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Tackling Walk-In Refrigerator and Freezer PMs - Part 2

Mar 25, 2015

Evaporator maintenance is only half the task, on to condenser loop maintenance.

The previous piece in this series looked at walk-in and commercial refrigerator evaporator coil and associated hardware preventive maintenance. The evaporator coil’s name refers to the refrigerant, Freon or newer types like HFC-132a, being evaporated, that is turn from a liquid to a gas. Evaporation is a process that absorbs heat, just as liquid water needs to absorb heat to boil. The amount of “heat” absorbed when the liquid refrigerant turns into a gas is small, but that small amount of heat absorbed from the refrigerator or freezer compartment is enough to keep it cool. To help visualize this, think of a CO2 cartridge in a seltzer maker or BB gun after it is used: it feels cold. The liquid CO2 inside the cartridge is evaporating and absorbing heat from the surrounding air.

The opposite takes place in the condenser loop. Here the gas is squeezed together by the compressor and turned into a liquid. And in doing so, the “heat” captured in the evaporator coil loop is released, heating up the compressor and condenser coils. Something like this happens when you are using a bicycle pump: the outlet of the piston tube gets very hot as many have found out when they inadvertently touched it. The air is not turned into a liquid, but compressing the air (gas) makes it hot and that heat can be more easily transferred to the air.

This heat generated during compression is expelled when the condenser coils heated by the compressed gas or liquid inside release their heat into the air surrounding the compressor coils. The process allows the refrigerant to be reused to pick up more heat. It’s amazing to think that this process, turning a refrigerant liquid into a gas to cool the refrigerator, then compressing the gas back into a liquid to expel the heat, happens continuously in our home refrigerators year after year with little maintenance and few failures. This is a tribute to the power of technology, good engineering and quality manufacturing.

Figures 1 & 2: Home refrigerator compressor and fan cooled compressor coils (Left Image) compared to commercial unit (Right Image) demonstrates similarities and differences, mostly in the larger size of the commercial unit.

Like home units walk-in compressor loops require maintenance. In fact, maintenance in commercial units is in most cases required more often than in home refrigerators and is more important than evaporator maintenance. Evaporator components operate in a relatively controlled, clean environment. Compressor components operate in the ambient air: from hot summers and warm kitchens to cold winters where they can be covered with snow or ice. Dust, dirt, greases and oils in this environment are serious concerns because dust and greases can adhere and accumulate on compressor coils or fins blocking airflow and reducing cooling efficiency. To accommodate for accumulated dust and dirt the compressor runs harder, longer and gets hotter, meaning it will be more prone to heat related damage or failure. Additionally dirty compressor coils lead to higher energy usage and cost.

Dust on the compressor coils is a significant issue in most sites. Unlike home units, commercial compressor coils often have fins attached to increase the ability to dissipate heat. Fans blow air across the fins and coils to help remove heat faster, and in doing so they draw in dirt, dust, greases and oils. The oils and grease stick to the coils and fins and coat them with a thin film, reducing heat transfer (cooling) efficiency. Additionally, these sticky films collect dust which then collects more dust, a process that ends up accumulating a significant amount of dust if not cleaned regularly.

Figures 3 & 4: Dust covered condenser coils (Left Image, Right Image) prevent proper heat transfer into the air, reducing efficiency, leading to higher energy costs, reduced compressor life and in some cases, spoiled food, especially seafood and dairy.

In the cases above, removing accumulated dust can be done by hand, vacuum cleaner with brush attachment or with a soft brush, being careful not to damage cooling fins, especially if they are very thin like those in a home window air conditioner. Additional cleaning with a spray cleaner like that used for the evaporator coils will help removed accumulated films. Care need be taken to avoid spraying cleaners into electrical components like fan motors; unplugging the unit or tripping the breaker during cleaning can help avoid problems.

The compressor itself as well as metal tubing connected to the compressor and cooling coils should also be cleaned. Here a soft cloth possibly dampened with appropriate cleaners can be used. Be careful if you clean the compressor and attached tubing right after powering down the unit because they may be very hot, enough to cause nasty burns in some cases.

Figures 5 & 6 Professional maintenance companies can provide both preventive and repair services when the job is too big or complicated or staff is not available. In the Left Image a service technician prepares a replacement compressor in a roof mounted unit. In the Right Image a commercial refrigerator is shown after professional cleaning and service.

The DIY vs Professional preventive maintenance is a decision managers must make. If you’re wondering if your or your staff is capable of proper cleaning and preventive maintenance, check out this YouTube video: Cleaning Your Condenser: Condenser Cleaning Video

There are many things a professional service regularly do that most managers or staff would find difficult when it comes to commercial and walk-in refrigerator maintenance, such as checking refrigerant pressure and electrical performance. Regardless of whether or not DIY or professional services are used for routine cleaning, annual or even biannual professional service is recommended, the latter for those units that run hard and whose compressor and compressor coils are in hot areas or those prone to accumulating dust and dirt.

Our next and final piece in the series will review the discussion, add some items to think about, and provide some thoughts on how to keep ahead of the maintenance requirements of commercial refrigerators and freezers.

Temperature@ert provides cost-effective, fault-tolerant wireless temperature monitoring solution for organizations of all sizes. Our products and services can help bring a food processor, distributor, wholesale or retail outlet into compliance with minimal training or effort. For information about Temperature@lert’s Cellular and SensorCloud offerings, visit our website at or call us at +1-866-524-3540.

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