• SkillCat Team

Refrigeration Equipments: Condenser Properties & Types

Updated: Jul 2

Refrigeration Equipment: Chapter 3


Condenser


In this module, we will go over the condenser component in more detail. We will also look to different types of condenser airflow. Skip to quiz!


Review: Condenser Function


In the refrigeration cycle, refrigerant flows from the compressor to the condenser through the discharge line. The condenser’s main job is to cool down the refrigerant. It does the opposite job of the evaporator.


Remember that the compressor increases the pressure of the refrigerant, which increases its temperature. By the time refrigerant gets past to the condenser, it is very hot.


The condenser cools down refrigerant by passing hot refrigerant through its coils. These coils are spaced out so that air can flow over them.


Heat always transfers from high temperature to low temperature. Because the condenser coils are hotter than its surroundings, heat transfers out of the condenser coils, which cools it down. This heat goes into the outdoor air, which carries the heat away.


As heat transfers from the refrigerant to the air, the refrigerant inside the condenser coils cool down. In summary,

  • The refrigerant cools down, and

  • The air around it heats up.

We need the refrigerant to be cooled down so that we can pass it back to the evaporator inside the home to continue absorbing more heat. This is why it’s called the refrigeration cycle, because the process repeats.


There are three types of airflow in a condenser:

  • Natural Airflow

  • Induced Draft Airflow

  • Forced Draft Airflow

Let’s take a look at each of these in a bit more detail.



Natural Airflow

Natural airflow is airflow without the use of fans. Natural airflow relies on the principle that hot air naturally rises and cool air sinks. This is how air naturally moves in the absence of a fan.


As hot refrigerant enters the condenser, it transfers heat to the air around it. This air becomes warm and starts to rise above the condensing unit. Then, air from the surroundings that is relatively cold fills in its place because cold air sinks.


This process repeats as the condenser runs:

  • Hot air keeps rising, and

  • Cool air sinks to take its place.


As the cycle repeats, this continues to create a natural flow of air. The air that has been heated by the condenser will move away, and cool air will take its place to continue cooling the condenser.


We tend to see natural airflow in older refrigerators.


Because natural airflow systems rely on air to move itself, we don’t have as much control over how fast we can provide cooling. It’s like waiting for a cool breeze on a hot summer day.


Induced vs Forced Airflow


This is why induced and forced airflow were invented. Both induced and forced draft airflow use fans to direct the flow of air. As the fans turn on and go faster or slower, we can better control the amount of air flowing over the condenser.


Both induced draft airflow and forced draft airflow use fans to direct air. So what’s the difference?


In induced draft airflow, the blower fan pulls cool air through the hot condenser coils. In forced draft airflow, the blower fan pushes cool air through the hot condenser coils.


To summarize,

  • Induced draft = pulling air

  • Forced draft = pushing air

In both cases, we are using a blower fan to control how air is flowing over the condenser coils to cool them.


To imagine the difference between induced and forced draft, let’s think about filling a glass with water. Imagine turning on your tap and filling your glass full of water. This is like forced draft because water is pushed into your glass.


Now, let’s imagine we have an empty glass, and we are in a pool. If we put the empty glass into the water, water will rush into the glass because it is empty. This is like an induced draft because the water is pulled into the glass.


Induced draft tends to be very noisy. Because of this, induced airflow is generally used only if noise is not an issue.


With induced air, remember that we are pulling cool air through the condenser coils. Because of this, there will be a buildup of dirt on the outside of the condenser coils. Because the external side of condenser coils is much easier to clean than the internal side, induced draft is generally the best choice.


Forced draft airflow is more quiet than induced draft. So we will use forced draft when noise is an important factor.


But with forced air, remember that we are pushing air through the condenser coils. Because of this, dirt and dust will collect on the internal side of the condenser coils. With forced airflow, we have to make sure to clean the inside of the condenser coils.


In some systems, both induced and forced draft are used to maintain balanced operating conditions.


In this module, we reviewed what the condenser component does and what types of airflow that are. Natural airflow operates without a fan. Induced and forced airflow requires a fan to direct air over the condenser coils. Next, we will talk about the components of a condenser.




Condenser Parts


In this module, we will go over the essential parts of a condenser. We will talk about what each part is responsible for. Skip to quiz!


Condenser Parts


As we discussed, the condenser’s main job is to cool down the refrigerant. It does this by passing hot refrigerant through its coils. Air flows over the condenser coils and cools down the hot refrigerant inside.


