Shasta Union High School District has undergone a $27 million, district-wide modernization over the past five years. Due to the project's magnitude, school administrators were not interested in a quick fix. Rather, they were committed to making sure that the improvements produced long-term cost savings and performance advantages. Now that the project is complete, the district is reaping tangible benefits, including fuel savings of more than 50%, achieved in part by the installation of nine AERCO boilers in five school buildings.
Engineer Keith Ritter, co-founder of M/E Systems Engineering, was retained by the school district for the renovation. It was an ambitious project, overhauling each building's HVAC system and making a host of other improvements, such as new windows and electrical upgrades. Of all the decisions Ritter had to make, one of the easiest was which boilers to install.
"I spec a lot of boilers in my job. For customers who are serious about efficiency, you can't beat 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 non-cycling operation than other modulating units," said Ritter.
The latter point was important as the school district is located in Redding, a town in the far north of California. Redding typically experiences long but moderate winters of 30°- 40°F and 3,500 heating degree-days each year. Ritter conducted evaluations of various boilers and decided that the AERCO KC1000 and Benchmark 2.0 boilers were the best choices. Not only are they designed to operate in condensing mode, but the one million BTU/hr. KC1000 units that were installed had 14:1 modulation and could match heating loads as low as 70,000 BTU/hr. before cycling off. Even better, the Benchmark boilers' industry-leading 20:1 burner turndown would enable it to match loads between 100,000 and two million BTU/hr. for outstanding seasonal efficiency. At low fire in condensing mode, these units can deliver thermal efficiencies up to 99%.
"No other boilers have AERCO's turndown or their track record with modulating technology," said Ritter. "While all aspects of this multi-faceted modernization were geared to maximize efficiency, I believe that the new space heating infrastructure contributed to the savings significantly."
Greg Schnable, senior sales engineer for Clyde Equipment Company, Inc., worked with Ritter and supplied the AERCO boilers. As part of the initial renovations in 2002, Shasta High School replaced their old Kewanee plant with two KC1000 boilers. A third KC1000 unit 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 Benchmark boilers were installed in Foothill High School, as part of the last phase of the district-wide renovation.
The success of the renovations is evident by the tremendous savings reported by the schools. During the 2005-06 heating season, the Learning Center, Enterprise High School, and Shasta High School reduced usage by 73%, 63%, and 49%, respectively, compared to 2001-02 consumption. A breakdown of the actual therms can be seen in the chart below.'01-'02 Therms'02-'03 Therms'03-'04 Therms'04-'05 Therms'05-'06 ThermsShasta Learning Ctr.63,98819,60219,47217,22217,209EnterpriseHigh School52,48537,10621,78722,74719,429ShastaHigh School77,28458,12643,42246,65939,656
Ritter and his team had to create a new loop that could work with the existing piping of the older boilers. The AERCO units' condensing technology provided some advantages in this respect. The boilers allowed for a high ΔT system, which made it easier to install, allowed for smaller piping, and was less expensive.
Because of the high ΔT system, the district is now reaping efficiency benefits. Ritter explained that the system operates at a 40° ΔT. During the winter, supply water is typically 120°-130° and the return water is typically 90°. Even in the rare instance when the supply water needs to go as high as 160°, it still operates at a 40° ΔT, which increases efficiency by 13%.
Now that the project is complete, post-modernization fuel bills are available and Max Laughlin, maintenance and operations director of the school district, is pleased with the results. The AERCO boilers have helped reduce costs and improve building operations.