Energy Efficiency and the Supermarket Coils Case Study
By Kent Penning – August 2011, Sunnyvale, CA
Several weeks ago Cold Craft Inc. received a trouble call from a small local supermarket. The cooling system for the meat walk-in cooler was not working. Upon arrival, the evaporator cooling coil (the one in the walk-in box) was found to be a block of ice. After some defrosting, this is what the coil was found to look like.
This particular chain of markets is known for being impeccably clean. So finding a coil this dirty and corroded was a surprise. This is the worst coil I have witnessed in my 30 years of being in the industry. We recommended the coil be replaced. The business owners quickly authorized the work. The picture below shows the new and old contrast.
The coil replacement is completed and the cooler is now cold again. The question remains:
What caused this 10 year old coil to be so bad, when all the other coils at this store are fine?
The best way to determine this is to ask questions and observe the usage of the store and the unit in question. After observing the operations of this incredibly busy store, it turns out that they are marinating meat, which doesn’t sound so terribly bad, but we discovered that there was one ingredient that makes the difference – they are marinating with orange juice. In a nut shell, the citric acid in the orange juice and other ingredients were tearing up this coil.
Reccomendations have been made to cover and seal the meat in cooler. Ironically it has been our expereicne that we have seen this type of corrosion near the ocean, in bar refrigeration units and in air conditioning units that are not serviced regularly.
Regular preventative maintenance inspections would have also caught this condition before it became this bad. Preentative maintenance also controls replacement of equipment in a more timely manner so there are fewer emergency replacements. When food is involved refrigeration problems are an emergency.
This situation also made this business pay an unseen cost – this cost was hidden in the higher than normal energy bills, because the unit was workign harder and the replaced unit is more energy efficient.
This system was found to be using the obsolete refrigerant R-22. This system had a hermetic compressor and it did not make sense to perform a refrigerant conversion at this time. Changing to an environmentally friendly refrigerant such as R-404A will be project for another day.
Cold Craft Inc. performs installation and remodel work for the smaller supermarkets in the San Francisco Bay Area of Northern California. We have worked with many clients doing energy saving projects such as heat reclaim, system optimization and CPC rack and temperature controllers.