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Supermarket technology is diversified and ever changing, as evidenced by a walk through the Food Marketing Institute (FMI) Expo each May in Chicago. But, once the folks who install and maintain store mechanicals get a hand in the process, the end result takes on dozens of variations beyond even those shown at the Chicago show.
That is evident each year during the FMI Energy & Technical Services Conference, which was held here recently. Those in charge of store mechanicals gathered to talk real-world applications.
Three presenters at the 20th annual meeting showed how they keep coolers and freezers up and running while keeping costs down.
Rob Uhl of Safeway talked of systems with parallel racks, semi-hermetic compressors, air-cooled or evaporating condensers, and heat reclaim. Piping is overhead to avoid the cost of having to dig up under-the-floor piping. Hot water reclaim is “used as much as possible” for store heating, he said.
R-22 hangs onNewer refrigerants R-507 and R-404A are being used in low- and medium-temperature applications, but the stores are sticking with R-22 for air conditioning, even though it is facing phaseout and alternatives to it are arriving on the market.
“Nobody has been convinced yet that there’s a better (air-conditioning) refrigerant (than R-22) for our purposes,” said Uhl.
Control technology mixes EPR valves with the cycling of liquid solenoid valves based on discharge temperatures, and allowing some cases just to run at rack pressure. Monitoring includes modem technology so adjustments can be made off-site.
Steve Little of Ukrop’s Super Markets Inc. uses R-22 across the board “purely for economic reasons,” but admitted “we are getting close to the time when we will have to consider changing to an HFC.”
Parallel rack variations include one system for medium-temp and one for low-temp use, with each system using split suction headers and with each system having a vertical surge receiver.
“We use a variable-speed drive on the largest compressor of each suction group to allow the compressor capacity to match the required load almost linearly,” he said.
The use of screw compressors is based, he said, on low noise level, a low failure rate, fewer moving parts, and such compressors’ ability to subcool their own liquid. The oil cooling system is siphon-based, he said. Liquid is returned through a plate heat exchanger to control the temperature of the oil.
Little gives the nod to air-cooled condensers because of what he said is “the high maintenance cost associated with evaporative condensers.” Variable-speed drives are used on the condenser to control the discharge pressure, save energy, control noise, and reduce spikes associated with fan cycling, he said.
Simply alarmingA key component to the successful operation of such systems is a Graphical Alarm and Monitoring System (GAMS). Little claimed the concept “makes alarms understandable for the layman. Store personnel are able to handle or verify the store’s problems rather than relying on outside help,” while “contractors and new personnel can easily view operations with limited training.”
One other cost saving advantage, he said, is that GAMS is an “off-the-shelf product.”
Edward Estberg of Raley’s focused on his chain’s remodeling that has switched the mechanicals from R-22 to R-404A in low, medium, and air conditioning applications.
He said he prefers electric defrost rather than hot gas, but noted the supermarket industry is split on the best method of defrost. He contended the electric method is simpler and more cost effective, especially in areas with low electric utility rates.
He said he relies on an “extensive use of remote communications,” including all technicians having laptop computers.
An example of the individuality of many decisionmakers in what refrigeration technology to use is the fact that Raley’s personnel design and make their own systems in a 2,500-sq-ft facility. There, employees make two types of systems, a two-stage, open-drive six-compressor system and a screw package with six compressors. All condensers are evaporative to help cope with a hot, dry climate in the daytime and sometimes sub-zero temperatures at night.
Heat reclaim is accomplished with a single desuperheater and circulating water in two circuits boosted with natural gas. No diverting valves or regulators are used.
A single-pipe system is used with most piping overhead. Only four pipes run throughout each store for main liquid, low-temp, medium-temp, and high-temp suction. Estberg said the concept lowers return gas temperatures and eliminates oil return problems.