EPA 608 Type III Practice Test 2 — Questions and Answers
Question 1: EPA Section 608 Type III certification is required for technicians servicing which type of equipment?
- Small appliances with hermetically sealed compressors
- High-pressure systems such as R-410A split systems
- Low-pressure systems such as centrifugal chillers using R-11 or R-123 (Correct answer)
- Motor vehicle A/C systems using R-134a
Correct answer: Low-pressure systems such as centrifugal chillers using R-11 or R-123
Type III certification covers low-pressure systems — large commercial and industrial chillers that use refrigerants such as R-11, R-113, and R-123 (HCFC-123). These refrigerants have saturation pressures below atmospheric pressure at normal operating temperatures, meaning the systems operate under vacuum. This unique characteristic requires special training and handling procedures.
Question 2: Why do low-pressure chiller systems (Type III) operate under vacuum rather than under pressure?
- To improve compressor efficiency at large tonnage
- Because their refrigerants have boiling points above typical evaporator temperatures, so evaporator pressure is below atmospheric (Correct answer)
- To prevent refrigerant from venting if there is a leak
- Because their refrigerants are too toxic to be stored under pressure
Correct answer: Because their refrigerants have boiling points above typical evaporator temperatures, so evaporator pressure is below atmospheric
Low-pressure refrigerants like R-11 and R-123 have atmospheric boiling points well above typical evaporator temperatures. At evaporator temperatures (35-45°F), these refrigerants would be below their normal boiling point, creating pressures below 14.7 psia (below atmospheric). This means the system operates in a vacuum on the low side, so air and moisture can be drawn in through any leaks rather than refrigerant leaking out.
Question 3: What is the most significant contamination risk specific to low-pressure chiller systems?
- Refrigerant oil mixing with compressor lubricant
- Air and moisture infiltration through vacuum-side leaks (Correct answer)
- High-side refrigerant blending with low-side refrigerant
- Corrosion from halide ions at high operating pressures
Correct answer: Air and moisture infiltration through vacuum-side leaks
Because low-pressure chillers operate below atmospheric pressure, any leak allows air and moisture to be drawn into the system rather than refrigerant escaping outward. Air in a chiller system reduces capacity, raises condenser pressure, and causes purge unit operation. Moisture creates acid that corrodes system components. Regular purge unit operation and leak tightness are critical for low-pressure chiller performance.
Question 4: What does the purge unit on a centrifugal chiller do?
- Removes refrigerant from the system before compressor startup
- Removes non-condensable gases (air) and moisture that have entered the chiller system (Correct answer)
- Purges lubricating oil from the refrigerant circuit
- Releases pressure if system pressure exceeds the safety limit
Correct answer: Removes non-condensable gases (air) and moisture that have entered the chiller system
The purge unit on a centrifugal chiller continuously removes non-condensable gases (primarily air and nitrogen) that infiltrate the low-pressure system through leaks. The purge unit separates the air from refrigerant vapor, releases the air to atmosphere while recovering the refrigerant. Excessive purge unit operation is a sign of refrigerant leaks or air infiltration.
Question 5: For a Type III low-pressure system with a charge of more than 200 lbs, what recovery efficiency is required using equipment made after November 15, 1993?
- 90% of charge must be recovered
- System must reach 25 mmHg absolute (25 Torr) (Correct answer)
- System must reach 29 inches of mercury vacuum
- System must reach 25 inches of mercury vacuum
Correct answer: System must reach 25 mmHg absolute (25 Torr)
For low-pressure systems with charges over 200 lbs, the EPA requires recovery equipment to achieve 25 millimeters of mercury absolute pressure (25 mmHg or approximately 25 Torr absolute). Since low-pressure systems already operate in a vacuum, the recovery standard is expressed in absolute pressure rather than vacuum depth. This extremely low absolute pressure ensures maximum refrigerant recovery.
Question 6: R-123 (HCFC-123) has which safety classification under ASHRAE Standard 34?
- A1 (no flame propagation, lower toxicity)
- B1 (no flame propagation, higher toxicity) (Correct answer)
- A2L (mildly flammable, lower toxicity)
- B2L (mildly flammable, higher toxicity)
Correct answer: B1 (no flame propagation, higher toxicity)
R-123 is classified as B1 by ASHRAE — "B" indicating higher toxicity (higher potential for harm at low exposures) and "1" indicating non-flammable. R-123 has a relatively low IDLH (Immediately Dangerous to Life and Health) concentration of 1,000 ppm, requiring proper ventilation and personal protective equipment when servicing R-123 chiller systems.
EPA 608 Type III Practice Test 2
EPA Section 608 Type III certification is required for technicians servicing which type of equipment?