Refrigeration System Keeps ‘Food For Thought’ Fresh at Ohio University
That was the daunting task in 1997 facing Bryan Sherman, associate director of engineering services at that time for Ohio University. Founded in 1804, Ohio University was the first institution of higher learning west of the Ohio River.
Sherman was responsible for updating the refrigeration design at Nelson Commons, a sprawling dormitory center at the university’s main campus in Athens. Built in 1965, it serves more than 4,000 meals per day in its dining center for students living in five dormitories.
Cutting-Edge DesignSherman envisioned a central rack system to operate multiple coolers and freezers at Nelson. To complicate his assignment further, Sherman and his staff needed to complete the transition from the existing system to a new one over a holiday break period. That time frame was shortened further by the need to have the refrigeration operating to serve a wedding on the weekend before Christmas.
Sherman knew he wanted to work with Heatcraft Refrigeration Products and contacted Tod Heath, sales manager for Miller Component Sales, Inc., which represents Heatcraft in Ohio, Kentucky, West Virginia, Indiana, Michigan, and western Pennsylvania. Sherman and Heath gathered the design data and calculated all the load requirements for the various refrigerated areas.
Heatcraft designed the parallel-piped refrigeration rack and the remote condenser section. The six-compressor rack consists of two different suction groups, with each group containing three same-size compressors. The low-temperature group operates at -40˚F SST with a 10-hp compressor, while the medium-temperature group operates at 22˚ SST with 7.5-hp compressors. “For total system redundancy,” added Heath, “Sherman had electromechanical controls incorporated into the system design.”
One advantage of the rack was the chance to use microprocessor control. “Sherman had some precise requirements in controls,” said Heath. “Heatcraft has experience with the CPC product line, so the two naturally came together.” The CPC refrigerant monitor case controller (RMCC) used on the rack balance compressor run-time controls capacity, operates defrost, provides a sophisticated alarm capability, and even includes modem access to oversee the system operation from a remote desk.
“What we have done here is design a system to run more efficiently by use of capacity control and by utilizing the load-matching features of the microprocessor. This is very important due to the fact that the refrigeration load varies dramatically, depending on when school is in session,” said Heath.
Progress Supply Inc. (Cincinnati), a hvacr wholesaler with offices in Cincinnati, Columbus, and Dayton, won the bid for the state contract for the refrigeration equipment. Terri Surber, branch manager for Progress Supply, was instrumental in dealing with the tight scheduling and shipping needs for the delivery. Progress Supply also provided installation parts and supplies. Surber then spearheaded provisions for extra items needed to complete the installation.
Tight TimeframeSherman’s staff then installed the equipment. “The real critical thing about this job,” is they had to totally take out the old equipment and install new equipment, and have it up and operational during the break between quarters. They had a real tight timeframe,” said Surber.
“The interesting thing in the way the job was bid is that a Heatcraft factory service representative would be onsite to basically troubleshoot and test the equipment when they fired it up,” Surber added. “So the service rep came in to the job site expecting nothing to be ready, just a few days after all of the equipment had been delivered. But Sherman and his university staff had already finished the job.”
Sherman thus confounded not only the consultants but also the Heatcraft representative as well with the speed and talent of his crew. “Heatcraft shipped evaporators one week, then shipped the rooftop condenser the following week, then delivered the rack system on Saturday of the third week,” said Sherman. “When they delivered the system for the roof we put it right on and had it plumbed and pressurized the next day. Our guys laid out the whole system, including piping schematics and layout.”
On Budget, On TimeHow thorough is the new operation? Sherman said that “what we have is a rack with a dual suction group: a medium-pressure suction group and a low-pressure suction group. They go out to a common discharge and then a 19-ft rise to a condenser on the roof, so there’s a double discharge riser. A liquid line then comes down and distributes to 10 evaporators in seven boxes. The boxes are for a blast freezer set for -30˚; a storage freezer for -10˚; a milk cooler, a cheese cooler, a produce case, and the cook’s cooler, into which racks of hot food are wheeled, all of which are designed for 35˚; and a thawing cooler set for 45˚.”
“Every component in the system is isolated with a full-port refrigeration ball valve,” said Sherman. “The piping includes pressure ports on either side of every component, so that we can measure the actual pressure drop for each component. Also, every evaporator has a drier and a sight glass (viewport).”
The folks at the university were also more than happy with the way Sherman managed his budget. “Gene Reed, director of food service for Ohio University, says we saved the school about $100,000 compared to the engineering consultants’ estimates,” said Sherman.