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Now that the project has been completed, the district is starting to reap tangible benefits, including fuel savings of more than 50 percent. These were achieved in part by the installation of nine new boilers in five buildings. Engineer Keith Ritter, co-founder of M/E Systems Engineering, Redding, Calif., was retained by the school district for the renovation. The project included overhauling each building’s HVAC system and making other improvements, such as new windows and electrical upgrades.
BOILER DECISIONSOne of the decisions Ritter had to make was which boilers to install. “I spec a lot of boilers in my job.” When it comes to customers with efficiency concerns, Ritter said he prefers Aerco units. “I’ve found they deliver the best long-term payback because they have better turndown, so they deliver a far greater range of noncycling operation,” he said.
The latter point was important because the school district is located in Redding, a town in the far north of California. The area typically experiences long but moderate winters (30-40°F) and 3,500 heating degree-days each year.
Ritter evaluated various boilers and decided that the KC1000 and Benchmark 2.0 were the best choices for this application. Designed to operate in condensing mode, the 1 million-Btuh KC1000 units had 14:1 modulation and could match heating loads as low as 70,000 Btuh before cycling off. The Benchmark boilers’ 20:1 burner turndown would enable it to match loads between 100,000 and 2 million Btuh.
At low fire in condensing mode, these units are estimated to deliver thermal efficiencies up to 99 percent, according to manufacturer Aerco. “While all aspects of this multifaceted modernization were geared to maximize efficiency, I believe that the new space heating infrastructure contributed to the savings significantly,” said Ritter.
PHASE OUTGreg Schnable, senior sales engineer for Clyde Equipment Co. Inc., worked with Ritter and supplied the boilers. In 2002, Shasta High School replaced its old Kewanee plant with two KC1000 boilers. A third KC1000 was installed in the high school three years later.
The Shasta Learning Center and Enterprise High School were each upgraded with two Benchmark 2.0 units in 2002 and 2003, respectively. Finally, in 2006, two Benchmarks were installed in Foothill High School, as part of the last phase of the district-wide renovation.
During the 2005-06 heating season, the Learning Center, Enterprise High School, and Shasta High School reduced usage by 73, 63, and 49 percent, respectively, compared to 2001-02 consumption. A breakdown of the actual therms can be seen in Tables 1-3.
To prevent disruptions, renovations were done wing by wing during the course of the school year. The new boilers were colocated and run simultaneously with the existing boilers during the extended transition.
Space also became a key consideration. The KC1000 unit occupies a 78- by 22- by 57-inch footprint, while all pairs of Benchmark (each measuring 79 by 28 by 55 inches) were installed with zero side clearance.
Ritter and his team had to create a new loop that could work with the existing piping of the older boilers. The new units’ condensing technology provided some advantages in this respect. The boilers allowed for a high delta T (ΔT) system, which made it easier to install, allowed for smaller piping, and was less expensive.
Because of the high ΔT, the district is now reaping efficiency benefits. Ritter explained that the system operates at a 40° ΔT. During winter, supply water is typically 120°-130° and the return water typically is 90°. Even in the rare instances when the supply water needs to go as high as 160°, it still operates at a 40° ΔT which increases efficiency by 13 percent.
Post-modernization fuel bills are available and Max Laughlin, maintenance and operations director of the school district, said he is pleased with the results. The new boilers have helped reduce costs and improve building operations.