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EPA 608 Technician Certification Low-Pressure Leak Detection and Leak Repair Summary

Checked 11/1/26

Low-Pressure Leak Detection and Leak Repair: key points

  • Leaks in a low-pressure system let air and moisture in.
  • Do not pressurize a low-pressure chiller above 10 psig for a leak test.
Importance
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About 9 of 25 Type III (Low-Pressure) questions (35%)

Why air and moisture leak into low-pressure chillers, signs such as frequent purging, how to pressurize for a leak test, the 10 psig limit, leak rate triggers, inspections, and chronic leak reports.

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Low-Pressure Leak Detection and Leak Repair: 10 sample questions

Practice questionReviewedType III (Low-Pressure) › Low-Pressure Leak Detection and Leak Repair★★★★★

Question 1. Most of a running low-pressure chiller is below atmospheric pressure. What happens when it has a leak?

  1. ① The chiller pressure rises above 100 psig
  2. ② Air and moisture leak into the system
  3. ③ Refrigerant sprays out of the leak at high pressure
  4. ④ Nothing, because low-pressure systems cannot leak
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Answer: ② Air and moisture leak into the system

Key point: Low-pressure leaks pull air and moisture in

Because much of a low-pressure system runs below atmospheric pressure (in a vacuum), a leak lets air and moisture enter the system. These noncondensables collect in the condenser and must be removed by the purge unit.

Wrong choices

  • The chiller pressure rises above 100 psig: A leak does not raise pressure that high.
  • Refrigerant sprays out of the leak at high pressure: Parts of the system below atmospheric pressure draw air in rather than pushing refrigerant out.
  • Nothing, because low-pressure systems cannot leak: Low-pressure systems can and do leak.
Practice questionReviewedType III (Low-Pressure) › Low-Pressure Leak Detection and Leak Repair★★★★★

Question 2. A comfort cooling chiller holds 900 pounds of R-123. Above what annual leak rate must the owner repair the leaks?

  1. ① 15 percent
  2. ② 20 percent
  3. ③ 10 percent
  4. ④ 30 percent
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Answer: ③ 10 percent

Key point: Comfort cooling chiller (HCFC): 10%

R-123 is an HCFC, so this chiller falls under 40 CFR 82.157. For comfort cooling appliances with 50 or more pounds, the leak repair trigger is 10 percent per year.

Wrong choices

  • 15 percent: 15 percent was an older comfort cooling trigger.
  • 20 percent: 20 percent is the trigger for commercial refrigeration.
  • 30 percent: 30 percent is the trigger for industrial process refrigeration.
Practice questionReviewedType III (Low-Pressure) › Low-Pressure Leak Detection and Leak Repair★★★★★

Question 3. What is the highest pressure normally used to leak test a low-pressure centrifugal chiller?

  1. ① 10 psig
  2. ② 100 psig
  3. ③ 1 psig
  4. ④ 50 psig
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Answer: ① 10 psig

Key point: Low-pressure chiller leak test: 10 psig max

The rupture disc on a low-pressure chiller's evaporator is usually set at 15 psig, so leak test pressure should not exceed 10 psig to avoid bursting it.

Wrong choices

  • 100 psig: 100 psig is far too high for a low-pressure chiller.
  • 1 psig: 1 psig is lower than needed; the usual maximum is 10 psig.
  • 50 psig: 50 psig would burst the rupture disc.
Practice questionReviewedType III (Low-Pressure) › Low-Pressure Leak Detection and Leak Repair★★★★★

Question 4. Which refrigerant is a low-pressure refrigerant?

  1. ① R-134a
  2. ② R-123
  3. ③ R-22
  4. ④ R-410A
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Answer: ② R-123

Key point: R-11, R-113, R-123 = low-pressure

40 CFR 82.152 defines a low-pressure appliance as one using a refrigerant with a liquid saturation pressure below 45 psia at 104°F. Examples are R-11, R-123, R-113, and R-245fa.

Wrong choices

  • R-134a: R-134a is a medium-pressure refrigerant.
  • R-22: R-22 is a high-pressure refrigerant.
  • R-410A: R-410A is a high-pressure refrigerant.
Practice questionReviewedType III (Low-Pressure) › Low-Pressure Leak Detection and Leak Repair★★★★★

Question 5. What is a common sign of a leak in a low-pressure chiller?

  1. ① The rupture disc gets smaller
  2. ② The condenser water gets colder
  3. ③ The purge unit runs much more than usual
  4. ④ The compressor oil turns blue
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Answer: ③ The purge unit runs much more than usual

Key point: Excessive purging = air leaking in

Air that leaks in collects in the condenser, and the purge unit must run more to remove it. Excessive purging is a key sign of a leak in a low-pressure system.

