Comfort At Work: Case Study

Slashing Energy Costs

Burdened with high energy costs and outdated equipment, a northeast Texas school district turns to a 'self-funding' hvac system for answers.

Engineered Systems cover
Reprinted with permission from
Engineered Systems magazine.

The White Oak Independent School District (ISD) in northeast Texas was burdened by high energy costs and outdated, inefficient air conditioning and heating equipment.

“We simply did not have a method to control our energy costs,” said District Superintendent Dr. Tim Sonnenberg. “They were much too high for a school district our size.”

The district serves approximately 1,350 students, kindergarten through grade 12. It has an elementary school, a middle school, a high school, and an administration building, all part of one large complex.

By the time the 1993 school year began, costs became unrealistic. Electricity alone averaged $17,000 per month between April and September. Most of the equipment was 20 to 30 years old, efficiency ratings were dismal and, other than a few mechanical timers on some of the units, there was virtually no way of monitoring the system’s use.

Carrier’s Total Retrofit Solutions (TRS) program helped the school district bring costs back into line. Implemented for the 1994 school year, TRS saved the district a total of $156,000 in cost-avoidance and reduced energy consumption during its first year, according to Dr. Sonnenberg.

In the eyes of the school district’s administration, the program also resulted in a more efficient and environmentally sound air conditioning system - all at no additional expense to taxpayers.

Program Overview

White Oak’s decision to participate in the TRS program was made possible through the performance contracting legislation, which Texas recently adopted, along with many other states. This legislation enables schools to contract with a private company if the company guarantees that the cost of the equipment will be offset by the direct and indirect savings it generates.
Most of the equipment was 20 to 30 years old,
efficiency ratings were dismal and, other
than a few mechanical timers on some of
the units, there was virtually no way
of monitoring the system’s use ....
In other words, the system must be “self-funding.”

In accordance with the law, Dr. Sonnenberg invited interested companies to propose a retrofit plan and energy management program. His past experience with a similar program as superintendent in Denton, TX, led him to believe that this idea might work in White Oak.

Ultimately, four companies responded to the district’s request. After an extensive review of their proposals, White Oak ISD selected Carrier. In making its decision, the school board, according to Dr. Sonnenberg, considered costs, 10-year energy savings, impact on the district, qualifications of the company, name recognition, and proximity to the Tyler, TX-based Carrier plant.

The board found Carrier’s “System Analysis Modeling” software useful in the decision-making process, too. The software analyzed data on the existing equipment, contrasted it with the recommended new equipment, and calculating the expected energy savings.

Under the terms of the TRS program, the customer faces no up-front costs - the calculated energy savings pay the cost of the new equipment. Carrier guarantees the savings. If the new system does not generate the calculated energy savings, the manufacturer says it will make up the difference.

Dollars, Sense

Although Carrier arranges financing as part of the TRS program, White Oak chose to finance for 10 years through the Texas Association of School Boards.

According to Dr. Sonnenberg, the fist-year savings for electricity during the 1994 school year were $52,274, exceeding the guaranteed savings by $23,565. White Oak’s cost-avoidance savings, including repairs and other miscellaneous costs related to the old system, were $104,000, said Dr. Sonnenberg. So, the total first-year savings for White Oak ISD surpassed $156,000.

Action Plan

Beginning in May, 1994, White Oak replaced 49 old rooftop units with more-efficient Carrier Model 50SS units, ranging from 3 to 30 tons. Then. The district replaced old chillers with Carrier 23XL screw chillers. The two new chillers have a capacity of 160 tons each, and a life expectancy of 20 to 25 years, the manufacturer said.

The elementary school retained its two original chillers, which use CFC-refrigerant R11, no longer produced in the U.S. As part of its refrigerant management service, Carrier equipped each chiller with a “PreVent” High Efficiency Purge System refrigerant containment device. According to the manufacturer, these devices are designed to help retain refrigerant vapor and return it to the chiller, curbing refrigerant leakage and, in turn, protecting the environment.

Later, White Oak installed a new cooling tower at the elementary school. The school district also retrofitted all district lighting. Using high-efficiency fluorescents and reflectors, Dr. Sonnenberg said the district maintained the quality of the light at a significantly reduced wattage and electricity usage.

Final Phase

Before the project was done, White Oak tied the retrofit together with the Carrier Comfort Network (CCN), a communicating controls system for managing and monitoring hvac equipment.

According to Dr. Sonnenberg, with CCN, the maintenance staff manages system operations and constantly monitors the system’s performance, observing such measurements as the current temperature in each section of every building, energy consumption in kilowatt meters, actual run-time of equipment, and even filter status. Through instant analytical reports comparing actual and estimated energy consumption, Dr. Sonnenberg said the district can always track its energy consumption and savings.

White Oak has programmed CCN to activate or de-active the hvac system at desired times in order to achieve better efficiency. The district has also found CCN to be extremely convenient for altering schedules on nights when the school is holding a meeting or extracurricular activity. In addition to pre-setting the hvac system, district personnel can also access, monitor, and manage hvac operations remotely, via a laptop computer.

Dr. Sonnenberg said the district has used CCN to examine valuable data on its energy costs. For example, White Oak officials now know exactly which parts of the building are best-suited for holding after-school functions, based on the amount of energy the rooms require to heat or cool. Prior to installing the system, Sonnenberg said, an individual building might have run a system at half capacity in order to cool one room.

“We’ve been able to control our energy costs much more effectively than ever before, and the system is user-friendly,” said Dr. Sonnenberg.

As part of the TRS program, White Oak ISD has a service agreement under which Carrier solves any major maintenance problems, added Dr. Sonnenberg.

According to school officials, Carrier technicians and representatives are also frequent visitors to White Oak, just to make sure things are running smoothly and to answer any questions on system operation and performance.

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