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Questions and Answers
Refrigerant removal from a low pressure system starts with what?
Refrigerant removal from a low pressure system starts with what?
Liquid removal
Which of the following actions will always be considered major?
Which of the following actions will always be considered major?
- Replacing the evaporator coil (correct)
- Changing the compressor
- Cleaning the condenser
- Repairing a minor leak
What is the maximum test pressure when leak testing a low pressure sensor with nitrogen?
What is the maximum test pressure when leak testing a low pressure sensor with nitrogen?
10 PSIG
What must be done after recovering the liquid refrigerant from a low-pressure chiller?
What must be done after recovering the liquid refrigerant from a low-pressure chiller?
What does ASHRAE standard 15 2013 require for room sensors in alarms?
What does ASHRAE standard 15 2013 require for room sensors in alarms?
Where does refrigerant go after it leaves the purge unit of a low pressure centrifugal system?
Where does refrigerant go after it leaves the purge unit of a low pressure centrifugal system?
What is the best method to determine a chiller's normal charge for leak rate calculations?
What is the best method to determine a chiller's normal charge for leak rate calculations?
How can charged low-pressure refrigeration machines be most effectively leak checked?
How can charged low-pressure refrigeration machines be most effectively leak checked?
At what approximate temperature will letter R-123 at 14.7 PSIA boil?
At what approximate temperature will letter R-123 at 14.7 PSIA boil?
What happens to liquid charged into a deep vacuum before refrigerant vapor is reintroduced to the chiller?
What happens to liquid charged into a deep vacuum before refrigerant vapor is reintroduced to the chiller?
What will a hydrostatic test kit determine?
What will a hydrostatic test kit determine?
Where does the purge unit on a centrifugal system take suction?
Where does the purge unit on a centrifugal system take suction?
What is the primary purpose of a purge unit on a low pressure chiller?
What is the primary purpose of a purge unit on a low pressure chiller?
Recycling recovery equipment must be labeled and certified to meet EPA's requirements.
Recycling recovery equipment must be labeled and certified to meet EPA's requirements.
What should be done to reduce refrigerant loss for purging on an R-123 chiller?
What should be done to reduce refrigerant loss for purging on an R-123 chiller?
What do room sensors and alarms help technicians detect according to ASHRAE standard 15 2013?
What do room sensors and alarms help technicians detect according to ASHRAE standard 15 2013?
What can the use of a severely oversized vacuum pump cause when evacuating a system?
What can the use of a severely oversized vacuum pump cause when evacuating a system?
How long must a technician keep records when evacuating refrigerant from appliances with a full charge of more than 5 pounds?
How long must a technician keep records when evacuating refrigerant from appliances with a full charge of more than 5 pounds?
When should an appliance not be evacuated all the way to the prescribed level?
When should an appliance not be evacuated all the way to the prescribed level?
Which methods can be used to pressurize the letter R-1233ZD system for the purpose of opening the system for non-major repair?
Which methods can be used to pressurize the letter R-1233ZD system for the purpose of opening the system for non-major repair?
What is a typical setting for the high-pressure cut-out control on a recovery unit used for evacuating the refrigerant from a low pressure chiller?
What is a typical setting for the high-pressure cut-out control on a recovery unit used for evacuating the refrigerant from a low pressure chiller?
Who is responsible for keeping records of all leaks, inspections, and completed leak repair verification tests?
Who is responsible for keeping records of all leaks, inspections, and completed leak repair verification tests?
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Study Notes
Refrigerant Removal and Recovery
- Initiating refrigerant removal from a low-pressure system begins with liquid removal.
- After liquid refrigerant recovery in a low-pressure chiller, vapor refrigerant must also be recovered.
Major Actions in Refrigeration
- Replacement of an evaporator coil is classified as a major action in refrigeration maintenance.
Leak Testing Parameters
- When using nitrogen for leak testing a low-pressure sensor, the maximum test pressure is 10 PSIG.
ASHRAE Standards and Safety
- ASHRAE Standard 15 (2013) mandates room sensors in alarms to detect all refrigerant safety groups.
Refrigerant Flow and Management
- In a low-pressure centrifugal system, refrigerant exits the purge unit and goes directly to the evaporator.
- The best approach to determine a chiller's normal charge for leak rate calculations is to use the charge specified on the equipment name plate.
Leak Check Techniques
- Effective leak checks on low-pressure refrigeration machines can be achieved by adding heat and using heating blankets for hot water circulation.
Refrigerant Properties
- Refrigerant R-123 at 14.7 PSIA will boil at approximately 82°F.
System Servicing and Refrigerant Charging
- Introducing vapor refrigerant before liquid into a chiller, especially in a deep vacuum, can lower temperatures, risking freezing of water in the heat exchanger tube bundle.
Purge Units and Noncondensibles
- A hydrostatic test kit is used to identify leaking tubes within a system.
- The purge unit on a centrifugal system takes suction from the top of the condenser to function effectively.
- The primary function of a purge unit in a low-pressure chiller is to eliminate noncondensibles from the system.
Recycling and Recovery Equipment
- Refrigerant recycling and recovery equipment must be labeled and certified to comply with EPA requirements.
Leak Prevention and Maintenance
- To minimize refrigerant loss in an R-123 chiller, performing a leak test and subsequent repairs is essential.
Refrigerant Leak Detection
- ASHRAE Standard 15 (2013) also requires alarms for detecting refrigerant leaks.
Evacuation Procedures
- Using an oversized vacuum pump can lead to issues such as trapped water freezing during system evacuation.
- Technicians must keep records of refrigerant evacuation events for appliances with charges exceeding 5 pounds for three years.
Evacuation Limitations
- A system may not be evacuated to the prescribed level if leaks prevent reaching that level.
System Pressurization Techniques
- To pressurize an R-1233ZD system for non-major repairs, warming the liquid refrigerant is an effective method.
Pressure Control Settings
- The typical high-pressure cut-out control setting on recovery units for evacuating refrigerants from low-pressure chillers is set at 10 PSIG.
Record Keeping Responsibilities
- The responsibility for maintaining records of leaks, inspections, and verification tests falls on the equipment owner and/or operator.
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