BY ROBERT P. MADER Of CONTRACTOR’s staff
TOWSON, MD. ¯ When the centrifugal chiller is busted and being used for parts and the only equipment working is an old steam absorption chiller, it’s time to upgrade the central plant. Which is exactly what officials at Towson University here did when they contracted to have the central chiller plant completely retrofitted.
Towson University is part of the University of Maryland system.
The university was moved both by plans to expand the campus and the need for energy savings, said Mike Lohman, the outside field superintendent on the job for mechanical Emjay Engineering & Construction Co., Gwynn Oak, Md. Emjay completed the job in the middle of this year.
The university bought two chillers and all the electrical control and switching equipment direct before the designed was completed, Lohman said, because of the long lead times involved. TA Engineering, Baltimore, designed the project.
The equipment is housed in a 2,100-sq.ft. building that held the old chillers and pumps. The building is next door to a central boiler plant that had been supplying the steam for the absorber. Chilled water is distributed underground to five buildings using all-welded pipe from 12-in. on down.
The university bought two 750-ton R-123 Trane centrifugals, far more than what is currently needed, Lohman said, because of plans to expand the campus.
Emjay performed all the demolition inside the chiller plant, and then grappled with the problem of the new chillers barely fitting inside. Emjay took out a window and created an opening 7-ft. by 9-ft. Lohman said the university planned to install a garage door in the opening. Coastal Crane Co., Baltimore, did the rigging and moved the old equipment out and the new equipment into the building.
The chillers were so heavy that they needed a pad to support them, but they didn’t have enough headroom in the 10-ft. high building to build a new pad. Emjay called on East Coast Concrete Cutting, Baltimore, which cut through and beneath a portion of the existing slab and poured a new 18-in. thick slab to support the chillers.
The chillers are piped both in series and parallel, with valves allowing either chiller to be taken completely out of the circuit for servicing.
Hudak Insulation, Baltimore, installed the central plant insulation.
Foreman Tommy Knight and his crew of five installed three Bell & Gossett 125-HP chilled water pumps, controlled by Square D variable frequency drives. The installation needs plenty of horsepower because of its layout - Emjay Project Manager Dave Rostek said miles of pipe runs underground, with one of the buildings located two miles from the chiller plant.
The system is closed, using evaporative condensers instead of cooling towers, but Rostek said that the ups and downs and twists and turns of the piping has given the college continual air problems. The school specified a 12-in Spirovent air eliminator from Spirotherm that cost $19,000. Rostek said Emjay offered Towson a credit if it used a standard air separator, but the university refused. It has found that the Spirovent is the only product that works for it, he said.
“They have had problems with air and this has been their savior,” Rostek said.
Chilled water goes through air handlers in the building used for makeup air and fan coil units in the zones. The devices are controlled thermostatically with two-way valves.
Three 75-HP B&G pumps move condenser water to existing Baltimore Air Coil evaporative condensers, or through a bypass valve during low load conditions.
Trane Co. was the controls subcontractor, using its Tracer System. Trane also supplied the variable frequency drives. The Square D electrical gear included a motor control center, 2000 kVa transformer, 2500 Amp main circuit breaker, and 13.2 kV main switch. J.M. Lippa Electric, Baltimore, was Emjay’s electrical subcontractor.
The Tracer System controls whether one chiller or both are running and the pump speed via the VFDs.
Emjay finished the building off, Lohman noted, with a refrigerant monitoring system and exhaust fans to meet requirement of the American Society of Heating Refrigerating & Air Conditioning Engineers Standard 15.
American Testing, Ellicott City, Md., tested and balanced the system.