Understanding Types of Defrost
23 days ago..

Last updated: 2019-08-30 15:09:11

Refrigeration has actively influenced the way we preserve food in both commercial and domestic spaces. Over the years, the refrigerators seen in the market have evolved and progressed to ensure that people get to enjoy the food preservation benefits that come with owning a refrigerator and foodservice businesses can make the most of fresh ingredients.

Despite the differences in branding, there are inherent similarities in all commercial refrigeration. They all have to keep food cold for a long as possible in precise, consistent temperatures conducive to preservation and freshness. The cooling process involves dropping the temperatures inside the refrigerator through a refrigeration cycle.

This cooling of the air inside the refrigerator causes it (the air) to condense into water before freezing and turning into ice crystals. This is called frosting. Over time, this ice build-up can accumulate inside the freezer potentially causing a decrease in performance, reduction in efficiency and a shorter life expectancy of refrigeration components.

Frosting comes with a number of disadvantages. These include:

  • The ice build-up takes up much-needed space inside the cabinet. This reduces the space available for stocking of food items.
  • Accumulation of ice crystals can damage components in the refrigerator.
  • It can cause freezer burn, a situation where ice crystals accumulate on the food surface and damage the quality of the food. The build-up also degrades food labels.

This accumulation usually happens in the evaporator, or freezer section of your equipment. As the temperatures get lower, the air around the cooling coils turns into water before crystallising and forming an ice build-up. To prevent this, fridges and freezers include a process called defrosting i.e. the process of removing ice build-up from the refrigerator.

There are different ways of defrosting your refrigerator.

Types of Defrost

There are two major methods of defrosting. These include: Automatic defrost and Manual defrost. In each, the idea is to prevent the build-up of ice crystals inside the refrigerator.

Manual defrostIce carving

The manual defrost system is the oldest method in the refrigeration industry. It is also known as the natural defrost system because it simply requires you to remove all the food from the refrigerator and leave the door(s) open for the ice crystals to melt.

The manual defrost system has a number of advantages.

  • It is cheaper than the automatic defrost models in terms of pricing and energy consumption levels.
  • It is able to properly maintain consistent temperatures for large quantities of products stored in the refrigerator.

The disadvantage of having a manual defrost refrigerator is that it takes more time and effort on your part as the owner to defrost.

Manual defrost functions are available in many types of commercial refrigeration including chest freezers such as the Tefcold GM500SS and ice cream freezers such as the Elcold Focus range.

Automatic defrost

Also known as the auto defrost, the automatic defrost was introduced as the need to have a less hands-on system of removing ice build-up increased. Fridges, especially freezers, with an automatic defrost system are also known as frost-free.

The automatic defrost requires no human intervention. It mainly comprises of a fan on the compressor and an electric timer which is factory set to control the temperature for the defrost process to take place.

The automatic defrost system has its advantages.

  • It is easy to maintain as it requires no human intervention to get rid of the ice build-up
  • It saves time
  • There is more space for your stock within the refrigerator thanks to the lack of ice build-up
  • Frozen food will not stick together
  • It is able to properly maintain food packages

Some of its disadvantages include:

  • It is more expensive in terms of cost and electricity usage
  • Automatic defrost refrigerators usually make more noise during their operation

Automatic defrost functions are supported by all manufacturer's and can be seen in the majority of types of refrigeration including but not limited to, Foster catering storage freezers, display freezers such as the Blizzard BL1SSCR and Artikcold preparation counters.

Automatic Defrost Variations

The automatic defrost system is a newer concept than natural defrost. As such, there are many automatic defrost systems, all different but designed to ensure that there is no ice build-up within the fridge. They include:

Hot Gas Defrost

This defrosts the refrigerator utilising the naturally occurring hot discharge vapour throughout the defrost cycle. The hot gas defrost system is efficient, reliable, safe and automatic. It also takes a shorter time compared with the rest.

During the defrosting process, the evaporator is turned into a condenser and hot air that would otherwise be directed into the condenser by the compressor in a normal refrigeration cycle is pushed back into the evaporator where the ice has accumulated.

The hot gas defrost system requires additional valves to control the flow of pressure and gas as well as a direct line which bypasses the condenser and the expansion valve. It can be found in a number of types of equipment such as ice machines from Prodis.

Water Defrost

The water defrost system basically uses water to get rid of the accumulated ice within the evaporator. It can be done using automatic or manual methods depending on the system and is mainly applied in industrial refrigerators.

The water defrost system is used in low-temperature refrigerators and works by applying heat directly to the accumulated ice. The water, plus melted ice then flows into a drain pan for elimination through evaporation.Glass of ice on heater

Some manual defrost system also use hot water.

Electric defrost

The electric defrost system contains electrical heating elements which are then placed on the evaporator coils. This system of defrosting is usually applied in cold rooms where temperatures tend to drop to extreme levels.

Electric defrost systems usually take longer to defrost the ice because most of the heat is not directed to the evaporator. Instead, only about 30% of the heat is used in the defrosting process while the remainder is dissipated into the cold room. This makes this process less efficient than methods such as gas defrost systems.

Many types of equipment use electric defrost methods including Di Rigo wallsite display freezers.

Off Cycle defrost

Off cycle defrost involves the temporary pause or cessation of the refrigeration cycle where refrigerant is prevented from entering the evaporator. This causes the evaporator temperature to increase therefore thawing any build-up of ice. At the end of the defrost cycle, the refrigeration cycle resumes. The length of an off cycle defrost is typically determined by a factory set timer.

Off cycle defrosts can be found with many types of chilling and freezing units including blast chillers and freezers from Interlevin.

Picking a Defrost Method

Before deciding on the most suitable defrost method for your business, there are a number of factors you need to consider. These include:

  • Cost - Refrigerators with automatic defrost systems cost more than those with a manual defrost system.
  • Application - Where are you using your fridge and what for? Automatic defrost systems can work well in commercial settings where efficiency is needed while a manually defrosting fridge will work well in domestic applications.
  • Maintenance – Manual defrost applications will require more time and elbow grease to get the job done therefore may not be suitable for businesses that have little spare time for maintenance. Automatic defrost systems are better at reducing maintenance costs than fridges with a manual defrost system. Automatic processes eliminate the hard work required to defrost equipment, although will have a higher energy usage.

Choosing a commercial fridge or freezer with a defrost method that fits your preferences will go a long way in ensuring that you continue to enjoy the benefits of refrigeration equipment in a business setting.

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