In order to do its job, the condenser has a few main components. In this module, we will talk about the condenser’s:

  • Inlet and Outlet Pipes

  • Coils,

  • Fan, and

  • Motor



Inlet and Outlet Pipes


The inlet pipes bring refrigerant into the condenser. Recall that refrigerant flows from the compressor to the condenser via the discharge line. So the discharge line leads through the inlet pipe to enter the condenser.


Before refrigerant enters the inlet pipe, the compressor has increased its temperature and pressure. As refrigerant enters the condenser’s inlet pipe, it is a high pressure and high temperature vapor.


The purpose of the outlet pipe is to lead the cooled refrigerant out of the condenser. Refrigerant leaving the condenser’s outlet pipe will flow through the liquid line to get to the metering device.


Refrigerant cools in the condenser and changes state to a liquid. After the refrigerant has been cooled in the condenser, it leaves the outlet pipe as a low temperature, but still high pressure liquid.


Condenser Coils

In the condenser, refrigerant enters through the inlet tubes, then moves through the condenser coils. The condenser coils increase the surface area over which refrigerant can flow. This cools down the refrigerant faster!


The condenser’s coils are similar to the evaporator coils that we covered in the Evaporator section. In both components, refrigerant flows inside the coils in order to transfer heat.


In our Evaporator modules, we talked about why as surface area increases, heat can transfer faster. In the evaporator, this means the refrigerant will heat up faster. In the condenser, this means that the refrigerant will cool down faster.


Another difference is that in the evaporator coils, we want to transfer heat into the refrigerant. And in the condenser coils, we want to transfer heat out of the refrigerant.


Like evaporator coils, condenser coils are made of metals like copper or aluminum. This is because metals are heat conductors. As heat conductors, metals will allow heat to transfer freely between the refrigerant and the air outside the condenser coils.


Condenser coils can have different shapes. We will talk about each of the different condenser coil shapes in a later module.


Condenser Fan


The condenser fan circulates air in the condenser to prevent overheating. This is just like how we would use a fan on a hot summer day to circulate air and cool down.


If the condenser gets too hot, the refrigerant will no longer be able to change state into a liquid. We can visualize this by thinking of putting out a forest fire. If the fire spreads too much, at the certain point, it will become very hard to put out.


To summarize, it is important that the condenser is not too hot. If the condenser is too hot, the refrigerant will remain a vapor. This means it can no longer absorb heat from the air, since it would be hotter than the air.


This is why it’s important that the condenser fan does its job of circulating more air to cool the condenser.


If the refrigerant inside the condenser coils gets too hot, the fan will direct more air to flow over the condenser coils. More air moving over the condenser coils means it will cool faster.


The condenser fan can be used in the following ways:

  • Fan Cycling Switch, or

  • Fan Speed Control

In fan cycling switch systems, the condenser fan will alternate between ON and OFF. This means the condenser fan can be functioning, or it can be off.


In fan cycling switch systems, the condenser fan will turn on when more air is needed to cool a hot condensing unit. And it will turn off when the condensing unit is cool enough.


Fan speed control is a way to control the speed of the fan. The fan will turn faster if the system senses that the condenser is too hot. And it will turn slower if the system is fine.



Condenser Fan Motor

The condenser Fan motor powers the condenser fan. The motor allows the condenser fan to rotate so that its blades turn to circulate air.


The motor has to be appropriately sized for the condenser fan. Depending on the size of the condenser fan, the size of the motor will vary. This is because we have to supply enough power turn the fan at the required speeds.


A malfunctioning motor can cause the same problems as not having a condenser fan. If the motor doesn’t work properly, the condenser fan can’t do its job of cooling down a heated condenser.


Some condenser motors need lubrication every year to work properly. It’s always a good idea to maintain the motor and condensing unit to prevent damages.


In this module, we took a look at the different components of a condenser. The inlet and outlet pipes bring refrigerant into and out of the condenser component. The condenser coils hold the refrigerant that needs to be cooled down.


The condenser fan moves air over the condenser coils to prevent overheating. And the condenser motor powers the fan. Next, we’ll take a look more closely at how a condenser works.




Condenser Properties


In this module, we will talk about the properties that affect how a condenser works. We will talk about how the condenser should be placed, operating conditions, types of airflow, and cleaning a condenser. Skip to quiz!


