A few months ago, I wrote an editorial about what the future of supermarket refrigeration may look like. Essentially, I noted that changing demographics, new technologies, and evolving regulations may result in wider acceptance of self-contained refrigeration units that utilize propane. Several readers took issue with this, noting that central rack refrigeration systems — which are traditionally used in supermarkets around the U.S. — are not going anywhere and that propane units have too many drawbacks to ever seriously be considered for large-scale use.
I heard the same arguments during several industry conferences I attended this year. At one such conference, a senior refrigeration engineer gave a presentation on the benefits of propane systems, noting that while it has always been accepted wisdom that central rack systems with remote cases are more energy efficient, cheaper to install, and very robust compared to traditional self-contained cases, propane is starting to change that perception.
The engineer predicted that self-contained propane systems will be used more extensively in the future because the new generation of cases is quiet, easy to maintain, energy efficient, and simple to install. In addition, he noted that self-contained propane units contain a very low charge of refrigerant, they are highly flexible for merchandising purposes, and they have a low leak rate of about 2 percent (compared to 10 percent in distributed systems). And they are already being used by a number of different retailers in the U.S., including Target and H-E-B.
The pushback from the audience was immediate, with conference attendees — like several of our readers — arguing that this will never come to pass. One of their primary concerns was the fact that self-contained air-cooled units reject heat into the store, so a supermarket’s HVAC system would have to be larger in order to compensate for the additional heat load on the sales floor. But that may not always be true, as many industry experts have argued that supermarkets are generally too cold anyway, so the heat rejected from the units can be used to directly warm the store, thus reducing energy costs.
Or, if the additional heat load is too great, supermarkets can direct the rejected heat to a water loop. This is the configuration H-E-B utilized in its 83,000-square-foot Austin, Texas, store, in which the majority of the cases are self-contained propane units. These units, along with a small number of DX-cooled refrigeration cases, are all connected to a water-cooled condenser, so heat is not rejected onto the sales floor.
Another concern, from readers and seminar attendees alike, was in regard to the additional maintenance involved with self-contained propane units. As one reader commented, “the fin spacing on air-cooled condensers is very close and easily gets clogged with the dust, dirt, and debris. Once clogged, the refrigeration unit cannot perform as designed, which may result in system failure.”
Many refrigeration OEMs have addressed this issue by including filters that are easy to remove and wash, so the maintenance personnel at any supermarket should be able to handle doing this on a monthly basis. Of course, in a large supermarket with numerous cases, it could take awhile to remove and clean all those filters, which could be a drawback.
Drain pans located under self-contained units also require regular maintenance, as water and mold can accumulate there if not cleaned regularly. If that happens, pans may fail, causing water to leak out onto the sales floor. According to refrigeration contractor Joe Kokinda, president and CEO of Professional HVAC/R Services Inc., Avon Lake, Ohio, there are several solutions to this problem.
“Many self-contained cases have condensate removal systems other than a float and pan assembly available,” he said. “For example, some units may use the heat from the compressor discharge line to complete the condensate boiling method. Many markets also have floor drains that are used for existing cases. When they do, we run small Tygon [plastic] tubing from the drain areas using pumps located under the cases.”
Obviously, propane is not the solution for every application, and there are serious concerns about where and how these self-contained units can be used. However, manufacturers are rolling out new and improved propane units at a brisk pace, and several major retailers have indicated that they like what they’re seeing. For contractors who service these types of businesses, it might be a good idea to learn a little more about this particular type of equipment, which could play a larger role in supermarkets going forward.
Publication date: 12/3/2018