What gets tested · Type III
The EPA 608 Type III section: low-pressure chillers
The EPA 608 Type III section certifies you to work on low-pressure appliances, such as centrifugal chillers running R-123, whose refrigerant has a saturation pressure below 45 psia at 104 °F (40 CFR 82.152, eCFR as of October 5, 2026). Because the evaporator side runs below atmospheric pressure, Type III turns several Type II habits upside down.
A low-pressure chiller at a glance
Type III against Type II
Where the low-pressure rules differ
| Item | Type II | Type III |
|---|---|---|
| Pressure class | Medium, high, very high: 45 psia and up at 104 °F | Low: below 45 psia at 104 °F |
| Example refrigerants | R-22, R-134a, R-407C | R-123, R-113, R-245fa |
| Disposal or major repair, newer recovery gear | 0 to 15 inHg vacuum | The table's deepest row, in mm Hg absolute |
| Before a non-major repair | Evacuate to 0 psig | Pressurize to 0 psig |
| Equipment-room sensors | Oxygen-deprivation sensor | Oxygen-deprivation sensor; refrigerant sensor for R-123 |
| Leak repair thresholds | 20 / 30 / 10% at 50 lb or more of ODS refrigerant | 20 / 30 / 10% at 50 lb or more of ODS refrigerant |
Yellow edge: the two columns say different things on this row.
Sources: 40 CFR 82.152, 40 CFR 82.156 and 40 CFR 82.157, eCFR as of October 5, 2026; sensor rows from ASHRAE 15 as summarized in the EPA test topics, checked October 7, 2026. Evacuation levels in full: required evacuation levels.
Which Type III numbers are rule, and which are practice
Type III prep treats every number as rule. Some are: the low-pressure row of Table 1 is written into 40 CFR 82.156(a), and the 50-lb leak-repair line into 82.157 (eCFR as of October 5, 2026). Others, such as a maximum pressure for leak testing a chiller or a cut-out setting on the recovery unit, are exam key and industry practice, not in the rule text. Learn those for the test, and on the job follow the chiller manufacturer's documentation.
Oil gets its own temperature: for Type III the test topics say to heat the oil to 130 °F before removing it (EPA test topics, checked October 7, 2026).
Recharging runs in a fixed order: vapor before liquid, and centrifugal chillers are charged through the evaporator charging valve (EPA test topics, checked October 7, 2026). The quiz asks why the order matters.
Leak repair works as it does on Type II equipment, explained on leak detection and repair; a chiller charged only with R-245fa, an HFC, isn't covered by the Section 608 leak rules, as leak-rate thresholds explains.
Equipment rooms are the safety thread. A refrigerant sensor is expected where R-123 is used, and an oxygen-deprivation sensor in any machinery room, because refrigerant vapor released in a closed room displaces the air you breathe before you notice it (ASHRAE 15, as summarized in the EPA test topics, checked October 7, 2026).
Two components exist because of the low side's pressure. A purge unit removes non-condensables, and one that runs far more than usual is a leak signal, per the test topics. The rupture disc protects the evaporator from overpressure. Each has its own page: purge units and the rupture disc.
Before you sit Type III
- You can place R-123, R-113 and R-245fa in the low-pressure class and say why.
- You convert between inches of vacuum, mm Hg absolute and microns without a chart.
- You know the recharging order and where a centrifugal chiller is charged.
- You can explain what the purge unit and the rupture disc each protect against.
- You know which Type III numbers come from the rule and which from the exam key.
- You've passed Core or have it scheduled: every type certificate requires it (40 CFR 82, Appendix D (a), eCFR as of October 5, 2026). Start with the Core section.
Chillers that run below atmosphere
Track whether each reading is gauge or absolute before you compare it with an option; many of the traps here are units.
0 right · 0 of 20 answered
Which method is recommended for detecting leaks in a low-pressure refrigeration unit during routine maintenance?
Why each option is right or wrong
Answer: A. Controlled hot water or heater blankets
- ACorrect: raising the temperature with controlled hot water or heater blankets lifts a low-pressure system above atmospheric pressure so refrigerant leaks out and can be found, without adding gas that must later be purged.
- BCO₂ is not used to pressurize a chiller for leak testing; it adds a non-condensable gas and gives a leak detector nothing to sense.