Overview of Properties


In previous modules, we have talked about how refrigerant cools down in the condenser. It does this because the refrigerant is hot while the outside air is cool. And heat will always transfer from hot to cold, so heat moves away from the hot refrigerant to the cool outside air.


Condenser coils provide a larger surface area for refrigerant to flow through. This larger surface area helps refrigerant cool faster.


In this module, we will talk about the following properties that allow the condenser to do its job:

  • Placement,

  • Operating Conditions, and

  • Cleaning



Placement

We can think of the condenser’s job as moving heat away from the space we are trying to cool. If we are trying to cool a room, we need to move heat out of that room.


Because of this, the condenser will generally be outside of the place we are cooling. For a refrigerator, the condenser coils are generally on the back of the refrigerator. This way, we can keep the contents of the fridge cool.


For split systems, the condensing unit will be outside of the house. This is the component that we see on the lawn or backyard.


Operating Conditions

The condenser needs to be free of any obstacles in order to work properly. We need to make sure that enough air can flow around the condensing unit.


This is because air needs to flow over the condenser coils to cool down the hot condenser coils. If there is something blocking the condenser coils, air cannot move over it, so there will not be enough cooling.


We can visualize this by thinking of a car exhaust pipe. The exhaust pipe in your car lets out all the fumes that we don’t want to be inhaling in the car. If the exhaust pipe is blocked, the car will overheat and break down. The same is true with the condenser.


Cleaning the Condenser


Over time, we will see a build up of dirt and dust on the condenser coils. We need to clean this off regularly to ensure that the condenser works properly.


If we don’t clean the condenser coils, this will be like blocking the condenser coils with an obstacle. Air will not be able to flow over the condenser coils so that will affect cooling.


Dirt stuck on the coil surface will decrease the surface area available for heat exchange. This can lead to overheating of the condenser and the whole system.


If the system cannot cool down, it will work harder until the refrigerant pressure is increased to dangerous levels. This is another reason why we need to keep the condenser coils clean. If the coils are clean, the condenser can do its job of cooling down the refrigerant.


When you start as an apprentice in the HVAC industry, you will likely be doing a lot of cleaning condenser coils. Most of the time, this will be using a coil cleaner solution to clean the coils. The solution will clean off the dirt, and then we will spray water to wash off the solution. Let’s look at a video of this.


In this module, we went over the different properties that affect how a condenser works. We talked about how a condenser should be placed, different types of airflow, and cleaning a condensing unit.





Condenser Types


Depending on the application, condensers will look different. In this module, we will go over the different types of condensers. Skip to quiz!


Overview

The condenser’s main job is to cool down the refrigerant. The condenser coils hold hot refrigerant. Air flows over the condenser coils and heat transfers from the hot condenser coils to the cool air. This heat transfer takes heat away from the refrigerant, so it cools it down.


Depending on the appliance or the system, the cooling requirement will vary. For example, for a large, commercial refrigeration system, the amount of refrigerant needed is larger. So it makes sense that the components would be larger, including the condenser.


Like we mentioned in a previous module, the condenser is a lot like the evaporator component. It does the opposite job of the evaporator. So it makes sense that the components would look similar.


In this module, we’ll be talking about the types of construction for condensers. There are:

  • Bare Tube Condensers,

  • Fin Tube Condensers,

  • Spine Fin Condensers, and

  • Microchannel Condensers


Bare Tube Condenser

Bare tube condensers are the most basic type of condenser. We generally see these in household refrigerators or small appliances because they are not as efficient as other condensers.


Bare tube condensers are generally made of aluminum or copper. These metals allow for easy heat transfer.


Hot refrigerant is contained inside the tube. When refrigerant flows over the tubes containing hot refrigerant, heat transfers out of the refrigerant.


Fin Tube Condenser


Let’s take a look at a video of how fin tube condensers work. In the following video, they will refer to fin tube condensers as heat exchanges. Heat exchangers can refer to either evaporators or condensers. This makes sense because heat is being exchanged in both components.


A fin tube condenser is shaped like a fin tube evaporator. Remember that fins are are basically metal plates. In fin tube condensers, fins are attached to the refrigerant tubing.


And as we discussed in the Evaporator modules, the higher the surface area, the faster heat can transfer. This is why fin tube condensers are more efficient than bare tube condensers.


