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Questions and Answers
Sketch a drawing of a system and include the compressor, oil separator, condenser, receiver, king valve, liquid line filter drier, TXV metering device with the bulb, evaporator, suction line accumulator. Label the lines.
Sketch a drawing of a system and include the compressor, oil separator, condenser, receiver, king valve, liquid line filter drier, TXV metering device with the bulb, evaporator, suction line accumulator. Label the lines.
Drawing should include all the listed components correctly connected and labeled.
What are two reasons a system would utilize a receiver?
What are two reasons a system would utilize a receiver?
To store excess refrigerant and to provide a liquid seal to the liquid line.
How is a refrigeration system with a king valve pumped down?
How is a refrigeration system with a king valve pumped down?
Close the liquid line king valve and allow the compressor to run until it pulls a vacuum on the low side.
What might occur during pump down if a system with a receiver has been excessively overcharged? (look at your drawing).
What might occur during pump down if a system with a receiver has been excessively overcharged? (look at your drawing).
How is a receiver sized for its application?
How is a receiver sized for its application?
How does a suction line accumulator meter the refrigerant and oil back to the compressor?
How does a suction line accumulator meter the refrigerant and oil back to the compressor?
What is an oil separator?
What is an oil separator?
Where is the oil separator located at in the refrigeration system?
Where is the oil separator located at in the refrigeration system?
How does the oil separate in the oil separator?
How does the oil separate in the oil separator?
What will be the result on the suction pressure if the bulb on a TXV loses its charge?
What will be the result on the suction pressure if the bulb on a TXV loses its charge?
What does a TXV maintain in the evaporator?
What does a TXV maintain in the evaporator?
On a water-cooled condenser, how is the head pressure decreased when using a water regulating valve?
On a water-cooled condenser, how is the head pressure decreased when using a water regulating valve?
How does an AXV differ from a TXV in regards to what they are trying to maintain?
How does an AXV differ from a TXV in regards to what they are trying to maintain?
How would you check to see if a filter drier is restricted?
How would you check to see if a filter drier is restricted?
What will occur in regards to refrigerant flow if you warmed the TXV bulb up in your hand?
What will occur in regards to refrigerant flow if you warmed the TXV bulb up in your hand?
Which type of metering device is found in most ductless mini splits?
Which type of metering device is found in most ductless mini splits?
What is the valve that allows a heat pump system to shift from cooling to heating?
What is the valve that allows a heat pump system to shift from cooling to heating?
Besides checking subcooling, what is a way you can check to ensure you have liquid refrigerant leaving the condenser if it has a sight glass?
Besides checking subcooling, what is a way you can check to ensure you have liquid refrigerant leaving the condenser if it has a sight glass?
What would the positions of the suction and discharge service valves be on a compressor if you are isolating it to replace it?
What would the positions of the suction and discharge service valves be on a compressor if you are isolating it to replace it?
What should the service valve position be during normal operation?
What should the service valve position be during normal operation?
In order for a technician to get a pressure reading on a system with service valves, what position are they in?
In order for a technician to get a pressure reading on a system with service valves, what position are they in?
What position would the service valves be in while evacuating a system?
What position would the service valves be in while evacuating a system?
What would happen to an operating system if you shut a refrigerant ball valve located on the liquid line after the receiver?
What would happen to an operating system if you shut a refrigerant ball valve located on the liquid line after the receiver?
What would happen to a systems superheat if we had an increase in heat load on the evaporator and the system utilizes a capillary tube metering device?
What would happen to a systems superheat if we had an increase in heat load on the evaporator and the system utilizes a capillary tube metering device?
What would happen to a systems superheat if we had an under charge of refrigerant and the system utilizes a capillary tube metering device?
What would happen to a systems superheat if we had an under charge of refrigerant and the system utilizes a capillary tube metering device?
Flashcards
What is a receiver in a refrigeration system?
What is a receiver in a refrigeration system?
A vessel for storing liquid refrigerant and ensuring a steady supply to the metering device.
Why use a king valve?
Why use a king valve?
To isolate refrigerant within the receiver for servicing or repairs.
What is an oil separator?
What is an oil separator?
It separates oil from the refrigerant and returns it to the compressor.
Location of an oil separator?
Location of an oil separator?
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What does a TXV Maintain?
What does a TXV Maintain?
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Valve to shift from cooling to heating?
Valve to shift from cooling to heating?
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Aside from subcooling, how do you check for liquid refrigerant?
Aside from subcooling, how do you check for liquid refrigerant?
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Normal service valve position?
Normal service valve position?
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Service valve position to take a pressure reading?
Service valve position to take a pressure reading?
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Increased evaporator heat load & capillary tube: superheat?
Increased evaporator heat load & capillary tube: superheat?
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Study Notes
- A system drawing should include the compressor, oil separator, condenser, receiver, king valve, liquid line filter drier, TXV metering device with the bulb, evaporator, and suction line accumulator, all with labeled lines.
- Two reasons a system would use a receiver include:
- To store excess refrigerant.
- To ensure a solid liquid line to the metering device.
- To pump down a refrigeration system with a king valve:
- Close the king valve.
- Run the compressor to pull the refrigerant out of the evaporator and suction line, storing it in the receiver.
- If a system with a receiver has been excessively overcharged during pump down, the receiver may overfill, leading to liquid refrigerant potentially backing up into the condenser or compressor.
- A receiver is sized based on the system's refrigerant charge and the amount of refrigerant needed during varying operating conditions.
- A suction line accumulator meters refrigerant and oil back to the compressor by:
- Storing any liquid refrigerant and oil that may have not evaporated in the evaporator.
- Gradually releasing the refrigerant and oil back to the compressor, preventing damage.
- An oil separator is a device designed to separate oil from the refrigerant in a refrigeration system.
- An oil separator is located in the discharge line between the compressor and the condenser.
- Oil separates in the oil separator through a combination of:
- Reducing the velocity of the refrigerant/oil mixture.
- Changing direction of flow.
- Using a coalescing filter to capture oil particles.
- If the bulb on a TXV loses its charge, the suction pressure will increase.
- A TXV maintains a constant superheat in the evaporator.
- On a water-cooled condenser, head pressure is decreased when using a water regulating valve by modulating the flow of water through the condenser.
- An AXV (automatic expansion valve) differs from a TXV (thermostatic expansion valve) in that an AXV maintains a constant evaporator pressure, whereas a TXV maintains a superheat.
- To check if a filter drier is restricted:
- Use a temperature sensor or thermal imaging to check the temperature difference across the filter drier. A significant temperature drop indicates a restriction.
- If the TXV bulb is warmed up in hand:
- It will sense a higher temperature and allow more refrigerant flow.
- A capillary tube is most often found as the metering device in most ductless mini splits.
- A reversing valve allows a heat pump system to shift from cooling to heating.
- Besides checking subcooling, the presence of liquid refrigerant leaving the condenser can be confirmed by observing a full sight glass (if equipped).
- When isolating a compressor to replace it, the suction and discharge service valves should be backseated and closed.
- During normal operation, the service valve position should be front seated and open.
- To get a pressure reading on a system with service valves, they should be mid-positioned, or front seated and open.
- While evacuating a system, the service valves should be front seated and open, allowing access for vacuum pump connection.
- If a refrigerant ball valve located on the liquid line after the receiver is shut, the system will be starved of refrigerant, leading to a decrease in cooling capacity and potential compressor damage.
- If there is an increase in heat load on the evaporator and the system utilizes a capillary tube metering device, the superheat will increase.
- If there is an undercharge of refrigerant and the system utilizes a capillary tube metering device, the superheat will increase.
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