- CTap water is the wrong idea: the method is to heat the refrigerant (often by circulating warm water through the tubes), not to put water anywhere on or in the system.
- DElectric fans move air across the unit but do not raise internal pressure, so the vacuum-side leaks stay hidden.
Controlled hot water or heater blankets warm the refrigerant and raise a low-pressure chiller slightly above atmospheric pressure, so a leak pushes refrigerant out where a detector can find it.
When pressure testing a low-pressure chiller, the maximum pressure to apply is:
Why each option is right or wrong
Answer: A. 10 psig.
- ACorrect: for a low-pressure chiller, test at no more than 10 psig, below a rupture disc that typically opens at about 15 psig (exam key and industry practice, not in the rule text).
- B30 psig is double the typical 15 psig rupture-disc setting of a low-pressure chiller, so it would burst the disc and vent the charge.
- C25 psig is still well above the roughly 15 psig rupture-disc rating of a low-pressure chiller.
- D50 psig is a pressure for testing high-pressure equipment, not a low-pressure chiller, whose rupture disc would open far below it.
Stay at or below 10 psig, under the rupture disc, which is usually set around 15 psig; both figures are exam key and industry practice, not in the rule text. Follow the manufacturer's limit.
What is the primary concern when using heating blankets on a low-pressure chiller during leak testing?
Why each option is right or wrong
Answer: A. Maintaining uniform temperature distribution
- ACorrect: heat evenly so no part of the shell overheats and the pressure rise stays controlled, below the test-pressure limit and the rupture-disc setting.
- BMaximum heat is exactly what to avoid; fast, intense heating can overshoot the pressure limit and pop the rupture disc.
- CKeeping the blanket dry is ordinary electrical care, not the main concern; the risk is uneven or excessive heating of the vessel.
- DPower use is a cost issue, not a safety or leak-test concern.
Temperature distribution must be uniform to prevent thermal stress and ensure accurate leak detection. Uneven heating can cause false readings and potentially damage the system.
A technician proposes using a mixture of trace gas and dry nitrogen to leak-check a low-pressure chiller, intending to pressurize the evaporator to 20 psig for easier leak detection. What is the main hazard of this plan?
Why each option is right or wrong
Answer: C. Activation of the system's rupture disc
- APermanent tube collapse is not the issue at 20 psig; the weak point is the rupture disc, which is designed to open first.
- BSubcooling the trace gas is not a real hazard of over-pressurizing; the danger is exceeding the vessel's relief setting.
- CCorrect: low-pressure chillers usually have a rupture disc set around 15 psig, so pressurizing to 20 psig would burst it and vent the charge; keep test pressure at or below 10 psig.
- DNitrogen and trace gas do not form acidic compounds just from being pressurized; acids come from moisture and breakdown of refrigerant and oil.
Pressurizing to 20 psig would burst the rupture disc, which on a low-pressure chiller typically relieves at about 15 psig, and vent the whole test charge. Keep test pressure within the manufacturer's limit, commonly 10 psig or less; both figures are exam key and industry practice, not in the rule text.
When injecting trace gas and nitrogen for leak detection on a low-pressure chiller, when must the technician isolate the nitrogen regulator?
Why each option is right or wrong
Answer: C. Before system pressure exceeds 10 psig.
- A10 inHg vacuum is a recovery-machine reading and has nothing to do with when to stop adding nitrogen for a pressure test.
- B25 mm Hg absolute is the evacuation level for low-pressure appliances, not a leak-test pressure limit.
- CCorrect: shut off the nitrogen before system pressure passes 10 psig, the usual ceiling (exam key and industry practice, not in the rule text) that keeps the test under the rupture disc.
- DWaiting for a high-pressure cutout to trip is backward; a chiller being pressure-tested is not relying on a cutout, and the regulator must be closed before any overpressure.
The usual ceiling for leak-testing a low-pressure chiller is 10 psig (exam key and industry practice, not in the rule text), safely under the rupture disc. Close off the regulator before the system passes it.
A technician is tasked with leak-testing a low-pressure chiller. To build pressure, they circulate unregulated hot water through the evaporator without checking relief devices. What is the primary risk of this procedure?
Why each option is right or wrong
Answer: C. Catastrophic rupture or internal tube failure from overpressurization
- AMoisture condensing at open purge connections is a minor side issue compared with uncontrolled pressure buildup.
