Late in the spring of 1998, Dennis Wald had just taken over the position of facilities director for Wausau School District in Wausau, Wis. At one of the district's 21 schools, 27-year-old, 273,000-sq-ft Wausau West High School, two of three boilers were not working; the chiller, an adsorption unit, had failed; classrooms would not heat or cool properly; teachers were threatening a work action; and energy was being used at the rate of 191,562 Btu per square foot per year. What's more, the fan systems serving the field house were so loud, they had to be turned off prior to events, while the built-up air handlers serving the main academic hub were so loud they could be heard three blocks away.

Wald's first challenge was repairing the chilled-water system. The district's engineer recommended replacing the failed 700-ton adsorption chiller with a new 400-ton screw chiller. After the machine was ordered, the district learned the additional electrical loads would overtax both the primary electrical service and the feed from the utility. Correcting those problems would add $500,000 to the cost of repair, and the utility estimated the school's already high electricity costs would increase by $40,000 a year. Additionally, the chiller modifications would not address the school's most pressing issue: ventilation, which air-quality testing showed was inadequate.

On July 15, with classes set to begin in just six weeks, Wald decided a fresh approach was needed. A new engineer was brought in.

EMERGENCY REPAIRS

The main academic wing was served by a classic field-erected duplex, constant-volume, dual-duct system with high-pressure distribution. After two days of field investigation, the underlying causes of the building's problems became clear:

• The four double-width-double-inlet centrifugal supply fans, which were designed to operate at 8 in. wc, were operating near stall conditions at 60-percent flow against 12 in. wc.

• One of the four vaneaxial return fans designed for 2 in. wc had exploded in its housing.

• The roll filters were inoperable, the ends of their media literally flapping at the inlets to the supply fans.

• The heating and cooling coils were fouled with years of dirt and corrosion (Photo A).

PHOTO A. A foulded reheat coil.

• The internal baffles of the dual-duct boxes were 60- to 80-percent obstructed.

• The accumulation of dirt had reduced the duct systems' effective cross-sectional area by 60 percent.

• The main air-handling systems were so fouled they could not move adequate amounts of air.

After being shown the problems, Wald concluded that the building's HVAC systems needed to be replaced.

“Classes are starting in six weeks, and these systems must be operational,” Wald told the new engineer. “I need the air-quality problems corrected, and I want you to try to pay for the repairs with energy savings.”

With time so severely limited, the initial objective was to get air moving and have heat and ventilation for the coming school year. Distribution-system modifications, new cooling and heating plants, and a complete control refit would have to wait for the following year. Initially, the scope of the repairs would be limited to the main academic area.