ODP ODP Refrigeration Systems and Equipment 1 — Questions and Answers
Question 1: Which type of refrigeration system is most commonly associated with large commercial buildings and was historically charged with CFC-11 or CFC-113?
- Centrifugal chiller (Correct answer)
- Reciprocating compressor system
- Window air conditioner
- Absorption refrigeration unit
Correct answer: Centrifugal chiller
Large centrifugal chillers used CFC-11 and CFC-113 as primary refrigerants, making them major contributors to ozone depletion and a key target of the Montreal Protocol.
Question 2: What characteristic of low-pressure CFC systems makes refrigerant recovery more challenging compared to high-pressure systems?
- They operate below atmospheric pressure, requiring air purging and special recovery techniques (Correct answer)
- They use very large refrigerant charges that take longer to recover
- Their refrigerant is flammable and requires explosion-proof equipment
- They use mixed refrigerants that are difficult to separate
Correct answer: They operate below atmospheric pressure, requiring air purging and special recovery techniques
Low-pressure systems like CFC-11 chillers operate in a vacuum, so air infiltration is common and must be purged during recovery to prevent contamination.
Question 3: In HVAC/R systems, what is the purpose of an 'air purger' on a low-pressure centrifugal chiller?
- To remove non-condensable gases like air and nitrogen that entered the system (Correct answer)
- To purge refrigerant from the system before service
- To remove moisture from the refrigerant charge
- To regulate compressor suction pressure
Correct answer: To remove non-condensable gases like air and nitrogen that entered the system
Air purgers on low-pressure chillers remove non-condensable gases that infiltrate the below-atmospheric system, which would otherwise reduce efficiency and increase purge emissions.
Question 4: Which retrofit refrigerant was commonly approved to replace CFC-11 in existing low-pressure centrifugal chillers?
- HCFC-123 (R-123) (Correct answer)
- HFC-134a (R-134a)
- R-410A
- R-404A
Correct answer: HCFC-123 (R-123)
HCFC-123 was the primary drop-in replacement for CFC-11 in centrifugal chillers due to its similar thermodynamic properties and lower (though not zero) ODP.
Question 5: What is the main reason CFC refrigerants were used extensively in large commercial refrigeration systems before the 1990s?
- They were non-flammable, non-toxic, chemically stable, and had excellent thermodynamic properties (Correct answer)
- They were the only refrigerants available at the time
- They were mandated by early EPA regulations
- They had the lowest global warming potential of all available options
Correct answer: They were non-flammable, non-toxic, chemically stable, and had excellent thermodynamic properties
CFCs were ideal commercial refrigerants because they were chemically inert, non-flammable, low-toxicity, and had thermodynamic properties well-suited for a wide range of applications.
Question 6: Which supermarket refrigeration system configuration contributed most to CFC/HCFC emissions due to its long piping runs and multiple leak points?
- Direct expansion (DX) rack system with remote cases (Correct answer)
- Self-contained display case units
- Secondary loop refrigeration system
- Absorption refrigeration system
Correct answer: Direct expansion (DX) rack system with remote cases
Traditional DX rack systems with long refrigerant piping throughout the store have many joints and connection points, making them prone to leaks that collectively release large amounts of refrigerant.
ODP ODP Refrigeration Systems and Equipment 1
Which type of refrigeration system is most commonly associated with large commercial buildings and was historically charged with CFC-11 or CFC-113?