- BPump cavitation is not the main danger; the hot water is heating the refrigerant side, which is what over-pressurizes.
- CCorrect: unregulated hot water can push the refrigerant pressure past what the vessel and its rupture disc can take, risking rupture or tube failure.
- DOil breakdown needs far higher temperatures than circulated hot water produces; the immediate risk is overpressure.
Unregulated hot water generates internal pressures exceeding vessel limits. Without verifying relief devices, this technique risks catastrophic vessel rupture or internal tube failure from extreme overpressurization.
A manufacturer specifies a maximum internal absolute pressure of 24.1 psia to prevent activating a low-pressure chiller's rupture disc. If current atmospheric pressure is 14.4 psia, what is the maximum safe gauge pressure for nitrogen testing?
Why each option is right or wrong
Answer: B. 9.7 psig
- A14.4 psig just repeats the atmospheric pressure and ignores the 24.1 psia limit.
- BCorrect: gauge pressure = absolute minus atmospheric, so 24.1 psia - 14.4 psia = 9.7 psig.
- C38.5 psig adds atmospheric pressure instead of subtracting it.
- D24.1 psig treats the absolute limit as a gauge reading, which would overshoot the limit by the full atmospheric pressure.
Gauge pressure equals absolute pressure minus atmospheric pressure. Subtracting 14.4 psia from the 24.1 psia absolute limit yields 9.7 psig. Test pressures must stay within manufacturer limits.
In a refrigeration system using a low-pressure chiller, what is the consequence of a leak occurring in the refrigerant piping?
Why each option is right or wrong
Answer: A. Air and moisture will be drawn into the system.
- ACorrect: a low-pressure chiller runs below atmospheric pressure on its low side, so a leak lets air and moisture in rather than letting refrigerant out.
- BAir and moisture entering the system raise head pressure and form acids, so efficiency drops rather than improves.
- CA small leak does not shut the system down at once; air simply accumulates until the purge unit runs excessively.
- DRefrigerant has no self-sealing property; leaks have to be found and repaired.
Low-pressure systems operate under a vacuum condition, and any leaks in the piping can lead to ambient air and moisture being drawn into the system, causing potential damage and inefficiencies. Maintaining a positive pressure inside the chiller helps mitigate such risks.
Which refrigerant is commonly found in low-pressure chillers?
Why each option is right or wrong
Answer: B. R-11
- AR-410A is a high-pressure refrigerant used in residential and light commercial AC, not in low-pressure chillers.
- BCorrect: R-11 (along with R-123) is the classic low-pressure chiller refrigerant, boiling near room temperature at atmospheric pressure.
- CR-290 is propane, a flammable hydrocarbon used in small self-contained equipment, not in low-pressure centrifugal chillers.
- DR-32 is a high-pressure A2L refrigerant for newer AC systems, not a low-pressure chiller refrigerant.
R-11 is a common refrigerant in older low-pressure chillers, operating at pressures below atmospheric. While being phased out due to its high ozone depletion potential, technicians still need to know how to handle it properly.
A technician observes a 29.1 inHg vacuum manifold reading with a 30.2 inHg local barometric pressure. Assuming standard sea-level pressure, they halt evacuation. What is the actual absolute pressure and consequence?
Why each option is right or wrong
Answer: D. 27.9 mm Hg; the system was opened prematurely
- A20.8 mm Hg is what you get by wrongly using the standard 29.92 inHg instead of the actual 30.2 inHg barometer reading.
- B739.1 mm Hg is roughly the gauge vacuum reading converted to mm, not the absolute pressure inside the system.
- C25.4 mm Hg is simply 1 inHg converted to mm and does not match the real 1.1 inHg absolute pressure here.
- DCorrect: absolute pressure = 30.2 - 29.1 = 1.1 inHg, about 27.9 mm Hg, which is above the 25 mm Hg requirement, so the system was opened before the required vacuum was reached.
Actual absolute pressure is 30.2 − 29.1 = 1.1 inHg (27.9 mm Hg). That is above the 25 mm Hg absolute requirement, so the system was opened before the required endpoint.
A compound gauge shows 29.0 inHg vacuum while a calibrated absolute micron gauge reads 28,500 microns during evacuation. Which statement correctly assesses the status and next step?