Wrong choices

  • The rupture disc gets smaller: Rupture discs do not shrink.
  • The condenser water gets colder: Condenser water temperature is not the usual leak sign.
  • The compressor oil turns blue: Oil color is not a standard leak sign.
Practice questionReviewedType III (Low-Pressure) › Low-Pressure Leak Detection and Leak Repair★★★★★

Question 6. What is the preferred way to raise the pressure of a low-pressure chiller for a leak test?

  1. ① Use controlled hot water or a built-in heating/pressurization device
  2. ② Use compressed air
  3. ③ Add R-22 until the pressure reaches 50 psig
  4. ④ Use oxygen
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Answer: ① Use controlled hot water or a built-in heating/pressurization device

Key point: Leak test pressure: hot water or heater first

EPA lists the order of preference for pressurizing a low-pressure system for leak testing: controlled hot water or a built-in system heating/pressurization device (such as Prevac) first, then nitrogen.

Wrong choices

  • Use compressed air: Compressed air brings in moisture and is unsafe.
  • Add R-22 until the pressure reaches 50 psig: Adding another refrigerant contaminates the charge and 50 psig is far too high.
  • Use oxygen: Oxygen can explode with oil.
Practice questionReviewedType III (Low-Pressure) › Low-Pressure Leak Detection and Leak Repair★★★★★

Question 7. A low-pressure chiller used for industrial process cooling holds 1,000 pounds of R-123. Above what annual leak rate must it be repaired?

  1. ① 35 percent
  2. ② 10 percent
  3. ③ 20 percent
  4. ④ 30 percent
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Answer: ④ 30 percent

Key point: Industrial process refrigeration: 30%

For industrial process refrigeration with 50 or more pounds of ozone-depleting refrigerant, the trigger leak rate is 30 percent per year under 40 CFR 82.157(c).

Wrong choices

  • 35 percent: 35 percent was the old trigger before the 2016 rule.
  • 10 percent: 10 percent is the trigger for comfort cooling.
  • 20 percent: 20 percent is the trigger for commercial refrigeration.
Practice questionReviewedType III (Low-Pressure) › Low-Pressure Leak Detection and Leak Repair★★★★☆

Question 8. A comfort cooling chiller with an ODS refrigerant has exceeded its leak rate. How often must leak inspections be done afterward?

  1. ① Once per calendar year until it stays below the rate for one year
  2. ② Only when the purge unit alarms
  3. ③ Once a month
  4. ④ Once every three months for two years
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Answer: ① Once per calendar year until it stays below the rate for one year

Key point: Comfort cooling over the rate: yearly inspections

Under 40 CFR 82.157(g), comfort cooling and other appliances not in the commercial or industrial groups need a leak inspection once per calendar year until the leak rate stays below the trigger for one year.

Wrong choices

  • Only when the purge unit alarms: Inspections follow a set schedule.
  • Once a month: Monthly inspections are not required.
  • Once every three months for two years: Quarterly inspections apply to commercial and industrial appliances with 500 pounds or more.
Practice questionReviewedType III (Low-Pressure) › Low-Pressure Leak Detection and Leak Repair★★★★☆

Question 9. A chiller with 50 or more pounds of ODS refrigerant leaked 125 percent of its full charge last calendar year. By what date must the owner report to EPA?

  1. ① December 31 of this year
  2. ② January 1 of this year
  3. ③ June 30 of this year
  4. ④ March 1 of this year
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Answer: ④ March 1 of this year

Key point: Chronic leak report due March 1

40 CFR 82.157(j) requires owners of appliances with 50 or more pounds that leak 125 percent or more of their full charge in a calendar year to submit a report to EPA by March 1 of the following year.

Wrong choices

  • December 31 of this year: December 31 is too late.
  • January 1 of this year: January 1 is not the reporting deadline.
  • June 30 of this year: June 30 is too late.
Practice questionReviewedType III (Low-Pressure) › Low-Pressure Leak Detection and Leak Repair★★★★☆

Question 10. An automatic leak detection system that senses refrigerant in the air can replace required leak inspections. At what concentration must it alert the owner?

  1. ① 100 parts per million
  2. ② 1,000 parts per million
  3. ③ 5 percent by volume
  4. ④ 10 parts per million
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Answer: ① 100 parts per million

Key point: Leak detector: detect 10 ppm, alert at 100 ppm

Under 40 CFR 82.157(g)(4), an automatic leak detection system that senses refrigerant in air must accurately detect 10 ppm and alert the owner at 100 ppm, and it must be audited or calibrated every year.

Wrong choices

  • 1,000 parts per million: 1,000 ppm is too high.
  • 5 percent by volume: 5 percent is far too high.
  • 10 parts per million: 10 ppm is the level the system must be able to detect accurately, not the alert level.

Test yourself.

Low-Pressure Leak Detection and Leak Repair: 5 questions →Type III (Low-Pressure): 5 questions →

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