In this chapter, you will discover all the commonly found components, devices and equipment on a refrigerator and freezer unit.

Understanding each component and their function is important to know when practicing refrigeration.

Refrigerant (Gas)

Refrigerant is a cooling agent that absorbs heat as it passes through an evaporator and dissipates the heat as it returns back to the compressor.

Each type of refrigerant has a specific application according to their properties. 

Although there is a wide range of refrigeration refrigerant types, we will focus on the most commonly used refrigerant found in the field.

The table below indicates what refrigerant is used and where it should be applied.

Refrigerant types and applications

Reclaiming refrigerant

Although it may seem economical to reclaim refrigerant from a system, it’s not recommended to reuse reclaimed gas as there is no telling if the refrigerant is suitable, mixed, or contaminated.

There is a high chance that there are contaminants or a mixture of different refrigerants if the fridge has been worked on before by another technician. This could cause endless headaches when using this reclaimed refrigerant.

Label your refrigerant

Because you can use substitute refrigerant, it is good practice to label what refrigerant you used along with a date. This can be a simple label made out of masking tape and a pen. 

Evacuating and disposal of refrigerants

It is against the law and environmental responsibility to evacuate refrigerant into the atmosphere.

To evacuate the refrigerant, a reclaiming cylinder can be used, or alternatively, an empty canister can be modified to evacuate the refrigerant. Disposal of the refrigerant can be arranged by local refrigerant suppliers or gas suppliers.

Compressors (Hermetic)

This is the “heart” of the fridge where it pumps refrigerant vapour though the refrigeration system at high pressure.

Once the refrigerant has cycled through the system, it returns to the compressor to complete the cycle.

Of all the components found in a refrigeration system, the compressor is the most vulnerable to damage, corrosion or stress.

When replacing a compressor or re-gassing a refrigerator, careful steps and processes must be followed in order to ensure trouble-free operation and to increase the life-span of the compressor. Refer to the Replacing a Compressor section.

Compressor Specifications

On each compressor there is a model number which indicates the Horse Power (HP) of the compressor. This number will require a search on Google or via your supplier..

Compressor HP determines the application of the compressor. For instance, a small fridge will use a lower HP than a larger refrigerator.

The marking on the compressor will also include the refrigerant type as well as the voltage / phases.

Most importantly, the name plate will also state the refrigerant type.

Below are two examples where the MODEL, Voltage/Phase and REFRIGERANT details can be found.

Compressor Start Relay, Overload and Capacitors

Compressors need a starting relay to initiate the start to run coils. Often these fail or burn out which prevents the compressor from running.

Capacitors are often found in certain compressors where higher torque is required. These aid the start to run cycle of the motor only.

The overload is there to protect the compressor if there is an issue with the system such as a blockage, too much refrigerant or a motor / pressure lock.

Service Valves

There are generally three common valves that can be found on a refrigeration unit. Piercing Valves, Shrader Valves and Service Valves.

Piercing Valves

A piercing valve is commonly found on refrigerators that have had work done on the piping system. 

They work by placing the valve over the refrigeration pipe and tighten the clamp until it pierces the pipe.

Usually, piercing valves are used by technicians who have watched way too many YouTube Videos, or don’t really like their trade.

Although they seem they can save time, they also lead to stress, heartache and endless trouble!

It is highly recommended to NEVER use a piercing valve for three reasons:

1. Vibration can cause the valve to leak. In addition, they do not always guarantee a perfect seal if the pipe is not perfectly round.
2. If pressure readings are needed, means the fridge is not functioning and possibly in need of re-gassing. Re-gassing without testing leaks, flushing the system, replacing the filter or checking for contamination will only be a temporary solution which will eventually cost more in the long run when the compressor fails due to oil trapped in the evaporator, contaminants in the old filter or contaminants in the system.
3. They’re tacky, unsightly, and scream “bad workmanship”.

Shrader Valves

Shrader valves are usually connected on the service side of a compressor. They won’t be found on a compressor that has been factory filled. Instead, manufacturers fill the refrigerators and then crimp the inlet pipe.

