Situated on a campus-like 100-acre site, Carpenter Home Church in Lakeland, Fla., has a sanctuary the size of three football fields (167,000 sq. ft.) that seats 10,000. The overall church building complex includes three multi-story buildings and covers some 300,000 square feet. Within the structure are an elementary school, cafeteria, radio and television stations, a bookstore, foreign ministry and administrative offices.

When construction plans were being finalized in 1984, church officials became concerned about the cost of cooling such a large facility via conventional electric air conditioning methods. City of Lakeland officials told church administrators that monthly electricity charges could approach $35,000. Basic electric charges averaged 4.7 cents per kilowatt hour, but peak rates in the area surged to 7.36 cents per kilowatt hour. So, utility costs alone for a special event in the sanctuary could add up to several thousand dollars.

But church officials found an innovative answer to their energy-saving prayers in a unique, award-wining chilled water system that was designed by Carpenter Home Director of Engineering Jack Collins, and then built with equipment and support from ITT Bell & Gossett and People's Gas System of Florida. Through the first several months of operation, chilled water air conditioning energy costs have run 70 percent less than what had been projected for a traditional electric system.

I've always been interested in reducing utility costs because they're recurring costs, said Joe Perez, Carpenter Home's general manager. We couldn't do much about the fixed unit cost of electricity, but we thought the peak demand charges could be reduced through a more efficient use of natural gas energy.

Engine-driven chilled water air conditioning systems are common in hospitals, airport terminals, meeting halls and other large structures designed to serve thousands of people daily. But chilled water systems aren't commonly found in churches. The initial costs of building and installing such a system are greater than initial expenses for traditional air conditioning systems. But our savings in electrical costs are greater than the payments on the equipment, explained Collins, who designed and built a computer program that oversees the cooling system.

Shortly after Carpenter Home opened, its first electricity bills averaged only $12,000 per month, thanks to the initial energy management system designed by Collins and R.T.H. Engineering. However, the chilled water system has resulted in even more dramatic energy and cost savings through the combined efforts of Energy Management & Sales (EM&S) of St. Petersburg, Fla., and George Israel Co., ITT Bell & Gossett's representative in Tampa, Fla.

When we first devised the energy management system, we said we'd be happy to get our costs to $10,000 a month, Perez reported. Once we got the first chiller on line, we were down to $7,700 a month and even as low as $6,000 a month in winter. We have done even better than we imagined.

The numbers have not only pleased church officials, but impressed government agencies. In 1990, the State of Florida presented one of seven Governor's Energy Office Awards to Carpenter Home for its efforts. The church also received the U.S. Department of Energy's National Award for Energy Innovation.

It's nice in these days when churches are being questioned as to their stewardship to get a national award, said Perez, who added that energy savings now allow Carpenter Home to spend more money on important projects, such as the support of foreign ministries.

To implement the energy saving chilled water project, Perez and Collins turned to People's Gas system of Florida and to George Israel Co. The local ITT Bell & Gossett rep had worked with EM&S and People's Gas System on the installation of gas engine-driven chilled water air conditioning systems for many years, and George Israel Co.'s close association with the local gas company has resulted in the use of B & G equipment in many utility projects.

People's Gas suggested the church install natural gas-fired engine-driven chillers, with B & G pumps to circulate cooled water through primary and secondary chilled water systems and to pump the condenser water.

In addition, Perez and Collins decided they would use a diesel-fueled generator (purchased to stand by in case of power outages) as a peak-saving tool to drive rooftop air conditioners on the sanctuary and to power stage lights for televised church services.

The plan made good sense to Collins, a native of New Zealand who already had devised his proprietary computerized system to track the church's energy use around the clock. The system is connected to temperature sensors throughout the sanctuary building, and it controls mechanical systems so that either air conditioning or cool outside air can be used to maintain pleasant temperatures inside the well-insulated structure, depending on which is most cost-effective.

Collins and Perez began switching their air conditioning system over to gas power in 1989 . One 150-ton chiller was installed in June of 1989, driven by a s 454-cubic-inch modified marine engine, which uses a twin-screw compressor to power a vapor compressor.

A second, 160-ton chiller has since been added, and two more are planned. Four Bell & Gossett Series 1531 secondary chiller loop pumps and condenser water pumps currently are used in conjunction with the chillers. Plans call for a 50 HP Bell & Gossett HSC primary loop pump to circulate chilled water though the sanctuary, 1,400 feet away from the engineering building.

The two on line chillers each cool water from 55 degrees to 44 degrees at a rate of 700 gallons per minute. Waste heat is captured and used to produce hot water to drive a supplemental single-effect absorption chiller for another 30 tons of cooling capacity.

B & G Series 1531 pumps deliver chilled water through several thousand feet of insulated pipe to blowing units in the school and to 14 roof air conditioning units which have been adapted to use water in place of freon in the unit coils.