The refrigerant tubing is generally made of copper or aluminum. And the fins are generally made of aluminum. This is because the fins are exposed and copper is soft so it would damage more easily.



Spine Fin Condenser


Like fin tube condensers, spine fin condensers have parts sticking out from its refrigerant tubes. But instead of small metal plates, we have metal spines in the shape of pins. Close up, they kind of look like a tube cleaning brush. Let’s take a look at a video of how they work.


The “spine fins” are attached to metal refrigerant tubes that carry the hot refrigerant. The spines are also made of metal. Just like the plate fins we just looked at, spine fins increase the surface area of the condenser.


Air can flow around the surface area of the spine fins, in addition to the remaining surface area of the refrigerant tubes. In fact, there’s even more surface area around the spine fins than the plate fins we just saw.


Because of the spine fins’ needle-like shape, we can fit a lot more fins on the surface of the metal refrigerant tubes. They are more efficient than fin tube condensers! This is because there is even more surface area than on a fin tube condenser.


Because they are more effective, spine fin condensers are used for large HVAC condensers. They are also more expensive, so the cost is more justified for larger systems that have a higher cooling requirement.



Microchannel Condenser


Microchannel condensers are pretty new in the industry. These condensers are the most efficient types of condensers.


Microchannel condensers are made of thin zig-zag aluminum fins. These wavy fins are the most distinctive feature of microchannel condensers.


Refrigerant flows in between these zig-zag or wavy aluminum fins. Let’s take a look at a video to see how they work.


The major advantage with these condensers is that wavy fins design allows for more surface area for refrigerant to flow through. Microchannel condensers have superior heat transfer.


The microchannel condensers are also lighter, small, and require less refrigerant.


Microchannel refers to the small spaces that are created by the wavy shape of the fins. Because of these small and delicate fins, we need to be careful when handling them to avoid damage.


We also need to clean them very carefully. Any contaminants stuck in the fins can affect the condenser’s performance. When brazing or soldering, be careful to not let shavings fall into the microchannels.


In this module, we discussed the different types of condensers. We talked about bare tube condensers, fin tube condensers, spine fin condensers, and microchannel condensers. Microchannel condensers are the most efficient type of condenser.





Question #1: The condenser’s job is to

  1. Take heat out of the system

  2. Provide a space for air to flow over refrigerant coils

  3. Both of these

  4. None of these

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Answer: Both of these

Both of these are true. It the condenser’s job to throw heat out of the system’s refrigerant. The condenser also provides the necessary space for air to flow over the refrigerant coils.


Question #2: In the condenser, heat transfers from

  1. The refrigerant to the coils

  2. The coils to the outside air

  3. To the compressor

  4. Both a and b

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Answer: Both a and b

Hot refrigerant enters the condenser. Heat transfers from the hot refrigerant to the condenser coils that hold the refrigerant. From there, the heat in the condenser coils transfers to the outside air. Because the coils hold the refrigerant, heat must transfer through the coils to reach the outside air.


Question #3: What is the principle that natural airflow relies on?

  1. Conservation of airflow

  2. Hot air sinks, cold air rises

  3. Hot air rises, cold air sinks

  4. All of these

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Answer: Hot air rises, cold air sinks

Hot air rises, and cold air sinks. Since natural airflow does not use fans, this is a natural principle that moves air.


Question #4: In natural draft airflow, there is a movement of air. As the cold air around the condenser is warmed up from contact with the hot condenser coils, it will rise. Cold air will sink to take its place. The cycle will repeat.

  1. True

  2. False

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Answer: True

This is true. This is how air naturally circulates with natural draft airflow.


Question #5: Induced airflow and forced airflow have what in common?

  1. They are are more effective than natural airflow

  2. They use fans

  3. Both of these

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Answer: Both of these

Both of these are true. As we mentioned before, natural airflow is not very effective because we don’t have control over airflow. With induced and forced airflow, we use fans to control airflow.


Question #6: In induced airflow, we use fans to ___ air.

  1. Push

  2. Pull

  3. Lift

  4. None of these

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Answer: Pull

In induced airflow, we use fans to pull air. This method pulls the outside air through the condenser coils.


Question #7: In forced airflow, we use fans to ___ air.

  1. Push

  2. Pull

  3. Lift

  4. None of these

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Answer: Push

In forced airflow, we use fans to push air. This method first pulls the outside air using the fans. It then pushes the air through the condenser coils.


