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Convenience stores contain various types of plug-in cooling appliances. Examples include food, beverage, ice cream and ice merchandisers, various types of display cases, and the like. All these units have a “self-contained” or “integral” condenser coil unit within the cabinet of the appliance.
The condenser coil is tasked with the rejection of heat drawn from the cooled enclosure into the store’s atmosphere. Since these coils are located within the store, they are exposed to the normal dust and debris common to the store environment. Over time, the coils get dusty and dirty, and the efficiency of the appliance suffers as a result.
In order to restore the unit to its intended performance, coil cleaning is needed at least quarterly, according to the respected Food Service Technology Center (FSTC). Despite the admonition of both the appliance manufacturers and other experts, these types of coils are rarely cleaned once placed in service.
One reason is that the coils lie out of sight behind a panel or grille, with their increasingly dirty condition going unnoticed. Another reason is that, unlike many other energy efficiency practices, coil cleaning requires a continued cleaning commitment every few months that creates a serious impediment to adoption. A final reason is a lack of knowledge of the benefits of a committed coil cleaning program.
Benefits of Coil Cleaning
One major benefit of having clean condenser coils is a reduction in unscheduled service calls since units with cleaned coils run more efficiently. As coils become dirty, they are increasingly compromised in their ability to reject heat from the condensing unit since the dust and dirt act as a growing insulation layer on the coils.
This progressively forces the unit’s compressor to work harder and raises the temperature within the condensing unit. Over time, problems develop with the ultimate being sudden compressor failure with potential loss of product inventory and very expensive repair or replacement of the appliance.
An additional benefit is significantly reduced electric needed to run the appliance. Only recently has good data on this benefit been reported. The FSTC studied the effect of cleaning four differing types of plug-in cooling appliances common to the foodservice industry. Clean coils allowed these units to each consume from about $220 a year to $625 a year less electric than the same units with dirty coils.
While the size and age of the units caused a variation in the yearly dollar savings, the percentage of electric savings for all four units ranged from about 45 percent to 50 percent. Stated differently, if you do not regularly clean the condenser coils of these units, you will be running them on about double the electric compared to a cleaned unit.
If you multiply the yearly per-unit dollar savings (e.g., perhaps an average value of $400 a year) by the number of units in your store(s), you can see that the electric savings can add up to a significant number.
Typical Cleaning Procedures
Traditionally, the use of a vacuum and brush has been employed in coil cleaning. This method, while effective in removing surface dust and dirt contamination, will often not remove contamination from deep inside the coil structure.
The previously described cleaning technique can be improved if the technician also uses specially configured coil cleaning brushes to dislodge deeply embedded dust and debris. This additional step, though, can be very time consuming.
A quick and easy way to do the coil cleaning is by using a blast of compressed air to blow out the entire coil structure. In indoor spaces where most of these dirty units reside, it is necessary to drape a damp fabric, for example, at one end of the coil structure and place the compressed air source at the opposite end. In this way, the dust and debris will be blown out in the direction of the fabric and will be captured.
While this technique also works, it is very messy with the technician being faced with either using the resulting dirty fabric on other coils, cleaning the fabric before reuse, or disposing of the dirty fabric when his cleaning operation is done. Sometimes, the damp fabric blows off during the cleaning operation, causing a mess in the surrounding area that needs additional cleanup.
Within the last few years, engineered dust containment devices have appeared on the market that greatly improve the compressed air cleaning of these coils using compressed air. One type is a dust containment bag that fits over the coils during the cleaning operation, with the technician directing a source of compressed air through one of two ports in the face of the bag with a vacuum hose removing the blown-off debris from a second port in the bag’s face.
A wet/dry vacuum with two hoses or a standard vacuum with a compressed air cylinder are the two differing options for supply of compressed air and vacuum with this type of implement. During the cleaning operation, airborne dust and debris blown out of the coil structure is safely contained within the bag during the entire cleaning operation preventing pollution of the surrounding area.
As a nation, we have about 27 million refrigeration and freezer units in commercial buildings of all types and most are probably running with dirty coils.
Using a $400 per unit per year energy waste value from the data above as an approximation, it totals $10.8 billion for the nation’s energy waste for not doing this coil cleaning. As a percentage of the nation’s total energy use of $410 billion, this represents 2.5 percent of the total.
Editor’s note: The opinions expressed in this column are the author’s and do not necessarily reflect the views of Convenience Store News.