Why each option is right or wrong
Answer: A. Endpoint not met; continue the vapor recovery
- ACorrect: 28,500 microns is 28.5 mm Hg absolute, which is above the 25 mm Hg requirement, so recovery must continue.
- BThe endpoint is not met at 28.5 mm Hg, and liquid removal comes before vapor recovery anyway, not after it.
- CIsolating the system now would stop short of the required 25 mm Hg absolute.
- D28.5 mm Hg is a higher (weaker) vacuum than 25 mm Hg, so the requirement has not been exceeded, and breaking to atmosphere would be premature.
The absolute gauge reading of 28,500 microns equals 28.5 mm Hg absolute. That is above the required 25 mm Hg absolute endpoint, so vapor recovery continues.
A technician's vacuum gauge reads exactly 25,000 microns during a low-pressure chiller evacuation. What is this pressure in mm Hg absolute?
Why each option is right or wrong
Answer: A. 25 mm Hg absolute
- ACorrect: 1 mm Hg equals 1,000 microns, so 25,000 microns is 25 mm Hg absolute, the evacuation level required for low-pressure appliances.
- B2.5 mm Hg is off by a factor of ten; that would be 2,500 microns.
- C250 mm Hg is ten times too high; that would be 250,000 microns.
- D2,500 mm Hg is more than three times atmospheric pressure and cannot be a vacuum reading.
1 mm Hg equals 1,000 microns. Dividing 25,000 microns by 1,000 yields exactly 25 mm Hg absolute, the required EPA evacuation endpoint.
During the process of evacuation in a low-pressure chiller system, why is it important to circulate water through the tubes?
Why each option is right or wrong
Answer: B. To prevent the water from freezing.
- AOil contamination is not affected by water flow in the tubes; it is managed by removing and heating the oil.
- BCorrect: as refrigerant pressure drops during evacuation its temperature falls, and moving water keeps the water in the tubes from freezing and splitting them.
- CCirculating water does not prevent water leaks; frozen water is what would cause tube damage and leaks.
- DWater circulation does not stop refrigerant leaks; it only protects the tubes from freezing.
Water is circulated through the tubes during evacuation so it doesn't freeze as the refrigerant pressure drops; frozen water can split the tubes.
What is the primary risk if liquid refrigerant is introduced into a low-pressure chiller that is currently at a 20 mm Hg absolute vacuum?
Why each option is right or wrong
Answer: C. Rapid flash boiling causing tube freeze-up.
- AA deep vacuum is far below the rupture-disc setting, so adding liquid does not open the disc.
- BOil carryover into the purge unit is not the main risk of charging liquid into a vacuum.
- CCorrect: liquid flashes violently at such a low pressure, its temperature plunges, and the water in the tubes can freeze and rupture them; charge vapor first.
- DThe compressor is not running during charging from a vacuum, so the immediate risk is tube freeze-up, not compressor failure.
Introducing liquid into a deep vacuum causes rapid flash boiling. The sudden temperature plunge freezes water in the chiller tubes, potentially rupturing them.
When recovering refrigerant from a low-pressure system, what is the recommended first step?
Why each option is right or wrong
Answer: D. Remove liquid refrigerant first
- AWrong: starting with vapor is slow, because vapor carries far less refrigerant mass than liquid.
- BWrong: adding nitrogen before recovery would mix with the refrigerant and isn't a recovery step.
- CWrong: a vacuum pump is never used to recover refrigerant; it would discharge the refrigerant to the air.
- DCorrect: remove the liquid first because it holds most of the charge, then recover the remaining vapor.
The most efficient method for recovering refrigerant from low-pressure systems is to first remove the liquid refrigerant, which speeds up the process by removing the bulk of the refrigerant mass quickly.
A major repair on a low-pressure chiller requires opening the system to the atmosphere. The system is currently in a deep vacuum following refrigerant recovery. Which medium must be introduced to safely raise the system pressure to atmospheric levels?
Why each option is right or wrong
Answer: C. Vapor phase dry nitrogen gas
- ARoom air carries moisture and non-condensables into a clean, evacuated system.
- BLiquid refrigerant would flash and could freeze the tubes, and any refrigerant added would be released once the system is opened.
- CCorrect: dry nitrogen breaks the vacuum without adding moisture or refrigerant that would then be vented when the system is opened.