When working on a compressor or when you need to re-fill a fridge, a shrader valve will need to be installed and NOT A PIERCING VALVE!!!

Pressure gauges are then connected to these valves for pressure readings, evacuation and re-gassing.

Before brazing a shrader valve, it’s important to remember to use the shrader cap as a removing tool to take the delicate valve out. Brazing with this valve on will damage it.

Shrader valves can also be found close to the evaporator, but it’s not that common on domestic units and more common on cold rooms or commercial units.

If there is no shrader valve or Piercing Valve, this means that the compressor has not been worked on before, or re-gassed.

Couplings and Fittings

Certain sections of piping will require bends and connector fittings. These fittings need to be brazed on to the pipe system. When the couplings are not correctly brazed, oil marks or powdery looking coatings that are either green or yellow will indicate a slow leak, which will require cleaning and re-brazing.

It may be tempting to take short-cuts, but not with refrigeration as it can cost you in the long run.

Always use refrigeration quality couplings and NOT plumbing couplings as these are a completely different grade and WILL rupture over time.

45° Coupling

90° Coupling

Equal Coupling

Reducer Coupling

Although these are refrigeration standard types, you may come across some refrigeration units with some rather inventive short-cuts taken by technicians who did not attend this course. 

Drip Pan Heaters

The purpose of these devices is to evaporate water that drips out of the fridge cabinet during a defrost cycle.

Drain pan heaters come in three types:

Electrical where this is just a heating element placed in a drip pan.

Passive Coil where a coil is added to the refrigeration piping system. The coil heats up from the high pressure refrigerant which in turn evaporates the drip water.

Top Pan which is just a pan located on top of the compressor which heats up from heat generated from the compressor.

Drip pans or drain need to be frequently cleaned as there is a constant build-up of dirt and grime caused from constant evaporation.

Condensers

The condenser is the component connected to the compressor via the discharge line. 

The hot, high-pressure refrigerant travels to the condenser to reject its heat to the environment, changing the refrigerant from a gas to a liquid in the process.

This is required to cool off the refrigerant to a nominal state in order to continue through the system. 

This allows heat to dissipate from the high pressure caused by the compressor.

Condensers come in two common applications, one being passive and the other being fan-cooled.

Passive Condensers

Passive condensers are located behind home fridges, which is a series of pipes with fins. Modern fridges can have these condensers concealed or use fan-cooling.

Commonly found on domestic fridges and freezers and small chillers.

This type of condenser relies on natural convection to dissipate heat through the fins. This type of condenser can only be used on small applications.

Fan Cooled Condensers

This is found in a multitude of applications and not only limited to commercial fridges. Often used on modern refrigerators, particularly on side-by-side fridges, beverage coolers and applications such as ice cream machines.

Fan-cooled-condenser fridges are efficient in terms of cooling, however, may not necessarily be considered as “economic” as electricity is used to run the cooling fans.

Fan cooled condensers are usually located close to the compressor, which serves to cool the refrigerant as well as the compressor at the same time.

This type of condenser has a higher cooling capacity however is vulnerable to requiring regular services due to dust build up caused by the fan.

Driers / Filters

Although driers are effectively filters, they have dual purpose to filter and dry. There is no difference between calling them either a filter or drier.

Driers / Filters are used to remove debris, moisture and contaminants from the refrigerant before it enters the Capillary Tube or Thermal Expansion Valve. 

It is also used to absorb water and moisture from the system which can cause acid build-up.

Water in the system can also cause a reaction with POEs called hydrolysis, forming organic acids which can corrode piping and deteriorate the motor winding.

Moisture can be trapped in the system from leaks, poor evacuation, mishandling of oils, or moisture trapped in new pipes.

Filters use desiccants which help with the absorption of moisture on a molecular level.

Filters are determined by the application of the refrigerator as well as the size of the compressor.

When performing any work to the piping system which will require re-gassing, it is highly recommended to replace the filter according to the refrigeration spec.

