooling chillers.
R-11 needed to service an existing CFC chiller today can be obtained:
- Only from recovered, reclaimed, or stockpiled supplies (correct answer)
- From domestic production allowed for servicing needs
- Under a special EPA production permit issued per job
- Only from newly imported virgin refrigerant
U.S. production and import of CFCs such as R-11 ended on January 1, 1996 under the Montreal Protocol phaseout, so existing machines survive entirely on refrigerant that has been recovered, recycled, reclaimed, or stockpiled — which is why careful recovery on every Type III job matters. The domestic-production option is tempting because the HCFC R-123 did retain a servicing allowance (until January 1, 2030), but no such servicing tail exists for CFCs.
ASHRAE Standard 15 calls for a mechanical equipment room housing an R-123 chiller to be equipped with:
- A carbon monoxide detector at the highest point
- A smoke detector wired to shut down the chiller
- No special detection, because R-123 is nonflammable
- A refrigerant vapor monitor that alarms at the exposure limit (correct answer)
R-123 is a low-toxicity (safety group B1) refrigerant, but it still has an occupational exposure limit, and its heavier-than-air vapor can pool in an equipment room and displace oxygen — so ASHRAE 15 calls for a refrigerant-specific vapor monitor that alarms before the exposure limit is reached, along with mechanical ventilation. "No special detection" is tempting because R-123 really is nonflammable, but nonflammability does nothing to address the inhalation and oxygen-displacement hazards.
A technician recovers a low-pressure chiller to 25 mm Hg absolute, closes the valves, and shuts off the recovery machine. Over the next hour the pressure climbs slowly, then levels off and holds steady. This indicates:
- Air is leaking steadily into the machine
- Refrigerant trapped in the oil has boiled off into the shell (correct answer)
- The rupture disc has begun to weep
- Water in the tubes has frozen
Refrigerant dissolved in the oil and clinging to cold surfaces continues to off-gas after recovery stops, so the pressure rises and then stabilizes once the vapor reaches equilibrium; the technician should recover that additional vapor before opening the machine. An air leak is the tempting answer, but inward leakage would make the pressure keep climbing steadily toward atmospheric — it would not level off and hold.
FAQ: The EPA 608 Type III Exam
What is a low-pressure appliance, exactly?
An appliance using a refrigerant whose liquid-phase saturation pressure is below 45 psia at 104°F — in practice, centrifugal chillers running R-11, R-123, or the newer R-1233zd. Because these machines operate below atmospheric pressure, air leaks in rather than refrigerant leaking out, which is why Type III has its own recovery, purge, and leak-testing rules.
What numbers does the Type III section test hardest?
Two above all: evacuation to 25 mm Hg absolute before opening a low-pressure appliance (with recovery equipment made after November 15, 1993), and the 10 psig maximum pressure when leak-testing a low-pressure centrifugal chiller — exceed it and you can rupture the rupture disc. Add ASHRAE Standard 15 equipment-room requirements (refrigerant sensors, ventilation, self-contained breathing apparatus availability) and you have the exam’s favorite territory.
Who actually needs Type III certification?
Technicians who maintain, service, repair, or dispose of low-pressure chillers — typically the central plants of office towers, hospitals, and campuses. It is the least commonly held Type on its own; most techs who need it earn Universal instead, since chiller work rarely comes without high-pressure equipment nearby. Like Type II, it requires passing the proctored Core section.
Are these questions taken from the real EPA 608 exam?
No. Real exam items belong to the EPA-approved certifying organizations (ESCO Institute, Mainstream Engineering, and others) and are confidential — be wary of any site claiming to have them. Our questions are original, written to mirror the style, difficulty, and published EPA test topics for each section. Scoring well here is strong evidence you are ready, not a preview of the exact questions you will see.
What score do I need to pass the real EPA 608 exam?
The regulation sets the pass mark at 70 percent per section, which in practice means 18 of 25 correct (72 percent) on each 25-question section. The one exception is the open-book Type I route, which requires 84 percent — 21 of 25 — in both its Core and Type I sections. Certification never expires once earned, so passing is a one-time job.
Is this practice test really free?
Yes. Every question, explanation, and score report on HVACTechTest is free, with no signup, no credit card, and no trial that expires. Retake any test as many times as you want.
The Other EPA 608 Sections
30 questions
Core — Required of Every Candidate
Ozone depletion, the venting prohibition, recovery/recycle/reclaim, safety, cylinders, and the HFC phasedown — the section everyone must pass.
25 questions
Type I — Small Appliances
Factory-sealed appliances with 5 lb of refrigerant or less: the small-appliance definition and the 90%/80% recovery requirements.
25 questions
Type II — High-Pressure Appliances
Split systems, heat pumps, rooftop units, and supermarket refrigeration: evacuation levels, leak-rate triggers, and P-T relationships.
Scoring above 70%? Time to book the real exam
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