Question #8: In induced airflow, which of the following issues do we tend to have?

  1. Dirt build up on the outside of condenser coils

  2. Dirt build up on the inside of condenser coils

  3. Energy waste

  4. All of these

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Answer: Dirt build up on the outside of condenser coils

With induced air, remember that we are pulling cool air through the condenser coils. Because of this, there will be a buildup of dirt on the outside of the condenser coils.


Question #9: In forced airflow, which of the following issues do we tend to have?

  1. Dirt build up on the outside of condenser coils

  2. Dirt build up on the inside of condenser coils

  3. Energy waste

  4. All of these

Scroll down for the answer...












Answer: Dirt build up on the inside of condenser coils

With induced air, remember that we are pushing cool air through the condenser coils. Because of this, there will be a buildup of dirt on the inside of the condenser coils.


Question #10: Refrigerant entering the condenser

  1. Passes through the inlet pipe

  2. Is high pressure and high temperature

  3. Is vapor

  4. All of these

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Answer: All of these

Refrigerant leaves the condenser through its outlet pipe. The other answer choices are incorrect. Leaving the condenser, the refrigerant is low temperature and is in liquid form because it has cooled down and condensed.


Question #11: Condenser coils

  1. Increase surface area refrigerant can flow over

  2. Increase surface area for heat exchange to happen

  3. Are made of metals

  4. All of these

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Answer: All of these

All of these are correct. The condenser coils are made of metals like copper or aluminum. These coils provide an increased surface area for the refrigerant to flow through and exchange the heat with the outside air.


Question #12: The condenser fan prevents overheating in the condenser. It circulates air to provide a fresh supply of air to cool down the hot refrigerant inside.

  1. True

  2. False

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Answer: True

This is true. The condenser fan provides circulation of air. This air takes heat away from the refrigerant in the condenser coils. So it prevents overheating in the condenser.


Question #13: No matter what, refrigerant will change phase from vapor to liquid.

  1. True

  2. False

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Answer: False

If the temperature of the refrigerant cannot cool down enough, the refrigerant will stay a vapor. The refrigerant has to be cooled past its condensation point or temperature to change the phase to a liquid.


Question #14: The fan cycling switch can turn on or off in order to

  1. Provide extra cooling when needed

  2. Make sure there is enough refrigerant

  3. Keep dirt away from the condenser coils

  4. All of these

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Answer: Provide extra cooling when needed

The fan cycling switch can turn on or off depending on whether the condenser is heating up. Turning on the fan will increase air circulating and help with cooling.


Question #15: Fan speed control

  1. Has more settings than a fan cycling switch

  2. Controls the speed of the condenser fan

  3. Both of these

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Answer: Both of these

Both of these are true. A fan speed control can be set over a range of settings. The high, low, and medium speeds are only a few examples of settings. It can be programmed to control the speed of the condenser fan.


Question #16: The condenser motor controls

  1. The condenser fan

  2. The condenser coils

  3. The amount of refrigerant

  4. All of these

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Answer: The condenser fan

The condenser motor controls the condenser fan.


Question #17: The condenser’s job is to remove heat from the system. In order to do this,

  1. Condenser coils are made of metal

  2. Condenser fans circulate air to prevent overheating

  3. Refrigerant has to cool down, changing phase from vapor to liquid

  4. All of these

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Answer: All of these

All of these are true. As metals are good conductors of heat, they allow easy transfer of heat in the condenser coils. Condenser fans circulate air that takes the heat away from the condenser coils.


Question #18: Why does condenser placement matter?

  1. The air surrounding the condenser coils has to be cooler

  2. Heat needs to transfer from hot to cold

  3. We need to move heat away

  4. All of these

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Answer: All of these

Condenser placement is important for all of these reasons. All these reasons play a major role in the transfer of heat from the refigerant to the outside air.


Question #19: Anything blocking the condensing unit will decrease its effectiveness. This is because we are blocking airflow that will cool the hot refrigerant in the condenser coils.

  1. True

  2. False

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Answer: True

This is true. Blocking the condensing unit blocks the path for air to flow. If there is no airflow, there is no way for the heat from the refrigerant to transfer and move out of the system.


Question #20: Dirty condenser coils will decrease the surface area of the coil that can effectively do heat transfer.

  1. True

  2. False

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Answer: True

This is true. This is why we need to keep the condenser coils clean.