If there is a refrigerant leak and the fridge needs to be re-gassed, there is a good chance that moisture and contaminants have entered the system. This will then be collected in the filter, however can cause acid to build up. 

The same rule applies if the compressor needs to be replaced. If a compressor blows, it releases carbon and debris which will contaminate the filter.

Pencil Drier

Commonly found on domestic and home fridges. Pencil driers are commonly used with refrigerators that use a capillary tube instead of a TXV.

When replacing or installing a pencil drier, it is recommended that the “exit” be pointed downwards. The reason for this is that inside the filter there are small beads which will ensure a better filtration if they remain at the bottom of the filter.

Commercial Drier

These driers are used in refrigerators where a TXV is used instead of a capillary tube.

Commercial driers can either come in Flared or Sweat-on.

Flared is where a flange is created on the pipe and then tightened with a nut. Sweat-on is using a brazed joint instead of a nut.

Although there is no difference in filtration with flared or sweat-on, it is, however, easier to use  flared type as no prep is needed to braze a replacement filter.

Metering Devices

Metering devices is the general term used for either a Capillary Tube or Thermal Expansion Valve (TXV).

The purpose of the metering device is to change the pressure of the refrigerant which renders the refrigerant “become cold”. 

Capillary Tube

Commonly found on domestic fridges, this is a thin pipe which enters the evaporator. When replacing this pipe, it is recommended to remove the original pipe and issue it to the supplier to match the inner diameter and lengths. 

To cut capillary tubes, it can only be done with either a capillary tube cutter or a Stanley knife to slowly cut around the pipe and score it to then bend it until a clean break is made.

Using a hacksaw will burr and damage the ends, and a side cutter will squash the pipe which will not allow the fridge to cool.

TXV (Thermal Expansion Valve

TXV’s are a little more complex than a capillary tube where it regulates the amount of refrigerant flow that is permitted into the evaporator. 

The flow of refrigerant is monitored by a sensing valve which is located on the exit side of an evaporator.

TXV’s are used with larger refrigerator systems which include Cold Rooms.

They are usually located inside the blower-coil (a unit that contains the evaporator in a Cold Room), or next to the evaporator unit.

Placement of the Sensing Bulb

The sensing bulb must always be tightly wrapped with insulation foam or armour-flex to obtain optimum readings from the suction line.

Horizontal Suction Lines

• On a horizontal run, the bulb needs to be positioned at 3, 5, 7 or 9 ‘o clock.

Vertical Suction Lines

• On a vertical run, the bulb can be placed anywhere on the pipe, however the pipe leading out the bulb should be on top to prevent refrigerant in the bulb from running down the pipe.

Thermostats

Thermostats are devices that control the temperature of a fridge. Once the fridge cabinet has reached the desired temperature, it turns off the compressor in order to stop the cooling process.

There are misconceptions about thermostats that the colder the better, or that thermostats will help with cooling. This is highly incorrect as the device is only used to cut off power from the compressor.

A thermostat left a “Maximum Cold” will not cause the fridge to get colder, instead it could damage the compressor as the compressor may not be able to deliver the set temperature. 

This causes the compressor to continuously operate which reduces the life-expectancy, as well as cause unnecessarily high electricity bills.

Mechanical Thermostats

These thermostats rely on mechanical switching and have no electronic features. They are the most reliable and can be replaced easily and are cost effective.

Digital Thermostats

These thermostats have a digital display and a control panel to adjust the operating temperatures. These units fail more often than the traditional mechanical thermostats due to power failures, surges and electronic faults. They are also complicated to program and often need a manual.

Digital thermostats are also expensive to replace and quite often, carry unnecessary electronic features and functions.

Modern refrigerators often contain electronic control boards which not only limit diagnosing, but can also fail quite often. These units are incredibly expensive to replace.

Testing these controllers can only be done with assistance of a manual.

