New technology refrigeration rack system fits right into your kitchen plans

Nation's Restaurant News, July 6, 1998 by Faster Frable Jr

The trend in foodservice refrigeration has been toward centralizing refrigeration strategies in air- or water-cooled rack systems often located on roofs or mechanical areas. The value of space and the cost of removing rejected heat from production areas dictate that more operators opt for remote compressors. Operators want to eliminate the need for servicing refrigeration compressors in cooking and preparation areas where service and maintenance disrupt the primary function of these areas.

Unfortunately, traditional rack systems have their problems:

* Larger centralized compressors are noisy and need to be located away from acoustically sensitive areas.

* Architectural design and zoning concerns are making it more challenging to place refrigeration racks on roofs or pads outside buildings.

* Conversion to new environmentally friendly refrigerants is considerably more expensive if it involves piping to remote refrigeration racks located in mechanical rooms or on roofs.

* Cooling compressors with city or chilled water is becoming a less-viable option in many areas. New applications using municipal water as a cooling medium, which then is dumped down a drain, is restricted in almost every major city because of environmental and water conservation concerns. Fewer buildings in the northern half of the United States now have chilled or condenser water system operating year-round. In large structures like hospitals and offices, chilled water is used for cooling large computer systems, and the system capacity could be shared with foodservice. Since newer computers no longer require cooling water for their processors, year-round cooling water no longer is provided. As water cooling become less popular for smaller compressor sizes, fewer manufacturers offer self-contained water cooling as an option. If the option is available, prices are often much higher than those of equivalent air-cooled models, and delivery times tend to be much longer.

At the request of several large food retail chains, the Hussman Corp. began a research program to develop a new type of refrigeration rack that addresses those problems. The Hussman Protocol system is based on the merging of three key elements into a new product category for a central refrigeration with shared compressors referred to as a parallel or multiplex rack system:

* The availability of superquiet Scroll compressors in smaller sizes that are designed for the foodservice industry. Scroll compressors were first introduced in commercial air-conditioning equipment in 1987. They are smaller, lighter, more reliable and much quieter than traditional reciprocating compressors.

* A new computerized management system that provides better energy management controls to en sure full redundancy and even wear on each compressor and totally automatic programming 24-hour operations.

* A new technology heat exchanger that is much smaller than traditional design, thereby allowing for a much smaller rack.

Together those elements combine in a compact acoustically insulated vertical or horizontal cabinet about the size of a single-door reach-in or two door under counter refrigerator. Unlike massive racks with noisy reciprocating compressors, the Protocol cabinet is intended to be located near the refrigeration load.

In a supermarket a typical location would be at the end of a lineup of refrigerated display cases or gondolas. In a foodservice kitchen a single cabinet centrally located in a kitchen could service all of the refrigeration loads in the entire operation. With a stainless-steel top the horizontal Protocol unit mounted on 6-inch legs becomes a standard 30- by 84-inch prep table. Inside the compact and quiet unit are as much as 36 HP of high- and low-temperature refrigeration capacity.

Unlike individual compressors sized and operated based on their maximum demand, refrigeration capacity in the Protocol system is designed to exchange only the amount of BTUs required at a particular time. For example, instead of having 10 3/4- to 1 1/2-HP compressors operating 10 individual coolers, the protocol system would have three 4-HP compressors. At night, when demand was low, the system would operate on a single 4-HP compressor. During the day, when the coolers and reach-ins are in use, a second 4-HP compressor would start to share the load. The third 4HP compressor would operate only if one of the other compressors were out of service. To ensure even wear, the system's computer automatically alternates between the compressors so that each unit is evenly run. Larger systems can have up to six compressors with three units required to service a 100-percent load during peak periods.

Since the compressors are piped in parallel, if a compressor fails, an alternate compressor would start to satisfy the refrigeration demand. Temperatures and pressure can be monitored, and alarms can be sent to your refrigeration service company by auto-dialer.

Utilizing such a refrigeration system eliminates the need for a mechanical equipment room or difficult-to-access roof-mounted equipment. It combines the advantages of a conventional rack system and a multiplex rack system: respectively, simplicity and energy efficiency and compressor backup. The air-conditioning load in kitchen and retail areas is significantly reduced when compared with self-contained equipment. Refrigeration piping and refrigerant charge are reduced, and the system can utilize either air or water cooling.