• SkillCat Team

Key Secondary Components

Updated: Mar 12

EPA 608 Type 2 Chapter 2 (Take full course for free)


In this module, we will learn about a few components that are not a part of the primary refrigeration cycle but play an important role for refrigeration appliances to work correctly. Skip to quiz!


1. Refrigeration Cycle - Secondary Components


Recall that the four critical components of a refrigeration cycle are:

  1. Evaporator

  2. Compressor

  3. Condenser

  4. Metering Device

Apart from these, the system's and other equipment's safe and smooth functioning requires a few other components in the refrigeration cycle.


Recall that refrigerant fluid flows in the refrigeration system. A storage container is required to store the refrigerant in the system, which is not in circulation. A receiver tank is that component that acts as a storage vessel.


Recall that the refrigerant comes out of the condenser through the liquid line. This refrigerant is a high-pressure liquid. The receiver tank stores this liquid. We install the receiver tank is on the liquid line as close as possible to the condenser coils' outlet.


A receiver tank is also known as a liquid line receiver tank. It is generally seen in heat pumps and residential split systems using a TXV/TEV as a metering device.


Recall that the vapor line connects the evaporator and the compressor. The refrigerant flowing out of the evaporator and into the compressor should ideally be complete vapor. But sometimes, there may be some liquid refrigerant along with the vapor.


The compressor of a refrigeration system is not manufactured to handle any liquid refrigerant. So to avoid the liquid refrigerant flowing into the compressor and damaging it, an accumulator tank is attached to the refrigeration circuit just before the compressor.


An accumulator tank is a component that protects the compressor in the system. It temporarily stores the liquid part of the refrigerant coming out of the evaporator through the suction line.


For servicing and repairing the refrigeration appliance, a component is required to allow easy access to the refrigerant flowing inside the tubes without venting it. A shut-off valve is that component. A shut-off valve is also called as the service valve.


As you can see by the arrows in the image, we can change the direction of the refrigerant fluid flowing inside the refrigerant tubes by pulling it back (back seated) or pushing it front (front seated). A gauge port is where the service hose or refrigerant gauges are connected.


To reiterate the positions of the shut-off valve, when the valve is

  • Back-seated: Service/gauge port is closed

  • Front-seated: The outlet port is closed

  • Neutral-seated: All ports are open

Memorize these positions!


The shut-off valve is found in both the suction and discharge lines of an appliance. The shut-off valve found on the suction side is called a suction shut-off valve. One on the discharge side is called the discharge shut-off valve.



2. Additional Components


A few other components are required in the refrigeration system that act as additional support for the appliance and the technician.


Recall that moisture present in the refrigeration cycle can form acidic sludge and damage the components if it reacts with the refrigerant. A filter drier is a component in the refrigeration cycle that filters out moisture and other solid contaminants from the refrigerant.

As the name suggests, moisture indicating sight glass is used to check for signs of moisture inside a refrigeration system.

It has transparent glass on it. If present in a system, moisture forms a cloudy mist on the sight glass, just like the mist formed on your car windshield on a cold day.


Recall that compressor heaters are used to heat the refrigerant oil in the compressor. When the system is shut down for long periods, the pressurized refrigerant goes to the compressor, mixing with the refrigeration oil in excess quantities. The mixed refrigerant dilutes the refrigerant oil and deteriorates its quality and properties.


Heating the oil increases its temperature and boils off the refrigerant present in the oil. Heating also facilitates an easy start of the appliance and protects the components from damage due to diluted oil.


Like a user manual for any device, the nameplate provides all the data about that system. The system's nameplate is a sheet where the system's manufacturer has written down all data about that particular system.


This data includes the

  • Type of refrigerant

  • Quantity of the refrigerant

  • The tonnage of the system

  • Working pressure of the system

  • The voltage, current, and other electrical details.

And a lot of other information related to that system.


3. Conclusion


In this topic, we learned about the different refrigeration components and secondary components of a refrigeration appliance. Knowledge of all these components is important in understanding a refrigeration appliance.


Question #1: What is the state of the refrigerant leaving the receiver in a refrigeration system?

  1. Low-Pressure Liquid

  2. Low-Pressure Vapor

  3. High-Pressure Liquid

  4. High-Pressure Vapor

Scroll down for the answer...











The receiver tank only acts as a storage vessel for the high-pressure liquid coming out of the condenser coils. It does no other function except storage. So the refrigerant leaving the receiver is also a high-pressure liquid.


Question #2: Which of the following component is located just before the compressor?

  1. Receiver

  2. Accumulator

  3. Condenser coils

  4. TEV

Scroll down for the answer...













The accumulator tank is the component that is located just before the compressor.


Question #3: What will backseating a suction shut-off valve close?

  1. Suction line and compressor port

  2. Compressor and gauge port.

  3. Compressor port

  4. Gauge port

Scroll down for the answer...











Back seating, a suction shutoff valve will close the gauge/service port of the valve.


Question #4: How would you remove moisture from refrigerants in a system?

  1. Purge the condenser.

  2. Drain the oil separator.

  3. Reduce water flow to the condenser.

  4. Use a filter drier.

Scroll down for the answer...














To remove moisture from refrigerants in a system, we use a filter drier.


Question #5: What are refrigeration and air-conditioning compressor heaters used for?

  1. To reduce the amount of refrigerant in the oil.

  2. To prevent refrigerant vaporization.

  3. To reduce the amount of entrained water in the receiver.

  4. To prevent acid pitting













The compressor heaters are used to heat the refrigerant oil and boil the refrigerant mixed with it. Heating reduces the amount of refrigerant mixed with the oil.


Question #6: What is the easiest way to check the type of refrigerant used in a 60 ton packaged rooftop unit?

  1. Look at the unit nameplate.

  2. Use your service gauge set and a PT chart.

  3. Ask the owner.

  4. Measure the condenser pressure.











The system's nameplate is a sheet where the system's manufacturer has written down all data about that particular system. So it is the best place to look for any such information.



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