Questions and Answers
On low-pressure chillers, moisture most frequently enters the refrigerant system through ___
leaks from areas with gaskets or fittings.
What precaution should be taken prior to recovering refrigerant from a chiller suspected of having tube leaks?
Drain the water sides of the evaporator and condenser.
Continuous excessive moisture collection in the purge unit of a low-pressure refrigeration system could indicate what condition?
The condenser or chiller barrel tubes are leaking.
Which component is particularly susceptible to leaks in low-pressure refrigeration systems with open drive type compressors?
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What must a system owner do once the threshold leak rate has been exceeded on any low-pressure system?
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When must the leak rate of an appliance using an ozone-depleting refrigerant be calculated?
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A chiller containing 150 pounds of HCFC refrigerant is leaking above the leak rate threshold. Unless granted additional time, what must be completed within 30 days?
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A typical setting for the high pressure cut-out control on a recovery unit used for evacuating the refrigerant from a low-pressure chiller is ___
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Refrigerant removal from a low-pressure system starts with ___
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What must be done after recovering the liquid refrigerant from a low-pressure chiller?
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Approximately how much refrigerant vapor is left in an average 350-ton R-123 chiller at 0 psig once all the R-123 liquid has been removed?
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When evacuating a system, the use of a severely oversized vacuum pump could ___
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How do you determine when enough vapor has entered the refrigeration system before you charge refrigerant liquid?
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What should you do after reaching the required recovery vacuum on a low-pressure appliance?
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Which of the following actions would always be considered 'major' under EPA's regulations?
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When should an appliance NOT be evacuated all the way to the prescribed level?
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Which of the following methods can be used to pressurize an R-1233zd system for the purpose of opening the system for a non-major repair?
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What evacuation level must technicians recover refrigerant to before disposing of a low-pressure appliance?
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Which of the following always falls under the EPA definition for 'major maintenance, service, or repair'?
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R-123 at a pressure of 18.1 inches Hg vacuum has a saturation temperature of ___
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Why do chillers using low-pressure refrigerants require purge units?
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Identify the pressure corresponding to 32°F for R-123.
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During evacuation of a system containing large amounts of moisture, it may be necessary to prevent freezing by increasing pressure using a gas such as ___
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What should be used to remove ice from sight glasses or viewing glasses?
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Where should the discharge from a rupture disc be piped for venting?
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Study Notes
Chiller Refrigerant Systems
- Moisture enters low-pressure chillers primarily through leaks at gaskets or fittings.
- Signs of tube leaks include continuous excessive moisture collection in the purge unit.
Refrigerant Recovery Procedures
- Drain water sides of the evaporator and condenser before recovering refrigerant from a suspected leaking chiller.
- Liquid refrigerant removal is the first step in recovering from a low-pressure system, followed by vapor recovery.
- After removing liquid refrigerant, ensure to recover vapor refrigerant for system integrity.
Leak Rate Management
- Once the leak threshold is exceeded in low-pressure systems, repairs must be made to lower the leak rate, or the appliance must be retrofitted or retired.
- Leak rates should be calculated when recharging systems with ozone-depleting refrigerants.
Maintenance and Repair Guidelines
- Major actions under EPA regulations include replacing evaporator coils and compressors.
- Do not evacuate a system fully if leaks make it unattainable.
Equipment Characteristics
- High pressure cut-out controls are typically set at 10 psig on recovery units for low-pressure chillers.
- R-123 chillers at 0 psig retain approximately 100 pounds of vapor refrigerant after liquid removal.
Evacuation and Vacuum Considerations
- An oversized vacuum pump can cause trapped water to freeze during evacuation.
- Technicians must recover refrigerant to 25 mm of Hg absolute before disposing of low-pressure appliances.
Operating Pressures and Temperatures
- R-123 at 18.1 inches Hg vacuum corresponds to a saturation temperature of 40°F.
- The pressure for R-123 at 32°F is 20 inches of Hg vacuum.
Safety and Environmental Precautions
- Use isopropyl alcohol to remove ice from sight glasses or viewing glasses.
- Discharge from rupture discs should be vented outdoors to ensure safety.
Special Techniques
- To open R-1233zd systems for non-major repairs, pressurization can be achieved by warming liquid refrigerant.
- When evacuating systems with excess moisture, preventing freezing may require the introduction of nitrogen gas.
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Description
This set of flashcards focuses on essential knowledge for Type III refrigerant handling, particularly related to low-pressure chillers. Key topics include moisture entry points and precautions before recovering refrigerant. Ideal for students and professionals in HVAC and refrigeration technology.