- DRefrigerant vapor would simply be released to the atmosphere when the system is opened, which is prohibited venting.
Dry nitrogen is used to break the vacuum before the system is opened. Air brings in moisture, and refrigerant added now would be released when the system is opened, which the venting prohibition forbids.
When checking for leaks in a low-pressure system, why is a soap solution often ineffective?
Why each option is right or wrong
Answer: B. Because the system operates below atmospheric pressure
- ASoap solution does not freeze at normal room temperatures where the leak check is done.
- BCorrect: much of a low-pressure system sits below atmospheric pressure, so air leaks in instead of refrigerant leaking out and no bubbles form.
- CSoap bubbles are not a chemical test of the refrigerant; the problem is the direction of the leak, not compatibility.
- DBubble size is not the issue; with the system in a vacuum, no bubbles form at all.
Soap solutions are ineffective for leak checking low-pressure systems because these systems operate below atmospheric pressure, meaning air would leak into the system rather than refrigerant leaking out during normal operation.
What is the primary risk of using a halide torch leak detector on a low-pressure system?
Why each option is right or wrong
Answer: D. It can decompose refrigerant into toxic phosgene gas
- AA halide torch can detect chlorine-containing refrigerants like R-11, so it is not useless on these systems.
- BA halide torch is a flame, not an electronic tool; its danger is chemical, not electronic.
- CA small torch flame cannot freeze a system; the hazard is decomposition of refrigerant in the flame.
- DCorrect: the open flame breaks down refrigerant into toxic gases such as phosgene, so it must not be used in an enclosed space with a lot of refrigerant.
The primary risk of using a halide torch leak detector on a low-pressure system is that it uses an open flame which can decompose refrigerant into phosgene gas, a toxic substance that poses serious health hazards.
Why should heat be applied to the oil sump when recovering refrigerant from a low-pressure chiller?
Why each option is right or wrong
Answer: B. To release refrigerant dissolved in the oil
- ALower oil viscosity is not the goal; the oil is not being pumped by the recovery unit.
- BCorrect: refrigerant dissolves in the oil, and heating the oil (to about 130 °F) drives it out so it can be recovered rather than left in the oil.
- CHeating the oil has no connection to running the purge unit.
- DMoisture entering through leaks is controlled by sealing the system, not by heating the oil sump.
Heat should be applied to the oil sump when recovering refrigerant from a low-pressure chiller because refrigerant dissolves in the oil, and heating helps release this trapped refrigerant, improving recovery efficiency.
What should the pressure setting be for a recovery unit's high-pressure cutout when working with a low-pressure air conditioning system?
Why each option is right or wrong
Answer: D. 10 psig
- A15 psig is the typical rupture-disc setting on the chiller itself, so a cutout there would leave no margin.
- BA 0 psig cutout would stop the recovery unit as soon as it pushed any refrigerant into the recovery vessel.
- C20 psig is above the chiller's 15 psig rupture-disc setting.
- DCorrect: by common practice and exam key, recovery units used on low-pressure systems have the high-pressure cutout set at 10 psig, below the rupture disc.
On a low-pressure system, the recovery unit's high-pressure cutout is set at 10 psig, below the chiller's rupture disc (exam key and industry practice, not in the rule text).
More practice across all four sections: Practice test · Timed mock
Concepts that get mixed up here
Scheduling the Type III test
Do you need Type II before Type III?
No. Each type test is Core plus one type section, so Core plus Type III earns Type III alone (40 CFR 82, Appendix D (a), eCFR as of October 5, 2026). Universal requires Core and all three types; the four options are compared on EPA 608 certification types.
Can the Type III test be taken remotely?
Yes, through programs that offer remote proctoring; Type III is always closed-book and proctored (40 CFR 82, Appendix D (a), eCFR as of October 5, 2026; EPA certifying programs, checked October 7, 2026). See EPA 608 testing online.
How long is the Type III test?
EPA doesn't set a time limit; each program sets its own. SkillCat, for example, allows 1 hour per type test and 2 hours for Universal (SkillCat FAQ, checked October 7, 2026).
Which refrigerants count as low pressure?
Any refrigerant whose saturation pressure is below 45 psia at 104 °F; R-123, R-113 and R-245fa are examples (40 CFR 82.152, eCFR as of October 5, 2026). Work on chillers using them needs Type III or Universal.