Placing the sensing bulb

• On domestic fridges that do not have an evaporator fan, the sensor can be located in the top section of the cabinet. Because heat rises, this will give better temperature control.
• Fridges with evaporator fans, it is recommended to locate the sensor on the evaporator to get a better reading and to turn off when the evaporator freezes.
• Cold rooms can have the sensor located behind the evaporator

Defrost Timers

Defrost timers is not found on all fridges. Defrost timers are used to prevent ice build up on the evaporator by turning off the compressor for a pre-determined amount of time.

Typically, a defrost cycle will be 4 times a day for 25 minutes. This will give enough time to break ice build up.

Although there are many types, the most commonly used are Dial type or dip-switch type. The only difference between the two is pricing.

On modern refrigerators, a control board is used with an integrated defrost timer.

How they work

When the defrost timer is on a “run” cycle, the compressor and condenser fan will run and have power supply to the thermostat to work as normal.

When a defrost cycle timer is starts, the relay in the timer will switch over to turn off the compressor and condenser. If there is a defrost element, this will turn on during the defrost cycle.

Evaporators

An evaporator is used to draw heat out of a fridge cabinet. Evaporators are always located inside the fridge cabinet.

The concept of refrigeration is that it removes heat instead of “making things cold”. In other words, heat is not “destroyed”, instead it is removed from the refrigerator cabinet and is converted outside. Therefore the function of an evaporator is to remove heat from the refrigeration cabinet.

As heat flows from warm to a cooler plane, the heat therefore moves from a food item towards the evaporator. This is why evaporators are located above a fridge as heat rises. 

In other applications where evaporators are located at the back of the cabinet, these fridges either have channels or fans to promote the movement of heat. 

In older fridges, freezer compartments were located on top of the fridge units.

In more modern fridges, freezer compartments that are beneath the fridge, however, they are in separate compartments. This design was adopted purely for aesthetic and convenience, which has nothing to do with heat exchange.

The principal can be understood that when the refrigerant passes through the evaporator, it “gives up it’s cold” by heating up from heat generated in a fridge.

Heat generated in a fridge is caused from heat entering through doors, insulation panels as well as the food or beverage items located in the fridge.

Therefore, a fridge, even though it may feel cold, is still considered as giving off “heat”, which is why fridges require constant cooling to draw the heat out as refrigerant passes through the system.

Pipes and Tubing

Refrigeration piping and tubing can come in different alloys. The most common being copper.

Only refrigeration grade tubing can be used for piping. Although pipes used for plumbing may seem similar, it is however weaker and cannot handle the pressures obtained by refrigeration systems.

Copper tubing

This is more commonly used on refrigerators that are used for commercial use as it is easier to repair and braze.

Very few home fridges use copper pipe as it is cheaper to use aluminium during manufacture.

Aluminium tubing

This can be used for cold rooms or air conditioning applications as it is cheaper. However, it becomes harder to use if you are repairing fridges due to space restrictions and the knowledge and skill needed to braze aluminium.

Stainless tubing

This is seldom used for repairs or installation of cold rooms. The reason being is that it is not as effective as copper or aluminium when long distance applications are needed.

In domestic applications, stainless steel tubing will often be found where the evaporator is built in the form of a shelf in freezer compartments.

Flexible tubing

This is seldom used, however, may be found on large cold room applications to minimise wear and tear from compressor vibration.

Hard drawn versus soft drawn copper

Hard drawn tubing is recommended for cold rooms where long runs may be required as it’s rigid and does not require as many supports. It’s also sturdy, so it is suitable for areas where the tubing may be damaged from high traffic. Hard drawn copper should not be bent, instead, elbows and 45 degree couplings need to be used for bends.

For general applications, soft-drawn can be used as it is easy to work with and can be bent with a suitable bender.

Determining Tube Sizes

All refrigeration tubes, parts and couplings are determined in inches.

As each refrigeration application and size is different, the tube sizes need to be carefully considered as it can cause harm to equipment or affect cooling efficiency.

The best application is to use the same size piping as the device. For instance, if the compressor outlet is ¼ inch, use the same size tubing. In situations where the compressor may be ¼ inch and the condenser is ⅛ inches, you could always use a reducer to change from one size to another.